Surface and Electrical Characterization of Bilayers Based on BiFeO 3 and VO 2 .

Thin films of BiFeO 3 , VO 2 , and BiFeO 3 /VO 2 were grown on SrTiO 3 (100) and Al 2 O 3 (0001) monocrystalline substrates using radio frequency and direct current sputtering techniques. To observe the effect of the coupling between these materials, the surface of the films was characterized by profilometry, atomic force microscopy, and X-ray photoelectron spectroscopy. The heterostructures, monolayers, and bilayers based on BiFeO 3 and VO 2 grew with good adhesion and without delamination or signs of incompatibility between the layers. A good granular arrangement and RMS roughness between 1 and 5 nm for the individual layers (VO 2 and BiFeO 3 ) and between 6 and 18 nm for the bilayers (BiFeO 3 /VO 2 ) were observed. Their grain size is between 20 nm and 26 nm for the individual layers and between 63 nm and 67 nm for the bilayers. X-ray photoelectron spectroscopy measurements show a higher proportion of V 4+ , Bi 3+ , and Fe 3+ in the films obtained. The homogeneous ordering, low roughness, and oxidation states on the obtained surface show a good coupling in these films. The I-V curves show ohmic behavior at room temperature and change with increasing temperature. The effect of coupling these materials in a thin film shows the appearance of hysteresis cycles, I-V and R-T, which is typical of materials with high potential in applications, such as resistive memories and solar cells.