CdZnTe共面栅探测器的电子俘获修正方法

采用有限元方法模拟共面栅探测器的权重势分布,通过计算器件的电荷感应效率(CIE)以及感应信号,研究了CdZnTe共面栅器件的电子俘获修正技术,结果表明采用调整两组栅极输出信号的相对增益G的方法,可以有效地修正由于电子俘获造成的器件响应在深度上的不均匀;通过将次外条收集栅和非收集栅分别加宽一倍可以使两组栅电极的权重势分布在器件宽度上具有良好的均匀性,在此基础上采用调整增益G值来修正电子俘获,可使CdZnTe共面栅器件在深度和宽度方向上均得到均匀的响应特性.     

CdZnTe核辐射探测器表面物理和化学钝化研究

表面漏电流引起的噪声会限制CAznTe(CZT)探测器的性能。尤其对于共面栅探测器,漏电噪声的大小与器件的电极设计和表面处理工艺密切相关。本文比较了探测器表面的物理和化学钝化工艺：采用H2O2溶液和KOH—KCl溶液对CZT样品进行湿化学钝化处理,采用RFPCVD法在CZT样品表面沉积类金刚石薄膜(DLC)进行物理干法钝化。借助俄歇电子能谱(AES)和显微拉曼光谱以及ZC36微电流测试仪等手段研究了CZT表面组成与器件电学性能之间的关系。AES结果表明KOH—KCl溶液钝化可以改善CZT样品表面的化学组分比,H2O2溶液钝化可以将表面富Te层转化为高阻氧化层,钝化前后的I-V特性曲线表明两种化学钝化方法均可以有效地减小器件表面漏电流,达到满意的钝化效果。CZT样品表面物理钝化通过在样品表面沉积DLC薄膜加以实现,显微拉曼光谱表明CZT表面钝化层是高sp^3含量的DLC薄膜,AES深度剖析表明DLC薄膜可以有效阻止CZT内部元素的外扩散,并且DLC薄膜内部C元素向CZT内部的扩散也是比较低的。DLC薄膜钝化后的CZT共面栅探测器表面栅距25μm的栅间电阻可以达到12GΩ,有效地降低了器件的表面漏电流。     

聚光型太阳电池表面栅电极的优化设计

对聚光型太阳电池表面栅极图形进行优化设计.对组成太阳电池表面栅电极的图形最小单元的各种功率损失进行了详细分析,得到了最佳栅电极间距的递推公式.优化计算了各种宽度的次栅之间的间距,并得到了相对应的功率损失比例.电极和半导体接触良好时,当次栅间距小于最佳值,电极的遮挡对于功率损失影响最大;而当次栅间距大于最佳值时,太阳电池体材料输运功率损失和次栅电极电流输运功率损失开始成为主要原因.对于高倍聚光型太阳电池来说,次栅电极的厚度相对要求厚一些.计算及分析结果可应用于聚光型太阳电池电极的设计中.     

CVD金刚石紫外探测器

CVD金刚石紫外探测器有极强的辐射硬度及耐腐蚀性,在宽禁带半导体紫外探测器中占有重要地位.本文主要对金刚石紫外探测器的发展进展、探测机理、电极模式及应用领域做了简要回顾.     

彩色PDP真空紫外辐射特性的分析

利用二维流体模型，对三电极结构的PDP单元在维持放电期间的辐射特性进行了模拟研究，发现增大两共面电极的长度或间隙，都会不同程度地提高PDP单元的激发效率和真空紫外辐射效率。在分析了此计算结果的基础上，对一种新型的五电极结构的PDP单元进行了模拟，与原来的传统三电极结构相比，其真空紫外辐射效率提高17％。     

分立纳米线提高电池的功率密度

由分立的纳米氧化锰构成的栅垫在美国宇航局喷气推进实验室被用作可充电电池及电容器的实验电极材料。由于是分别独立的，因而在栅垫中的这些纳米线是可充分交流的。由于这些纳米线的密度很高，制成的电极与电解液的接触有很大的表面积，对进出电极的离子扩散通道也很短。这些因素使电池的充电放电能以很高速率进行，因而提高了功率密度。     

载流子输运性能对CdZnTe晶体脉冲X射线响应特性的影响

采用生长态高电阻CdZnTe晶体制备出平面电极探测器,室温下测试了其在脉冲X射线作用下的诱导电流曲线。分析了脉冲电流的上升时间以及脉冲衰减过程,发现脉冲上升时间约为2 ns,且不受外加偏压影响,而脉冲衰减过程可分为3阶段。利用α粒子结合飞行时间技术研究了CdZnTe晶体的载流子传输特性,分析了结构缺陷的散射和俘获-佉俘获对载流子传输特性的影响。同时对比了不同厚度的CdZnTe探测器在不同电压下对脉冲X射线的响应特性。结果表明,当外加电场强度增加时,诱导脉冲电流曲线的半峰宽呈指数衰减,但当探测器厚度大于0.2 mm时,随着探测器厚度的增加变化不明显。可能是由于材料中结构缺陷的浓度增加,对载流子的俘获和散射作用加剧,严重影响了载流子的传输过程和复合时间。     

高性能In0.53Ga0.47AsPIN光电探测器的研制

报道了采用GSMBE方法研制的In0.53Ga0.47As PIN光电探测器，器件结构中引入了宽禁带InP窗口层和聚酰亚胺钝化工艺，减小了暗电流，提高了器件性能。在反向偏压为5V时器件的暗电流为640pA，反向偏压为10V时测得器件的上升时间为37.2ps，下降时间为30.45ps，半高宽为43.9ps。对影响探测器暗电流的因素和提高响应速度的途径进行了讨论。     

铅酸蓄电池三维网络碳化硅板栅和极板内电流的分布

用有限元方法分析了铅酸蓄电池用三维网络碳化硅板栅和极板内电流的分布.结果表明,与常规板栅相比,三维网络碳化硅板栅与极板内电流分布比较均匀.极耳的形状和位置对板栅和极板内电流分布的影响很大,当极耳具有夹心结构时,电流分布的均匀性有非常明显的改善,尤其是在厚度方向具有类似三明治的极耳夹心结构时,板栅和极板内的电流分布极为均匀,且电流的数值比较小.     

石英板夹层中窄电极结构与材料对直流放电的影响

研究了一种石英板夹层窄电极放电装置的低气压直流放电过程,重点探讨了电极结构与电极材料对等离子体参数的影响,其中电极要求宽高为4mm,间距大于40mm。实验采用朗缪尔双探针法诊断,通过改变气压、放电功率等条件分析了电极结构对自制的直流等离子体放电装置的电子密度分布及电子温度的影响。结果表明:通过增加电极表面积,采取特殊的电极结构都可以有效地提高等离子体密度。实验中还发现,随着气压降低,正柱区逐渐缩小、等离子体密度沿电场方向变化趋于平缓,阳极的直流等离子体密度逐渐升高,这时等离子体空间分布均匀度提高,且在16Pa时取得最大值。     

Measurement of the tunnel rate in SIS' tunnel junctions as function of bias voltage

Cryogenic detectors with superconducting tunnel junctions can provide an energy resolution improved by at least one order of magnitude compared with standard semiconductor detectors. While the detection principle was already demonstrated many years ago, the past years were dedicated to the transition from the laboratory sample to practical detectors. Our most favored detector design gives rise to tunnel junctions with electrodes of unequal energy gaps. In such hetero tunnel junctions bias conditions can be established which cause a negative signal current. We report the experimental verification of this effect, and we discuss the yield of charge signal of cryogenic detectors based upon superconducting tunnel junctions.     

The effect of cathode bias (field effect) on the surface leakage current of CdZnTe detectors

Surface resistivity is an important parameter of multi-electrode CZT detectors such as coplanar-grid, strip, or pixel detectors. Low surface resistivity results in a high leakage current and affects the charge collection efficiency in the areas near contacts. Thus, it is always desirable to have the surface resistivity of the detector as high as possible. In the past the most significant efforts were concentrated to develop passivation techniques for CZT detectors. However, as we found, the field-effect caused by a bias applied on the cathode can significantly reduce the surface resistivity even though the detector surface was carefully passivated. In this paper we illustrate that the field-effect is a common feature of the CZT multi-electrode detectors, and discuss how to take advantage of this effect to improve the surface resistivity of CZT detectors.     

maXs: Microcalorimeter Arrays for High-Resolution X-Ray Spectroscopy at GSI/FAIR

Highly-charged heavy ions like U⁹¹⁺ provide unique conditions for the investigation of relativistic and quantum electrodynamical effects in strong electromagnetic fields. We present two X-ray detectors developed for high-resolution spectroscopy on highly-charged heavy ions. Both detectors consist of metallic magnetic calorimeters (MMCs) forming linear eight-pixel arrays. The first detector, maXs-20, is developed for the detection of X-rays up to 20?keV with an energy resolution below 3?eV. The second device, maXs-200, is designed for X-ray energies up to 200?keV with an energy resolution of 40?eV. The results of characterization measurements of single detectors of both arrays will be shown and discussed. In both cases, the performance of the detectors agrees well with their design values. Furthermore, we present a prototype MMC for soft X-rays with improved magnetic flux coupling. In first characterization measurements the energy resolution of this device was 2.0?eV (FWHM) for X-rays up to 6?keV.     

Optimised filtering for improved energy and position resolution in position-sensitive TES based X-ray detectors

We report on a new optimal filtering algorithm for improved energy and position resolution in position sensitive Transition Edge Sensor (TES) based X-ray detectors. This algorithm takes account of the noise correlation between the detector outputs to minimise the variance on the estimated photon energy and position. Using numerical methods we show that improved energy and position resolution can be obtained than from previously published methods. Our simulations also reveal the trade-offs resulting from changes in the thermal conductances and heat capacities of the detector elements.     

High resolution detection of x-rays with a Nb-based STJ detector

A high energy-resolution of 88 eV has been achieved for 5.9-keV x-rays with a large area (178×178 µm²) Nb/Al-AlOx/Al/Nb superconducting tunnel junction (STJ) detector, which is stable at room temperature and robust to thermal cycles. The energy resolution is higher than those of semiconductor detectors. The resolution and the short shaping-time-constant, 2 µs, of the main amplifier used to obtain the energy resolution indicate that STJ detectors can be developed as nuclear radiation detectors with high energy resolution even for high rate radiations. Besides, a theoretical limit of energy resolution due to the statistical fluctuation of signal charges is discussed.     

A WIMP Dark Matter Detector Using MKIDs

We are pursuing the development of a phonon- and ionization-mediated WIMP dark matter detector employing microwave kinetic inductance detectors (MKIDs) in the phonon-sensing channel. Prospective advantages over existing detectors include: improved reconstruction of the phonon signal and event position; simplified readout wiring and cold electronics; and simplified and more reliable fabrication. We have modeled a simple design using available MKID sensitivity data and anticipate energy resolution as good as existing phonon-mediated detectors and improved position reconstruction. We are doing preparatory experimental work by fabricating strip absorber architectures. Measurements of diffusion length, trapping efficiency, and MKID sensitivity with these devices will enable us to design a 1 cm²×2 mm prototype device to demonstrate phonon energy resolution and position reconstruction.      

Evaluation of silicon active pixel sensors for alpha particle detection

Alpha particles can be used as a test stimulus offering several advantages for probing materials of micrometre thicknesses. In this work a silicon CMOS Active Pixel Sensor (APS) is evaluated for alpha particle detection and imaging. These devices can replace traditionally used solid-state track detectors, giving advantages of increased sensitivity, improved linearity and higher dynamic range. CMOS APSs offer high detection efficiency, low noise and digital readout. Qualitative and quantitative analysis of the back-illuminated back-thinned (BT) and standard sensor response to 5.5 MeV alpha particles is presented. Alpha particle detection efficiency was estimated and energy resolution was measured. Imaging capabilities were assessed and quantified. Cluster centroiding algorithms were implemented for image quality improvement.     

H+ and He+ spectroscopy using silicon pin photodiodes

Silicon PIN photodiodes have been used in detecting H⁺ and He⁺ ions from a 1 MeV accelerator. Energy resolutions (FWHM) from 2.0 keV (at 16 keV) to 4.7 keV (at 1 MeV) for H⁺ and from 3.4 keV (at 22 keV) to 9.8 keV (at 700 keV) for He⁺ have been measured at room temperature. Resolution measurements over this energy range using a premium PIPS detector have also been performed. A comparison between the two detectors shows that the photodiodes exhibit better energy resolution over the whole energy range for H⁺, and comparable resolution for He⁺. It is argued that the resolution of the photodiode can be further improved by manufacturing a device with thinner entrance window.     

Metallic magnetic calorimeters (MMC): detectors for high-resolution X-ray spectroscopy

X-ray detectors based on the concept of magnetic calorimetry are well suited for high-resolution spectroscopy. Metallic magnetic calorimeters (MMC) make use of a metallic paramagnetic temperature sensor, which is in tight thermal contact with a metallic X-ray absorber. The paramagnetic sensor is placed in a small magnetic field. Its magnetization is used to monitor the temperature, which in turn is related to the internal energy of the calorimeter. High-energy resolution can be obtained by using a low-noise, high-bandwidth DC SQUID to measure the small change in magnetization upon the absorption of an X-ray. With recent prototype detectors an energy resolution of ΔE_FWHM=3.4 eV for X-ray energies up to 6.5 keV has been achieved. We discuss general design considerations, the thermodynamic properties of such calorimeters, the energy resolution, and the various sources of noise, which are observed in MMCs.     

Possible use of bulk superconductor with tunnel junctions for nuclear radiation spectroscopy

Nuclear radiation detectors with Josephson junctions, as hitherto reported, were composed of thin superconducting strips and had a poor energy resolution. A conceptual study is made on improvement of these detectors, with special consideration of quasiparticle collection. A bulk superconductor is shown to be appropriate as a radiation detector. Superconducting tunnel junctions of two types are proposed for superconducting radiation detectors of excellent energy resolution. These have high barrier penetrability and large area in order to collect all the quasiparticles generated in the superconductor by nuclear radiation.