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The electric gating on the transport properties of two-dimensional electron gas (2DEG) at the interface of LaAlO3/SrTiO3 (LAO/STO) heterostructure has attracted great research interest due to its potential application in field-effect devices. Most of previous works of gate effect were focused on the LAO/STO heterostructure containing only one conductive interface. Here, we systematically investigated the gate effect on high-quality LAO/STO superlattices (SLs) fabricated on the TiO2-terminated (001) STO substrates. In addition to the good metallicity of all SLs, we found that there are two types of charge carriers, the majority carriers and the minority carriers, coexisting in the SLs. The sheet resistance of the SLs with a fixed thickness of the LAO layer increases monotonically as the thickness of the STO layer increases. This is derived from the dependence of the minority carrier density on the thickness of STO. Unlike the LAO/STO heterostructure in which minority and majority carriers are simultaneously modulated by the gate effect, the minority carriers in the SLs can be tuned more significantly by the electric gating while the density of majority carriers is almost invariable. Thus, we consider that the minority carriers may mainly exist in the first interface near the STO substrate that is more sensitive to the back-gate voltage, and the majority carriers exist in the post-deposited STO layers. The SL structure provides the space separation for the multichannel conduction in the 2DEG, which opens an avenue for the design of field-effect devices based on LAO/STO heterostructure.

Temperature dependence on rectifying and photoelectronic properties of La0.67Sr0.33MnO3/Nb:SrTiO3 (LSMO/STON) junctions with the thickness values of LSMO film varying from 1 nm to 54 nm are systematically studied. As shown experimentally, the junctions exhibit good rectifying properties. The significant differences in photoemission property among the LSMO/STON junctions are observed. For the junction in a thicker LSMO film, the photocurrent shows a monotonic growth when temperature decreases from 300 K to 13 K. While for the junction in an ultrathin LSMO film, the behaviors of photocurrent are more complicated. The photocurrent increases rapidly to a maximum and then smoothly decreases with the decrease of temperature. The unusual phenomenon can be elucidated by the diffusion and recombination model of the photocarrier.

The anisotropic transport property was investigated in a phase separation La0.67Ca0.33MnO3 (LCMO) film grown on (001)-oriented NdGaO3 (NGO) substrate. It was found that the resistivity along the b-axis is much higher than that along the a-axis. Two resistivity peaks were observed in the temperature dependent measurement along the b-axis, one located at 91 K and the other centered at 165 K. Moreover, we also studied the response of the resistivities along the two axes to various electric currents, magnetic fields, and light illuminations. The resistivities along the two axes are sensitive to the magnetic field. However, the electric current and light illumination can influence the resistivity along the b-axis obviously, but have little effect on the resistivity along the a-axis. Based on these results, we believe that an anisotropic-strain-controlled MnO6 octahedra shear-mode deformation may provide a mechanism of conduction filaments paths along the a-axis, which leads to the anisotropic transport property.