Ultrathin Pt and Mo films on Al_1-xSc_xN: an interface investigation

Aluminum scandium nitride (Al1-xScxN) with attractive ferroelectric and piezoelectric properties is a promising material for next-generation device applications. However, the understanding of interface properties between integrated ultrathin metal electrodes and Al1-xScxN films is still limited, despite their significant impact on device performance. In the study, we investigated the growth mechanism and interfacial chemistry of ultrathin platinum (Pt) and molybdenum (Mo) films deposited on the high-crystalline Al1-xScxN (x = 0.2) surface. The chemical and electronic structure evolutions of the interface during the deposition process were probed by in-situ X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). The structural properties of the interface were further characterized by cross-sectional transmission electron microscopy (TEM), X-ray diffraction spectroscopy (XRD), and atomic force microscopy (AFM). Our results reveal the formation of ionic Pt2+-N bonds at the Pt/Al1-xScxN interface, while Mo does not bond with the substrate. Furthermore, we identified electron transfer induces upward band-bending like effects on the Al1-xScxN surface upon both Pt and Mo interactions. Our work on the chemical and structural research of ultrathin metal electrodes and Al1-xScxN interfaces provides guidance towards designing high-performance micro-electromechanical (MEMS) devices.