Optimized growth and dielectric properties of barium titanate thin films on polycrystalline Ni foils

Barium titanate(BTO) thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition(PAD) technique.The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion.Crystal structures,surface morphologies,and dielectric performance were examined and compared for BTO thin films annealed under different temperatures.Correlations between the fabrication conditions,microstructures,and dielectric properties were discussed.BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with εr～ 400 and tan δ < 0.025 at 100 kHz.The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.     

The influence of thermally assisted tunneling on the performance of charge trapping memory

We evaluate the influence of the thermally assisted tunneling (TAT) mechanism on charge trapping memory (CTM) cell performance by numerical simulation, and comprehensively analyse the effects of the temperature, trap depth, distribution of trapped charge, gate voltage and parameters of TAT on erasing/programming speed and retention performance. TAT is an indispensable mechanism in CTM that can increase the detrapping probability of trapped charge. Our results reveal that the TAT effect causes the sensitivity of cell performance to temperature and it could affect the operational speed, especially for the erasing operation. The results show that the retention performance degrades compared with when the TAT mechanism is ignored.     

Scaling properties of phase-change line memory

Phase-change line memory cells with different line widths are fabricated using focused-ion-beam deposited C-Pt as a hard mask. The electrical performance of these memory devices was characterized. The current-voltage (I-V ) and resistance-voltage (R-V ) characteristics demonstrate that the power consumption decreases with the width of the phase-change line. A three-dimensional simulation is carried out to further study the scaling properties of the phase-change line memory. The results show that the resistive amorphous (RESET) power consumption is proportional to the cross-sectional area of the phase-change line, but increases as the line length decreases.     

实时离子探测器——塑料闪烁体性能的实验研究

利用静电离子加速器对实时离子探测器——塑料闪烁体的特性 (包括灵敏度、动态范围、能量响应, 及空间分辨等)进行了实验研究,并对闪烁体探测器与其他传统的离子探测器的特性进行了比较. 对闪烁体在激光等离子体实验的离子束诊断中的可能应用进行了探讨.塑料闪烁体的应用可满足高重复频率激光等离子体离子加速实验高效率运行的要求,为实验研究提供强有力的支持.     

藏药珠西的化学成分与结构分析

采用X射线荧光(XRF)、电感耦合等离子体发射光谱(ICP-OES)和X射线衍射(XRD)对不同来源藏药珠西中的元素成分和结构组成进行测定,以期揭示其药理作用的物质基础。XRF和ICP-OES分析结果表明,藏药珠西中主要元素为Fe,S和O,及少量的Si,Na,Mg,Al,K,Ni,Ca,Ti等元素。XRD分析表明,藏药珠西中主要存在立方晶系FeS2,此外还含有少量的斜方晶系Fe+3O(OH)等。通过XRF,ICP-OES和XRD分析,获得了藏药珠西的化学成分和结构组成基本数据,为其药理作用物质基础的揭示和质量标准的制定提供了科学依据。     

Geometric phases in qubit-oscillator system beyond conventional rotating-wave approximation

In this work we investigated the geometric phases of a qubit-oscillator system beyond the conventional rotating- wave approximation. We find that in the limiting of weak coupling the results coincide with that obtained under rotating-wave approximation while there exists an increasing difference with the increase of coupling constant. It was shown that the geometric phase is symmetric with respect to the sign of the detuning of the quantized field from the one-photon resonance under the conventional rotating-wave approximation while a red-blue detuning asymmetry occurs beyond the conventional rotating-wave approximation.     

Effect of Cu doping on the magnetic and electrical properties of n=2 Ruddlesden-Popper manganates

A series of polycrystalline Cu-doped n=2 Ruddlesden-Popper manganates La1.2Sr1.8CuzMn（2-x）O7 （x=0, 0.04, 0.13） were synthesized by the solid state reaction method. The effect of Cu doping on the magnetic and transport properties has been studied. It is found that Cu substitution for Mn greatly affects the magnetic and electrical properties of the parent phase La1.2Sr1.8Mn2O7. With the increase of Cu content, the system undergoes a transition from longrange ferromagnetic order to the spin glass state and further to an antiferromagnetic order. A little of Cu dopant can lead to the samples showing semiconductor or insulator behaviour in the whole observed temperature range while the parent phase has a metal-insulator transition. These samples show colossal magnetoresistance at low temperatures and the value of it decreases with increasing Cu content.     

二维椭圆量子台球中的谱分析

研究了二维椭圆台球中的量子谱和经典轨道之间的对应关系.为尝试求解没有解析波函数和本征能量又不能分离变量的体系，采用了定态展开方法(expansion method for stationary states，简称EMSS)得到尽可能精确的数值解，这是闭合轨道理论被推广到计算开轨道的情况.比较了傅里叶变换谱和经典轨道，发现量子谱的峰位置与经典轨道的长度在可分辨的范围内符合得很好，这是半经典理论为经典与量子力学的联系提供桥梁作用的又一个例子. 关键词： 椭圆量子台球 定态展开方法 闭合轨道理论 量子谱     

Three-dimensional Monte Carlo simulation of bulk fin field effect transistor

In this paper,we investigate the performance of the bulk fin field effect transistor(FinFET) through a threedimensional(3D) full band Monte Carlo simulator with quantum correction.Several scattering mechanisms,such as the acoustic and optical phonon scattering,the ionized impurity scattering,the impact ionization scattering and the surface roughness scattering are considered in our simulator.The effects of the substrate bias and the surface roughness scattering near the Si/SiO2 interface on the performance of bulk FinFET are mainly discussed in our work.Our results show that the on-current of bulk FinFET is sensitive to the surface roughness and that we can reduce the substrate leakage current by modulating the substrate bias voltage.     

Monte Carlo simulation of spin-wave excitation for the magnetic films with structure and interaction fluctuations

Monte Carlo simulation studies are performed to examine influence of structure and interaction fluctuations on magnetic properties of a ferromagnetic system modelled with a Heisenberg Hamiltonian. It is found that the spontaneous magnetization at low temperature for the multilayered films decreases with temperature in a Bloch law of spin-wave excitations. Both Bloch coefficient B and exponent b vary evidently because of a strong surface and size effect in the finite magnetic films with free boundaries. For the disordered bulk FCC magnet with periodic boundary, the Bloch T^3/2 law is followed at low temperature and B is greatly influenced by the structure and interaction fluctuations. At the same time, Bloch coefficient B of the amorphous magnet with the coordination and interaction fluctuations has been derived. The simulated results are in good agreement with the theoretical predictions of spin-wave excitation, and explain the experimental facts well.