EXAFS characterisation of Ge nanocrystals in silica

The formation and structure of Ge nanocrystals produced in silica by ion-implantation and thermal annealing were studied with transmission electron microscopy, Raman spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy. We compare results derived from these complementary techniques, focusing on the use of EXAFS to study the short-range order about Ge atoms. Utilizing this synchrotron-radiation-based analytical method, we show the nanocrystal inter-atomic distance distribution deviates from that of bulk Ge, exhibiting enhanced structural disorder of both Gaussian and non-Gaussian forms in the first, second and third nearest-neighbour shells. The extent of disorder in the nanocrystalline sample is comparable to that of relaxed amorphous material