TY  - JOUR
AU  - De Souza, R. A.
AU  - Gunkel, F.
AU  - Hoffmann-Eifert, S.
AU  - Dittmann, R.
TI  - Finite-size versus interface-proximity effects in thin-film epitaxial $SrTiO_3$
JO  - Physical review / B
VL  - 89
IS  - 24
SN  - 1098-0121
CY  - College Park, Md.
PB  - APS
M1  - FZJ-2014-04651
SP  - 241401
PY  - 2014
AB  - The equilibrium electrical conductivity of epitaxial SrTiO3 (STO) thin films was investigated as a function of temperature, 950≤ T/K ≤1100, and oxygen partial pressure, 10−23≤ pO2/bar ≤1. Compared with single-crystal STO, nanoscale thin-film STO exhibited with decreasing film thickness an increasingly enhanced electronic conductivity under highly reducing conditions, with a corresponding decrease in the activation enthalpy of conduction. This implies substantial modification of STO's point-defect thermodynamics for nanoscale film thicknesses. We argue, however, against such a finite-size effect and for an interface-proximity effect. Indeed, assuming trapping of oxygen vacancies at the STO surface and concomitant depletion of oxygen vacancies—and accumulation of electrons—in an equilibrium surface space-charge layer, we are able to predict quantitatively the conductivity as a function of temperature, oxygen partial pressure, and film thickness. Particularly complex behavior is predicted for ultrathin films that are consumed entirely by space charge.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000336917700001
DO  - DOI:10.1103/PhysRevB.89.241401
UR  - https://juser.fz-juelich.de/record/155485
ER  -