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Applied Science and Convergence Technology 2008; 17(4): 311-316

Published online July 1, 2008

Copyright © The Korean Vacuum Society.

Simulation of Energy Resolution of Time of Flight System for Measuring Positron-annihilation induced Auger Electrons

J. H. Kim,T. K. Yang,C. Y. Lee,B. C. Lee

Abstract

Since the presence of the chemical impurities and defect at surfaces and interfaces greatly influence the properties of various semiconductor devices, an unambiguous chemical characterization of the metal and semiconductor surfaces become more important in the view of the miniaturization of the devices toward nano scale. Among the various conventional surface characterization tools, Electron-induced Auger Electron Spectroscopy (EAES), X-ray Photoelectron Spectroscopy (XPS) and Secondary Electron Ion Mass Spectroscopy (SIMS) are being used for the identification of the surface chemical impurities. Recently, a novel surface characterizaion technique, Positron-annihilation induced Auger Electron Spectroscopy (PAES) is introduced to provide a unique method for the analysis of the elemental composition of the top-most atomic layer. In PAES, monoenergetic positron of a few eV are implanted to the surface under study and these positrons become thermalized near the surface. A fraction of the thermalized positron trapped at the surface state annihilate with the neighboring core-level electrons, creating core-hole excitations, which initiate the Auger process with the emission of Auger electrons almost simultaneously with the emission of annihilating gamma-rays. The energy of electrons is generally determined by employing ExB energy selector, which shows a poor resolution of 6--10eV. In this paper, time-of-flight system is employed to measure the electrons energy with an enhanced energy resolution. The experimental result is compared with simulation results in the case of both linear (with retarding tube) and reflected TOF systems.

Keywords: Auger 전자,표면분석,TOF 시스템,에너지 측정기,양전자 소멸,Auger Electron,Positron annihilation,surfaces,TOF system,Energy selector

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