1994 Fiscal Year Final Research Report Summary

Physical Properties of Nano-size Pore Surfaces and Metal Films on Pore Surfaces of Porous Silicon

Research Project

Project/Area Number	05650024
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	表面界面物性
Research Institution	Tokyo Gakugei University
Principal Investigator	MURAKAMI Hideoki Tokyo Gakugei University, Department of Education, Professor, 教育学部(第三部), 教授 (30011000)
Project Period (FY)	1993 – 1994
Keywords	Surface Science / Porous Silicon / Positronium / Positron
Research Abstract	The yield of ortho-positroniums with a lifetime of a few ten nanosecond, which is shortened upon exposure to oxygen gas, has been found in a porous silicon made by anodization of a silicon single crystal of 2.0OMEGAcm. The lifetime becomes long from 33ns to 45ns, and the full width at half maximum of the Doppler-broadened annihilation radiation increases, as the temperatere is decreases from 300 K to 85 K,and both of them level off at temperatures lower than 85 K.The intensity of ortho-positroniums decreases from 22 % to 15 % as the temperature goes down from 300 K to extrapolated 0 K.Temperature-dependent positronium annihilation is understood in terms of the temperature dependence of unpaired electron density on pore surfaces. The formation of ortho-positroniums has not been found in a porous silicon made with a silicon single crystal of 0.02 OMEGAcm. No positronium formation has been explained mainly on the low surface density.