High-K substrate effect on thermal properties of 2D InSe few layer

Two-dimensional thin layers of indium selenide (InSe) have attracted much attention due to their potential applications in optoelectronics as highly responsive photo-detectors and field-effect transistors. In the present work, we explore thermal properties of InSe thin layers on a high-k substrate with a thin SiO2 passivation layer using temperature and power dependent Raman spectroscopy. The first order temperature coefficients for in-plane (E12g) and out-of-plane (A21g) modes of InSe few-layers on a Al2O3 substrate were found to be −0.00507 and −0.00310 cm−1/K, respectively, which are much smaller than the corresponding values −0.00612 and −0.00528 cm−1/K of similarly prepared sample on SiO2 substrate. The difference in temperature coefficients is attributed to compressive strain introduced by the Al2O3. Further, the average thermal conductivity of a 4 nm thin InSe layer on the Al2O3 substrate at room temperature was found to be ∼53.4 W/m-K, which is significantly larger than those of InSe layers prepared on SiO2 substrate (∼28.7 W/m-K). The existed interface charges between the Al2O3 and InSe layers cause the observed improvement of thermal conductivity by electron-phonon interactions.