Modulation of rectifying behaviour by oxygen contents in La _0.5Sr_0.5CoO_3-δ/0.7 wt% Nb-doped SrTiO₃ heterojunctions

Heterojunctions composed of La_0.5Sr_0.5CoO _3-δ and 0.7 wt% Nb-doped SrTiO₃ were deposited at different oxygen partial pressures and display opposite rectifying shapes: the junctions fabricated at a lower oxygen pressure show a backward shape and they gradually display a forward shape by tuning up the oxygen partial pressures. The former tends to form degenerate p-n junctions due to oxygen deficiency, which is responsible for the backward rectifying shape. The latter, however, can be viewed as a Schottky-type diode. The oxygen contents for the junctions can be estimated from their x-ray diffraction patterns, and are also confirmed from their resistance and magnetization measurements.