Chemical order around Ge atoms in binary germanium selenide glasses: Results from 73Ge solid-state NMR spectroscopy at 19.6 Tesla

The coordination environment of Ge atoms in binary GexSe100-x glasses with 75 >= x >= 60 is probed using Ge-73 solid-state NMR spectroscopy at an ultra-high magnetic field of 19.6 T. Two different types of Ge coordination environments can be identified in the Ge-73 NMR spectra of glasses with x >= 66.7, one is a relatively symmetric GeSe4 tetrahedral site with all heteropolar Ge-Se bonds and the other is a distorted GeSe4-nGen tetrahedral site with one or more Ge-Ge homopolar bonds. The compositional variation of the relative fractions of these two types of Ge sites provides unique information regarding degree of chemical order and nature of the spatial distribution of Ge-Ge bonds in these glasses. These results also demonstrate the potential of Ge-73 solid-state NMR as an important technique for future structural studies of Ge containing crystalline and amorphous materials. (C) 2010 Elsevier B.V. All rights reserved.