Ultrathin junctions based on the LaSrMnO$_3$/Nb:SrTiO$_3$ functional oxide interface

Abstract : High-quality all-oxide thin film metal–semiconductor junctions, fabricated of a half-metallic ferromagnet La$_{0.7}$ Sr$_{0.3}$ MnO$_3$ and of a niobium doped n-type semiconductor SrTiO$_3$ (SrTi$_{0.8}$Nb$_{0.2}$O$_ 3$) by pulsed laser deposition, were studied in terms of their electronic transport properties in a wide temperature range. A fabrication process for ultrathin film metal–semiconductor junctions with micrometre-sized mesas has been established. The cur-rent–voltage characteristics of the junctions were found at variance with the conventional thermionic emission theory often applied to explain the transport properties of Schottky contacts. This discrepancy is tentatively ascribed to the very high electric field in the ultrathin SrTi$_{0.8}$Nb$_{0.2}$O$_ 3$ layer and its effect on carrier depletion and dielectric constant.