Structural, optical, and electrical properties of strained La-doped SrTiO3 films

Abstract

The structural, optical, and room-temperature electrical properties of strained La-doped SrTiO3 epitaxial thin films are investigated. Conductive La-doped SrTiO3 thin films with concentration varying from 5 to 25% are grown by molecular beam epitaxy on four different substrates: LaAlO3, (LaAlO3)0.3(Sr2AlTaO6)0.7, SrTiO3, and DyScO3, which result in lattice mismatch strain ranging from −2.9% to +1.1%. We compare the effect of La concentration and strain on the structural and optical properties, and measure their effect on the electrical resistivity and mobility at room temperature. Room temperature resistivities ranging from ∼10−2 to 10−5 Ω cm are obtained depending on strain and La concentration. The room temperature mobility decreases with increasing strain regardless of the sign of the strain. The observed Drude peak and Burstein-Moss shift from spectroscopic ellipsometry clearly confirm that the La addition creates a high density of free carriers in SrTiO3. First principles calculations were performed to help understand the effect of La-doping on the density of states effective mass as well as the conductivity and DC relaxation time.

Final-state effect on x-ray photoelectron spectrum of nominallyd1andn-dopedd0transition-metal oxides

“…The experimental details are given in Ref. [19]. Keeping states up to four p-h pairs almost reproduces the exact spectrum.…”

“…First, the Ti 3+ peak position is dopant independent and is an intrinsic property of the Ti atom, or more precisely the TiO 6 cluster. Indeed, in lightly n-doped SrTiO 3 , the Ti 3+ peaks all appear in the same position relative to the Ti 4+ peak [17][18][19] (Fig. 5) [47]), demonstrate the XPS spectra showing multiple components.…”

“…In this paper, we reexamine the origin of the multi-peak structure in the XPS spectra of nominally d 1 transition metal oxides including NbO 2 , SrVO 3 [16], and LaTiO 3 , as well as that of lightly n-doped d 0 SrTiO 3 (STO) [17][18][19],…”

Quasi-two-dimensional electron gas at the epitaxial alumina/SrTiO3 interface: Control of oxygen vacancies

“…More details of the experimental system can be found elsewhere. 35,36 All substrates were outgassed in the MBE chamber at 700 for 30 min under ultra-high vacuum (UHV) prior to alumina deposition. The substrate temperature was measured by a thermocouple (calibrated by pyrometer measurement of a silicon substrate) in close proximity to the substrate heater.…”

Oxide Materials at the Two-Dimensional Limit

“…More details of the experimental system can be found elsewhere. [87,161] All substrates were outgassed in the MBE chamber at 700° for 30 min under ultra-high vacuum (UHV). The substrate temperature was measured by a thermocouple (calibrated by pyrometer measurement of a silicon substrate) in close proximity to the substrate heater.…”