Han Ru-Qi

Improved Resistive Switching Characteristics of Ag-Doped ZrO2 Films Fabricated by Sol-Gel Process

Ag-doped and pure ZrO2 thin films are prepared on Pt/Ti/SiO2/Si substrates by sol-gel process for resistive random access memory application. The highly reproducible resistive switching is achieved in the 10% Ag-doped ZrO2 devices. The improved resistive switching behaviour in the Ag doped ZrO2 devices could be attributed to Ag doping effect on the formation of the stable filamentary conducting paths. In addition, dual-step reset processes corresponding to three stable resistance states are observed in the 10% Ag doped ZrO2 devices, which may be implemented for the application of multi-bit storage.

Simulation of carrier transport in heterostructures using the 2D self-consistent full-band ensemble Monte Carlo method

We demonstrate a two-dimensional (2D) full-band ensemble Monte–Carlo simulator for heterostructures, which deals with carrier transport in two different semiconductor materials simultaneously as well as at the boundary by solving self-consistently the 2D Poisson and Boltzmann transport equations (BTE). The infrastructure of this simulator, including the energy bands obtained from the empirical pseudo potential method, various scattering mechanics employed, and the appropriate treatment of the carrier transport at the boundary between two different semiconductor materials, is also described. As verification and calibration, we have performed a simulation on two types of silicon-germanium (Si-Ge) heterojunctions with different doping profiles—the p-p homogeneous type and the n-p inhomogeneous type. The current-voltage characteristics are simulated, and the distributions of potential and carrier density are also plotted, which show the validity of our simulator.

Monte Carlo simulation of Cu-resistivity

We have developed an optimized model for electron behavior in Cu-line and we have implemented it using Monte Carlo method. Our model takes into account not only four normal scatterings but also the grain boundary scattering and the surface roughness scattering. The model has been tested with different line width and providing a good agreement with both calculated results and ITRS data.

Effects of Conduction Electron Band Structure on Transport of Quantum Dot Systems

We study the effects of the energy band structure of conduction-electron on the transport properties of an interacting quantum dot system. By applying the nonequilibrium Keldysh Green function technique, we show that the finite width of electron band in leads causes the negative differential conductance in some regions of the applied voltage. We also show that the van Hove singularities in the density of states of conduction-electron do not qualitatively change the differential conductance of the system, and hence can be safely ignored. Therefore, the wide band approximation used in the previous investigations is partially justified.

Effect of trapped charge accumulation on the retention of charge trapping memory

The accumulation process of trapped charges in a TANOS cell during P/E cycling is investigated via numerical simulation. The recombination process between trapped charges is an important issue on the retention of charge trapping memory. Our results show that accumulated trapped holes during P/E cycling can have an influence on retention, and the recombination mechanism between trapped charges should be taken into account when evaluating the retention capability of TANOS.

A comparative study of double gate MOSFET with asymmetric barrier heights at source/drain and the symmetric DG-SBFET

Double gate SBFET with asymmetric barrier heights at source/drain and the symmetric DG-SBFET are simulated. A comparative study between them is made. We have found that the DG-ASBFET is more appropriate for LOP and LSPT applications. Furthermore, the DG-ASBFET shows a better scale ability and better immunity to the short channel effects.

Carriers recombination processes in charge trapping memory cell by simulation

We have evaluated the effects of recombination processes in a charge storage layer, either between trapped electrons and trapped holes or between trapped carriers and free carriers, on charge trapping memory cells performances by numerical simulation. Recombination is an indispensable mechanism in charge trapping memory. It helps charge convert process between negative and positive charges in the charge storage layer during charge trapping memory programming/erasing operation. It can affect the speed of programming and erasing operations.

Fabrication and characteristics of high-K HfO2 gate dielectrics on n-germanium

This paper reports that the high-K HfO2 gate dielectrics are fabricated on n-germanium substrates by sputtering Hf on Ge and following by a furnace annealing. The impacts of sputtering ambient, annealing ambient and annealing temperature on the electrical properties of high-K HfO2 gate dielectrics on germanium substrates are investigated. Experimental results indicate that high-K HfO2 gate dielectrics on germanium substrates with good electrical characteristics are obtained, the electrical properties of high-K HfO2 gate dielectrics is strongly correlated with sputtering ambient, annealing ambient and annealing temperature.

Annealing characteristics of ultra-thin high-K HfO2 gate dielectrics

Ultra-thin HfO2 gate-dielectric films were fabricated by ion-beam sputtering a sintered HfO2 target and subsequently annealed at different temperatures and atmospheres. We have studied the capacitance-voltage, current-voltage and breakdown characteristics of the gate dielectrics. The results show that electrical characteristics of HfO2 gate dielectric are related to the annealing temperature. With increase annealing temperature, the largest value of capacitance decreases, the equivalent oxide thickness increases, the leakage current reduces and the breakdown voltage decreases.

Reactive Radiofrequency Sputtering-Deposited Nanocrystalline ZnO Thin-Film Transistors

The structural and electrical properties of ZnO films deposited by reactive radiofrequency sputtering with a metallic zinc target are systematically investigated. While the as-deposited ZnO film is in a poly-crystalline structure when the partial pressure of oxygen (pO2) is low, the grain size abruptly decreases to a few nanometers as pO2 increases to a critical value, and then becomes almost unchanged with a further increase in pO2. In addition, the resistivity of the ZnO films shows a non-monotonic dependence on pO2, including an abrupt transition of about seven orders of magnitude at the critical pO2. Thin-film transistors (TFTs) with the nanocrystalline ZnO films as channel layers have an on/off current ratio of more than 107, an off-current in the order of pA, a threshold voltage of about 4.5 V, and a carrier mobility of about 2cm2/(V?s). The results show that radiofrequency sputtered ZnO with a zinc target is a promising candidate for high-performance ZnO TFTs.