用纵向振动法测量弹性模量的实验装置

把待测样品制备成细长棒,受到一定拉力时细长棒有一定伸长,这可等效为弹簧,通过测量由细长棒与质量块构成的振子的固有频率可准确测量劲度系数,若测得了其劲度系数即可得该材料的弹性模量.基于以上思路设计了纵向振动法测量弹性模量的实验装置,使弹性模量测量实验既保留了光杠杆法物理概念清晰的优点,又吸取了振动法的长处.     

相对湿度对磁场下45钢摩擦学性能与表面氧化的影响

电磁制动和电磁弹射是典型磁场条件下的摩擦学系统.相对湿度对其摩擦学性能和摩擦稳定性有重要影响.本文中研究了湿度对磁场下45钢自配副的摩擦磨损性能的影响，通过摩擦表面形貌演化分析了摩擦机理和磨损机制的转变，利用能量色散光谱仪(EDS)和X射线光电子能谱仪(XPS)表征了摩擦表面铁元素的氧化程度和氧化形式.结果表明：随着湿度增加，磁场下45钢自配副的摩擦系数单调增加，磨损率先增加后减少，30%RH为转变点；10%～70%RH范围内随湿度增加，摩擦表面的氧化程度升高，氧铁比变化率下降，表面Fe²⁺占比增大，OH^-占比减小；70%RH时铁氧化物的水合物析出，氧的存在形式由OH^-向FeO_x·H₂O转化.     

Kr—O2相互作用势研究

利用量子力学方法的ＩＯＳＡ近似，通过对Ｋｒ－Ｏ２混合气体中Ｏ２的碰撞驰豫截面的理论计算值与实验值比较，考察了四组Ｋｒ－Ｏ２相互作用等效势模型参数，发现新近的势阱深度和势阱位置较好地反映了Ｋｒ－Ｏ２相互作用的客观情况，可用于进一步的计算中     

Observation of Electromagnetically Induced Transparency in a Zeeman—Sublevel System in Rubidium Atomic Vapour

We observed electromagnetically induced transparency (EIT) in a Zeeman-sublevel system using rubidium atomic vapour at the temperature of 75~C, in which the width of the EIT signal is only 0.6 MHz. Two different methods were performed to observe the EIT signal in our experiment.     

外加静电场下激光诱导等离子体特性的实验研究

在外加静电场下，准分子激光诱导等离子体中Ｍｇ原子５５２．８４、５１６．７３、４７０．３０ｎｍ三条发射谱线展宽的时间分辨特性的实验研究，实验测定结果表明，外加静电场导致了原子发射谱线展宽超过Ｓｔａｒｋ展宽，这种额外展宽的大小在０．１ｎｍ左右，其中４７０．３ｎｍ谱线的加宽和线移最大，采用量子理论计算表明这种额外展宽是由于在外电场中作用下作定向运动的电子与激发态原子碰撞所致。     

S在Cu(111)表面吸附的第一性原理研究

基于广义梯度近似的投影缀加平面波(Projector augmented wave)赝势和具有三维周期性边界条件的超晶胞模型,采用第一原理方法计算并分析了由S吸附所形成的S/Cu(111)界面体系的吸附结构、吸附能和局域电子结构,考虑了不同覆盖度(1,0.25 ML)下S在不同吸附位置的吸附特性.结果表明:S原子倾向于...     

Migration of weakly bonded oxygen atoms in a-IGZO thin films and the positive shift of threshold voltage in TFTs

Amorphous indium-gallium-zinc oxide (a-IGZO) thin films are prepared by pulsed laser deposition and fabricated into thin-film transistor (TFT) devices. In-situ x-ray photoelectron spectroscopy (XPS) illustrates that weakly bonded oxygen (O) atoms exist in a-IGZO thin films deposited at high O₂ pressures, but these can be eliminated by vacuum annealing. The threshold voltage (V_th) of the a-IGZO TFTs is shifted under positive gate bias, and the V_th shift is positively related to the deposition pressure. A temperature variation experiment in the range of 20 K-300 K demonstrates that an activation energy of 144 meV is required for the V_th shift, which is close to the activation energy required for the migration of weakly bonded O atoms in a-IGZO thin films. Accordingly, the V_th shift is attributed to the acceptor-like states induced by the accumulation of weakly bonded O atoms at the a-IGZO/SiO₂ interface under positive gate bias. These results provide an insight into the mechanism responsible for the V_th shift of the a-IGZO TFTs and help in the production of reliable designs.     

A Low-Pump-Threshold High-Repetition-Rate Intracavity Optical Parametric Generator Based on Periodically Poled Lithium Niobate

A low-pump-threshold high-repetition-rate intracavity optical parametric generator （IOPG） by using a periodically poled lithium niobate （PPLN） is reported. The PPLN, which is 18.7mm long and has a grating period of 28.93tzm at room temperature, is inserted in a diode-end-pumped Nd：YV04 laser with an acousto-optic Q switch. The parametric generation threshold is 1.3 W （diode laser power） at a Q-switch repetition rate of 19 kHz. At an incident diode pump power of 5 W, an average signal output power of 280mW has been achieved. The signal pulse duration is approximately 85 ns. By changing the crystal temperature from 120℃ to 250℃, the signal wavelength can be tuned from 1.493μm to 1.538μm.     

“听到光”实验

用交变光波照射一个半涂黑玻璃瓶,可听到瓶中发声.其物理原因是交变光能激发了瓶中的一个声波共振模.     

锐钛矿相和金红石相Nb:TiO_2电学性质的GGA(+U)法研究

采用基于密度泛函理论第一性原理GGA和GGA+U相结合的方法研究了不同掺杂浓度下锐钛矿相和金红石相Nb:TiO2的晶体结构、电子结构以及稳定性.结果表明:锐钛矿相Nb:TiO2能带结构与简并半导体类似,呈类金属导电机理.金红石相Nb:TiO2呈半导体导电机理.Nb原子比Ti原子电离产生出更多的电子.锐钛矿相Nb:TiO2中Nb原子的电离率比金红石相Nb:TiO2的大.以上结果说明锐钛矿相Nb:TiO2比金红石相Nb:TiO2更适宜用作TCO材料;掺杂浓度对其杂质能级,费米能级和有效质量都有影响.Nb原子掺杂浓度越高,材料电离率呈降低趋势;形成能计算结果显示:在富钛条件下不利于Nb原子的掺杂,而在富氧条件下有利于Nb原子的掺杂.对于金红石相和锐钛矿相Nb:TiO2,不论是在贫氧或富氧条件下,随着Nb原子掺杂浓度的提高,形成能均增大.