Polaron transport and thermoelectric behavior in La-doped SrTiO3 thin films with elemental vacancies

TL;DR

This study explores how elemental vacancies and polaron formation influence the thermoelectric properties of La-doped SrTiO3 thin films, revealing a correlation between vacancy-induced polaronic effects and enhanced thermoelectric performance.

Contribution

It demonstrates the impact of controlled elemental vacancies on polaron formation and thermoelectric behavior in La-doped SrTiO3 thin films, providing new insights into defect-engineered thermoelectric materials.

Findings

Increased elemental vacancies correlate with lattice expansion and higher carrier density.

Polaron formation is evidenced by mid-infrared absorption in optical spectra.

Thermopower can be modulated from -120 to -260 μV/K, indicating enhanced polaronic mass.

Abstract

Electrodynamic properties of La-doped SrTiO3 thin films with controlled elemental vacancies have been investigated using optical spectroscopy and thermopower measurement. In particular, we observed a correlation between the polaron formation and thermoelectric properties of the transition metal oxide (TMO) thin films. With decreasing oxygen partial pressure during the film growth (P(O2)), a systematic lattice expansion was observed along with the increased elemental vacancy and carrier density, experimentally determined using optical spectroscopy. Moreover, we observed an absorption in the mid-infrared photon energy range, which is attributed to the polaron formation in the doped SrTiO3 system. Thermopower of the La-doped SrTiO3 thin films could be largely modulated from -120 to -260 {\mu}V K-1, reflecting an enhanced polaronic mass of ~3 < mpolron/m < ~4. The elemental vacancies generated in the TMO films grown at various P(O2) influences the global polaronic transport, which governs the charge transport behavior, including the thermoelectric properties.