Electronic transport behavior of off-stoichiometric La and Nb doped SrxTiyO3−δ epitaxial thin films and donor doped single-crystalline SrTiO3

Abstract

Above room temperature electronic transport properties of SrxTiyO3−δ films with cation A/B = (La + Sr/Nb + Ti) ratios of 0.9 to 1.2 are compared to STO single crystals with combined Hall carrier densities of 3 × 1016 cm−3 ≤ nH ≤ 1022 cm−3. In contrast to Hall mobility which is single crystal-like (μH ≈ 6 cm2/Vs) only near A/B = 1, the Seebeck coefficient (S) is single crystal-like over a range of nonstoichiometry. For nH < 1020 cm−3, S is well described by nondegenerate band-like transport with a constant effective mass m∗/mo ≈ 5–8. For nH > 1021 cm−3, S is metallic-like with m∗/mo ∼ 8. No marked increase in m∗ with decreasing nH owing to a carrier filling dependence is observed.