High pressure lattice dynamics study of few layer-$\alpha$-In${}_2$Se${}_3$

Abstract

Few-layer $\alpha$-In${}_2$Se${}_3$ has been studied under pressure using Raman spectroscopy in a diamond anvil cell up to 60 GPa (at room temperature). A combination of AFM and Raman was used to estimate the thickness of the specimens. While few-layer $\alpha$-In${}_2$Se${}_3$ shows identical structural evolution with the one of the bulk powder-like form of $\alpha$-In${}_2$Se${}_3$ ( $\alpha$ $\to$ ${\beta }^{{}^{\prime }}$ $\to$ IV ), an abrupt ${\beta }^{{}^{\prime }}$ $\to$ IV phase transition (at 45 GPa) was observed, in contrast with the case of the bulk specimen where the two phases coexist over a wide pressure range. This is attributed to the difference in specimens morphology, $i.e.$ single crystal and powder in the case of few-layer and bulk $\alpha$-In${}_2$Se${}_3$, respectively. This study documents the significance of specimens morphology on the observed pressure-induced phase transitions. The methodology developed in this study for performing high-pressure Raman measurements can be applied to other nanodimensional layered materials.

7 pages, 6 figures