Oscillations in the thickness dependences of the Seebeck coefficient in SnTe thin films

Abstract

The objects of this study were SnTe films grown by thermal evaporation in vacuum on [001]KCl substrates. The dependences of the Seebeck coefficient S and the Hall coefficient R/sub H/ on the SnTe film thickness (d = 5 - 700 nm) were obtained at room temperature. Distinct oscillations in the d-dependences of S and R/sub H/ were observed and attributed to the size quantization in SnTe thin films. The discrepancy between the experimentally determined oscillation period /spl Delta/d and the theoretical /spl Delta/d estimated using the model of a quantum well with infinitely high walls is explained by an oversimplification of the model. The monotonic component of the d-dependences of S and R/sub H/ changes with increasing thickness up to d/spl sim/100 nm, and then remains constant. It is suggested that this behavior can result from the dependence of the equilibrium concentration of non-stoichiometric cation vacancies on the SnTe film thickness.