Thermal expansion coefficient of few-layer MoS 2 studied by temperature-dependent Raman spectroscopy

The thermal expansion coefficient is an important thermal parameter that influences the performance of nanodevices based on two-dimensional materials. To obtain the thermal expansion coefficient of few-layer MoS 2 , suspended MoS 2 and supported MoS 2 were systematically investigated using Raman spectroscopy in the temperature range from 77 to 557 K. The temperature-dependent evolution of the Raman frequency shift for suspended MoS 2 exhibited prominent differences from that for supported MoS 2 , obviously demonstrating the effect due to the thermal expansion coefficient mismatch between MoS 2 and the substrate. The intrinsic thermal expansion coefficients of MoS 2 with different numbers of layers were calculated. Interestingly, negative thermal expansion coefficients were obtained below 175 K, which was attributed to the bending vibrations in the MoS 2 layer during cooling. Our results demonstrate that Raman spectroscopy is a feasible tool for investigating the thermal properties of few-layer MoS 2 and will provide useful information for its further application in photoelectronic devices.