Analysis Of The Forgotten Parts Of The Ge K Edge Spectra: Life Before The Exafs Oscillations

The white line and X-ray absorption near edge spectroscopy (XANES) spectral regions of the Ge K edge, similar to 11100 to 11112 eV, and between 11112 and 11180 eV and beyond, contain electronic structure information that complements near-neighbor bonding information in the single-scattering EXAFS regime. The multiple-scattering XANES features are not generally addressed in EXAFS studies that are targeted to obtain bonding information. There are systematic changes in the X-ray photon energy of the spectral peak of the white line for Ge-Sb-Te (GST) alloys, GeSb and GeTe model compounds, and other Ge alloys that scale directly with average bond ionicity. The spectral widths of these features correspond tp electronic transitions important in optical memory devices. There are other features in the XANES region associated with shake-off effects for shallow atomic core states that reveal bonding information important in analysis of the oscillatory features in the EXAFS regime. These include bonding pairs that are addressed in the fit procedures; e. g., Ge-Te and Ge-Sb in GST 225. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim