Semiconducting high manganese silicides (HMS) have attracted great research interest in the past decades for potential applications as novel optoelectronic and photovoltaic devices integrated on Si chips. The fundamental electronic properties in HMS are still unclear, and the band-gap energy was reported to scatter from 0.42 eV to 0.98 eV in the past decades. In this work, single phase semiconducting Mn₄Si₇ precipitates and thin films have been synthesized by ion implantation. Optical absorption spectra obtained by transmission measurements demonstrated the existence of a direct band gap in all samples. The band gap values varied in the range of 0.77 eV to 0.93 eV, corresponding to varied strain states due to different microstructures. The electronic band structures of Mn₄Si₇ under different strain states have been theoretically investigated by means of a full-potential linear augmented plane wave method and compared with the experimental results. From ab initio calculations, the Mn₄Si₇ compound is found to be a pseudo-direct band-gap semiconductor with a fundamental gap increasing linearly with the compression along c- or a-axis. This trend is in good agreement with the experimental results.

Date Published: 11 March 2008
PDF: 4 pages
Proc. SPIE 6984, Sixth International Conference on Thin Film Physics and Applications, 69840F (11 March 2008); doi: 10.1117/12.792271

Published in SPIE Proceedings Vol. 6984:
Sixth International Conference on Thin Film Physics and Applications
Wenzhong Shen; Junhao Chu, Editor(s)