Anomalously large measured thermoelectric power factor in Sr$_{1-x}$La$_x$TiO$_3$ thin films due to SrTiO$_3$ substrate reduction

TL;DR

This study reveals that La-doped SrTiO3 thin films grown on SrTiO3 substrates exhibit exceptionally high thermoelectric power factors at 300K due to substrate reduction and doping effects, unlike films on other substrates.

Contribution

It demonstrates that substrate reduction during growth significantly enhances thermoelectric properties of SrTiO3 films, a novel insight into substrate-film interactions affecting thermoelectric performance.

Findings

High thermopower and power factor observed at 300K.

Substrate reduction induces n-type doping in SrTiO3.

Low backside resistance indicates substrate doping effect.

Abstract

We report the observation that thermoelectric thin-films of La-doped SrTiO3 grown on SrTiO3 substrates yield anomalously high values of thermopower to give extraordinary values of power factor at 300K. Thin-films of Sr0.98La0.02TiO3, grown via pulsed laser deposition at low temperature and low pressure (450C, 10-7Torr), do not yield similarly high values when grown on other substrates. The thin-film growth induces oxygen reduction in the SrTiO3 crystals, doping the substrate n-type. It is found that the backside resistance of the SrTiO3 substrates is as low (~12ohm/square) as it is on the film-side after film growth.