Ultrathin junctions based on the LaSrMnO3/Nb:SrTiO3 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 current-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.

Low noise all-oxide magnetic tunnel junctions based on a La0.7Sr0.3MnO3/Nb:SrTiO3 interface

“…There are several invaluable features of the Nb:STO insulator that acts as a tunnelling barrier for electrons. 7 First, the magneto-resistance versus magnetic field curve ( Fig. 1(c)) demonstrates the typical TMR behaviour observed in junctions with an undoped STO insulator.…”

“…5 In contact with LSMO, Nb:STO forms a metalsemiconductor interface, providing a structure similar to a Schottky junction. 6,7 Thus, a different type of STO-based tunnel junction arises: MTJ with a double Schottky barrier instead of the conventional insulating tunnel barrier. The use of a semiconducting barrier can be traced back to the pioneering work of M. Jullière.…”

Rectifying Characteristics of the Perovskite Oxide La1−xSrxMnO3/Nb‐0.7 wt%‐Doped SrTiO3 Heterojunction

“…The Coulomb repulsion energy ( U = 4 eV) and the exchange interaction ( J = 1 eV) came from ref. [33]. An energy cutoff of 400 eV and a 4 × 4 × 4 Monkhorst–Pack k‐point grid were adopted.…”

“…The Schottky barrier height (SBH) φ b can be extracted by fitting the data with the well‐known expression of the thermionic emission current density. [ 33–35 ]…”

“…[ 25–28 ] As shown in Figure a, the energy band diagram can be used to explain the change in depletion. [ 33 ] In general, there is a dead layer between the manganite thin film and the substrate. The dead layer has a highly disordered lattice structure and exhibits high resistance as the current flows through the dead layer.…”