ELECTRICAL PROPERTIES AND STRUCTURES OF SOLID AND LIQUID GeS, SnS, AND PbS

Abstract

The electrical conductivity of germanium(II) sulfide in the liquid state has been measured with a capillary-type cell. Both a-c. and d-c. methods were used. The conductivity of liquid GeS increases regularly with tempersature from 1.33 Ω⁻¹ cm⁻¹ at 664 °C to 2.52 Ω⁻¹ cm⁻¹ at 705 °C. The experimental facts lead to the conclusion that GeS remains a semiconductor in the liquid state with a conduction band situated at 2.5 eV above the valence band.The energy gaps of GeS, SnS, and PbS in the solid state are compared with those of the corresponding liquids. It is concluded that these sulfides, in the liquid state, have structures very similar to that of the solids. Liquid PbS has a structure somewhat similar to that of metals. In the case of SnS and GeS, heating and melting are accompanied by a gradual loosening of the double layers which constitute the crystals. Accumulated evidence indicates that the molecular character of SnS and GeS is increased on going from the solid to the liquid state.