Ultrathin platinum diselenide synthesis controlling initial growth kinetics: Interfacial reaction depending on thickness and substrate

Platinum diselenide (PtSe₂) is an emerging transition-metal dichalcogenide showing both strong interlayer coupling and remarkable electrical properties. Because field-effect transistors (FETs) recently fabricated using PtSe₂ films grown by various methods have not shown the high mobilities and on–off ratios compared with exfoliated PtSe₂ and predicted by theoretical calculations, the PtSe₂ growth mechanism must be better understood to prevent the degradation of electrical properties and improve the electrical performances of PtSe₂-based devices. Therefore, molecular beam epitaxy is used in the current study to grow PtSe₂ films, and a correlation is demonstrated between the initial PtSe₂ growth kinetics and the electrical performances of PtSe₂-based devices. X-ray photoelectron spectroscopy and annular dark field–scanning transmission electron microscopy show that metallic Platinum (Pt) is present in the thin PtSe₂ films, as explained by the density functional theory calculations comparing Pt–Pt bond with Pt–Se bond. Electrical measurements of the PtSe₂-based FETs show that the electrical performances are closely correlated with the initial growth kinetics of the PtSe₂ films, indicating that removing Pt (which degrades device performance) is the most important aspect of growing thin PtSe₂ films to optimize device performance.