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利用射频磁控溅射方法,在n+-Si衬底上淀积SiO2/Si/SiO2 sub>纳米双势垒单势阱结构,其中Si层厚度为2至4nm,间隔为0.2nm,邻近n+-S i衬底的SiO2层厚度固定为1.5nm,另一SiO2层厚度固定为3nm.为了 对比研究,还制备了Si层厚度为零的结构,即SiO2(4.5nm)/n+-Si 结构.在经过600℃氮气下退火30min,正面蒸上半透明Au膜,背面也蒸Au作欧姆接触后,所 有样品都在反向偏置(n+-Si的电压高于Au电极的电压)下发光,而在正向偏压 下不发光.在一定的反向偏置下,电流和电致发光强度都随Si层厚度的增加而同步振荡,位 相相同.所有样品的电致发光谱都可分解为相对高度不等的中心位于2.26eV(550nm)和1.85eV (670nm)两个高斯型发光峰.分析指出该结构电致发光的机制是:反向偏压下的强电场使Au/( SiO2/Si/SiO2)纳米双势垒/n+-Si结构发生了雪崩击穿 ,产生大量的电子-空穴对,它们在纳米SiO2层中的发光中心(缺陷或杂质)上复 合而发光.
关键词:
电致发光
纳米双势垒
高斯型发光峰
雪崩击穿 相似文献
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WU Jin-Jie HENG Yue-Kun SUN Zhi-Jia WU Chong ZHAO Yu-Da YANG Gui-An JIANG Chun-Hua 《中国物理C(英文版)》2008,32(3)
A new charge measurement method, time over threshold (TOT), has been used in some gas detectors lately. Here TOT is studied for TOF system, made of plastic scintillator counter, which can simplify the electronics of the system. The signal characteristics are measured and analyzed with a high quality oscilloscope, including noise, pedestal, signal amplitude, total charge, rise time and the correlation between them. The TOT and charge are related and can be fitted by some empirical formula. The charge measurement resolution by TOT is given and this will help the design of TOF electronics. 相似文献
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The endcap of time-of-flight (ETOF) detector in BES (Beijing Spectrometer) III is planned to be upgraded by using multi-gap resistive plate chambers (MRPCs) and the designed time resolution of the MRPCs is around 50 ps. Thus a time-zero (T0) detector needs to be built to offer a high quality reference time for the MRPCs beam test. So a T0 detector is built using plastic scintillator tiles (BC420) to couple with four fast phototubes (PMTs, Hamamatsu H6533). The timing properties of the detector is studied by using a cosmic ray test and factors related to the time resolution, such as plastic scintillator size, readout mode and angle effects, are discussed. T0 detector timing resolutions of ~41-62 ps are achieved, which means that the T0 detector can be used in the MRPC beam test. 相似文献
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基于Euler-Bernoulli梁理论,利用广义Hamilton原理推导得到弹性地基上转动功能梯度材料(FGM)梁横向自由振动的运动控制微分方程并进行无量纲化,采用微分变换法(DTM)对无量纲控制微分方程及其边界条件进行变换,计算了弹性地基上转动FGM梁在夹紧-夹紧、夹紧-简支和夹紧-自由三种边界条件下横向自由振动的无量纲固有频率,再将控制微分方程退化到无转动和地基时的FGM梁,计算其不同梯度指数时第一阶无量纲固有频率值,并和已有文献的FEM和Lagrange乘子法计算结果进行比较,数值完全吻合。计算结果表明,三种边界条件下FGM梁的无量纲固有频率随无量纲转速和无量纲弹性地基模量的增大而增大;在一定无量纲转速和无量纲弹性地基模量下,FGM梁的无量纲固有频率随着FGM梯度指数的增大而减小;但在夹紧-简支和夹紧-自由边界条件下,一阶无量纲固有频率几乎不变。 相似文献
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A prototype multi-gap resistive plate chamber (MRPC) with a 2×6 gap structure is developed for the upgrading of the endcap time-of-flight (ETOF) detector in the Beijing Spectrometer (BESⅢ). The prototype MRPC is tested in the E3 beam line of the Beijing Electron Positron Collider (BEPC) with secondary charged particles (π and p, etc) of 600 MeV/c. The test results show that the time resolution of the MRPC can reach 50 ps and that the detection efficiency is greater than 98%. 相似文献
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普通化学教学改革与探索 总被引:1,自引:0,他引:1
结合近几年的普通化学教学实践,我们分析了普通化学教学实践过程中存在的一些问题,并提出了培养学生的创新能力,不断更新教学内容,将理论教学与实验教学相结合等几方面建议。 相似文献
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