INFLUENCE OF SILICON ADDITION ON SEEBECK COEFFICIENT OF MnSi1.7 FILMS

Abstract

MnSi 1.7 films with different thicknesses (16–242 nm) are prepared by magnetron sputtering and electron beam evaporation. When the MnSi 1.7 film thickness is about 40 nm or above, MnSi 1.7 films are p-type in the whole temperature range (300–700 K) in agreement with reports in literature. By co-sputtering of MnSi 1.85 and silicon targets or deposition of Si / Mn multi-layers with a larger thickness ratio, silicon is added to the films and the Seebeck coefficients transform from positive to negative with increasing temperature. The Seebeck coefficients at room temperature and 633 K are +0.098 mV/K and -0.358 mV/K, respectively. By reducing the MnSi 1.7 film thickness to 27 nm, the transition of Seebeck coefficient from positive to negative is also observed although silicon is not added intentionally. When an ultra-thin aluminum layer is deposited between MnSi x(x < 1.7) and Si layers to enhance silicon diffusion, the p- to n-type transition temperature decreases about 100 K. The silicon-added MnSi 1.7 films usually have higher electrical resistivity.