We investigated the resistive switching characteristics of Au/Ar+bombarded SrTi 0.993 Nb0.007O3/In sandwiches.The evolution of the resistive switching polarity with sweeping voltage was observed.Our experiments showed that under a macroscopic electrode the homogeneous trapping-detrapping-type conduction and filament-type conduction coexist and compete with each other.For a large sweeping voltage range,the trapping-detrapping-type conduction dominates.However,for a small range the latter dominates. If the bias voltage is too large,the filament conduction could be destroyed.These results will help deepen the understanding of the resistive switching polarity,and will aid in future device design.
The oxygen adsorption can drastically alter the electronic properties of the two-dimensional(2D)materials,which is usually dificult to be removed.In this work,we report the ultraviolet(UV)ilumination induced desorption of the O2 molecules from the monolayer MoS2 surface by using the atmosphere dependent transport measurement,Kelvin probe microscopy,photoluminescence spectroscopy and X-ray photoelectron spectroscopy.Obvious increasing of the conductivity,rising of the Fermi level,and red shift of the photoluminescence peaks of the MoS2 were observed after the UV ilumination in vacuum,indicating the elimination of the depletion effect from the oxygen adsorption.Such parameter changes can be reversibly recovered by the subsequent O2 exposure.Furthermore,obvious decreasing of the oxygen concentration after the UV ilumination was also observed by X-ray photoelectron spectroscopy.Thus the UV induced O2 photodesorption effect is evidenced.The photo-excited charge transfer mechanism is proposed to account for the photodesorption effect.These results provide a nondestructive way to clean the MoS2 surface and manipulate the performance of the MoS2 based devices.
Spinel vanadates possess rich physics arising from the interaction among spin,orbital and lattice degrees of freedom.We report the dielectric properties of polycrystalline Fe1.8V1.2O4.A thermally activated dielectric relaxation appeared in low temperature due to the inhomogeneous conductivity between grains and grain boundaries.We found an artificial ferroelecticity in this sample.An abnormal frequency-independent dielectric peak appeared at room temperature when the samples were measured during warming in ambient air.However,this peak disappeared in the following cooling process.By dielectric frequency spectrum and equivalent circuit analysis in detail,we found the sample had a surface layer in warming but not in cooling process.We also confirmed that this surface layer was induced by the adsorption of water,which is responsible for the dielectric peak.
