The two-electron exchange between the U– tin centers in crystal and glass-like chalcogenide semiconductors

Abstract

The two-electron exchange between neutral and doubly ionized U^– tin centers in the partially compensated Pb_0.96Sn_0.02Na_0.01Tl_0.01S hole solid solutions in the temperature range of 80–900 K and in the partially compensated Pb_0.965Sn_0.015Na_0.01Tl_0.01Se hole solid solutions in the temperature range of 80–600 K was studied by ^119mmSn(^119mSn) Mössbauer spectroscopy. The activation energy of this process for the Pb_0.96Sn_0.02Na_0.01Tl_0.01S solid solutions is comparable with the depth of the tin energy levels in the PbS band gap and amounts to 0.11(2) eV, while in the Pb_0.965Sn_0.015Na_0.01Tl_0.01Se solid solutions it is comparable with the correlation energy of the donor U^– tin centers in PbSe and amounts to 0.05(1) eV. It is established that the exchange is implemented by the simultaneous transfer of two electrons with the valence band states involved. In the glass-like (As₂Se₃)_0.3(GeSe)_0.6(SnSe)_0.1 alloy containing quadruply charged six-coordinated tin (singly ionized donor center) and doubly charged three-coordinated tin (singly ionized acceptor center), no traces of the electronic exchange between differently charged tin states was observed up to a temperature of 480 K, which is explained by the fact that the doubly charged and quadruply charged tin centers are in different coordination states.