Anomalously large measured thermoelectric power factor in Sr1-xLaxTiO3 thin films due to SrTiO3 substrate reduction

We report the observation that thermoelectric thin films of La-doped SrTiO(3) grown on SrTiO(3) substrates yield anomalously high values of thermopower to give extraordinary values of power factor at 300 K. Thin films of Sr(0.98)La(0.02)TiO(3), grown via pulsed laser deposition at low temperature and low pressure (450 degrees C, 10(-7) Torr), do not yield similarly high values when grown on other substrates. The thin-film growth induces oxygen reduction in the SrTiO(3) crystals, doping the substrate n type. It is found that the backside resistance of the SrTiO(3) substrates is as low (similar to 12 Omega/square) as it is on the film side after film growth. (C) 2008 American Institute of Physics.