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 MoS2, suspended MoS2 and supported MoS2 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 MoS2 exhibited prominent differences from that for supported MoS2, obviously demonstrating the effect due to the thermal expansion coefficient mismatch between MoS2 and the substrate. The intrinsic thermal expansion coefficients of MoS2 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 MoS2 layer during cooling. Our results demonstrate that Raman spectroscopy is a feasible tool for investigating the thermal properties of few-layer MoS2 and will provide useful information for its further application in photoelectronic devices.

In this work, magneto-Raman mapping was performed on monolayer MoS2 at 4 K, which exhibited a prominent magnetic field-induced modulation of phonon intensity. Interestingly, structural microinhomogeneity in MoS2 was observed in the mapping images under certain magnetic fields, indicating the existence of lattice defects in monolayer MoS2. Remarkably, the magneto-optical Raman intensity for the defect zone was only 26% of that for the regular zone, which could be attributed to the scattered electron motion by lattice defects. These results provided a deeper understanding of the mechanisms behind the magneto-optical Raman effects in MoS2. Moreover, it was demonstrated that the low-temperature magneto-Raman mapping technique could be a highly sensitive tool to directly examine the microstructure in two-dimensional (2D) transition-metal dichalcogenides.