Nonlinear Thickness and Grain Size Effects on the Thermal Conductivity of CuFeSe2 Thin Films

Abstract

A crucial issue in realizing the applications of high-density semiconductor devices is no more than heat dissipation, especially in the direction perpendicular to the substrate. For the past decades, crystallization effects on thermal conductivity have been intensively studied, whereas the quantitative analysis on this aspect is rare. In this study, a series of CuFeSe2 thin films with grain sizes 20-40 nm controlled by the thickness were fabricated for the quantitative study of the grain size effect on the thermal conductivity perpendicular to the subtract. The results reveal that larger grain sizes have higher thermal conductivity and the trend agreed well with the simplified theory of the phonon-grain boundary interaction. From the data of electrical conductivity and the Wiedemann-Franz law, the thermal conductivity is mainly contributed by the lattice thermal conductivity, and is nonlinearly dependent on the grain size and the thickness of the films. In addition, the ～ 2.6×10^(-8) K-m^2/W film-substrate interfacial thermal resistance (comparable to that of 200 nm films) is also a non-negligible factor and has to be taken into account.