U.S. patent application number 10/448039 was filed with the patent office on 2004-01-29 for apparatus and method for characterizing libraries of different materials using x-ray scattering.
This patent application is currently assigned to Symyx Technologies, Inc.. Invention is credited to Bennett, James, Hajduk, Damian, Jain, Rakesh.
Application Number | 20040017896 10/448039 |
Document ID | / |
Family ID | 22802904 |
Filed Date | 2004-01-29 |
United States Patent
Application |
20040017896 |
Kind Code |
A1 |
Hajduk, Damian ; et
al. |
January 29, 2004 |
Apparatus and method for characterizing libraries of different
materials using x-ray scattering
Abstract
An apparatus for characterizing a library containing an array of
samples. The apparatus includes an x-ray beam directed at the
library, a chamber housing the library and a beamline for directing
the x-ray beam onto the library in the chamber. The chamber may
include a translation stage that holds the library and that is
programmable to change the position of the library relative to the
x-ray beam and a controller that controls the movement of the
translation stage to expose an element to the x-ray beam in order
to rapidly characterize the element in the library. During the
characterization, the x-ray beam diffracts upon impinging the
element and a detector detects the diffracted x-ray beam in order
to generate characterization data for the element.
Inventors: |
Hajduk, Damian; (San Jose,
CA) ; Bennett, James; (Santa Clara, CA) ;
Jain, Rakesh; (Sunnyvale, CA) |
Correspondence
Address: |
SONNENSCHEIN NATH & ROSENTHAL LLP
P.O. BOX 061080
WACKER DRIVE STATION, SEARS TOWER
CHICAGO
IL
60606-1080
US
|
Assignee: |
Symyx Technologies, Inc.
|
Family ID: |
22802904 |
Appl. No.: |
10/448039 |
Filed: |
May 22, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10448039 |
May 22, 2003 |
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|
09667119 |
Sep 20, 2000 |
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6605473 |
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09667119 |
Sep 20, 2000 |
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09215417 |
Dec 18, 1998 |
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Current U.S.
Class: |
378/208 |
Current CPC
Class: |
B01J 2219/00707
20130101; B01J 19/0046 20130101; B01J 2219/00745 20130101; B01J
2219/00659 20130101; Y10T 436/25 20150115; G01N 23/20 20130101;
B01J 2219/00315 20130101; B01J 2219/00511 20130101; C40B 40/18
20130101; B01J 2219/00596 20130101; B01J 2219/00704 20130101; B01J
2219/00585 20130101 |
Class at
Publication: |
378/208 |
International
Class: |
H05G 001/00 |
Claims
What is claimed is:
1. Apparatus for characterizing a library containing a plurality of
samples, said apparatus comprising: an x-ray source for producing
an x-ray beam; a chamber positioned in the x-ray beam having an
interior sized and shaped for holding said library of samples; a
stage connected to the chamber for moving the library containing
the plurality of samples relative to the x-ray beam to align a
pre-selected sample of said plurality of samples with the x-ray
beam to expose the pre-selected sample to the x-ray beam thereby
causing the x-ray beam to diffract and form a diffraction pattern
characteristic of materials present in the pre-selected sample; and
a detector mounted adjacent the stage for detecting the diffraction
pattern resulting from the diffracted x-ray beam thereby permitting
characterization of the pre-selected sample of said plurality of
samples in the library.
2. Apparatus as set forth in claim 1 further comprising a beamline
positioned along the x-ray beam for directing the x-ray beam toward
the library containing the plurality of samples when the library is
positioned in the interior of the chamber.
3. Apparatus as set forth in claim 2 wherein at least one of the
detector and the beamline are moveable with respect to the stage so
as to permit changes in an angle between a first line extending
from the beamline to the preselected sample of said plurality of
samples and a second line extending from the pre-selected sample
and the detector.
4. Apparatus as set forth in claim 1 further comprising a
controller operatively connected to the stage for controlling
movement of the stage thereby determining which sample of said
plurality of samples in the library is exposed to the x-ray
beam.
5. Apparatus as set forth in claim 4 wherein the controller
includes a computer system having a user interface permitting
independent user selection of which sample of said plurality of
samples in the library is exposed to the x-ray beam and of an order
in which said samples are selected for exposure to the x-ray
beam.
6. Apparatus as set forth in claim 1 wherein the stage comprises a
first positioning mechanism for moving the library containing the
plurality of samples in a first direction relative to the x-ray
beam and a second positioning mechanism for moving the library
containing the plurality of samples in a second direction relative
to the x-ray beam different than said first direction.
7. Apparatus as set forth in claim 6 wherein said second direction
extends normal to said first direction.
8. Apparatus as set forth in claim 6 wherein each of said first and
second positioning mechanisms includes a stepper motor.
9. Apparatus as set forth in claim 1 in combination with a library
containing a plurality of samples.
10. A method for operating an x-ray characterization apparatus for
characterizing a library containing a plurality of samples arranged
in a predetermined pattern, said apparatus comprising an x-ray
source for producing an x-ray beam, a stage for moving the library
to align a pre-selected sample of said plurality of samples with
the x-ray beam, and a detector for detecting a diffraction pattern,
said method comprising the steps of: loading a library into the
apparatus; activating the x-ray source to produce an x-ray beam
traveling along a beampath; zeroing the stage when the library is
in a predetermined position relative to the beampath to establish
an reference origin for stage movement; actuating the stage to move
the library to a first position in which a first pre-selected
sample of said plurality of samples in the library is aligned with
the beampath along which the x-ray beam travels; exposing the first
pre-selected sample of said plurality of samples in the library to
the x-ray beam thereby causing the x-ray beam to diffract and form
a diffraction pattern characteristic of materials present in the
first pre-selected sample; detecting with the apparatus detector
the diffraction pattern resulting from exposure of the first
pre-selected sample to the x-ray beam; recording the diffraction
pattern resulting from exposure of the first pre-selected sample to
the x-ray beam; activating the stage to move the library to a
second position in which a second pre-selected sample of said
plurality of samples in the library is aligned with the beampath
along which the x-ray beam travels; exposing the second
pre-selected sample of said plurality of samples in the library to
the x-ray beam thereby causing the x-ray beam to diffract and form
a diffraction pattern characteristic of materials present in the
second pre-selected sample; detecting with the apparatus detector
the diffraction pattern resulting from exposure of the second
pre-selected sample to the x-ray beam; and recording the
diffraction pattern resulting from exposure of the second
pre-selected sample to the x-ray beam.
11. A method as set forth in claim 10 further comprising the steps
of: processing the diffraction pattern resulting from exposure of
the first pre-selected sample to the x-ray beam to determine the
materials present in said first pre-selected sample of said
plurality of samples in the library; and processing the diffraction
pattern resulting from exposure of the second pre-selected sample
to the x-ray beam to determine the materials present in said second
pre-selected sample of said plurality of samples in the
library.
12. A method as set forth in claim 11 wherein the steps of
processing the diffraction pattern resulting from exposure of said
first pre-selected sample to the x-ray beam and activating the
stage to move the library to the second position occur during
overlapping time intervals.
13. A method as set forth in claim 10 wherein the library is in
said first position when the stage is zeroed.
14. A method as set forth in claim 10 wherein the apparatus
comprises a safety shutter and the method comprises the step of
opening the safety shutter.
15. A method as set forth in claim 10 wherein the stage includes a
stepper motor and the step of activating the stage to move the
library to said second position includes signaling the stepper
motor to take a predetermined number of steps.
16. A method as set forth in claim 10 wherein the step of
activating the x-ray source occurs before the step of actuating the
stage to move the library to the first position.
17. A method as set forth in claim 10 wherein the step of
activating the x-ray source occurs before the step of zeroing the
stage.
18. A method as set forth in claim 10 further comprising the step
of adjusting environmental conditions surrounding the library.
19. Apparatus for characterizing a library containing an array of
material members comprising: an x-ray beam source; a beamline being
adapted to direct, with a predefined beam cross-section, the x-ray
beam onto the library; a chamber adapted to hold the library;
library positioning means adapted to position the library relative
to the x-ray beam so as to make each member exposable to the x-ray
beam; and a detector allowing the detection of a photon scattered
by one of the members exposed to the x-ray beam in order to
generate characterization data for said one member.
20. A method for characterizing a library containing an array of
members, comprising the steps of: adjusting environmental
characteristics surrounding the library; directing an x-ray beam
generated by an x-ray source and having a predefined beam
cross-section onto the library by means of a beamline; moving the
library by a library positioning means in a predetermined manner to
expose a member of the library to the x-ray beam in order to
rapidly characterize each member in the library; and detecting
photons scattered by the member in order to characterize the
member.
Description
[0001] This application is a divisional of U.S. patent application
Ser. No. 09/667,119, filed Sep. 20, 2000, which is a divisional
application of U.S. patent application Ser. No. 09/215,417, filed
Dec. 18, 1998, now abandoned, both of which are incorporated by
reference in their respective entireties.
BACKGROUND OF THE INVENTION
[0002] This invention relates generally to an apparatus and method
for rapidly determining the characteristics of an array of diverse
materials which have been created on a surface of a substrate, and
in particular, to an apparatus and method for rapidly determining
the characteristics of a library of diverse materials using high
energy electromagnetic radiation.
[0003] Combinatorial material science refers generally to methods
for creating a collection of chemically diverse compounds or
materials and to methods for rapidly testing or screening this
library of compounds or materials for desirable characteristics or
properties. The combinatorial technique, which was introduced to
the pharmaceutical industry in the late 1980s, has dramatically
sped up the drug discovery process. Recently, combinatorial
techniques have been applied to the synthesis of inorganic
materials. Using various surface deposition techniques, masking
strategies or processing conditions, it is possible to generate
hundreds or thousands of materials with distinct compositions per
square inch in an array of elements which form a library. The
materials generated using these combinatorial techniques have
included high temperature superconductors, magnetoresistors,
phosphors and pigments. The discovery of new catalysts should also
benefit from these combinatorial techniques. General combinatorial
material science methodologies are disclosed, for example, in U.S.
Pat. No. 5,776,359, which is incorporated herein by reference.
[0004] The problem is that, although these libraries of hundreds or
thousands of new potential materials have been generated, these
libraries need to be screened for performance characteristics or
properties and conventional screening techniques are not
sufficiently fast. Another problem for conventional
characterization techniques is the low concentration of components
in each element of the library. It is therefore necessary to be
able to accurately measure these low concentration levels.
[0005] In general, x-ray scattering is a well-known
characterization technique. In addition, the various pieces of an
x-ray scattering apparatus are well-known. For example, U.S. Pat.
Nos. 5,757,882, 5,646,976 and 5,163,078 describe a multilayer
mirror being used in an x-ray beamline. The use of flat glass
mirrors for x-ray optics is disclosed in Franks, A., British
Journal of Applied Physics., Volume 9, page 349 (1958) and Milch,
J. R., Journal of Applied Cryst., Volume 16, page 198 (1983). X-ray
beamlines with rotating anode sources and two flat glass mirrors
are disclosed in Milch, J. R., Journal of Applied Cryst., Volume
16, page 198 (1983) and Hajduk, D. A., Morphological Transitions in
Block Copolymers, Ph.D. dissertation, Princeton University (1994).
In addition, x-ray detectors, such as multiwire area detectors (See
U.S. Pat. Nos. 3,911,279 and 4,076,981) and CCD-based detectors
with integral memories (See U.S. Pat. No. 5,629,524) are known.
Many x-ray detectors have also been described in various journals
and other publications including Gruner, S. M., Curr. Op. Struct.
Biol. 1994, 4, 765; Gruner, S. M., Rev. Sci. Inst. 1989, 60, 1545;
Ilinson, N. M., Nucl. Inst. Methods Phys. Res. 1989, A275,587; and
Eikenberry E. F. et al., "X-Ray Detectors: Comparison of Film,
Storage Phosphors and CCD Detectors" in Morgan, ed. Photoelectric
Image Devices Bristol: Inst. of Physics Conf. Ser. No. 121,
Institute of Physics 1992, 273.
[0006] One conventional technique for structural characterization
is x-ray scattering. In this technique, a monochromatic, collimated
x-ray beam illuminates a material of interest, and the spatial
distribution of the scattered radiation is analyzed to provide
information about the structure, dimensions, and degree of ordering
of the specimen. Low concentrations of strongly scattering
constituent atoms or substructures may also be detected and
quantified by this technique. Similar results may be obtained by
analyzing the distribution of photon energies scattered into a
fixed region of space from a polychromatic x-ray beam. Although the
low photon flux and brilliance characteristics of commercially
available instruments are acceptable for measurements of individual
samples, it is of limited value for combinatorial materials science
work. Typical measurements using conventional sources require at
least fifteen minutes per specimen, implying at least 24 hours to
characterize a 96-element library. Obviously, the total screening
time will increase dramatically as the total number of elements
increases. Therefore, it is desirable to provide an apparatus and
method for characterizing libraries of different materials using
x-ray scattering to solve the above problems associated with
conventional systems and techniques. It is to this end that the
present invention is directed.
SUMMARY OF THE INVENTION
[0007] An apparatus and method for characterizing a library of
different materials using x-ray scattering in accordance with the
invention provides numerous advantages over conventional
characterization apparatus. For example, compared to conventional
instruments, the apparatus advantageously delivers both a higher
total photon flux and a higher flux per unit area to each library
element. This reduces the time required to analyze each element
thereby reducing the total time needed for library
characterization. It also reduces the time required for calibration
of the instrument as described below. The light generated by such
an intense beam when it strikes a phosphorescent screen is easily
detected by the eye which facilitates alignment of the instrument
prior to the measurement. The apparatus also has a modular sample
stage which supports and moves a library containing a plurality of
elements so that the plurality of elements may be tested more
rapidly than with conventional apparatus. The apparatus in
accordance with the invention may perform spatial scanning so that
arrays and libraries of materials may be rapidly analyzed and
characterized. The positioning of the library in relation to the
x-ray beam may be computer controlled so that the apparatus may
automatically characterize and analyze each element on the library
by moving the library a predetermined distance. This automatic
movement of the library relative to the x-ray beam eliminates human
error and avoids having a human reposition the library after each
element is characterized.
[0008] In accordance with another aspect of the invention, a method
for preparing a library of materials for characterization and
analysis by the x-ray apparatus is provided. The library may be
prepared several different ways. In the embodiments below, samples
which are powders are being used, but the library preparation
method may be used with other types of samples. In a first
embodiment, a plate having a predetermined thickness may have an
array of holes drilled through the plate. The holes may be sealed
at one end with a chemically inert material which is nearly
transparent to x-rays of the appropriate wavelength and that does
not generate appreciable x-ray scattering in the angular regime of
interest. Suitable materials may include poly(imide) (Kapton.TM.),
poly(ethylene terephthalate) (Mylar.TM.), thin aluminum foils and
thin beryllium foils. Once the different materials have been
deposited into the appropriate hole, the open ends of the holes may
be sealed with the same material. The library is now ready for
characterization using the x-ray apparatus. In a second embodiment,
the same metal plate with a first end covered by the plastic
material may be used and then the powders to be placed in each hole
may be suspended in a non-solvent liquid with a low vapor pressure
and deposited in the appropriate holes using a liquid handling
robot. During the loading process, the plate may be heated to
promote evaporation of the non-solvent liquid and the other end of
the holes may be sealed with the same plastic which leaving the
powder in the hole for characterization. In a third embodiment, the
sample powders may be blended with a viscous, non-solvent binder
and each sample may be deposited onto a piece of the plastic film.
Once the elements are dried, the plastic film may be mounted on an
aluminum frame to provide mechanical support and strength to the
film which contains the dried elements.
[0009] In a fourth embodiment of the library preparation method,
the first ends of the holes in the same metal plate are blocked by
a sheet of material, and the wells thus formed are filled by a
solution of the materials of interest in a volatile solvent. The
blocking material is chosen so as to be nonreactive with respect to
the solution of interest and to be insoluble in the solvent. The
blocking material may therefore include fluorinated polymers such
as Teflon.TM., poly(imide) or metals. The solvent is removed by air
drying, by vacuum drying or by exposure to an oxygen-free
environment followed by gentle heating in a vacuum. Once the
solvent has been removed, the remaining materials of interest may
form a film which completely fills and remains in each well so the
blocking material may be removed. If the remaining materials of
interest do not form a film with sufficient mechanical strength to
remain in the wells when the blocking material is removed, the
blocking material must be made from a material that is
substantially transparent to x-rays as described above. Suitable
materials may include poly(imide) (Kapton.TM.), poly(ethylene
terephthalate) (Mylar.TM.), thin aluminum foils and thin beryllium
foils.
[0010] Thus, in accordance with the invention, an apparatus for
characterizing a library is provided in which the library contains
an array of elements. Each element contains either a chemically
distinct combinations of materials, or a chemical composition which
may be identical to that existing elsewhere on the library but has
been subject to distinct processing conditions. The apparatus
comprises an x-ray beam directed at the library, a chamber which
houses the library, and a beamline for directing the x-ray beam to
illuminate a region on the library in the chamber. The chamber
further comprises a translation stage that holds the library and
that is programmable to change the position of the library relative
to the x-ray beam and a controller that controls the movement of
the translation stage to expose each element to the x-ray beam in
order to rapidly characterize each element in the library.
[0011] In accordance with another aspect of the invention, a method
for characterizing a library is provided in which the library
contains an array of elements, each element contains either a
chemically distinct combinations of materials, or a chemical
composition which may be identical to that existing elsewhere in
the library but has been subject to distinct processing conditions.
The method comprises directing an x-ray beam generated by an x-ray
source toward the library housed within a chamber and moving the
library in a predetermined manner to expose each element of the
library separately to the x-ray beam in order to rapidly
characterize each element in the library.
[0012] In accordance with another aspect of the invention, an
apparatus for characterizing a library is provided in which the
library contains an array of elements and each element contains
either a chemically distinct combinations of materials, or a
chemical composition which may be identical to that existing
elsewhere in the library but has been subject to distinct
processing conditions. The apparatus comprises means for generating
an x-ray beam which is directed toward the library, a chamber which
houses the library and means for directing the x-ray beam onto the
library in the chamber. The chamber further comprises means for
holding the library, means for changing the position of the library
relative to the x-ray beam and means for controlling the movement
of the translation stage to expose each element to the x-ray beam
in order to rapidly characterize each element in the library.
[0013] In accordance with yet another aspect of the invention, a
method for preparing a library is provided in which the library
contains an array of elements and each element contains either a
chemically distinct combinations of materials, or a chemical
composition which may be identical to that existing elsewhere on
the library but has been subject to distinct processing conditions.
The method comprises forming an array of holes from a first side of
a plate through to a second side of the plate, sealing a first side
of the plate with a film to form wells in the plate, depositing a
predetermined amount of one or more materials into each well of the
plate, and sealing the second side of the plate with a second piece
of film to trap the deposited one or materials in each of the wells
in the plate so that a beam may impinge upon each element
containing the one or more materials and characterize the elements
of the library.
[0014] In accordance with yet another aspect of the invention, a
method for preparing a library is provided in which the library
contains an array of elements and each element contains either a
chemically distinct combinations of materials, or a chemical
composition which may be identical to that existing elsewhere on
the library but has been subject to distinct processing conditions.
The method comprises forming one or more deposition compounds, each
deposition compound comprising one or more materials blended into a
viscous, non-solvent liquid, depositing the deposition compounds
onto a sheet of film at predetermined locations to form an array of
elements, drying the deposition compounds onto the film to form a
library of one or more materials, and mounting the film with the
dried deposition compounds onto a frame to provide support to the
plastic film so that the deposition compounds may be rapidly
characterized.
[0015] In accordance with still another aspect of the invention, a
method for preparing a library is provided in which the library
contains an array of elements and each element contains either a
chemically distinct combinations of materials, or a chemical
composition which may be identical to that existing elsewhere on
the library but has been subject to distinct processing conditions.
The method comprises blocking the first ends of holes in a metal
plate with a sheet of material so that the wells thus formed are
filled by a solution of the materials of interest in a volatile
solvent. The blocking material is chosen so as to be nonreactive
with respect to the solution of interest and to be insoluble in the
solvent. The solvent is then removed by air drying, by vacuum
drying or by exposure to an oxygen-free environment followed by
gentle heating in a vacuum. Once of the solvent has been removed,
the remaining materials of interest may form a film which
completely fills and remains in each well so that the blocking
material may be removed. If the remaining materials of interest do
not form a film with sufficient mechanical strength to remain in
the wells when the blocking material is removed, the blocking
material must be made from a material that is substantially
transparent to x-rays as described above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a block diagram illustrating an x-ray
characterization apparatus in accordance with the invention;
[0017] FIG. 2A is a diagram illustrating more details of a
transmission mode x-ray characterization apparatus in accordance
with the invention;
[0018] FIG. 2B is a diagram illustrating more details of a
reflective mode x-ray characterization apparatus in accordance with
the invention;
[0019] FIG. 3 is a diagram illustrating an example of a
library;
[0020] FIG. 4 is a side view of the translation stages in
accordance with the invention;
[0021] FIG. 5 is a top view of the translation stages shown in FIG.
4;
[0022] FIGS. 6 and 7 are diagrams illustrating the sealing plates
which connect the combinatorial sample chamber to the detector;
[0023] FIG. 8 is a block diagram illustrating more details of the
library holder in accordance with the invention;
[0024] FIG. 9 is a flowchart illustrating a method for controlling
the x-ray characterization apparatus in accordance with the
invention;
[0025] FIGS. 10A and B are diagrams illustrating a first and second
embodiments of a method for preparing a library in accordance with
the invention;
[0026] FIG. 11 is a diagram illustrating a third embodiment of a
method for preparing a library in accordance with the
invention;
[0027] FIG. 12 is a graph showing an example of the results
obtained using the x-ray characterization apparatus to characterize
block copolymers; and
[0028] FIG. 13 is a graph illustrating an example of the results
obtained using the x-ray characterization apparatus to characterize
a pigment library.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0029] The invention is particularly applicable to an apparatus and
method for characterizing a library of materials in powder form
using x-ray scattering and it is in this context that the invention
will be described. It will be appreciated, however, that the
apparatus and method in accordance with the invention has greater
utility because it may be used to characterize other materials.
[0030] An x-ray characterization apparatus and method in accordance
with the invention may provide various advantages over conventional
characterization apparatus. For example, the apparatus in
accordance with the invention significantly reduces the total
amount of time typically necessary to characterize a library of
materials since the apparatus reduces the time needed to analyze
each element of the library. The apparatus also advantageously
delivers more energy flux to the surface of the library which
reduces the time each element must be exposed to the x-ray beam.
The apparatus also has a modular sample stage which supports and
moves the library so that the elements of the library may be tested
more rapidly than with a conventional apparatus. The apparatus in
accordance with the invention may perform spatial scanning so that
arrays and libraries of materials may be rapidly analyzed and
characterized. The positioning of the library in relation to the
x-ray beam may be computer controlled so that the apparatus may
automatically characterize and analyze each element of the library
by moving the library a predetermined distance. This automatic
movement of the library relative to the x-ray beam eliminates human
error and avoids having a human slowly re-position the library
after each element is characterized. Now, an x-ray characterization
apparatus in accordance with the invention will be described.
[0031] FIG. 1 is a block diagram illustrating an x-ray
characterization system 12 in accordance with the invention which
may include a computer system 14 and an x-ray characterization
apparatus 20. The computer system may be a personal computer or any
other type computer system. The computer system 14 may control the
operation of the x-ray characterization apparatus 20 including the
opening or closing of a servo-mechanically controlled safety
shutter as described below, the positioning of an element in a
library 46 as described below in front of an x-ray beam 15,
receiving the scattering image data from the x-ray characterization
apparatus 20 and processing the scattered image data. The
positioning of the library 46 and the reception and processing of
the scattering image data may be performed by a software
application 16 which may be stored in the computer system and
executed by a microprocessor (not shown) contained in the computer
system. The software application may be one or more pieces of code.
Thus, the software may, for example, automatically properly
position each element in the library in front of the x-ray beam so
that each element may be characterized rapidly.
[0032] In operation, the x-ray characterization apparatus 20
generates an x-ray beam 15 which is directed by a beamline 17
towards an element of the library 46. The x-ray beam is then
scattered by the element it strikes. The individual photons
scattered may be detected and a position of each photon in a X-Y
mesh of wires of a multiwire detector may be determined. The
multiwire detector may be preferably used due to the high speed at
which data may be transferred from the detector to the computer
system. However, instead of the multiwire detector, other x-ray
detectors known to those skilled in the art, such as a CCD detector
or storage phosphors (also known as image plates) may also be used
to detect the scattered photons. The output of the detector for
each scattering may be sent to the computer system 14. Once the
characterization of an element has been completed, the software
application 16 may automatically move the library to expose another
element in the library 46 to the x-ray beam and generate scattering
data for that element. In this fashion, each element in the library
is automatically positioned in front of the x-ray beam 15 and
characterized. Thus, the speed with which a library containing a
plurality of elements may be characterized is greatly increased.
Now, more details of the x-ray characterization apparatus 20, which
may include a transmission mode embodiment as shown in FIG. 2A and
a reflective mode embodiment as shown in FIG. 2B, will be
described.
[0033] FIG. 2A is a diagram illustrating an embodiment of the x-ray
characterization apparatus 20 in accordance with the invention.
This embodiment is a transmission mode embodiment in which the
generated x-rays may pass through the elements in the library and
the scattered energy may be recorded by a detector behind the
library as described below. The x-ray characterization apparatus 20
may include a source 22 of intense x-ray radiation, an optional
multi-layer mirror 24, a safety shutter 26, a foil 28, a vertical
focusing mirror 30, a horizontal focusing mirror 32, a set of
primary slits 34, a set of windows coated with a film 36, an
optional first chamber 38, a set of parasitic slits 40, a flight
tube 42, a combinatorial sample chamber 44 in which a library 46
may be characterized using the intense x-ray beam, a beam-stop
translation assembly 48 and a x-ray ray detector 50. Each of these
elements of the x-ray characterization apparatus will now be
described in more detail.
[0034] The intense x-ray radiation source 22 may generate a beam of
x-rays which are directed towards the library 46 in order to
scatter the x-ray off of (reflection mode) or through (transmissive
mode) an element in the library. In a preferred embodiment, the
intense x-ray radiation source 22 may be a rotating anode x-ray
generator, such as a Rigaku RU-200BH model, which may include a
microfocus point focus cathode and a copper target. As is well
known, an electron beam is generated by passing an electric current
through a tungsten filament and then accelerating the resulting
free electrons through a potential difference of 40 kV to produce
60 mA of beam current. The x-ray radiation may be focused to
illuminate a predetermined spot size, such as 0.2.times.2 mm, on
the target surface, which may be foreshortened to 0.2.times.0.2 mm
when viewed along the beam axis. This generates a broad spectrum of
x-rays comprised of a number of discrete x-ray lines superimposed
on a broad background.
[0035] In another embodiment of the invention, a synchrotron may be
used as the source of the intense x-ray radiation. Although
synchrotron sources are capable of much higher photon fluxes and
brilliances than can be obtained with laboratory sources (fixed
anode or rotating anode x-ray generators), such devices are
considerably more complex and expensive than laboratory sources.
The high fluxes associated with a synchrotron also places severe
constraints on the performance of the associated x-ray detectors,
requiring detectors of greater cost and complexity as well.
[0036] The radiation may exit the shielded enclosure of the source
22 through a beryllium window in the wall of the generator and may
pass through a window made of a material substantially transparent
to x-rays, such as Kapton.TM., into the multi-layer mirror 24. The
multi-layer mirror is an optional element which may be removed from
the apparatus 20. The mirror may be oriented so that it meets the
Bragg criterion for the copper K.alpha. wavelength (1.54 .ANG.)
which composes a majority of the total x-ray output by the source
22 and the multi-layer thickness is varied along the length of the
mirror to convert the diverging radiation beam from the source 22
into a parallel, nearly monochromatic beam. To minimize absorption
or scattering of the x-ray radiation, the multi-layer mirror
chamber may be filled with helium gas. In a preferred embodiment,
the multi-layer mirror may be a multi-layer mirror manufactured by
Osmic Corp. of Auburn Hills, Mich.
[0037] To avoid accidents, the x-ray generator 22 may have a
servomechanically actuated lead shutter immediately after the
beryllium window which blocks the beam when it is not use. To
provide further backup to the shutter in the generator 22, the
apparatus may include a mechanical shutter 26. The output from the
shutter, if open, is then passed through the foil 28. The material
of the foil may be selected to exhibit preferential absorption for
photons with energies higher than a desired energy which further
monochromaticizes the beam. For the copper K.alpha. radiation being
used, the foil may be made out of nickel. If other x-ray target
materials such as molybdenum are used, then a different foil
material may be used.
[0038] Once the beam passes through the foil, it strikes the
vertical focusing mirror 30 and the horizontal focusing mirror 32,
each of which may be a well-known Franks mirror. The focusing
mirrors 30, 32 may be a grazing incident mirror constructed from
two float glass flats coated with a thin layer of nickel and
oriented so as to reflect x-rays with wavelengths equal to or
greater than the K.alpha. wavelength. Thus, higher energy photons
pass through both of the mirrors. The mirrors, by means of a
bending press, may each be curved so as to focus the parallel beam
from the multi-layer mirror 24 to a point at the location of the
detector 50. To minimize unwanted absorption and scattering of the
x-ray beams, the vertical and horizontal focusing mirrors 30, 32
may be maintained in a helium atmosphere.
[0039] Once the beam passes through the vertical and horizontal
focusing mirrors 30, 32, the beam passes through the set of primary
slits 34 which helps to determine the exact dimensions of the beam
striking the elements on the library and to block unwanted
unreflected radiation which may be present. At this point, the
x-ray beam exits the optical beam line which is helium filled, as
described above, through the set of windows 36 made from a nearly
transparent material, such as Kapton.TM., for example, into the
optional first chamber 38 which may have a vacuum applied to it. In
this apparatus, the first chamber is not used for a sample since
this chamber can only contain a single sample. Therefore, instead
of the first chamber 38, a flight tube may replace the first
chamber. If the first chamber is used, the beam may strike a set of
parasitic slits 40, located about 10 cm downstream from the set of
primary slits 34, which eliminate any parasitic scattering caused
by the set of primary slits. When the flight tube is used instead,
the parasitic slits may be mounted at the end of the flight
tube.
[0040] For the characterization measurements in accordance with the
invention, the flight tube 42 may be attached to the first chamber
if the first chamber is used. The flight tube 42 may be a
predetermined length, such as 50 cm, which is chosen such that
radiation scattered through the angle(s) of interest strikes the
detector with sufficient lateral separation from the transmitted
radiation so as to distinguish between transmitted photons and
scattered photons. The angles are dictated by the wavelength of the
incident x-rays and the dimensions of the scattering features
within the sample. The flight tube 42 may be manufactured out of
aluminum and may have a vacuum applied. The flight tube 42 may
serve as an evacuated beampath for the transmitted and scattered
radiation when the first chamber 38 is being used for
characterizing a single sample. The back end of the flight tube 42
may be connected to the combinatorial sample chamber 44 to form a
continuous evacuated beampath.
[0041] As the intense x-ray beam passes through the combinatorial
sample chamber 44, the beam passes through or reflects off of an
element in the library positioned in front of the beam, as
described below. The transmitted, scattered and reflected radiation
exits the combinatorial sample chamber 44. In the transmissive
embodiment of the invention, the radiation transmitted through the
element may be blocked by the beamstop translation assembly 48
which may be a lead disk mounted on a strip of material, such as
Mylar.TM.. The material is attached to a two-axis translation
system which permits the location of the beamstop to be adjusted
(i.e., behind the element currently being characterized) while the
combinatorial sample chamber 44 is kept evacuated. The radiation
scattered off of the element in the library may then be detected by
the detector 50. In a preferred embodiment, the detector 50 may be
Siemens HI-STAR multiwire area detector. Now, the combinatorial
sample chamber 44 will be described in more detail with additional
details being provided below.
[0042] The combinatorial sample chamber 44 may be attached to an
optical rail on which the detector is also placed so that the
position of the library 46 in the combinatorial sample chamber 44
relative to the detector 50 may be adjusted. In particular, for
elements with small features and therefore large scattering angles,
the library may be closer to the detector (approximately 1-4 cm),
while for a element with larger features and therefore smaller
scattering angles, the library may be 1-2 m from the detector.
[0043] The combinatorial sample chamber 44 may permit a variety of
different environmental characteristics to be changed so that the
effects of changes in the environmental characteristics on the
elements may be measured. For example, the combinatorial sample
chamber 44 may be pressurized to a positive pressure or a vacuum to
determine, for example, the effects of a determined time at a
particular pressure on the library or even on a particular element.
In this case, additional pressure-tight nearly transparent windows
may be mounted at the apertures where the x-rays enter and exit the
chamber 44. As another example, an electric or magnetic field may
be applied to one or more elements in the library as described in
co-pending U.S. patent application Ser. No. 09/174,986, filed Oct.
19, 1998, on behalf of the same assignee as this patent and which
is incorporated herein by reference. In addition, some form of
mechanical stress, such as shear stress or stretching stress, may
be applied to the library. The temperature or the gases within the
combinatorial sample chamber 44 may also be changed to determine
the effects of different temperature or gases on the elements.
Finally, to look at the thermal changes of a element, such as a
catalyst, each element in the library may include an embedded
thermal sensor and heater.
[0044] Within the combinatorial sample chamber 44, there may be two
orthogonally mounted linear translation stages, as described below.
A frame attached to one of the translation stages, as described
below, may accept a library containing a plurality of elements or
elements, such as ninety-six elements in a preferred embodiment.
The samples or elements may be powders, solutions, suspensions or
films deposited on transparent substrates as will be described
below with reference to FIGS. 11 and 12. In the transmissive
embodiment shown in FIG. 2, the frame is oriented by the
translation stages to be normal to the x-ray beam so that some
fraction of the incident photons are scattered out of the main beam
as it passes through the library element. To position the stages, a
pair of computer-controlled motors, such as stepper motors, may be
used as described below. The stepper motors may be controlled by
the software application 16 shown in FIG. 1. In one embodiment of
the invention, closed-loop motor control may be used. In another
embodiment, no closed-loop motor control is used so that the
software application 16 directs each motor to step an appropriate
number of times in the desired direction to obtain the desired
displacement from the starting point to a particular point at which
a particular element is in front of the x-ray beam.
[0045] To calibrate the x-ray characterization apparatus 20 to
characterize elements of the library, a radioactive source may be
installed on the frame which normally holds the library at the
proper spatial location so the focused x-ray beam passes through
the radioactive source. The characteristics of the detector are
then determined as specified by well-known procedures. Next, the
radioactive source is removed and a second frame containing a
calibrant powder is installed. The calibrant powder may be supplied
by the National Institute of Standards and Technology (NIST) and
may be lanthanum hexaborate (d=4.157 .ANG.). The scattering from
this calibrant powder may be used to determine the
library-to-detector distance needed for subsequent
measurements.
[0046] During the characterization of each element in a library,
the various commands needed to acquire and process the data for
each element in the library may be written into a text file which
may be read by the detector as is well known. Once a library is
inserted into the frame, the translation stages may be moved so
that the x-ray beam passes through a first element. The x-ray
safety shutter may then be opened and the first scattering image is
recorded. The translation stage control software may then move the
library to bring the next element of the library into the path of
the x-ray beam. After recording the second image, the library is
moved to the next element. While the library is being moved, which
takes several seconds, the detector may process and save the image.
The computer controlling the detector and the computer software
controlling the motors may or may not communicate with each other.
If the software application do communicate with each other, then
the next exposure may proceed as soon as the library is properly
positioned. In this manner, each element in the library may be
characterized.
[0047] During the processing of the scattering data, which may
occur in the detector or in the computer system, various operations
may occur. For example, the raw scattering data may be corrected
for detector response characteristics, such as spatial distortion
or non-uniform sensitivity. This correction may be followed by a
determination of the total number of counter (crossings of the
detector wires) as a function of scattering angle (2.theta.) over a
fixed range of azimuthal angles (X). Now, a reflective mode
embodiment of the x-ray characterization apparatus 20 in accordance
with the invention will be described.
[0048] FIG. 2B is a diagram illustrating a reflective mode
embodiment of the x-ray characterization apparatus 20 in accordance
with the invention. For the description of this embodiment, many
parts are similar to the transmission mode apparatus described
above and these parts will not be described here in any detail.
Thus, the reflective mode apparatus 20 may include an intense x-ray
source 22, an optional multi-layer mirror. 24, a safety shutter 26,
foil 28, first and second sets of focusing mirrors 30, 32, primary
slits 34, a window 36, a flight tube 42 and a set of parasitic
slits 40. In this embodiment, however, one end of the flight tube
42 is connected to the second set of focusing mirrors 32 and the
parasitic slits 40 are connected to the other end of the flight
tube 42 since the library 46 and the combinatorial sample chamber
44 are now separate from the rest of a beamline so that the
beamline and the detector 50 may rotate relative to the library 46
as will be described below. In particular, for the reflective
embodiment of the apparatus, a beamline 52 and a detector assembly
54 may be rotated about a fixed combinatorial sample chamber 44.
Therefore, the beamline 52 and the detector assembly 54 may each be
connected to a typical rotation stage arm (not shown) to permit the
beamline 52 and detector assembly 54 to be rotated relative to the
library 46. Thus, the positions of the beamline and detector may be
adjusted to the proper reflection angle to detect the x-rays
reflected by the library.
[0049] The beamline 52 has the same elements as described above and
performs the same function of generating an intense focused x-ray
beam and directing it towards the library 46. The detector assembly
54 in this embodiment may include a beamstop assembly 48, a
detector 50, a flight tube 55 and a window 56 through which the
scattered x-ray beams may enter the detector assembly. In this
embodiment, there may be an alternate combinatorial sample chamber
57 which may be used for large scattering angles. The alternate
combinatorial sample chamber 57 may include a window 58 through
which the x-rays may pass. The combinatorial sample chamber 44 may
have a cylindrical shape and may be filled with helium gas to
reduce unwanted scattering. As above, the combinatorial sample
chamber 44 may have a mechanism, as described below with reference
to FIGS. 4 and 5, to position the library in the proper position.
As above, the positioning of the library may be computer
controlled. Now, an example of a library will be described.
[0050] FIG. 3 is a diagram illustrating an example of a library 60.
The library may be mounted on the frame to characterize each
element in the library. The library may comprise a plate 62, which
may be made of a metallic material such as aluminum, having a
predetermined thickness, such as 1/8", and a plurality of holes 64
through the plate in a predetermined pattern. In this example, the
holes may be drilled through the plate, may be in a rectangular,
two-dimensional array pattern, and there may be a total of
ninety-six elements in the library. For each hole in the plate,
there may be a sample deposited within and sealed into the hole so
that the x-ray beam may characterize the characteristics of the
sample. The library 60 in accordance with the invention may have
other shapes and more or less elements than shown in FIG. 3.
Several different embodiments for preparing a library in accordance
with the invention will be described below with reference to FIGS.
10A, 10B and 11. Now, more details of the translation stages in
accordance with the invention will be described.
[0051] FIGS. 4 and 5 are a side view and top view, respectively, of
translation stages located within the combinatorial sample chamber
44 in accordance with the invention. As shown in FIG. 5, within the
combinatorial sample chamber 44 may be a library holder assembly 70
which positions the library 46 relative to the x-ray beam entering
the combinatorial sample chamber 44 from the flight tube 42. The
combinatorial sample chamber 44 may be attached to the detector 50
which detects the scattering of the x-rays by the elements in the
elements of the library. The position of the detector 50 may be
adjusted relative to the position of the library as described
below.
[0052] The library holder assembly 70, as shown in FIG. 4, may
include a pair of rails 72 which hold the library 46. The rails 72
may be attached to a first positioning assembly 74. The first
positioning assembly 74 may permit the library to move back and
forth along a first axis 75 using a motor 76, such as a stepper
motor, which may be controlled by the software application being
executed by the computer system as shown in FIG. 1. The first
positioning assembly 74 may be connected to a second positioning
assembly 78 which may include a stepper motor 80 which moves the
library back and forth along a second axis 82. The second
positioning assembly 78 may also be controlled by the software
application being executed by the computer system as shown in FIG.
1. Thus, using the computer controlled first and second positioning
assemblies 74, 78, the library 46 may be automatically positioned
so that each element of the library may be characterized using the
x-ray beam which increases the speed at which the library may be
characterized. The order in which the elements of the library are
actually analyzed is not critical to the invention. The library
holder assembly 70 may also include a system 84 for rotating the
library, and first and second manual positioning assemblies 86, 88,
such as laboratory jacks, for positioning the combinatorial sample
chamber during initial installation and calibration.
[0053] To adjust the position of the detector 50 relative to the
library 46, the detector may be mounted on a sliding plate
mechanism 90. As shown in FIGS. 6 and 7, the sliding plate
mechanism 90 may include a seal 92, such as an O-ring, on the outer
surface of the combinatorial sample chamber 44 and a sealing plate
94 attached to the face of the detector. The sealing plate 94 may
include a seal 96, such as an O-ring, which seals the sealing plate
94 to the detector 50. Thus, the detector 50 and the sealing plate
94 may be moved relative to the combinatorial sample chamber 44 and
the seal 92 in a direction T. When the detector 50 is properly
positioned, the sealing plate 94 may be clamped to the wall of the
combinatorial sample chamber 44 so that the seal 92 forms an
air-tight seal between the combinatorial sample chamber 44, the
detector and the sealing plate. Now, the details of an embodiment
of the rails 72 which hold the library will be described
briefly.
[0054] FIG. 8 is a block diagram illustrating an embodiment of the
rails 72 which hold the library. In this embodiment, the rails 72
may include a first rail 100 having a channel 102 at its center and
a second rail 104 having a channel 106 at its center so that a
library may slide between the rails 100, 104 in the channels 102,
106 and be supported by the rails during the characterization of
the elements in the library. Now, a method for controlling the
x-ray characterization apparatus will be described.
[0055] FIG. 9 is a flowchart illustrating a method 110 for
controlling the x-ray characterization apparatus in accordance with
the invention to rapidly characterize each element in a library. In
step 112, the x-ray apparatus may be calibrated as described above.
Once the apparatus is calibrated, a library may be inserted into
the rails of the library holder mechanism in step 114. At this
point, the first and second positioning assemblies are activated to
move the library to the position as commanded by the software
application executed on the computer system in order to
characterize each element in the library rapidly. Thus, in step
116, the first and second positioning assemblies are commanded to
take a certain predetermined number of steps to place the library
in an initial position in which a first element of the library is
aligned with the x-ray beam. Next, in step 117, the counters
associated with the motors are zeroed since this embodiment of the
invention does not use closed loop feedback so that each movement
of the motors is from an origin which is set to the initial element
of the library. Once the library is positioned in the first
position, the safety shutter may be removed and the scattering
image generated in step 118 when the x-ray beam passes through the
first element is recorded by the detector. For most libraries, this
first element may be a calibration element. Once the image for the
first element is processed and recorded, the software application
commands the stepper motors in the first and second positioning
assemblies to step a predetermined number of steps, in step 120, to
position the library so that the next element in the library may be
characterized. In accordance with another embodiment of the
invention in which only selected elements of the library may be
characterized, a list of elements and their positions may be
provided to the motor controller which then moves the library to
the appropriate locations to expose the selected library elements.
In one embodiment of the invention, which does not use closed loop
feedback techniques, each motor is commanded to step a
predetermined number of times from the origin to position the
library properly based on information about the library and the
position of each element in the library previously generated and
available to the software application. The invention may also
operate with a closed loop feedback system in which the motors may
be commanded to perform a predetermined number of steps and then
any error in the positioning may be corrected.
[0056] Once the library has been positioned so that next element
may be exposed to the x-ray beam, the element is exposed to the
x-ray beam in step 122 and an image of the scattering is generated
by the detector. In step 124, the detector may process the image as
described above and store the image in a memory which may be in the
computer system or in the detector. While the detector is
processing the image, the software application may determine if
there is another element to be characterized in step 126, and loop
back to step 120 and command the stepper motors to move the library
so that the next element is exposed to the x-ray beam. In this
manner, the processing of the image by the detector and the
movement of the first and second positioning assemblies to a next
element may occur simultaneously which reduces the total time to
characterize each element in the library. In one embodiment of the
invention, the detector does not communicate with the software
application so that the total time to characterize each element is
limited to the slower step (i.e., either the processing or the
movement of the stepper motors). In another embodiment of the
invention, the detector and software application may communicate
with each other so that, as soon as the processing of the image and
the movement of the stepper motors is completed, the next element
may be characterized which may further reduce the total time
necessary to characterize each element in the library. When each
element in the library has been characterized, the method has been
completed.
[0057] In addition to serially characterizing each element in a
library, the x-ray apparatus may also be controlled by the software
application so that the user of the x-ray apparatus may select to
characterize any individual element, a plurality of elements of the
library by simply specifying the library element(s) to be
characterized using a simple user interface screen which permits
the user to select one or more elements in the library from a
graphical representation of the library. For example, once the
particular elements are specified by the user, the software
application may automatically determine the appropriate number of
steps for the first and second positioning assemblies to take in
order to position the library to bring the selected element into
the x-ray beam. In this manner, the user of the apparatus may
determine the elements of interest in the library and the apparatus
automatically positions the library which greatly increases the
speed at which the characterization of element(s) in the library
may occur. The software also permits individual elements of the
library to be independently addressable. Now, another embodiment of
the characterization method in which the detector computer running
the software that controls the detector and the motor controller
computer running the software which controls the motors that move
the library are separate computer systems will be described in
which more details of the method are provided.
[0058] In the embodiment of the invention where the detector
computer and the motor controller computer are separate, the
general steps performed are similar, but the details are different
since the two computer systems do not communicate with each other.
Thus, in this embodiment, after recording all of the detector
correction files as specified by the detector manufacturer and
calibrating the sample-to-detector distance, the library is placed
in the library holder, and positioned so that the x-ray beam passes
through the upper left element of the library (typically denoted by
A1). The library position counters may then be zeroed, as described
above, to indicate to the motor controller computer that the
library is positioned in the initial position. Using a user
interface at the motor controller computer, the user may specify
the library elements to be analyzed, the exposure time to be used
for each element, and the manner in which the two-dimensional
images are to be reduced to a one-dimensional profile of counts as
a function of position. The motor controller may then generate a
list of the position of each element(s) chosen, and a script (e.g.,
a list of instructions) which is transferred to the detector
computer.
[0059] The data collection begins when the detector computer is
directed to start reading commands from the script. At the same
time, the motor computer software is placed into a program mode
which locks out manual control of the motor position. In this mode,
the motor computer waits for a signal from the detector computer to
step to the next element in the position list. Once that signal is
received, the motor computer steps the horizontal and vertical
motors the appropriate amount to bring the next element into the
x-ray beam.
[0060] For each element, the detector computer integrates the
photons received by the x-ray detector for a preset time period.
Once the image collection is complete, the detector computer
signals the motor computer to move to the next element. While the
motor computer is executing this translation of the library, the
next image is corrected for detector response characteristics,
written to a hard disk and collapsed into a one-dimensional format
which is also written to disk. The detector assumes that the
translation of the library is complete at this point (which is
appropriate due to the motor's rate of speed) and immediately
starts acquiring the next image. Once the motor computer steps to
the last element in the position list, it returns to "normal" mode
in which the motors may be operated by the user.
[0061] In the preferred embodiment described with reference to FIG.
9, the detector computer and the motor controller computer are
preferably one computer system running a software application to
handle the detector control and running another software
application which controls the motors so that the two processes may
communicate with each other. In addition, in the preferred
embodiment, the detector controller and the motor controller may
signal each other so that the motor controller may indicate to the
detector controller that the library is appropriately positioned so
that the next image may be generated and stored by the
detector.
[0062] Thus, in accordance with the invention, an entire library, a
portion of a library or a single element in the library may be
rapidly positioned and characterized. With a conventional
characterization apparatus, an element in a ninety-six element
library may require approximately 15 minutes to characterize while
the characterization of the entire library may require at least 24
hours to complete. With the x-ray apparatus in accordance with the
invention, however, each element may take approximately 3 minutes
to characterize so that the entire library may be characterized in
approximately 2.5 hours. The increase in the characterization speed
of the library is due to several factors.
[0063] First, the x-ray source in accordance with the invention
generates an x-ray beam which is more intense (directs more flux to
the library) than the conventional x-ray apparatus. The greater
intensity x-ray beam results in a reduced exposure time for each
library element. A conventional x-ray apparatus and associated
optics typically generate a beam containing on the order of 10,000
photons per second while the x-ray apparatus in accordance with the
present invention may generate at least 6 million photons per
second. The intensity of the x-ray beam is increased due to a
stronger x-ray source and a better beamline which reduces unwanted
scattering and ensures the focused x-ray beam arrives at the
library.
[0064] The increase in the characterization speed of the x-ray
apparatus in accordance with the invention is also due to the first
and second positioning assemblies in combination with the software
application which permit the library to be rapidly and
automatically positioned to characterize each element of the
library rapidly. Now, several embodiments of methods for preparing
a library that may be used with the x-ray apparatus will be
described.
[0065] FIGS. 10A and 10B are diagrams illustrating first and second
embodiments of a method for preparing a library in accordance with
the invention. As shown in FIG. 10A, a library 129 may include a
plate 130, which may be manufactured out of a material sufficiently
strong to support the library. For example, the plate may be made
from a metallic material such as aluminum. The plate may have a
predetermined pattern of holes 132 formed through the plate. The
holes may be formed, for example, by drilling the holes through the
plate. In the example shown, a rectangular array of holes is shown.
Once the holes are formed, a piece of adhesive tape or film 134 may
be attached to the back surface of the plate as shown by the arrow
in FIG. 10A to form a predetermined pattern of wells into which
samples 135 may be deposited so that the elements may be
characterized. The film 134 may be translucent and/or may permit
the x-ray which impinges upon the sample in the well to pass
through the film. In a preferred embodiment of the invention, the
adhesive film may be Kapton.TM..
[0066] In one embodiment, once dry samples 135 have been manually
or automatically deposited in each well, a second film 136, as
shown in FIG. 10B, may be placed on top of the plate 130 to seal
the samples into their individual wells in the plate. The second
piece of adhesive film/tape may be translucent and/or may permit
the x-rays which impinge upon the sample in the well to pass
through the film and may preferably be Kapton.TM.. The prepared
library 129 in accordance with this embodiment of the invention is
shown in FIG. 10B.
[0067] In accordance with a second embodiment of the invention,
each sample may be mixed with a non-solvent liquid and then the
combination of the liquid and dry sample may be deposited in each
well of the library using a liquid dispensing robot. Prior to the
second film 136 being applied to the plate to seal the samples, the
plate and samples may be heated to evaporate the liquid. Once the
liquid is evaporated, the second film may be applied to the plate.
The end result of this second embodiment is the same library shown
in FIG. 10B. Now, a third embodiment of the method for preparing a
library will be described.
[0068] FIG. 11 is a diagram illustrating a third embodiment of a
method for preparing a library 129 in accordance with the
invention. In this embodiment, a film 138, which may be translucent
and/or permit x-rays to pass through the adhesive film, such as
Kapton.TM., may be used as a base for the preparation of the
library. In particular, a plurality of samples 140 to be included
in the library may be mixed with a non-solvent liquid and then
deposited on the film in a predetermined pattern similar to the
pattern formed by the holes in the plate in the above embodiments.
The samples may be deposited by typical semiconductor deposition
techniques. Once the deposited samples are dried, a frame 142 may
be attached to the side of the film opposite the samples to support
the film and elements during characterization by the x-ray beam. In
accordance with all of these embodiments, a library 129 is prepared
which may be inserted into the x-ray characterization apparatus in
accordance with the invention. Now, an example showing the
preparation of a pigment library will be briefly described.
[0069] To prepare a library containing pigments, the pigment
samples are synthesized on commercially available polypropylene
filter plates. After the synthesis is complete and the library is
dried, the solid at the bottom of each well is crushed using a
96-pin tool for a 96 element library. Once the samples are crushed,
a 96-well aluminum plate, which has a film attached to its back
surface, may be placed on top of the filter plate. The assembly may
then be inverted and shaken to load the library contents into the
wells in the aluminum plate. The aluminum plate may then be covered
with an adhesive tape, such as Kapton.TM., to seal the contents
into each well in the aluminum plate. The preparation of the
pigment library has now been completed.
[0070] In addition to the embodiments of the x-ray apparatus
described above, the x-ray apparatus may also use a well known
synchrotron to generate the intense x-rays. When using the
synchrotron, a more intense x-ray beam is generated so that the
exposure time for each element in the library is further reduced to
about 1-2 seconds per element. To capture the scattered x-rays
generated by the synchrotron, however, a typical multiwire detector
used in the prior embodiments is too slow so that a specialized
multiwire detector, or an integrating detector, such as a charge
coupled device (CCD), may be used. Now, two examples of the results
obtained using the x-ray characterization apparatus will be
described.
[0071] FIG. 12 is a graph 150 showing an example of the results
obtained using the x-ray characterization apparatus to characterize
block copolymers. In particular, the data in the graph is recorded
from a film of commercially available poly(styrene)-poly(butadiene)
block copolymer obtained from Sigma-Aldrich Co. (catalog number
43,249-0) containing 30% by weight styrene and characterized as
received. A 0.125" thick aluminum sample plate containing
96{fraction (3/32)}" diameter holes arranged in an 8.times.12 array
was used for this measurement. One face of the plate was compressed
against a Teflon.TM. substrate such that one end of the holes was
blocked which formed wells in the plate. Each well was initially
filled with approximately 50 ul of a concentrated solution
(approximately 25% by weight) of this polymer in toluene. The plate
was then dried in a fume hood at ambient temperature, pressure and
oxygen content for approximately one hour. 20 ul of the
concentrated polymer solution was then added to each well and the
drying process was repeated. This process was repeated until each
well was filled with the solid polymer.
[0072] Any residual solvent was then removed by drying the plate
and the Teflon.TM. backing in a vacuum atmosphere for 24 hours at
room temperature, followed by a slow heating to 135 C and
subsequent annealing in vacuum at that temperature for 48 hours. At
this point, after slow cooling to room temperature, the plate was
returned to atmospheric pressure and the Teflon.TM. backing was
removed. For these samples, an x-ray exposure minimum time of 10
seconds at rotating anode power settings of 40 kV accelerating
voltage and 60 mA of beam current was used. An exposure time of 300
seconds was used in the representative image, recorded from element
A5 of the plate, in order to obtain higher order diffraction data.
The reflections appear at angular position ratios of 1:2:4:5 which
is characteristic of the alternating layers of polystyrene and
polybutadiene. Although no sample-to-detector calibration was
recorded for these data, prior calibration indicated that this
distance is approximately 205 cm. Assuming this value leads to the
angular values shown on the x-axis; the peak positions correspond
to an interlayer spacing of approximately 40 nm. Now, a second
example of the results obtained using the x-ray characterization
apparatus to characterize a pigment library will be described.
[0073] FIG. 13 is a graph 160 illustrating an example of the
results obtained using the x-ray characterization apparatus to
characterize a library of pigment powders. The library was prepared
by the preparation method outlined above. An integration time of 60
seconds was used for each element in the library and the
sample-to-detector distance was calibrated using the known spacing
of lanthanum hexaborate prior to the measurement. In the graph,
three traces are shown, one for a solid solution of two pigments,
and one for each of the component pigments (A and B). The
scattering of the solid solution, based on the results displayed in
the graph, is not given by a linear combination of the scatterings
for the two components since the former exhibits several peaks (at
6.8, 24.1, 31.0 and 32.3 degrees) that do not appear in the traces
for either component.
[0074] While the foregoing has been with reference to a particular
embodiment of the invention, it will be appreciated by those
skilled in the art that changes in this embodiment may be made
without departing from the principles and spirit of the invention,
the scope of which is defined by the appended claims.
* * * * *