Investigation of the oxidation process in GeTe-based phase change alloy using Ge K-edge XANES spectroscopy

• Published in: Pure and applied chemistry Vol. 91; no. 11; pp. 1769 - 1775
• Main Authors: Krbal, Milos, Kolobov, Alexander V., Fons, Paul, Nitta, Kiyofumi, Uruga, Tomoya, Tominaga, Junji
• Format: Journal Article
• Language: English
• Published: Berlin De Gruyter 01.11.2019; Walter de Gruyter GmbH
• Subjects: Crystal structure; Crystallinity; Crystallization; Germanium compounds; High temperature; local structure; Oxidation; Oxygen atoms; Phase change materials; Phase transitions; phase-change memory; Spectroscopy; Spectrum analysis; SSC-2018; X-ray absorption spectroscopy
• ISSN: 0033-4545; 1365-3075
• DOI: 10.1515/pac-2018-1229

In this work, we clearly demonstrate the efficacy of using XANES spectroscopy in conjunction with a Pilatus detector as a sensitive tool to allow the study of the oxidation process in GeTe alloys via depth profile analysis. On the basis of Ge K-edge XANES spectra, it was found that GeTe alloys do not oxidize readily after an initial native surface oxidation that occurs upon exposure to oxygen in the air at the elevated temperatures, 100 °C and 330 °C. We demonstrate that amorphous GeTe possesses a higher predisposition to oxidation than crystalline GeTe when exposed to the air at temperature of 100 °C. When the temperature is set to 330 °C in an air ambient, we show that the amorphous to crystal phase transition affects the oxidation process more significantly than the simple annealing of crystalline GeTe. We suggest that the higher tendency of GeTe films to oxidize during the phase transition is a consequence of the breaking of Ge–Ge bonds in the presence of oxygen atoms which subsequently leads to the extra formation of Ge–O bonds during crystallization.