In situ deposition and characterization of c-axis-oriented Al1-xScxN thin films on Al (111) for ferroelectric memory applications

The increasing demand for high-speed, energy-efficient data processing has intensified research on ferroelectric materials for in-memory computing and non-volatile memory applications. Aluminum scandium nitride (Al1-xScxN) is a promising candidate due to its complementary metal-oxide-semiconductor (CMOS) compatibility, thermal stability, and strong spontaneous polarization. However, its ferroelectric properties are highly sensitive to deposition conditions, substrate choice, and scandium concentration, which directly influence crystal orientation and polarization switching. In this work, we demonstrate in-situ reactive co-sputtering of Al1-xScxN thin films on Al(111) bottom electrodes deposited on sapphire substrates. Structural characterization using x-ray diffraction (XRD) reveals a highly textured wurtzite structure with strong c-axis orientation, evidenced by pronounced Al1-xScxN(0002) and Al(111) diffraction peaks at 35.4° and 38.5°, respectively. The c-axis lattice parameter, expanded relative to pristine AlN, indicates successful scandium incorporation and potential elastic softening, which may enhance ferroelectric switching. X-ray photoelectron spectroscopy (XPS) confirms a scandium concentration of approximately 29 atomic%, optimal for robust polarization. Depth-profile XPS further demonstrates that surface oxidation arises from ambient exposure, whereas the bulk film maintains a low-oxygen. These results highlight that careful control of deposition parameters and in-situ growth on Al (111) electrodes enables uniform, c-axis-oriented Al1-xScxN films, offering reliable ferroelectric performance and promising integration for next-generation non-volatile memory and in-memory computing devices.