Positron-annihilation study of the structure of pure and hydrogenated amorphous silicon

Autor:	Jia-Jiong Xiong, Wei-Zhong Yu, Kang Long, Ai-Lien Jung, Li-Qing Shi, Jian-Zhong Song, David Adler, Bi Song Cao, Gang Liu, Hui-Lin Jiang
Rok vydání:	1985
Předmět:	Amorphous silicon Annihilation Materials science Radiation Condensed Matter Physics Spectral line Electronic Optical and Magnetic Materials Positronium Momentum chemistry.chemical_compound chemistry Materials Chemistry Ceramics and Composites Atomic physics Positron annihilation Line (formation)
Zdroj:	Journal of Non-Crystalline Solids. :221-224
ISSN:	0022-3093
DOI:	10.1016/0022-3093(85)90643-x
Popis:	We report measurements of positron annihilation in both pure and hydrogenated amorphous silicon, including lifetime spectra, Doppler-broadening and ACPAR (angular correlation of the positron annihilation radiation). Both the pure (aSi) and the hydrogenated (aSi:H) samples exhibit a lifetime component of about 410 ps which we attribute to small vacancies consisting of about 4 missing atoms. The corresponding defect is analyzed and the concentration is estimated to be of the order of 1017 cm−3. Only aSi:H exhibits a long-lived line with τ > 5 ns, which can represent only the pick-off annihilation of orthopositronium. This is direct evidence for the existence of large microvoids in aSi:H, and is consistent with recent reports of the presence of occluded H2 gas under high pressure in such films. We also measured the Doppler-broadened spectra and angular correlation curves to study the momentum distribution of the e− - p+ pairs in both types of films. Again, only the aSi:H sample showed evidence of positronium formation, consistent with the results of the lifetime spectral analysis.
Databáze:	OpenAIRE
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