Xinan Zhang

Coexistence of the bipolar and unipolar resistive switching behaviours in Au/SrTiO3/Pt cells

The bipolar and unipolar resistive switching (BRS and URS) modes are first observed to coexist in the Au/SrTiO3/Pt cell fabricated by pulsed laser deposition. These two switching modes can be activated separately depending on the different current compliance (CC) during the electroforming process: with a lower CC (1 mA) the asymmetric BRS behaviour is measured in the voltage range −1.2 to +1 V, while the URS behaviour is observed with a higher CC (10 mA). On the basis of current–voltage characteristics, the switching mechanisms for the BRS and URS modes are considered as a change in Schottky-like barrier height and/or width at the Au/SrTiO3 interface and the formation and disruption of conduction filaments, respectively. The conversion between BRS and URS is reversible. Because each switching mode has a specific advantage, selecting the desired switching mode can broaden the application scope of the cell and enable large flexibility in terms of memory architecture.

Study on Resistance Switching Properties of Na0.5Bi0.5TiO3Thin Films Using Impedance Spectroscopy

The Na0.5Bi0.5TiO3(NBT) thin films sandwiched between Au electrodes and fluorine-doped tin oxide (FTO) conducting glass were deposited using a sol–gel method. Based on electrochemical workstation measurements, reproducible resistance switching characteristics and negative differential resistances were obtained at room temperature. A local impedance spectroscopy measurement of Au/NBT was performed to reveal the interface-related electrical characteristics. The DC-bias-dependent impedance spectra suggested the occurrence of charge and mass transfer at the interface of the Au/NBT/FTO device. It was proposed that the first and the second ionization of oxygen vacancies are responsible for the conduction in the low- and high-resistance states, respectively. The experimental results showed high potential for nonvolatile memory applications in NBT thin films.

Bottom-gate amorphous In2O3 thin film transistors fabricated by magnetron sputtering

In this letter, bottom-gate thin film transistors using amorphous In2O3 as the n-channel active layer were fabricated on SiO2/Si substrates by direct current magnetron sputtering at room temperature. By controlling the sputtering time, In2O3 can be grown into the amorphous phase. Compare to its crystalline counterpart, amorphous In2O3 offer distinctive attractions such as smoother surfaces, better film uniformity, while maintaining comparable or greater carrier mobility. The device with amorphous channel layer shows good performance with the mobility of 15 cm2/Vs and the current on-off ratio of 106. The device operates in enhancement mode with the threshold voltage of 1.4 V. Excellent device performance and low fabrication temperature make the In2O3-TFTs suitable for the potential applications in the large-area electronics.

Fabrication and characterization of thin-film transistors with SnO2 channel by spray pyrolysis

Bottom-gate thin-film transistors with a SnO2 channel layer were fabricated on thermally oxidized silicon wafer. SnO2 films were deposited by a simple and low-cost spray pyrolysis technique with stannic chloride as the precursor. The films were structurally characterized by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). The results revealed that the thin films were amorphous in nature. Electrical measurement revealed that the devices exhibited excellent saturation and pinch-off characteristics. The saturation mobility of about 0.37 cm2 V−1 s−1, current on–off ratio of 106, threshold voltage of −2 V, and subthreshold voltage swing of 2 V/dec have been determined.

High-Performance Indium Oxide Thin Film Transistor with ITO Source/Drain Electrodes Fabricated by Reactive Sputtering

We report on the fabrication of bottom gate thin film transistors with indium oxide (In2O3) thin films as the active channel layers. The films were deposited on SiO2/Si substrate at room temperature by direct current (DC) magnetron sputtering. The ITO films were used as source and drain electrodes. The In2O3 films were structurally characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The results revealed that the films were amorphous in nature. Electrical measurement has revealed that the devices operate as an n-channel enhancement mode and exhibit an on/off ratio of 106. The threshold voltage is-3V and the channel mobility on the order of 22.3 cm2/Vs has been determined.