Exploring charge transfer and schottky barrier modulation at monolayer Ge₂Sb₂Te₅-metal interfaces

Monolayer Ge₂Sb₂Te₅exhibits great potential in non-volatile memory technology due to its excellent electronic properties and phase-change characteristics, while the fundamental nature of Ge₂Sb₂Te₅-metal contacts has not been well understood yet. Here, we provide a comprehensive<i>ab initio</i>study of the electronic properties between monolayer Ge₂Sb₂Te₅and Pt, Pd, Au, Cu, Cr, Ag, and W contacts based on first-principles calculations. We find that the strong interaction interfaces formed between monolayer Ge₂Sb₂Te₅and Pt, Pd, Cr, and W contacts show chemical bonding and strong charge transfer. In contrast, no apparent chemical bonding and weak charge transfer are observed in the weak interaction interfaces formed with Au, Cu, and Ag. Additionally, our study reveals the presence of a pronounced Fermi level pinning effect between monolayer Ge₂Sb₂Te₅and metals, with pinning factors ofSn=0.325andSp=0.350. By increasing the interlayer distance, an effective transition from<i>n</i>-type Ohmic contact to<i>n</i>-type Schottky contact is facilitated because the band edge of Ge₂Sb₂Te₅is shifted upwards. Our study not only provides a theoretical basis for selecting suitable metal electrodes in Ge₂Sb₂Te₅-based devices but also holds significant implications for understanding Schottky barrier height modulation between semiconductors and metals.