冉绍尔-汤森效应及其电流电压关系

电子流在与气体闸流管中稀有气体作用时,出现经典理论无法解释的冉绍尔-汤森效应,即气体散射截面和电子速度有关.研究了此过程中几何因子、散射概率和总散射截面随电子速度的变化规律,验证了冉绍尔-汤森效应.探究了实验中出现的阴极电流和加速电压偏离二分之三关系的现象,利用排除法确定了可能的原因:经典Drude模型无法较好地描述电子和气体的碰撞.     

Transient Hole Trapping in Individual GeSi Quantum Dot Grown on Si（001） Studied by Conductive Atomic Force Microscopy

Electrical properties of individual self-assembled GeSi quantum dots grown on Si substrates are investigated by using conductive atomic force microscopy at room temperature. By controlling the bias voltage sweep in a certain fast sweep rate range, a novel current peak is observed in the current-voltage characteristics of the quantum dots. The current peaks are detectable only during the backward voltage sweep immediately after a forward sweep. The current peak position and intensity are found to depend strongly on the voltage sweep conditions. This kind of current-voltage characteristic under fast sweep is very different from the ordinary steady state current behaviour of quantum dots measured previously. trapping in the potential well formed bottom Si substrate. The origin of this phenomenon by the quantum dot sandwiched can be attributed to the transient hole between the native oxide layer and the     

Degenerate Four-Wave Mixing in SO2 in Free Jets

A rotational excitation spectrum of SO2 [^-A^1A2(511)←^-X^1A1(000)] at about 33331cm^-1 in free jets was observed by using the forward degenerate four-wave mixing (DFWM).Twelve lines of the G band and 11 ones of the E band were marked based on the rotational constants according to Hamada‘s result [Can.J.Phys.53(1975)2555].The relation between the DFWM signal intensity and the pressure of the buffer gas in free-jets was experimentally investigated.     

外加气体对碘的简并四波混频的影响

研究了入射激光能量密度,外加气体(N~2,CO~2,NO~2)对碘的简并四波混频(DFWM)光谱和信号强度的影响,测定了I~2的DFWM信号的饱和强度与外加气体压强之间的关系。结果表明外加气体对I~2的DFWM光谱结构的影响不大,但对信号强度的影响较大,而且与激光能量密度有关。I~2的DFWM信号的饱和强度(I~s~a~t)与N~2压强(p)之间的关系为I~s~a~t∝p^0^.^7。当激光能量密度足够大时,外加气体对信号的增强作用是热光栅所产生的。     

离子束溅射致Si(110)表面形貌随样品温度变化的演化

本文研究了离子能量为1.5keV、束流密度为20?A/cm2正入射Ar+离子束溅射致Si(110)表面形貌随样品温度变化的演化过程。在温度自室温上升至 800?C的过程中, Si(110) 的表面形貌由不规则的纳米点和纳米孔图案变为密集的量子点阵列，同时表面粗糙度也随温度上升不断增加。被通常采用的 Bradley-Harper 模型无法解释上述实验数据。 在考虑溅射过程中存在Ehrlich-Schwoebel 效应后, 进行了已连续动态模型为基础的理论模拟，模拟工作很好的重复了实验结果。     

Ion-Sputter-Induced Nanodots on Si（110）： Ion Energy Dependence

Nanodot arrays were formed on Si(110) surface under normal-incident Ar ion sputtering at substrate temperature of 800℃ The ion flux was 20μA/cm^2, and the ion energies were 1-5keV. The surface was imaged by an atomic force microscope (AFM). It was found that with the increasing ion energy, the average e11ipticity of the dots changes in an oscillating manner; meanwhile the average dot size increases monotonously. Based on a dynamic continuum model, and taking into consideration the asymmetry of the Ehrlich-Schwoebel diffusions along the(100) and (110) crystallographic directions, we carry out the simulations, which reproduce the experimental results qualitatively.     

Ga2O3薄膜的光致发光及激光烧蚀产物的分布

采用脉冲激光沉积技术在氧气氛中制备了Ｃａ２Ｏ３薄膜,Ｘ射线衍射表明薄膜属于β单斜晶系,薄膜的颗粒在纳米量级;原子力显微镜显示随着氧气压强的增加,薄膜颗粒增大,测定了薄膜的光致发光,发现沉积时氧气压强的增加可以提高纯Ｇａ２Ｏ３薄膜的发光强度,且峰位红移,Ｇａ２Ｏ３靶物质中掺杂少量的ＣｅＯ２后所得到的薄膜,其发光强度可以明显地增加,此外,还利用发光光谱技术研究了由激光烧蚀所产生的羽状物中Ｇａ原子或离     

Nanostructuring of Si（lO0） by Normal-Incident Ar＋ Ion Sputtering at Low Ion Flux

We investigate Si(100) surface morphology evolution under normal-incident Ar^ ions sputtering with low ion flux of 20μA/cm^2. The results indicate that under the low flux ion sputtering, the nanostructuring process of Si(lO0) is governed by the Ehrlich-Schwoebel (ES) mechanism, rather than by the Bradley-Harper (1311) one for the case of high flux (normally the order of 10^2 μA/cm^2 or larger). This work reveals that the ion flux plays an important role in the surface morphology evolution under ion sputtering, and a usually accepted classification that the ES mechanism is related to metal single-crystals under ion sputtering, while the BH one is to amorphous,and semiconductor targets is questionable.     

上海口岸入境外国旅游流的空间扩散和网络结构研究

应用一手数据研究了上海入境外国旅游流的分布和扩散规律及网络结构特征,发现：（1）上海口岸入境外国旅游流集中分布在胡焕庸线东南部,北京、桂林、西安、成都和昆明等城市以及长三角地区、珠三角地区构成的主体骨架,并在全国范围内呈由长三角地区向西北方向、西南方向扩散的态势;（2）上海口岸入境的韩国旅游流空间分布呈“倒皇冠”型,主要由“上海-杭州-苏州”、“上海-杭州-西安”和“上海-杭州-广州”3个三角形构成;美国旅游流空间分布呈“Z”型,由“上海-南京-杭州-桂林-北京”连接而成;美国游客比韩国游客活动范围更广,游览目的地更多,对上海口岸的依赖程度较低;（3）网络中的节点可划分为枢纽节点、中转节点、重要节点和一般节点,其中,上海、北京、桂林、西安、杭州和苏州等11个节点属于枢纽节点;（4）上海口岸入境外国旅游流网络规模较大,整体结构较松散,围绕核心节点集聚或扩散的趋势较强,具有小世界网络特性.