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Ferrimagnetic magnetite, Fe3O4, is a self-doped highly conductive oxide demonstrating p-type coductivity. Due to high Curie temperature value (Tc 858 K) and almost 100% of spin-polarized carriers it is one of the most promising oxide materials for room temperature spintronics applications. For fabrication of various devices, there is increasing interest in heterostructures and possible p-n structures containing Fe3O4. In this work, we report preparation and investigation of three different p-n heterostructures based on Fe3O4 thin films grown on electronically doped Si(001) and SrTiO3(001) <0.01 of Nb> single crystal substrates as well as highly conducting indium tin oxide In2O3:Sn (ITO) underlayers. The Fe3O4 thin films with thickness ranging from about 0.1 to 0.3 m were grown in situ at 400 K by dc magnetron sputtering while the ITO films were magnetron sputtered onto lattice-matched monocrystalline ZrO2:Y2O3(100). As far as both ITO and Fe3O4 exhibit high carrier density, the intermediate In2O3 (IO) layer was introduced in order to reduce carrier density at the interface and to reveal rectifying electrical properties of the heterostructures. Microstructure of the films was studied by means of X-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED) techniques. Composition of the prepared p-Fe3O4/(IO)ITO, p-Fe3O4/n-Si and p-Fe3O4/n-SrTiO3:Nb heterostructures was investigated by X-ray Photoelectron Spectroscopy (XPS). Transport properties of the films were measured at 78÷300 K by applying standard four point-probe method while the interface resistance and current versus voltage (I-U) dependencies of the heterostructures were measured by applying either four or three point-probe method (with current flowing through the interface between p- and n-type materials). Significant nonlinearity and asymmetry of the current-voltage characteristics (in a forward and reverse directions) were indicated for the heterostructures at low temperatures (T 150 K). |