Method of three-dimensional atomic imaging

• US 5,095,207 A
• Filed: 01/07/1991
• Issued: 03/10/1992
• Est. Priority Date: 01/07/1991
• Status: Expired due to Fees

• Current Assignee: Board of Regents of The University of Wisconsin (University of Wisconsin System)
• Original Assignee: University of Wisconsin System
• Inventors: Tong, David S. Y.
• Primary Examiner(s): Anderson, Bruce C.
• Application Number:
  US07/638,351
• Time in Patent Office: 428 Days
• Field of Search: 250/306, 250/307, 250/397
• US Class Current: 850/63
• CPC Class Codes: G03H 5/00 Holographic processes or apparatus using particles or using waves other than those covered by groups G03H1/00 or G03H3/00 for obtaining holograms; Processes or apparatus for obtaining an optical image from them G03H1/22 takes precedence; construction of electron microscopes H01J37/26; investigating or analysing materials by the use of microwaves G01N22/00, by the use of particles wave or X-rays G01N23/00, G21K7/00
• CPC Class Codes: H01J 2237/228 Charged particle holography
• CPC Class Codes: H01J 2237/2614 Holography or phase contrast, phase related imaging in general, e.g. phase plates
• CPC Class Codes: H01J 37/295 Electron or ion diffraction tubes

Abstract

A method of three-dimensional imaging of the atomic environment of atoms near the surface of the sample involves forming a localized source electron diffraction pattern, detecting the intensity of the distribution of the pattern, and generating data corresponding to the intensity distribution. The intensity data is normalized and corrected for a phase shift error to produce data corresponding to a hologram. The process may be repeated at a several predetermined emitted electron energies, and the data at each energy is combined to yield a composite image intensity having improved resolution. The method of the invention can provide a lenseless electron microscope having a resolution better than one angstrom and which overcomes distortions caused by multiple scattering.

Claims

1. In a method for three-dimensional imaging of the atomic environment of a sample, including the steps of directing a beam against said surface to form a localized source electron diffraction interference pattern, detecting the intensity distribution of said pattern, calculating numerical image intensity data corresponding to said intensity distribution, and reconstructing the interference data to form a pattern indicating the location of a scatterer atom on said surface relative to an associated emitter atom on said surface, the improvement which comprises:

phase shift-correcting the data using a function P_i (k) dependent on the polar angle between the emitter atom and a scatterer atom i.

2. A method for three-dimensional imaging of the atomic environment of a sample, comprising the steps of:

(a) directing a beam against said surface to form a localized source electron diffraction interference pattern;

(b) detecting the intensity distribution of said pattern;

(c) calculating numerical image intensity data corresponding to said intensity distribution;

(d) normalizing the intensity data;

(e) phase shift-correcting the normalized data; and

(f) reconstructing the corrected interference data to form an image indicating the location of a scatterer atom on said surface relative to an associated emitter atom on said surface.

3. The method of claim 2, wherein the sample is a crystal having short range order.

4. The method of claim 3, wherein said beam is an X-ray beam.

5. The method of claim 4, wherein said beam is an electron beam.

6. The method of claim 2, wherein step (e) further comprises determining the polar angle of the scatterer relative to the emitter, and dividing the data χ

(k) by a function P_i (k) dependent on the polar angle between the emitter atom and the scatterer atom (i).

7. The method of claim 6, further comprising repeating steps (e) and (f) for each different polar angle of each scatterer atom relative to the emitter atom.

8. The method of claim 2, wherein step (f) further comprises forming a holographic image of said atoms on said surface by multiplying the corrected data by a function corresponding to the amplitude distribution of a reconstructing coherent electron beam.

9. The method of claim 2, further comprising repeating steps (a)-(d) at several predetermined localized source electron energies, and step (f) further comprises combining data from each such repetition to form the image.

10. The method of claim 9, wherein the emitter and scatterer atoms have forward-scattering geometry, further comprising reconstructing the image of each scatterer atom using only diffraction data in an angular cone oriented in the forward-scattering focusing direction of each scatterer atom.

11. The method of claim 10, wherein said cone is described by an angle θ

_c.

12. An apparatus for three-dimensional imaging of the atomic environment of a sample, comprising:

means for directing a beam against said surface to form a localized source electron diffraction interference pattern;

means for detecting the intensity distribution of said pattern;

means for calculating numerical image intensity data corresponding to said intensity distribution;

means for normalizing the intensity data;

means for phase shift-correcting the normalized data; and

means for reconstructing the corrected interference data to form an image indicating the location of a scatterer atom on said surface relative to an associated emitter atom on said surface.

13. The apparatus of claim 12, further comprising means for combining data generated at several predetermined localized source electron energies to form the image.

14. The apparatus of claim 12, further comprising means for reconstructing the image of each scatterer atom using only diffraction data in an angular cone oriented in the forward-scattering focusing direction of each scatterer atom.