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Excitation-induced effects in selenium clusters: molecular-orbital analyses

K. TANAKA1,*

Affiliation

  1. Department of Applied Physics, Graduate School of Engineering, Hokkaido University, Sapporo, Japan

Abstract

Covalent chalcogenide glasses are known to exhibit unique features, including p-like conduction, midgap photoluminescence and photoinduced phenomena. To obtain fundamental insights into such characteristics, addition effects of an electron, hole and exciton to an Se8 ring and H-nSe-H (n ≤ 10) chains have been analyzed using an ab initio molecular-orbital calculation package GAMESS. The electron addition tends to expand or dismember the clusters, the hole compacts them, and the exciton produces distortions. In chain dimers, a hole enhances interchain interaction through π-type wavefunctions. These deformations accompany polaronic energy shifts, which are consistent with higher hole mobility and sub-midgap luminescence in amorphous and trigonal Se. When the deformed clusters are neutralized or deexcited, successive relaxation recovers initial structures, with a few exceptions that produce disordered clusters and intimate valence-alternation pairs, which may cause meta-stable photoinduced structura changes.

Keywords

Selenium, Polaron, electronic properties, Photoinduced phenomena.

Submitted at: May 22, 2017
Accepted at: Oct. 10, 2017

Citation

K. TANAKA, Excitation-induced effects in selenium clusters: molecular-orbital analyses, Journal of Optoelectronics and Advanced Materials Vol. 19, Iss. 9-10, pp. 586-594 (2017)