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

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_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_H were observed and attributed to the size quantization in SnTe thin films. The discrepancy between the experimentally determined oscillation period Δd and the theoretical Δd 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_H changes with increasing thickness up to d∼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.