Evolution of Raman spectra of MoS2 heterostructure based on thickness and laser power dependence

Abstract

This study investigated a 2D material called MoS₂, which has potential applications in optoelectronic devices. The researchers used a technique called Raman spectroscopy to examine MoS₂ samples with different numbers of layers, specifically looking at two peaks called A_1g and E¹_2g in the 350‒450 cm^‒1 range. They found that the distance between these peaks was much smaller in samples with fewer layers (around 1‒5 layers) compared to samples with more layers (around 10‒20 layers). When the researchers examined individual samples with varying laser power, they observed that both peaks shifted to the left as the laser power increased. This shift was more pronounced in the A_1g peak than the E¹_2g peak in samples with fewer layers. The researchers suggest that the decrease in material thickness leads to the stiffening of the E¹_2g peak and the softening of the A_1g peak. This change in the material properties results in a weaker thermal softening effect for the E¹_2g peak and a stronger thermal softening effect for the A_1g peak.