Investigation of fluctuations on oxygen stoichiometry near grain boundaries in ion-beam thinned YBa_2Cu_3O_(7-δ) by scanning transmission electron microscopy

摘要

Oxygen K-absorption edge spectra have been obtained from a grain boundary region in ion-beam thinned YBa_2Cu_3O_(7-δ). Fluctuations in oxygen stoichiometry can be inferred from changing features in the near-edge structure of these absorption edges. In addition, the small probe afforded by the STEM allows these fluctuations to be observed with nanometre spatial resolution. Results show that these fluctuations can be quantified to within ～2% error in absolute oxygen stoichiometry. The interpretation of observed fluctuations take into account the growth of an amorphous phase at the boundary, caused ion-beam milling.