Method of producing a freestanding thin film of nano-crystalline graphite

Patent metadata

Field	Value
Publication number	US-9908778-B2
Application number	US-201414560919-A
Country	US
Kind code	B2
Filing date	Dec 4, 2014
Priority date	Dec 4, 2013
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

A freestanding thin film of nano-crystalline graphite is described, as well as a method of producing a freestanding thin film of nano-crystalline graphite including:
providing a freestanding thin film of amorphous carbon, heating the freestanding thin film to a high temperature in an inert atmosphere or in a vacuum; and allowing the freestanding thin film to cool down,

as a result of which a freestanding thin film of nano-crystalline graphite is formed.

The films can be used, for example, as phase plates in a Transmission Electron Microscope.

First claim

The invention claimed is:

1. A method of producing a freestanding thin film of nano-crystalline graphite, the method comprising the steps of: providing a freestanding thin film of amorphous carbon, locally heating the freestanding thin film to a high temperature in an inert atmosphere or in a vacuum, allowing the freestanding thin film to cool down; and as a result of which a freestanding thin film of nano-crystalline graphite is formed.

2. The method of claim 1 in which the local heating is performed by irradiating the freestanding thin film with a laser beam.

3. The method of claim 2 in which the wavelength of the laser, the power of the laser, the size of the irradiated area and the thickness of the thin film are such that the free-standing thin film absorbs locally between 0.1 MW/m 2 and 20 MW/m 2 .

4. The method of claim 1 in which during local heating the temperature of the freestanding thin film rises locally to between 1000 K and 3700 K.

5. The method of claim 1 in which the freestanding thin film is locally heated for at least 1 second.

6. The method of claim 1 in which the freestanding thin film has a thickness of less than 1 μm.

7. The method of claim 1 in which the freestanding thin film is allowed to cool down in an environment of less than 500 K.

8. The method of claim 1 in which the freestanding thin film is allowed to cool down to a temperature below 1000 K in less than 1 ms.

9. The method of claim 1 in which the freestanding thin film is supported by a TEM grid.

10. The method of claim 1 , the method further comprising the additional step of forming one or more holes in the film for passing beams of undiffracted or diffracted electrons, as a result of which a phase plate or phase mask for a transmission electron microscope is formed.

11. A phase plate for a transmission electron microscope, the phase plate comprising or made of a freestanding thin film of nano-crystalline graphite, wherein the freestanding thin film of nano-crystalline graphite comprises a multiplicity of layers.

12. A transmission electron microscope comprising the phase plate of claim 11 .

13. The method of claim 10 , wherein the one or more holes are formed by a method selected from the group of ion beam milling, gas-assisted electron beam etching, and laser beam irradiation.

14. The method of claim 1 , wherein, after processing, the presence of a diffraction ring at 0.334 nm due to stacked layers, characteristic of normal graphitic carbon, is substantially reduced or eliminated.

15. The method of claim 1 , wherein the film is cleaned before processing by pre-heating in a vacuum, preferably to a temperature of approximately 250° C.

16. The phase plate of claim 11 , wherein the crystal size in the nano-crystalline graphite is less than 100 nm.

17. A method of observing a sample in a transmission electron microscope, the method comprising:
forming a freestanding nano-crystalline graphite film in accordance with claim 1 ; and
directing a portion of an electron beam through the nano-crystalline graphite film, the nano-crystalline graphite film shifting the phase of the portion of the electron beam, wherein the freestanding thin film of nano-crystalline graphite comprises a multiplicity of layers.

18. The method of claim 17 , in which directing a portion of an electron beam through the nano-crystalline graphite film comprises directing a portion of an electron beam through the nano-crystalline graphite film in a diffraction plane of the transmission microscope, or an image of the diffraction plane.

19. A phase plate for a transmission electron microscope made in accordance with the method of claim 1 , wherein the freestanding thin film of nano-crystalline graphite comprises a multiplicity of layers.

20. The phase plate of claim 11 further comprising one or more holes in the free stranding film of nano-crystalline graphite for passing beams of undiffracted electrons.

21. The phase plate of claim 19 wherein the freestanding thin film of nano-crystalline graphite has a thickness of between about 19.9 nm and 30.8 nm.

Assignees

• Fei Co
• Max Planck Gesellschaft

Inventors

• Buijsse Bart
• Danev Radostin Stoyanov
• Sader Kasim

Classifications

• C01B32/205

  Preparation · CPC title

• H01J37/20 Primary

  Means for supporting or positioning the object or the material; Means for adjusting diaphragms or lenses associated with the support · CPC title

• H01J37/26

  Electron or ion microscopes; Electron or ion diffraction tubes · CPC title

• H01J37/31

  for cutting or drilling · CPC title

• H01J37/22

  Optical {, image processing} or photographic arrangements associated with the tube · CPC title