Summary of Research Project Results under JSPS FY2003
"Research for the Future Program"



1.Research Institution Waseda University
2.University-Industry Cooperative Research Committee 141st Committee on Microbeam Analysis
3.Term of Project FY 1999 - FY 2003
4.Project Number 99R14101
5.Title of Project Development of Ultra-coherent Electron Beam

6.Project Leader
Name InstitutionCDepartment Title of Position
Chuhei,Oshima Waseda University,School of Science and Engineering Professor

7.Core Members

Names Institution,Department Title of Position
Hroshi,Shimoyama Meijyo University,Faculty of Science and Technology Professor
Susumu,Kurihara Waseda University,School of Science and Engineering Professor
Akitoshi,Mogami JEOL,R&D Manager

8.Summary of Research Results

   It was presumed for a long time that conventional sources emit electrons incoherently. In this project, for the first time, we pointed out the highly coherent electron emission from the finite nano-scaled areas. The first one is the electron emission from multi walled carbon nanotubes (MWCNT), and the second is emission from nano-area of a normal tungsten tip at low temperature. The third is nano- pyramids of various elements on Tungsten and Nickel tips. The coherence of the emitted electrons is related to the coherence of its original states of the emitter.
(1) The carbon nano-tubes emit the coherence electron emission in all the directions. Clear Young's interference fringes were detected in the FEM pattern from MWCNT.
(2) We clarified that transverse coherence length of the electrons was related with the coherence length of the original states. Instead of the natural silts in MWCNT, we used the nano-biprism to generate the interference fringes, and observed the beautiful interference fringes of the electron emitted from tungsten tips by a nano-biprism. With decreasing the source temperature from RT to 78K, the visibility of the interference fringe increases by a factor of 3, and the band of interference pattern widens by a factor of 5. 
(3) We have developed an electron optical instrument for evaluation of multi emitters such as field emitter arrays and carbon nanotubes. The instrument is equipped with a beam illumination system that irradiates the specimen with electron beam or UV light for obtaining secondary (or reflected) electrons or photo electrons from the specimen, and is enabling us to obtain quantitative knowledge as to the percentage of actually working emitters out of the whole emitters, stability of the emission current from each individual working emitters, and so on.
(4) We have found that during the remolding process the initially hemispherical emitter tip surface deforms into a polyhedral shape in which the emitter surface eventually consists of large plane facets separated by sharp edges and corners. As a result, the field emission pattern of the processed tip often shows a single spot pattern from only a specific crystal plane of the tip apex. A proper combination of the remolding field and the remolding temperature has been found to be essential for sharpening of a specific crystal plane.
(5) In the potential and field calculation by 3-D boundary charge method (surface charge method), we must calculate the coefficient matrix elements, that is, the potential and field coefficients, which are expressed as double integral and are usually obtained by direct double numerical integration. This is a serious obstacle to practical use of the method because of an extremely long computation time. To overcome this situation, we have developed an improved 3-D boundary charge method in which the first integration in the double integral of the coefficient matrix element can be done analytically, thereby greatly improving the computation time of the potential and electric filed distributions without any loss of accuracy. The method has successfully been extended to high accuracy calculation of electric field in the composite dielectric system where there is a great difference in magnitude of the permittivity between neighboring dielectric materials. On the basis of the formal correspondence between a static magnetic field and an electrostatic field, we have furthermore developed an improved 3-D boundary magnetic charge method for high accuracy calculation of magnetic field.

9.Key Words
(1)Coherent Beams   (2)Nano Electron Emitter   (3)Low-Temperature Emitter
(4)Electron Microscope   (5)Electron Holography   (6)Field Emitter Array
(7)LEEM/PEEM/FEEM   (8)Remolding   (9)Boundary Charge Method

 

 


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