Structure and phonon behavior of crystalline GeTe ultrathin film

摘要

We report the drastic effect of film thickness on the structure and corresponding phonon behavior of crystalline GeTe ultrathin film. GeTe film with film thickness at ∼5 nm still shows good crystallization behavior and this highly scaled dimension confined almost all the crystallites to have preferred [111] orientation. The large specific interface area in ultrathin film give rise to the increase of tetrahedral coordinated Ge atoms and a rising Raman mode at low frequency is observed. These findings give implications for the thermal and electrical characters of phase change ultrathin films and thus for relevant scaling properties of Phase Change Memory.