SiC-pn结二极管α粒子辐射效应

为了研究6H-SiC材料制作的pn结二极管探测器的辐照特性,采用蒙卡程序模拟研究了4.3和1.8 MeV能量的α粒子在辐照探测器中的物理过程。介绍了二极管探测器的工艺制作和物理参数,根据其结构建立了仿真模型,利用蒙卡程序进行了α粒子照射的仿真研究。研究结果直观地反映了α粒子在探测器中的输运情况。α粒子在探测器中的辐射效应主要是电离作用,电离产生的电子-空穴对形成一定的分布。给出了α粒子在探测器中的电离能量损失分布及二极管探测器的电荷收集效率表达式。     

4H-SiC pn结型二极管击穿特性中隧穿效应影响的模拟研究

基于4H-SiC材料特性，建立了4H-SiC pn结型二极管的击穿模型.该模型在碳化硅器件中引入 雪崩倍增效应和隧穿效应.利用该模型，分析了隧穿效应对器件击穿特性的影响；解释了不 同的温度和掺杂条件下，器件的击穿机理.该模型较好地反映了实际器件的击穿特性. 关键词： 4H-SiC 二极管 击穿特性 隧穿效应 碰撞离化 模型     

硅光电二极管陷阱辐射定标研究

介绍ＣｒｙｏＲａｄｌ低温绝对辐射计（ＨＡＣＲ），给出通过激光功率控制器（ＬＰＣ）调制过的Ｈｅ－Ｎｅ激光对所研制的Ｓｉ光电二极管陷阱探测系统进行定标的实验及结果分析     

金纳米粒子对黑色素瘤细胞的重离子辐射增敏效应研究

采用配体交换法合成了粒径15 nm左右的11-巯基十一烷酸包被的金纳米粒子（mAuNPs）,使用透射电镜和纳米粒度电位仪对合成后的金纳米粒子进行了表征,然后用MTT法检测了mAuNPs对体外培养小鼠黑色素瘤B16-F10细胞的毒性。在传能线密度（LET）为50 keV/μm的碳离子束照射下,利用香豆素-3-羧酸（3CCA）作为荧光探针检测mAuNPs对水溶液中羟自由基的增强效应、二氯荧光素双醋酸盐（DCFHDA）检测mAuNPs对细胞内活性氧（ROS）的增强效应、克隆形成法检测mAuNPs对B16-F10细胞的辐射增敏效应。实验结果表明:mAuNPs对小鼠黑色素瘤B16-F10细胞基本无毒;mAuNPs对水溶液中的羟自由基产额增强为1.08~2.95倍;在共培养浓度为5 μg/mL情况下mAuNPs增加了胞内活性氧水平,mAuNPs在10%细胞存活水平下的辐射增敏比（SER）为1.15。因此,mAuNPs在黑色素瘤细胞中展现出对重离子的辐射增敏效应。     

α粒子的散射

本文同时采用直角坐标系与极坐标系分别推出α粒子相对不动原子核心、动核心及质子的散射中有关物理量的关系式。     

轴对称平板二极管空间电荷限制流的2维效应

 应用精度较高的体积加权电荷、电流分配模型,对轴对称平板二极管的空间电荷限制流2维效应进行了粒子模拟研究。选取电压分别为100 kV和1 MV两种情况,对空间电荷限制流受二极管尺寸影响的规律进行了模拟。模拟结果表明,2维效应使空间电荷限制流密度随二极管形状因子(阴极发射半径与阴阳极间隙的比值)的减小而增大,且受相对论效应的影响不明显。经数值拟合得到了空间电荷限制流2维效应与形状因子相关的二阶经验公式,其一阶系数与一阶理论结果基本一致,约为1/4。     

轴对称平板二极管空间电荷限制流的2维效应

应用精度较高的体积加权电荷、电流分配模型,对轴对称平板二极管的空间电荷限制流2维效应进行了粒子模拟研究。选取电压分别为100 kV和1 MV两种情况,对空间电荷限制流受二极管尺寸影响的规律进行了模拟。模拟结果表明,2维效应使空间电荷限制流密度随二极管形状因子(阴极发射半径与阴阳极间隙的比值)的减小而增大,且受相对论效应的影响不明显。经数值拟合得到了空间电荷限制流2维效应与形状因子相关的二阶经验公式,其一阶系数与一阶理论结果基本一致,约为1/4。     

氧化钆纳米粒子对A549肺癌细胞的辐射增敏效应研究

采用氧化钆纳米粒子（GON）,研究钆基纳米粒子对X射线和碳离子束的辐射增敏效应。首先,通过透射电镜观察材料粒径,使用DLS检测材料的水合半径及Zeta电位,并用紫外吸收谱证实GON在培养基中稳定性较好;研究发现钆（Gd）浓度为10.0 μg/mL的GON对30 keV/μm碳离子束辐照水溶液产生的羟自由基的增强系数为1.13;GON对A549肺癌细胞和正常MRC-5肺细胞没有明显的毒性,且在人肺癌A549细胞中的摄取量随共培养浓度的增加而增加,在10.0 μg/mL共培养浓度下,细胞摄入Gd的量为0.73 pg/cell;进一步采用克隆存活实验证明,GON的加入对X射线和碳离子辐照A549细胞所产生的损伤具有明显的增强,在10%的细胞存活水平下,GON对A549细胞在X射线及碳离子辐照下的辐射增敏分别达15.5%和10.1%。鉴于钆材料常被用于磁共振成像（MRI）,所获得的GON有望作为X射线和碳离子的诊疗一体化材料。     

4H-SiC探测器的γ辐照影响研究

为研究4H-SiC探测器的抗γ辐照性能,使用40万Ci级的⁶⁰Co源对4H-SiC探测器进行了数次辐照,累积辐照剂量最大为1 MGy(Si),并在辐照后对4H-SiC的性能进行了测试。随着累积辐照剂量增加,4H-SiC探测器的正向电流增大,而反向电流恰好相反;根据4H-SiC探测器的正向I-V曲线可提取理想因子和肖特基势垒,理想因子从1.87增加到2.18,肖特基势垒从1.93 V减小至1.69 V;4H-SiC探测器对²⁴¹Am源产生的α粒子进行探测时,探测器的电荷收集率从95.65%退化到93.55%,测得能谱的能量分辨率由1.81%退化到2.32%。4H-SiC探测器在受到1 MGy(Si)的γ辐照后,与未受到辐照时相比,在探测能量为5.486 MeV的α粒子时能量分辨率和电荷收集率仅退化了28.18%和2.2%,仍具备优良的探测性能。     

4H-SiC肖特基二极管的电荷收集特性

针对极端环境下耐辐照半导体核探测器的研制需求,采用耐高温、耐辐照的4H碳化硅(4H-SiC)宽禁带材料制成肖特基二极管,研究了该探测器对241Am源粒子的电荷收集效率。从电容-电压曲线得出该二极管外延层净掺杂数密度为1.991015/cm3。从正向电流-电压曲线获得该二极管肖特基势垒高度为1.66 eV,理想因子为1.07,表明该探测器具备良好的热电子发射特性。在反向偏压高达700 V时,该二极管未击穿,其漏电流仅为21 nA,具有较高的击穿电压。在反向偏压为0~350 V范围内研究了该探测器对3.5 MeV 粒子电荷收集效率,在0 V时为48.7%,在150 V时为99.4%,表明该探测器具有良好的电荷收集特性。     

Determination of the range of alpha particles in SSNTD by optical density method

A technique based on the optical density (D) measurement of the etched track is useful for charged particles spectroscopy using SSNTD. It was shown that the stopping power of alpha particles in CR-39 is proportional to D. We measured the optical density and derived an expression to estimate the range of alpha particles in CR-39 detector as a function of the bulk etching rate and etching time. The relation between the etching time, track parameters (depth, radius) and D for different alpha particles energy and etching conditions were studied. A relation describing D as a function of track size is proposed.     

Analysis and simulation of a 4H-SiC semi-superjunction Schottky barrier diode for softer reverse-recovery

In this paper,a 4H-SiC semi-superjunction (SJ) Schottky barrier diode is analysed and simulated.The semi-SJ structure has an optimized design and a specific on-resistance lower than that of conventional SJ structures,which can be achieved without increasing the process difficulty.The simulation results show that the specific on-resistance and the softness factor depend on the aspect and thickness ratios,and that by using the semi-SJ structure,specific on-resistance can be reduced without decreasing the softness factor.It is observed that a trade-off exists between the specific on-resistance and the softness of the diode.     

Analysis and simulation of a 4H-SiC semi-superjunction Schottky barrier diode for softer reverse-recovery

In this paper, a 4H-SiC semi-superjunction (SJ) Schottky barrier diode is analysed and simulated. The semi-SJ structure has an optimized design and a specific on-resistance lower than that of conventional SJ structures, which can be achieved without increasing the process difficulty. The simulation results show that the specific on-resistance and the softness factor depend on the aspect and thickness ratios, and that by using the semi-SJ structure, specific on-resistance can be reduced without decreasing the softness factor. It is observed that a trade-off exists between the specific on-resistance and the softness of the diode.     

4H-SiC肖特基二极管的电荷收集特性

针对极端环境下耐辐照半导体核探测器的研制需求,采用耐高温、耐辐照的4H碳化硅(4H-SiC)宽禁带材料制成肖特基二极管,研究了该探测器对241Am源粒子的电荷收集效率。从电容-电压曲线得出该二极管外延层净掺杂数密度为1.991015/cm3。从正向电流-电压曲线获得该二极管肖特基势垒高度为1.66 eV,理想因子为1.07,表明该探测器具备良好的热电子发射特性。在反向偏压高达700 V时,该二极管未击穿,其漏电流仅为21 nA,具有较高的击穿电压。在反向偏压为0~350 V范围内研究了该探测器对3.5 MeV 粒子电荷收集效率,在0 V时为48.7%,在150 V时为99.4%,表明该探测器具有良好的电荷收集特性。     

Study of 4H-SiC junction barrier Schottky diode using field guard ring termination

This paper reports that the 4H-SiC Schottky barrier diode, PiN diode and junction barrier Schottky diode terminated by field guard rings are designed, fabricated and characterised. The measurements for forward and reverse characteristics have been done, and by comparison with each other, it shows that junction barrier Schottky diode has a lower reverse current density than that of the Schottky barrier diode and a higher forward drop than that of the PiN diode. High-temperature annealing is presented in this paper as well to figure out an optimised processing. The barrier height of 0.79 eV is formed with Ti in this work, the forward drop for the Schottky diode is 2.1 V, with an ideality factor of 3.2, and junction barrier Schottky diode with blocking voltage higher than 400 V was achieved by using field guard ring termination.     

The effect of Pb2+ dopant in the crystal of CsI and its application as scintillation detector: a study of alpha particles

Scintillation crystals have been used in various fields, such as high energy physics, nuclear instrumentation, radiation measurements, medical imaging, nuclear tomography, astrophysics and other fields of science and engineering. For these applications, the development of scintillation crystals with good performance is required. Scintillation crystals based on cesium iodide (CsI) matrix are matters with relatively low hygroscopicity, easy to handle and of low cost, characteristics that favor their use as radiation detectors. In this study, pure CsI crystal and lead doped CsI crystals were grown using the Bridgman vertical technique. The concentration of the lead doping element (Pb) was studied in the range of 10^?2 to 5×10^?4 M. The distribution of the doping element in the crystalline volume was determined by atomic absorption technique. The CsI:Pb crystal with nominal concentration of 10^?3 M was cut into 14 slices of 6 mm. The results show a higher concentration at the top of the crystal with a decrease in the initial phase of growth. The dopant concentration of Pb showed good uniformity from the slice 2 to the slice 12: the region is, therefore, suitable for use as a radiation detector. The luminescence emission of these crystals was measured. A predominant luminescence band near 450 nm and a single broad band around 320 nm were found with the addition of the Pb²⁺ ions in the CsI matrix. Alpha particles spectrometry measurements were carried out to evaluate the developed scintillators.The resolution of 5.6% was obtained for the CsI:Pb 5×10^?4 M crystal, when excited with alpha particles from a ²⁴¹Am source, with energy of 5.54 MeV.