Local order of Ge atoms in amorphous GeTe nanoscale ultrathin films

Abstract

We demonstrate the drastic effect of film thickness on the local order of Ge sites in amorphous GeTe ultrathin films by Surface Enhanced Raman Scattering study. The relative intensity of the two prominent peaks around 125 cm−1 and 160 cm−1 changes greatly as a function of the film thickness from 100 nm to 3 nm. We suggest that this change originates from the variation of the fraction of Ge atoms in tetrahedral- and defective octahedral-like sites. Ab initio Molecular Dynamics simulations show that more Ge atoms in ultrathin films are tetrahedrally coordinated. The result is consistent with the experimental observation of Raman spectroscopy.