World Journal of Condensed Matter Physics, 2016, 6, 68-74 Published Online May 2016 in SciRes. http://www.scirp.org/journal/wjcmp http://dx.doi.org/10.4236/wjcmp.2016.62010 How to cite this paper: Saleh, A.S. (2016) Metal-Semiconductor Interfaces Investigated by Positron Annihilation Spectros- copy. World Journal of Condensed Matter Physics, 6, 68-74. http://dx.doi.org/10.4236/wjcmp.2016.62010 Metal-Semiconductor Interfaces Investigated by Positron Annihilation Spectroscopy Abdulnasser S. Saleh Department of Physics, University of Benghazi, Benghazi, Libya Received 12 February 2016; accepted 2 May 2016; published 5 May 2016 Copyright © 2016 by author and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ Abstract Variable-energy positron annihilation spectroscopy has been applied to study interfaces in Al/Si, Au/Si and Au/GaAs structures. Computational fittings of ROYPROF program were used to analyze Doppler broadening results in order to determine kinds of regions that positrons were likely to sample. The interfaces were found acting as a capturing thin layer with negligible positrons stopped in them and their characteristics came only from positrons diffusing to these interfaces, the positron work function of these materials were taken into consideration. In all fittings, the in- terfaces are found to have 1 nm thickness and act as an absorbing sink for all thermal positrons diffusing towards them, and this indicates either the existence of open volume defects or a weak- ness of known theoretical models for positron affinities. The result is supported by measurements obtained by applying external electric fields on Al/Si sample. Theoretical fittings have clearly demonstrated the sensitivity of interfaces in these attempts and their importance in data analyz- ing and in developing of fitting cods. Keywords Positron Annihilation, Interface, Metal-Semiconductor, Defects 1. Introduction The importance of metal semiconductor interfaces comes from the fact that most electronic devices are inter- connected using metallic wiring that forms metal-semiconductor contacts. The properties of these contacts can vary considerably depending on the nature of the interface with the semiconductor. The emergence of variable low-energy positron beams enabled depth resolved studies at near-surface and in-