Effect of doping on global and local order in crystalline GeTe

Effect of nitrogen and carbon doping on the structure of GeTe has been investigated using x-ray diffraction and extended x-ray absorption fine structure (EXAFS) spectroscopies. While Bragg diffraction which probes the global structure exhibits a clear transition upon doping from the rhombohedral phase to the cubic (rocksalt) phase, the local structure probed by EXAFS remains rhombohedrally distorted across the compositions studied. The apparent inconsistency between the results of the two techniques used is attributed to disordering upon doping and the resulting order-disorder transition that is seen by site-averaging diffraction as a displacive rhombohedral-to-cubic transition. (C) 2011 American Institute of Physics. [doi:10.1063/1.3598384]