Coherence measuring device for spin-polarized electron beam and method using the same

Patent metadata

Field	Value
Publication number	US-9881767-B2
Application number	US-201515516976-A
Country	US
Kind code	B2
Filing date	Sep 28, 2015
Priority date	Oct 9, 2014
Publication date	Jan 30, 2018
Grant date	Jan 30, 2018

Abstract

A path of a spin-polarized electron beam is split into two by a splitter. A spin direction of the spin-polarized electron beam is rotated by a spin direction rotator disposed on a first path, and delayed by a first delay device. On a second path, the electron beam passes through a sample stage. The spin-polarized electron beams split into the first path and the second path are superposed by a biprism, and its intensity distribution is measured. Coherence is measured from a relation between a spin direction rotation angle, a delay time, and a visibility of an interference fringe.

First claim

The invention claimed is:

1. A coherence measuring device for a spin-polarized electron beam, the device comprising:
a semiconductor photocathode configured to emit a spin-polarized electron beam of which spin direction is polarized;
a splitter configured to split a path of the spin-polarized electron beam emitted from the semiconductor photocathode into two paths;
a spin direction rotator and a first delay device that are disposed on a first path which is one of the split two paths split by the splitter;
a sample stage disposed on a second path which is another of the two paths split by the splitter;
a biprism configured to superpose spin-polarized electron beams split into the first path and the second path; and
an intensity distribution measuring device configured to measure an intensity distribution of the spin-polarized electron beams superposed by the biprism.

2. The coherence measuring device according to claim 1 , further comprising
a second delay device disposed on the second path.

3. A method of measuring a change a sample imparts to a traveling speed of a spin-polarized electron beam using the coherence measuring device according to claim 2 , the method comprising:
measuring a relation between a time difference between a delay time by the first delay device and another delay time by the second delay device and a visibility of an interference fringe obtained when the intensity distribution is measured; and
specifying a time difference with which the interference fringe is clearest.

4. An electron microscope in which the coherence measuring device according to claim 2 is incorporated, wherein
the semiconductor photocathode is further configured to function as an electron source for the electron microscope.

5. An electron microscope in which the coherence measuring device according to claim 2 is incorporated, wherein
both the spin-polarized electron beam traveling on the first path and the spin-polarized electron beam traveling on the second path pass through a sample lens of the electron microscope.

6. The electron microscope according to claim 5 , wherein the biprism is disposed downstream of the sample lens.

7. The electron microscope according to claim 6 , wherein the splitter is disposed upstream of the sample stage.

8. A method of measuring a rotation angle by which a sample rotates a spin direction of a spin-polarized electron beam using the coherence measuring device according to claim 2 , the method comprising:
measuring a relation between the rotation angle by the spin direction rotator and a visibility of an interference fringe obtained when the intensity distribution is measured; and
specifying a rotation angle with which the interference fringe is clearest.

9. An electron microscope in which the coherence measuring device according to claim 1 is incorporated, wherein
the semiconductor photocathode is further configured to function as an electron source for the electron microscope.

10. An electron microscope in which the coherence measuring device according to claim 1 is incorporated, wherein
both the spin-polarized electron beam traveling on the first path and the spin-polarized electron beam traveling on the second path pass through a sample lens of the electron microscope.

11. The electron microscope according to claim 10 , wherein the biprism is disposed downstream of the sample lens.

12. The electron microscope according to claim 11 , wherein the splitter is disposed upstream of the sample stage.

13. A method of measuring a rotation angle by which a sample rotates a spin direction of a spin-polarized electron beam using the coherence measuring device according to claim 1 , the method comprising:
measuring a relation between the rotation angle by the spin direction rotator and a visibility of an interference fringe obtained when the intensity distribution is measured; and
specifying a rotation angle with which the interference fringe is clearest.

Assignees

• Univ Nagoya Nat Univ Corp

Inventors

• Kuwahara Makoto
• Tanaka Nobuo
• Ujihara Toru
• Saitoh Koh

Classifications

• H01J2237/24557

  Spin polarisation (particles) · CPC title

• H01J37/26 Primary

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

• G01N23/20

  by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials · CPC title

• H01J2237/2614

  Holography or phase contrast, phase related imaging in general, e.g. phase plates · CPC title