Aluminum scandium nitride (Al1−xScxN) is a promising material for ferroelectric devices due to its large remanent polarization, scalability, and compatibility with semiconductor technology. By doping AlN with Sc, the bonds in the polar AlN structure are weakened, which enables ferroelectric switching below the dielectric breakdown field. However, one disadvantage of Sc doping is that it increases the material's tendency towards oxidation. In the present study, the oxidation process of tungsten-capped and uncapped Al0.83Sc0.17N thin films is investigated by hard X-ray photoelectron spectroscopy (HAXPES). The samples had been exposed to air for either two weeks or 6 months. HAXPES spectra indicate the replacement of nitrogen by oxygen, and the tendency of oxygen to favor oxidation with Sc rather than Al. The appearance of an N2 spectral feature thus can be directly related to the oxidation process. We present an oxidation model that mimics these spectroscopic results of the element-specific oxidation processes within Al1−xScxN. Finally, in operando HAXPES data of uncapped and capped AlScN-capacitor stacks are interpreted using the proposed model.
@article{arxiv.2410.21132,
title = {Long-term stability and oxidation of ferroelectric AlScN devices: An operando HAXPES study},
author = {Oliver Rehm and Lutz Baumgarten and Roberto Guido and Pia Maria Düring and Andrei Gloskovskii and Christoph Schlueter and Thomas Mikolajick and Uwe Schroeder and Martina Müller},
journal= {arXiv preprint arXiv:2410.21132},
year = {2026}
}