Blocking Apparatus And Method Utilizing A Low-energy Ion Beam

Abstract

Apparatus and method for producing a blocking pattern of the crystalline structure of a solid surface using a low-energy ion beam is shown wherein the low-energy ion beam is focused to a predetermined cross section and directed by an extended bored member onto a predetermined area of the solid surface at an angle greater than 5.degree. and less than 90.degree. enabling the ions to be scattered from the solid surface to produce a projected blocking pattern which impinges upon a fluorescent screen positioned substantially parallel to and spaced a predetermined distance from the solid surface for producing as a visual image the projected blocking pattern representing the crystalline structure of the solid surface. The extended bored member also collimates the focused ion beam into a smaller predetermined cross section and produces secondary electrons while collimating the focused beam to thereby produce a cloud of electrons which neutralize any charge at the solid surface produced by incidence of the collimated ion beam.

Description

Low-energy ion scattering apparatus and method are known in the art. Such apparatus and methods are described in an article entitled "The Influence of Absorbed Gases On Surface Analysis For Low-Energy Ion Scattering" by David P. Smith which appeared in the Oct. 1966 Transactions of the Thirteenth National Vacuum Symposium of the American Vacuum Society at pages 189 and 190 and in an article entitled "Scattering Of Low-Energy Noble Gas Ions From Metal Surfaces" by David P. Smith which appeared in the Jan. 1967 Journal of Applied Physics at pages 340--347.

The above-noted articles clearly and sufficiently describe the use of low-energy ion scattering wherein the energy of a scattered primary gas ion is used for surface compositional analysis of a solid surface.

In a recent article entitled "Proton Scattering Microscopy" by R. S. Nelson which appeared in the Apr. 1967 Philosophical Mag., Volume 15 at pages 845--854, a method and apparatus are disclosed for producing what Nelson considers to be proton blocking patterns on a fluorescent screen using protons having an energy in excess of 20 Kev.

The use of high-energy proton beams having energies in the order of 20 Kev. for producing proton blocking patterns to represent the atomic structure of a crystalline surface have several inherent disadvantages. For example, the use of high-energy protons extracted from conventional plasma-type sources and utilized to produce a blocking pattern representing the crystal structure of the surface of an insulating material causes the insulating material to store a charge thereon which has the effect of establishing a field which repels the proton beam being directed onto the surface thereof.

Other disadvantages of the prior art apparatus include that a mass analyzer must be used to obtain an ion beam of desired mass and energy and that the apparatus must operate at high voltage levels in the order of 20 kv. or higher. In addition, when samples to be analyzed are of an insulating material, it appears that the sample builds up a positive surface charge which may repel the ion beam. Also, the samples must be separately cleaned and prepared by separate apparatus and methods for use before the solid surface thereof can be analyzed by the prior apparatus.

The present invention overcomes the disadvantages of the prior art apparatus and method for analysis of the crystalline structure of the surface of material by use of a unique and unusual means for directing an ion beam onto the surface of the material. The ion beam directing means includes an extended bored member which is capable of collimating a focused ion beam of a predetermined cross section into a collimated ion beam of a smaller predetermined cross section, of directing the collimated ion beam to a predetermined area of the material surface, and of producing secondary electrons while collimating the ion beam to produce a cloud of electrons which are attracted to the material surface to prevent a surface charge built up on the surface of the material which otherwise would repel or interfere with the ion beam being directed upon the material surface. The neutralizing capability is particularly significant when producing a blocking pattern from an insulating material.

Another advantage of the present invention is that low-energy ions having an energy level in the order of less than 10 Kev. can be used for producing the ion blocking pattern illustrating the atomic structure of a solid surface.

Another advantage of the present invention is that an ion beam generating source is disclosed which is capable of precisely directing an ion beam of a predetermined cross section onto a predetermined area of a solid surface which is to have an ion blocking pattern produced illustrating the crystal structure of the solid surface.

Yet another advantage of the present invention is that a unique and novel method for generating an ion blocking pattern representing the crystalline structure of a solid surface by use of low-energy ions scattered from the surface is disclosed.

Still another advantage of the present invention is that in a preferred embodiment one ion beam including both scattering ions and sputtering ions can be used for producing a blocking pattern of the solid surface being analyzed and for sputtering or eroding the solid surface at a controlled rate. The inclusion of both sputtering and scattering ions in the ion beam has the advantage of providing a convenient means for preparing a surface by sputtering to remove the atoms of any amorphous or foreign material from the solid surface to be analyzed while the sample is mounted for observation by the scattering ion in the beam.

These and other advantages become readily apparent in light of the detailed description of the preferred embodiment disclosed herein taken together with the drawing wherein:

FIG. 1 is a frontal cross-sectional view of an ion generating source capable of producing low-energy ion beams having a predetermined cross section;

FIG. 2 is a pictorial representation illustrating the relationship between the end of the ion source relative to a solid surface which is to have a projected blocking pattern of its crystalline structure produced on a substantially parallel and fluorescent screen spaced at a predetermined distance from the solid surface;

FIG. 3 is a frontal sectional view of a portion of apparatus for selectively positioning a selected one of a plurality of samples adjacent an ion source for generating a visual blocking pattern which can be observed by means of a window;

FIG. 4 is a graphic representation of a blocking pattern of the crystalline structure of a gold crystal produced by a low-energy ion beam directed at and scattered from the surface thereof; and

FIG. 5 is a schematic diagram partially in block form illustrating a control system for automatic control of the operation of the apparatus of FIG. 3.

Briefly, the apparatus and method disclosed herein is capable of producing a blocking pattern of a solid surface of a sample by means of a low-energy ion beam. In one embodiment, the apparatus includes a means for generating a low-energy ion beam having a predetermined mass and energy. A means which cooperates with the generating means is utilized for focusing the ion beam into a predetermined cross section. A directing means is operatively coupled with the focusing means and collimates the ion beam into a smaller predetermined cross section. The directing means also directs the collimated ion beam at an angle greater than about 5.degree. and less than about 90.degree. onto a predetermined area of the solid surface enabling the ions to slightly penetrate the solid surface and be scattered from the solid surface as a function of the crystal structure of the atoms forming said solid surface to produce a blocking pattern representing as a projected pattern the crystalline structure of the solid surface and formed of scattered ions from the smaller predetermined cross-section ion beam. A fluorescent means is positioned substantially parallel to and spaced a predetermined distance from the solid surface. The fluorescent means receives ions scattered from the smaller predetermined cross-section ion beam forming the blocking pattern for producing as a visual image the blocking pattern which represents as a blocking pattern the crystalline structure of the atoms forming the solid surface.

FIG. 1 illustrates a novel and unique ion source which includes a collimating member having an extended aperture. An ion source support, generally designated as 10, formed of a conductive material is utilized for supporting the ion source, generally designated as 12, ion focusing means, generally designated as 14, and an ion directing means, generally designated as 16. The directing means 16 forms the collimating member having an extended aperture, which in this embodiment is an extended bore 100. The support 10 is grounded to a common conductor, generally designated as 20.

The ion source 12 includes a heatable metallic filament 22 which in the preferred embodiment is formed of a thoriated tungsten wire. The wire filament 22 is supported by filament supports 24 and 26 which are isolated from the conductive support 10 by means of insulators 28 and 30 respectively. The filament supports 24 and 26 are formed of a conductive material and are operatively coupled to the secondary winding of a filament isolation transformer, generally designated as 32. The filament isolation transformer 32 is in turn energized from a power source which may be a variac transformer, generally designated as 34, operatively coupled to a source of alternating current potential (not shown).

A first or scattering gas source 36 and a second or sputtering gas source 38 are operatively coupled via a first valve 40 and a second valve 42 respectively to a tube 43. Tube 43 in turn is connected into an enclosed housing, generally designated as 44, which defines a chamber 46 enclosing the wire filament 22. The tube 43 is supported as it passes through the support 10 by means of a ceramic insulator 48. The housing 44 defining the chamber 46 is mounted on support 10 by means of a raised cylindrically shaped support 50 which is integral with the planar portion of the support 10. Ceramic spacers 52 are used as supports between the raised cylindrically shaped support 50 and a conductive shield and support member 54 having raised outer edges 56. The shield member 54 is in turn operatively connected to the housing 44 thereby providing a rigid support for the housing and preventing light emanating from the filament 22 from passing outside of the ion source.

The housing 44, which defines the chamber 46, terminates in an annular-shaped opening 60. Interposed between the wire filament 22 and the opening 60 is a conductive wire mesh 62 which in this embodiment is selected to be tungsten mesh.

Ions which are to be scattered from the solid surface of a sample to be analyzed are generated within the chamber 46 by establishing a potential difference between the wire filament 22 and wire mesh 62 to produce a localized source of electrons and by opening valve 40 and closing valve 42 to pass gas from the scattering gas source 36 via tube 43 into the chamber 46 and in the vicinity of the heated wire filament 22. The gas molecules are bombarded by and interact with the electrons passing between the filament 22 and wire mesh 62 to produce the gas ions. The resulting gas ions pass through the conductive mesh 62 and exit through the opening 60 of housing 44.

In the preferred embodiment, the scattering gas is hydrogen. When the hydrogen gas molecules are bombarded by the electrons from filament 22, several ions are produced; namely H.sub.1 .sup.+, which is an atomic ion, and H.sub.2 .sup.+, which is a molecular ion.

It appears that about equal quantities of each ion are produced. Therefore, mass analysis of the ions is unnecessary and the resolution of the ion blocking pattern is not seriously affected by the patterns produced by scattering of each type ion. Also, heavier gas atoms could be used as the scattering ion source, such as for example helium, where hydrogen atoms upon being ionized forming ions would be detrimental due to chemical reactivity with the surface being analyzed.

If desired, the second or sputtering gas source 38 can be used either alternately or simultaneously with the scattering gas source to clean the surface being analyzed. Typically, an inert gas is used for sputtering, such as for example argon. The sputtering gas can be passed from gas source 38 into chamber 46 via tube 43 by opening valve 42. The resulting sputtering gas beam passes along the same path as the scattering ion beam.

By using the teachings of the present invention, it is possible to observe the crystal structure of the solid surface while the same is being sputtered or cleaned. This is accomplished by opening both valves 40 and 42. Such a feature has wide utility in that a crystalline sample with a contaminated or amorphous surface layer can be placed into the ion blocking apparatus, be sputtered and then have its crystalline structure displayed. Also, by using the scattering gas source and sputtering gas source concurrently, one can observe the crystal structure of the solid surface being developed due to cleaning during the sputtering process. By knowing ion current densities, sputtering yields and sputtering times required to produce a blocking pattern representative of a crystalline surface, it is possible to measure or determine the thickness of the amorphous or noncrystalline layer. This technique would have wide utility, such as, for example, to measure the thickness of destruction layers produced by mechanically polishing of semiconductor crystals for use in an electron beam laser.

The focusing means 14 is formed of a plurality of spaced parallel annular-shaped lens elements 70-78. Each of the annular-shaped lens elements 70-78 has an opening of predetermined diameter, namely the ions emanating from opening 60 to pass therethrough. The elements 70-78 are stacked in a coaxial aligned relationship and are spaced from each other by means of a plurality of insulating spacers, generally designated as 80. The combination of annular-shaped members having an aperture therethrough positioned in aligned coaxial relationship and which form an electrostatic focusing means is generally known as an Einzel focusing lens. As is readily apparent, the diameter of the apertures in each of the lens elements or plates is selected so that the beam can be focused to a predetermined cross section at the opening of the last aperture plate 78.

In the embodiment illustrated in FIG. 1, aperture plate 74 is electrically connected to a variable voltage dividing network, generally designated as 84, so that an appropriate focusing potential can be applied to the ions to form the same into an ion beam. The other aperture plates 70, 72, 76 and 78 are electrically connected to the common conductor 20. A high voltage source, generally designated as 86, is operatively connected to the voltage dividing network 84 which is in turn connected to conductor 20 for providing the desired high voltage focusing potential. Typically, the high voltage source 86 will provide a variable high voltage output in the order of 0-10 kv.

A second lower voltage source, generally designated as 88, is operatively connected between the housing 44 and one of the filament supports 26. The high voltage source 88 is used to control the amount of bias applied to the wire filament 22.

In the preferred embodiment, the aperture plate 74 is formed of stainless steel having a thickness in the order of about one-half inch (about 12 mm.) while the other aperture plates 70, 72, 76 and 78 are formed of stainless steel having a diameter in the order of about one-quarter inch (about 6 mm). The spaces between each of the aperture plates 70-78 are selected to be about three-fourths inch (about 18 mm). The voltage dividing network 84 is formed of four 4.7--megohm resistors and a potentiometer having a rating of 5 megohms. The voltage source 88 is selected to have a voltage in the order of 100 to 150 volts DC. The high voltage source 86 is selected to be in the order of 5 kv. However, in some experiments, a voltage in the order of 1 kv. was operative.

At the outlet of the focusing means 14 is mounted the directing means 16 or collimating member having an extended aperture which in the preferred embodiment is in the form of an extended bored member 100. The bored member 100 is attached to the aperture plate 78 in alignment with the axis thereof. The bored member 100 may be formed of a stainless steel needle having an inside diameter in the order of about .030 inch (about .75 mm). It is contemplated that a conductive material, which includes semiconductive material, can be used as the directing means. If desired, an insulating material can be used as the directing means, such as, for example, a thin layer of aluminum oxide on an aluminum surface.

In this manner, the focusing means 14 can focus the ions emanating from opening 60 of housing 44 into an ion beam of predetermined cross section at a focal point located on the outer surface of annular plate 78 and in alignment with the aperture thereof. The ion beam of predetermined cross section then passes through the bored member 100 and is collimated into an ion beam having a cross section which is precisely determined by the inside cross section of the bored member 100.

It has been determined that the outer portion of the ion beam contacts the inner surface of the bored member 100 and results in the creation of secondary electrons which in turn build up a space charge of electrons near the outlet of bored member 100. The so-generated space charges are attracted to any positive surface charges located on the surface of the sample being bombarded. By this technique, the space charges of electrons neutralize the positive surface charges enabling the ion beam to bombard the surface of the sample and be scattered from the surface of the sample without the ion beam being repelled or deflected.

FIG. 2 pictorially represents the end of the bored member 100 positioned adjacent a crystalline surface 110 which is mounted onto a support 112. The ion beam, generally designated by line 114, emanates from the outlet of bored member 100 which is positioned just adjacent the surface of solid 110. The ion beam 114 is directed at a predetermined angle .theta. relative to the surface of the support 112. It has been determined that the angle .theta. should be greater than 5.degree. and less than 90.degree. such that the ions from the ion beam 114 are scattered into a pattern, generally designated as 116. During scattering, some of the scattered ions are neutralized by the electrons in the sample. The scattered ions and other particles including the neutralized ions or atoms bombard a fluorescent means 120 which converts the ion blocking pattern into a visual ion blocking pattern. The fluorescent means 120 may be a fluorescent screen 120 which is positioned substantially parallel to and spaced a predetermined distance from the solid surface 110.

When a post accelerating negative voltage was applied to the fluorescent phosphor screen to accelerate positive scattered ions, no detectable increase in brightness of the fluorescent phosphor was observed as would be expected if the scattered ions were not efficiently neutralized. Thus, it appears that the blocking pattern is formed substantially of neutralized ions which, of course, is a blocking pattern formed of scattered ions from the smaller predetermined cross section ion beam.

The so-produced visual ion blocking pattern is a projected image of the crystallographic directions in the bombarded sample. The prominent dark areas of the visual ion blocking pattern represent the directions of rows of atoms in the crystal which inhibit scattering of ions.

The angle limits of greater than 5.degree. and less than 90.degree. set forth above are practical limits on the angle between the ion beam of smaller predetermined cross section and the solid surface. Generally, an angle in the order of 20.degree. is preferred.

In the preferred embodiment, the fluorescent screen comprises a thin optically transparent layer of tin oxide deposited on Pyrex glass and which is coated with a uniform thin layer of Pl type phosphor. The predetermined distance between the fluorescent screen 120 and the support 112 is in the order of one-fourth inch to 1 inch (about 6 mm. to 25 mm).

FIG. 3 illustrates an apparatus adapted for producing an ion blocking pattern of the crystalline structure of a solid surface. The apparatus includes a vacuum chamber, generally designated as 200, which includes an ion gun chamber 204 and a sample support chamber 206. The ion gun chamber 204 is positioned at a predetermined angle relative to the sample support chamber 206 such that the ion beam can be directed at a predetermined angle onto the surface of the solid which is to have the ion blocking pattern of its crystal structure produced on a fluorescent screen. A support 208 bearing a disk-shaped sample holder 210 provides a means for positioning any one of several samples and materials for bombardment by the ion beam for generating the ion blocking patterns of the atomic structure of its surface. The support shaft 212 extends to the outside of vacuum chamber 200 and is capable of rotating the sample holder 210. A geared positioning member 214 is mounted in a support 215 having a plurality of openings therein. The geared positioning member 214 is operatively attached to rotatable shaft 226 and is capable of being rotated to position screen support 232 a predetermined distance relative to the sample holder 210. Rotatable shaft 226 extends to the outside of the apparatus so that it can be rotated.

A fluorescent screen 230 is supported by a screen support 232 a predetermined distance from the sample holder 210. By rotating shaft 226, this distance can be selectively changed to vary the magnification of the blocking pattern. A window 236 is located on the exterior portion of vacuum chamber 200 in alignment with the fluorescent screen 230 and the disk-shaped member 210. The window 236 enables a viewer to observe the ion blocking pattern formed on the fluorescent screen 230 when the ion beam from the bored member 220 is scattered from the surface of a sample located on the sample support 208. The sample support vacuum chamber 206 is evacuated via a pumping port 217 and support 215 to a pressure in the order of 10.sup.-.sup. 5 Torr during operation. Samples within the pumped vacuum of the sample support chamber 206 can be selectively positioned by rotating the sample support shafts 212 and 226 thereby enabling a viewer to observe ion blocking patterns from a plurality of samples without interruption of the vacuum. Samples can be removed and placed onto the sample support 208 by admitting atmospheric pressure into the sample support chamber 206 and by removing a cover 238 which is located in alignment with the ion gun chamber 204. After the samples have been positioned onto the sample support 208, the cover 238 can be repositioned onto the sample support chamber 206 and the entire chamber can then be repumped to the desired vacuum level and operation of the apparatus reestablished.

FIG. 4 illustrates a typical ion blocking pattern produced from a single crystal gold surface. The pattern is formed by the ions from the scattering gas source penetrating a few atomic layers into the solid surface and being scattered back out of the solid. Depending on the crystalline structure of the sample, which for gold is face centered cubic, the rows of atoms block or interrupt some of the scattered ions in a manner analogous to an object interrupting a light beam to produce a shadow. This results in the scattered ions, neutralized ions and other particles being scattered in a pattern of varying density wherein some of the particles are blocked. Thus, the scattered particles impinge fluorescent screen 230 which results in a visual pattern which is a projection of the crystalline structure of the sample.

If desired, the visual ion blocking pattern can be used as a means for identifying crystalline surfaces. For example, it is possible to utilize a computer to determine calculated ion blocking patterns by means of a mathematical model. Known output devices can be used to plot the calculated ion blocking pattern. By comparing the calculated ion blocking pattern to the observed ion blocking patterns, a crystalline identification process or technique can be obtained.

If the sample to be observed on the fluorescent screen 230 of the apparatus of FIG. 3 is an insulating material, the secondary electrons produced in bored member 100 are accelerated to any positive surface charge on the insulating surface to eliminate the build up of positive surface charge on the insulating material. By reducing the build up of positive surface charges, the low-energy ion beam is not repelled by charges on the surface of the insulating material and thereby permits ions to scatter from the surface of the insulating material and to produce an ion blocking pattern of the atomic structure of the insulating material on the fluorescent screen 230. This clearly is an unexpected and novel result in that the patterns produced by scattering of low-energy ions are not a function of electrical conductivity of the samples.

FIG. 5. is a schematic diagram illustrating control circuitry for automatic operation of the apparatus of FIG. 3. The apparatus is energized from a conventional alternating current source by means of a plug member 300 which when energized from the alternating current source and when a main switch 302 is in its ON position energizes a master relay 304. Relay 304 energizes a cooling fan 306 and a main control relay 308. The control relay 308 in turn is operatively coupled to vacuum gauges located within the sample support chamber 206 and performs the function of automatically controlling the vacuum pumping within the sample support vacuum chamber 206 to obtain the desired vacuum in the order of 10.sup.-.sup.5 Torr. The control relay 308 controls in a predetermined sequence operation of various valves as the desired vacuum is obtained in the sample support vacuum chamber 206. Also, if it is desired to vent the sample support vacuum chamber 206 to atmosphere for addition of various samples, the control relay 308 selectively controls the rate at which venting occurs by means of relays, generally designated as 312. Vacuum and pressure indications are displayed on the control panel of the apparatus of FIG. 3 by indicating means 314. The portion of the cycle for both pumping the vacuum and venting of the vacuum is indicated by a cycle indicator, generally designated as 316. In this manner, the entire operation as to pumping the sample support chamber 206 to an appropriate vacuum and the venting thereof to permit easy and quick insertion of the samples for subsequent generation of its ion blocking pattern is completely under control of the automatic vacuum circuit. In this manner, misoperation or interruption of the operation during the time the vacuum is ON can be precisely controlled.

In addition to the aforementioned embodiment in which the blocking pattern is sensed by viewing the projected pattern produced by scattered ions impinging a fluorescent means, another means of sensing this pattern may be employed with this invention. For example, a screen array which channels secondary emission of electrons upon bombardment of ions and other particles can be positioned to be impinged upon by the scattered ions. Used with the said aforementioned embodiment, the array can be positioned between the solid surface 110 and the fluorescent means 120. Such a screen array is described in the articles "The Channel Electron Multiplier, A New Radiation Detector," by J. Adams and B. W. Manley, which appeared in the 1967 Philips Technical Review, Vol. 28, page 156, and "Electron Multipliers Utilizing Continuous Strip Surfaces," by W. C. Wiley and C. F. Hendee, which appeared in the 1962 Proceedings of the IEEE, Transaction of Nuclear Science, Vol. 9, page 103. With this screen array so positioned, the blocking pattern defined by the scattered ions impinging thereupon can be transformed into an electron emission defining the blocking pattern. Such secondary electrons can then be accelerated to impinge a fluorescent means. Upon such electron emission impinging the fluorescent means, the blocking pattern can be visualized.

By interposing such a screen array between the sample from which ions are scattered and the fluorescent means, there can be also provided means which appreciably retard the relatively rapid deterioration of the fluorescent means caused by impingement of the ions and like particles conveying the intelligence to be discerned and to retard contamination of the fluorescent means by deposition of atoms sputtered thereon.

This screen array can be prepared to impart a high gain to the intensity of the bombardment, thereby providing a sensing means of higher sensitivity. As a result, a lower primary ion current density beam can be used to scatter the ions from the sample.

Another alternative embodiment for sensing the ion blocking pattern comprises scanning the projected pattern with a single channel electron multiplier. The output signal from such scanning means can be fed into a suitable display device such as a recorder or an oscilloscope.

Claims

We claim:

1. Apparatus for producing a blocking pattern of a solid surface of a sample by means of a low-energy ion beam comprising

generating means for generating a low-energy ion beam having a predetermined mass and energy;

focusing means cooperating with said generating means for focusing said generated ion beam into a predetermined cross section;

directing means including an extended bored member operatively coupled with said focusing means for collimating said focused ion beam into a smaller predetermined cross-section and directing said collimated ion beam at an angle greater than about 5.degree. and less than about 90.degree. onto a predetermined area of said solid surface enabling said ions to slightly penetrate said solid surface and be scattered from said solid surface as a function of the crystal structure of the atoms forming said solid surface to produce a blocking pattern representing as a projected pattern the crystalline structure of said solid surface and formed of scattered ions from said directed smaller predetermined cross-section ion beam, which extended bored member has an inside cross-section corresponding to said smaller predetermined cross-section, and the interior of which extended bored member includes material capable of producing secondary electrons when the extended bored member is collimating said focused ion beam to thereby produce a cloud of electrons to neutralize any charge at said solid surface produced by incidence of said collimated ion beam; and means for sensing said blocking pattern.

2. The apparatus of claim 1, wherein the extended bored member includes a converging portion at the entry of said focused ion beam into the extended bored member.

3. The apparatus of claim 1, wherein the extended bored member is formed of a needle having an inside cross-section corresponding to said smaller predetermined cross-section.

4. The apparatus of claim 1, wherein the extended bored member is formed of a stainless steel needle having an inside cross-section corresponding to said smaller predetermined cross-section.

5. The apparatus of claim 1, wherein the interior of said extended bored member comprises a conductive material including semiconductive material.

6. The apparatus of claim 1, wherein the interior of said extended bored member comprises an insulating material.

7. The apparatus of claim 1, further comprising

a scattering gas source, to which the generating means is operatively coupled for producing ions to be focused, directed onto, and scattered from said predetermined area of said solid surface; and

a sputtering gas source, to which the generating means is operatively coupled for producing ions to be included in said generated, focused, and directed ion beam for sputtering said predetermined area of said solid surface.

8. Apparatus for producing a blocking pattern of a solid surface of a sample by means of a low-energy ion beam comprising

generating means for generating a low-energy ion beam having a predetermined mass and energy;

focusing means cooperating with the generating means for focusing said generated ion beam into a predetermined cross-section;

directing means operatively coupled with the focusing means for collimating said focused ion beam into a smaller predetermined cross-section and directing said collimated ion beam at an angle greater than about 5.degree. and less than about 90.degree. onto a predetermined area of said solid surface enabling said ions to slightly penetrate said solid surface and be scattered from said solid surface as a function of the crystal structure of the atoms forming said solid surface to produce a blocking pattern representing as a projected pattern the crystalline structure of said solid surface and formed of scattered ions from said directed smaller predetermined cross-section ion beam;

sensing means for sensing said blocking pattern;

a scattering gas source, to which the generating means is operatively coupled for producing ions to be focused, directed onto, and scattered from said predetermined area of said solid surface; and

a sputtering gas source, to which the generating means is operatively coupled for producing ions to be included in said generated, focused, and directed ion beam for sputtering said predetermined area of said solid surface.

9. The apparatus of claim 8, wherein the first gas source is selected to be hydrogen or helium and the second gas source is selected to be an inert gas such as argon.

10. The apparatus of claim 8, further comprising

means for either alternatively or simultaneously operatively coupling the sputtering gas source with the generating means.

11. A method for producing a blocking pattern of a solid surface of a sample with a low-energy ion beam comprising the steps of

generating a low-energy ion beam having a predetermined mass and energy;

focusing said generated ion beam into a predetermined cross-section;

directing said focused ion beam with an extended bored member at an angle greater than about 5.degree. and less than about 90.degree. onto a predetermined area of said solid surface enabling said ions to slightly penetrate said solid surface and be scattered from said solid surface as a function of the crystal structure of the atoms forming said solid surface to produce a blocking pattern representing as a projected pattern the crystalline structure of said solid surface and formed of scattered ions from said directed ion beam, which directing step includes the steps of

collimating said focused ion beam with said extended bored member having an inside cross-section corresponding to a smaller predetermined cross-section to collimate said focused ion beam into a smaller predetermined cross-section for direction onto said solid surface, and

producing secondary electrons with the extended bored member when the extended bored member is collimating said focused ion beam to thereby produce a cloud of electrons to neutralize any charge at said solid surface produced by incidence of said collimated ion beam; and

sensing said blocking pattern.

12. A method according to claim 11, further comprising the steps of

providing a scattering gas for producing ions to be focused, directed onto, and scattered from said predetermined area of said solid surface; and

providing a sputtering gas for producing ions to be included in said generated, focused, and directed ion beam for sputtering said predetermined area of said solid surface.

13. A method for producing a blocking pattern of a solid surface of a sample with a low-energy ion beam, comprising the steps of

generating a low-energy ion beam having a predetermined mass and energy;

focusing said generated ion beam into a predetermined cross-section;

directing and collimating said focused ion beam into a smaller predetermined cross-section and at an angle greater than about 5.degree. and less than about 90.degree. onto a predetermined area of said solid surface enabling said ions to slightly penetrate said solid surface and be scattered from said solid surface as a function of the crystal structure of the atoms forming said solid surface to produce a blocking pattern representing as a projected pattern the crystalline structure of said solid surface and formed of scattered ions from said directed and collimated smaller predetermined cross-section ion beam; and

sensing said blocking pattern; wherein the method further includes the steps of

providing a scattering gas for producing ions to be focused, directed onto, and scattered from said predetermined area of said solid surface; and

providing a sputtering gas for producing ions to be included in said generated, focused, and directed ion beam for sputtering said predetermined area of said solid surface.