Papers by Author: Xiao Min Li

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Authors: Rui Dong, Qun Wang, Li Dong Chen, Xiao Min Li
Abstract: A simple chemical solution deposition method was developed for the preparation of La0.7Ca0.3MnO3 (LCMO) thin films. The LCMO thin films were prepared on Si/SiO2/TiO2/Pt substrates by spin-coating method, followed by heat-treatment at 900°C. The fabrication process of the LCMO thin film was investigated by means of TG-DSC, FTIR, XRD, FE-SEM and EPMA. The electric pulse induced reversible resistance switching is observed in the Ag-LCMO-Pt sandwich structure.
Authors: Qun Wang, Rui Dong, Li Dong Chen, Tong Lai Chen, Xiao Min Li
Abstract: A novel electric-pulse-induced reversible resistance (EPIR) change effect was observed in Ag/Ln1-xCaxMnO3/Pt (Ln= Pr, La) sandwich structure at room temperature without applied magnetic field. The Ln1-xCaxMnO3 films were grown on Pt/Ti/SiO2/Si substrate. The resistance of the Ag/Ln1-xCaxMnO3/Pt sandwich structure increases and reaches at a saturated high resistance state after applying a certain number of electric-pulse from Pt bottom electrode to Ln1-xCaxMnO3 layer, while it decreases and switches to a saturated low resistance state when the pulse polarity reversed. It is also found that the EPIR effect in the /Ln0.7Ca0.3MnO3/Pt system exhibits “fatigue” behavior, that is, for the high resistance state activated by electric-pulse, along the time after pulsing, the resistance decreases slowly after a certain stable stage; otherwise, the resistance change ratio decreases as the number of the high-low resistance switching circle increases. For the fatigue phenomenon with time, a resistance change with three stages was observed and a simple mechanism of the EPIR was proposed.
Authors: X. Cao, Xiao Min Li, Wei Dong Yu, Rui Yang, Xin Jun Liu
Abstract: Polycrystalline NiO thin films were fabricated on Pt (111)/Ti/SiO2/Si substrates by thermal oxidation of the evaporated Ni films. Pt/NiO/Pt structures were prepared, and they showed reversible resistance switching behaviors. When the compliance set current was varied from 5 mA to 40 mA, the on-state currents increased, while the on-state resistances decreased. It is probably attributed to higher current compliance resulted in the formation of stronger and less resistive filaments, which in turn need more energy and power for their rupture. The resistive switching in NiO thin films is closely related to the formation and rupture of conducting filaments.
Authors: Ji Ming Bian, Xiao Min Li, Xiang Dong Gao, Wei Dong Yu
Abstract: Ultrasonic spray pyrolysis has been applied to deposit MgO thin films on Si(100) and quartz glass substrate. The microstructures and properties of the as-grown MgO thin films were examined by X-ray diffraction, scanning electron microscopy, spectrophotometer and semiconductor resistivity meter. The results indicates that the MgO thin films deposited under optimal conditions shows smooth and dense surface without visible pores or defects over the substrate, and as well as good thickness uniformity. Almost completely (100)-oriented MgO films with the transmission higher than 90% in UV/VIS region and the resistivity at least in the order of 107Ω-cm were obtained. MgO thin film with such a crystal quality seems to be very suitable for acting as a buffer layer for the subsequent epitaxial growth of films.
Authors: Xiao Min Li, Jian Ling Zhao, Ji Ming Bian, Wei Dong Yu
Abstract: ZnO thin films were grown on single-crystal Si(100) substrate by pulsed laser deposition (PLD) technique. The crystal structure and electrical properties were investigated as a function of oxygen partial pressure. Results indicate that highly c-axis oriented ZnO films can be obtained at all oxygen pressure range. With the increase of oxygen pressure, the crystallinity is further enhanced and the film presents smooth, uniform and dense packed columnar microstructure. Hall measurement indicates the resistivity of ZnO films increases with oxygen pressure. ZnO film grown at optimum conditions is employed to fabricate the MSM structured UV detectors with Ti/Pt/Au interdigital electrode configuration by standard photolithography and lift-off technique. The I-V characteristic and photo response measurement indicate a good ohmic contact between the ZnO film and electrode, and significant photoresponsivity under ultraviolet illumination.
Authors: Wei Dong Yu, Xiao Min Li, Yi Wen Zhang, Rui Yang, Qun Wang, Li Dong Chen
Abstract: A noncrystalline SrTiO3 (STO) thin film was grown on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. The Pt thin film was deposited on STO film as top electrode, forming a symmetric structure (Pt/STO/Pt) to exclude the influence of the electrical difference in STO-electrode interfaces. It was found that a stable bipolar resistive switching was obtained in this structure. In a current sweep, an obvious S type negative differential conductance (NDC) phenomenon was found in both polarities. And in a voltage sweep, no NDC was observed due to the current control mechanism of S type NDC effect. The possible mechanism of this effect is discussed preliminarily.
Authors: Tong Lai Chen, Xiao Min Li
Abstract: Atomic-scale smooth Pt electrode films have been deposited on MgO/TiN buffered Si (100) by the pulsed laser deposition (PLD) technique. The whole growth process of the multilayer films was monitored by using in-situ reflection high energy electron diffraction (RHEED) apparatus. The Pt/MgO/TiN/Si(100) stacked structure was also characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). The HREED observations show that the growth mode of the Pt electrode film is 2D layer-by-layer growth. It is found that the (111)-oriented Pt electrode film has a crystallinity comparable to that of monocrystals. The achievement of the quasi-single-crystal Pt electrode film with an atomic-scale smooth surface is ascribed to the improved crystalline quality of the MgO film.
Authors: Yi Wu, Chuan Qiang Yin, Zheng Guang Zou, Xiao Min Li, Yu Fang Shen, Lang Zhou
Abstract: Steel-bonded cemented carbide GT35 was fabricated from natural ilmenite by in-situ synthesis and vacuum pressureless sintering. The thermodynamics of the synthesis process were analyzed. The results indicated that the stable phases were TiC and iron in the FeTiO3-C system. During the synthesis process, ilmenite was reduced by graphite via a series of titanium oxides to obtain hard phase (TiC) and the steel matrix as the ultimate products. The experimental results shown that GT35 had a reasonable phase composition and fine TiC particles embedded uniformly in the steel matrixes. The composites exhibited excellent mechanical properties: the relative density was higher than 97%, the hardness reached HRC 61.5 and the maximal bending strength was about 1270MPa.
Authors: Rui Yang, Xiao Min Li, Wei Dong Yu, Xin Jun Liu, Q. Wang
Abstract: A series of La0.7Ca0.3MnO3 films are fabricated by pulsed laser deposition under controlling the oxygen partial pressure or adding an oxygen post-annealing process. The film after oxygen post-annealing shows an orientation change and has more non-lattice oxygen near the surface than those of the films without annealing. Moreover, only the structure of Ag/La0.7Ca0.3MnO3/Pt with the oxygen annealed film behaves a big current-voltage hysteresis and stable resistance switching properties by applying voltage pulse. Experimental results indicate that the increase of non-lattice oxygen content induced by oxygen annealing in the vicinity of the Ag/La0.7Ca0.3MnO3 interface contributes to the occurrence of resistance switching. And with the accurate controlling of the oxygen annealing parameters, the improvement of resistance switching property of the La0.7Ca0.3MnO3 film can be expected.
Authors: Fang Peng, Xiao Min Li, Xiang Dong Gao
Abstract: Zinc oxide films have been deposited on ITO/glass substrate by a two-step electrodeposition method from zinc nitrate aqueous solution. The two-step electrodeposition process included a potentiostatic pre-deposition and a galvanostatic deposition. Obtained ZnO film possesses high c-axis preferential orientation, smooth and compact morphology, high transmittance in the visible band, and optical band gap of 3.43eV. Compared with the film prepared by direct galvanostatic deposition, the crystalline quality and optical properties of ZnO films were significantly improved.
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