NONDESTRUCTIVE INVESTIGATION OF MICROSTRUCTURES AND DEFECTS AT A SRTIO3 BICRYSTAL BOUNDARY

The effects of thermal annealing on the microstructure at the grain bo undary of a 36.8 degrees symmetric [100] tilt SrTiO3 bicrystal were st udied. Scanning tunneling microscopy and atomic force microscopy were used for nondestructive observation of the boundary structures. Anneal ing the bicrystalline substrates at temperatures as low as 780 degrees C led to the formation of grooves at their boundaries. This provides direct evidence that the thickness depression of YBa2Cu3O7-delta films at the bicrystal boundaries originates from the underlying grooved su bstrates. Defects characterized as holes with diameters ranging from s imilar to 30 nm to similar to 200 nm were also observed. (C) 1998 Amer ican Institute of Physics. [S0003-6951(98)03925-4].