The preparation and some physical properties of thin amorphous Ge-Bi-S films

摘要

Amorphous Ge-Bi-S thin films having n-type conductivity were prepared by thermal evaporation from two boats. The dc electrical conductivity (sigma) of these films in the "low"-temperature region only weakly depends on temperature. This indicates (i) the possible presence of an "impurity-like" conduction due to the donor-like band located in the proximity of the conductivity band or (ii) a hopping type conduction due to the variable range hopping. Of interest is the fact that the dc electrical conductivity reaches considerably high values (sigma(300 K)=2.7 OMEGA~(-1) cm~(-1) for Ge_(18.6)Bi_(25.3)S_(56.1) thin film). Far-infrared transmission spectra of the studied films indicate a typical two-mode behavior due to the Ge-S and Bi-S stretching modes.