Concentration dependences at the critical temperatures in vacuum topotaxial Ag2Se thin layers

Ag2Se thin epitaxial layers were grown under vacuum conditions. The starting components were evaporated sequentially on various substrates and followed by annealing to obtain topotaxial layers, which were either poly- or monocrystalline, depending on the substrate. Ag2Se undergoes a reversible first order phase transition at about 133 °C. The temperatures of the phase transitions are different on heating and cooling and these transitions and associated hysteresis can be demonstrated also by Hall measurements of electron concentration and electron mobility. The mobility shows a sudden decrease at the critical temperature on heating and a sudden increase on cooling. In the present experiments concentration dependences of the mobilities and of the resistivity at the critical temperatures defining the onset of hysteresis (four points), were measured for both types of structure. The μ(n) and ρ(n) dependences show a c0n-c power type character with exponents −0.33 and −0.43 for mobilities and −0.58 and −0.72 for the resistivity. The slopes are only slightly different for the poly- and monocrystalline samples. Also the ratios of c0-s are about 1.4 and 1.6, respectively.