Manipulating Electrical Properties of Nanopatterned Double-Barrier Schottky Junctions in Ti/TiO _x /Fe Systems

This work characterizes the transport properties of double-barrier Schottky junctions with nanopatterned titanium oxide as a semiconductor. Nanoporous titanium oxide thin films with varying pore diameters are created by using electrochemical anodization. These films are then covered with a 50 nm thick iron layer, forming patterned Ti/TiOx/Fe junctions. SEM images confirm the nanoporous morphology of the titanium oxide, while XRD measurements show that the junctions are polycrystalline, with multiple phases of titanium oxide formed after annealing. UV-vis spectroscopy verifies the semiconducting nature of the titanium oxide, revealing a band gap of 2.3 eV. The I-V characteristics demonstrate nearly linear behavior, but deviations from Ohmic dependence occur when calculating the differential resistance. Interestingly, the pore diameter strongly influences the differential resistance at low temperatures. The magnetoresistance (MR) of the junctions exhibits different signs: positive values at room temperature and negative values at 5 K for all samples. Nanopatterning enhanced this effect. Detailed characterization uncovers that the positive MR originates from the titanium/titanium oxide interface, while the negative MR arises from the titanium oxide/iron interface regardless of temperature. The change in the MR sign is attributed to the different temperature dependences of the individual junctions, namely, Ti/TiOx and TiOx/Fe.