SCANNING-TUNNELING-MICROSCOPY AND SPECTROSCOPY OF N-DOPED BATIO3 CERAMICS

The methods of scanning tunnelling microscopy and spectroscopy have be en applied to study the surface electronic properties of vacuum reduce d n-doped BaTiO3 ceramics. These methods allow the acquisition of topo graphical images of the surface of semi-conducting ceramics and at the same time to collect the I-V tunnelling spectra at the points of inte rest. Our results on polished BaTiO3 ceramics have shown the presence of negative potential barriers at the ceramic's surface. Spontaneous p olarization along with extrinsic surface states were considered as the major reasons for the formation of surface potential barriers. Hyster esis was observed in the I-V characteristics at 60% of the surface sit es examined and this was attributed to the response time of the tunnel ling current as a result of the charging and discharging kinetics of t he extrinsic surface states (i.e. adsorbed oxygen or surface defects) with a trap depth of up to 0.7 eV. (C) 1998 Elsevier Science Limited. All rights reserved.