Atomic-precision determination of the reconstruction of a 90° tilt boundary in YBaCuO by aberration corrected HRTEM
by Lothar Houben, Andreas Thust, Knut Urban
Aberration corrected high-resolution transmission electron microscopy has been used to determine the reconstruction of atomic bonds of a 90° [1 0 0] grain boundary in YBaCuO. A precise measurement of atom positions within the grain boundary and the assessment of the oxygen stoichiometry required at the same time a high control of residual lens aberrations of the electron microscope and a good signal-to-noise ratio. This goal was achieved by the combination of spherical-aberration correction in the microscope with the numerical exit-plane wave function reconstruction from focal series.
Atomic column positions for individual cations and anions have been determined by the regression analysis of peak maxima in the phase image of the retrieved exit-plane wave function. The measurement accuracy was quantitatively assessed, including the statistical error related to residual noise. Changes in bondlengths between copper atoms and the apical oxygen have been measured, indicating the distortion of the square pyramidal oxygen coordination of plane copper sites and the square coordination of chain copper sites in the grain boundary.
Further reading: Ultramicroscopy 106 (2006) 200-214