 Abstract interfaces with surrounding materials, such as charged impurities and surface roughness, can significantly affect the electrical and optical properties of two-dimensional materials. By examining the results of encapsulating MOS2 with hexagonal boron nitride, HBN, it was found that the portion of the phonon modes caused by intrinsic factors and the portion caused by the interface effect could be separated. For example, the frequency of the A1G peak of MOS2 supported by silicon dioxide decreased by approximately 4CM1 in air for a thickness reduction from 10 layers to monolayers. Of this decrease, roughly 2CM1 was attributed to the weakening of the van der Waals-Interlayer interaction, while the remaining 2CM1 was due to the interface effect. It was also found that the types and concentrations of impurities at the interface between MOS2 and SiO2 were similar to those between MOS2 and air. When completely encapsulated with HBN, the width of the A1G peak of few-layer MOS2 became comparable, or equal to that of bulk MOS2. This article was authored by Da Kim Lee, Nam Hee Kim, Su Young Young, and others. We are article.tv, links in the description below.