共查询到18条相似文献,搜索用时 523 毫秒
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碲锌镉(Cadmium Zinc Telluride, CZT)是碲镉汞(Mercury Cadmium Telluride, MCT)红外焦平面器件的重要衬底材料,其合成过程存在强烈的放热现象。因此控制放热是CZT多晶材料合成工艺平稳进行的基本条件。通过改变初始旋转倾角可有效调控合成反应的放热强度和放热速率:大倾角有利于获得缓慢且稳定的工艺过程。基于实验结果和热力学计算分析可知,合成反应经过镉-碲的液-固相反应和液-液相反应两个阶段完成。同时实验结果表明,反应的放热量大小决定了在高温下是否会发生第二次反应。最后对二次反应发生的相关机理进行了分析。 相似文献
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作为碲锌镉衬底表面加工的重要工序,化学机械抛光(Chemical Mechanical Polishing, CMP)的加工效果决定了碲锌镉衬底的表面质量和生产效率。抛光液是CMP的关键影响因素之一,直接影响衬底抛光后的表面质量。对碲锌镉衬底CMP工艺使用的抛光液进行了研究,探究了以二氧化硅溶胶和过氧化氢为主体的抛光液体系在不同pH值、不同磨料浓度下对衬底抛光表面质量和去除速率的影响。结果表明,使用改进后的抛光液体系对碲锌镉衬底进行CMP,能够在获得超光滑表面的同时实现高效率加工,为批量化制备高表面质量的碲锌镉衬底奠定了良好基础。 相似文献
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高质量的碲锌镉单晶是制备碲镉汞红外焦平面器件的理想衬底材料,然而目前碲锌镉材料中的第二相夹杂物严重制约着晶体的质量.根据红外透射形貌的描述和表征,碲锌镉晶体的常见夹杂物被分成了五类,并在此基础上讨论了各自的形成机制,A、B和C类夹杂物与化学配比及其变化密切相关,而D和E类夹杂物与源材料中或者在生长工艺控制过程中氧含量相关.进一步的研究表明大尺寸、高密度的Te夹杂物将会严重降低红外透过率,同时腐蚀坑密集分布在与Cd夹杂对应的六重对称线上,该结果揭示了第二相夹杂物会产生其他缺陷的增殖,但夹杂物引起的应力影响区域是局限的. 相似文献
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为了研究液相外延碲镉汞薄膜表面缺陷形成机制,采用光刻工艺结合化学腐蚀方法在碲锌镉衬底表面实现了网格化,研究了碲锌镉近表面富碲沉积相与外延薄膜表面缺陷的关系.结果表明:衬底近表面富碲沉积相会导致碲镉汞薄膜表面孔洞、类针形凹陷坑缺陷以及三角形凹陷坑聚集区;在液相外延过程中,高温碲镉汞熔液与CdZnTe衬底间的回熔作用可以减少与富碲沉积相相关的表面缺陷,薄膜表面缺陷与衬底表面富碲沉积相的匹配度与回熔深度负相关;回熔过程以及富碲沉积相形态、深度影响HgCdTe薄膜表面缺陷形态和分布. 相似文献
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研究了碲锌镉衬底(111)晶面的不同极性对水平推舟液相外延生长碲镉汞薄膜的影响。实验结果显示,(111)A面碲锌镉衬底水平液相外延生长碲镉汞薄膜材料组分和厚度均与常规(111)B面碲锌镉衬底碲镉汞薄膜材料相当;碲镉汞母液在采用(111)A面、(111)B面衬底进行液相外延生长的碲镉汞薄膜上接触角分别为(50±2)°和(30±2)°,结合微观模型分析确认碲镉汞母液在碲镉汞薄膜(111)A面存在更大的表面张力;观察并讨论了(111)A面碲镉汞与(111)B面碲镉汞薄膜材料表面微观形貌的差别;实验获得的(111)A面碲镉汞薄膜XRD半峰宽为33.1arcsec。首次报道了(111)晶面选择对母液残留的影响,研究结果表明,采用(111)A面碲锌镉衬底进行碲镉汞水平推舟液相外延生长,能够在不降低晶体质量的情况下,大幅减小薄膜表面母液残留。 相似文献
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研究了一种新的钝化CdZnTe(CZT)器件表面的工艺,即先采用KOHKCl溶液对CZT表面进行处理,再用NH4F/H2O2溶液对其进行表面氧化的二步法钝化工艺.并借助俄歇电子能谱(AES)、微电流测试仪等手段对其表面钝化层的质量进行了鉴别,同时与KOH KCl和NH4F/H2O2两种工艺进行了比较.AES能谱分析表明,采用二步法工艺钝化,既可获得化学计量比较好的CZT表面,又可在表面形成一层起保护作用的氧化层.I-V特性曲线显示,两步法钝化后CZT器件的漏电流与KOH KCl和NH4F/H2O2钝化相比都有一定程度的下降.说明文中提出的新工艺在CZT器件制备方面具有良好的应用前景. 相似文献
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R. B. James B. Brunett J. Heffelfinger J. Van Scyoc J. Lund F. P. Doty C. L. Lingren R. Olsen E. Cross H. Hermon H. Yoon N. Hilton M. Schieber E. Y. Lee J. Toney T. E. Schlesinger M. Goorsky W. Yao H. Chen A. Burger 《Journal of Electronic Materials》1998,27(6):788-799
The material showing the greatest promise today for production of large-volume gamma-ray spectrometers operable at room temperature
is cadmium zinc telluride (CZT). Unfortunately, because of deficiencies in the quality of the present material, high-resolution
CZT spectrometers have thus far been limited to relatively small dimensions, which makes them inefficient at detecting high
photon energies and ineffective for weak radiation signals except in near proximity. To exploit CZT fully, it will be necessary
to make substantial improvements in the material quality. Improving the material involves advances in the crystallinity, purity,
carrier lifetimes, and control of the electrical compensation mechanism. A more detailed understanding of the underlying material
problems limiting the performance of CZT gamma-ray detectors is required; otherwise, problems with supply, delivery times,
and unit cost of large-volume (>5 cm3 active volume) CZT spectrometers are expected to continue. A variety of analytical and numerical techniques have been employed
to quantify crystallinity, strain, impurities, compositional and stoichiometric variations, bulk and surface defect states,
carrier mobilities and lifetimes, electric field distributions, and surface passivation. Data from these measurements were
correlated with spatial maps of the gamma-ray and alpha particle spectroscopic response, and feedback on the effectiveness
of crystal growth and detector fabrication procedures has been generated. The results of several of these analytical techniques
will be presented in this paper. 相似文献
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R. Raman Ashok Kumar Kapoor Shiv Kumar Akhilesh Pandey 《Journal of Electronic Materials》2009,38(10):2046-2051
Colloidal silver is observed to affect the transmittance of p-type Cd1−y
Zn
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Te (CZT) single-crystal substrate material at room temperature. The optical transmittance spectra have been analyzed in the
near-infrared (NIR) and mid-infrared (MIR) regions. The transmittance characteristics of CZT showed significant reduction
in absorption due to split-off valance band transitions in the NIR region and intervalence band absorption in the MIR region
upon coating CZT substrates with silver paste. This reduction in absorption has been explained to be due to the compensation
of the acceptor defects (native and foreign). Silver atoms incorporated from the silver coating help in compensation of these
defects. A similar effect on transmittance characteristics of mercury cadmium telluride (MCT) epilayers grown on CZT substrates
after coating silver paste on the CZT substrate side was also observed. An improvement in the transmittance of CZT substrates
after the application of silver paste was observed. A similar improvement in transmittance is usually achieved by annealing
the substrates in a Cd/Zn atmosphere. The results are explained by considering the formation of neutral complexes of acceptors
(cadmium vacancies) and the interstitial silver. This study also points to the important conclusion that silver paste on CZT
should be applied with caution for measurement purposes since it diffuses even at room temperature and modifies the optical
characteristics. 相似文献
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Surface passivation of cadmium zinc telluride radiation detectors by potassium hydroxide solution 总被引:1,自引:0,他引:1
Kaushik Chattopadhyay Miguel Hayes Jean-Olivier Ndap Arnold Burger W. J. Lu Hylton G. McWhinney Tony Grady Ralph B. James 《Journal of Electronic Materials》2000,29(6):708-712
The spectral resolution of cadmium zinc telluride (CZT) room temperature nuclear radiation detectors is often limited by the
presence of conducting surface species that increase the surface leakage current. Surface passivation plays an important role
in reducing this surface leakage current and thereby decreasing the noise of the detectors and improving the spectral energy
resolution. Chemical etching with a Br-MeOH solution leaves CZT surfaces rich in Te and is considered as one of the primary
causes of the increased surface leakage current. Previous studies have shown that hydrogen peroxide (H2O2) forms oxides of tellurium on the CZT surface and thus acts as a good passivating agent. In this study we will present results
on the use of potassium hydroxide (KOH) as an alternative passivating agent. The KOH aqueous solution leaves a more stoichiometric
(evaluated from the trends in the surface Cd:Te ratio) and smoother CZT surface. The passivation effects of KOH solution on
the surface of the CZT have been characterized by current-voltage measurements for different KOH concentrations and etching
times for both parallel strip electrodes as well as a metal-semiconductor-metal configuration. The surface chemical composition
and its morphology were studied by scanning x-ray photoelectron spectroscopy and atomic force microscopy. The comparison and
demonstration of improvements in the spectral resolution of the CZT detectors (based on 241Am spectra) with and without the KOH treatment are presented. 相似文献
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Colin Hackett Haim Hermon Eilene Cross Patrick Doty Edward Tarver Ralph James 《Journal of Electronic Materials》1999,28(6):774-784
A method to measure the elemental composition of both major and minor species that is spatially resolved along and below the
surface of Cd-Zn-Te (CZT) crystal specimens is described. This method uses laser ablation sampling (LAS) for material introduction
into an inductively coupled plasma (ICP) source quadrupole mass spectrometer (QMS) system for subsequent elemental analysis.
Mass spectra are acquired at discrete locations on the surface of each CZT specimen, mounted inside a LAS cell. This cell
allows argon sweep gas to transport the ablation products into the ICP-QMS for analysis. Since three component movement of
the CZT specimen surface relative to the LAS site is possible under computer control, elemental analysis at specific locations
on the surface can be obtained. Additional mass spectra are obtained by repetitive LAS at progressively deeper locations beneath
the surface at a fixed position, and at difference sites of interest anywhere on the surface of the CZT specimen. These spectra
are analyzed to obtain the relative ionic abundances of all detectable isotopes of the major (CZT matrix) and the minor (trace)
elements. From these data, the ensemble atom mass concentrations are calculated for each LAS procedure. The relative mass
fraction of each element specie within a particular LAS data set is then determined by calculating the ratio of its abundance
to the whole ensemble mass in that sample. 相似文献
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H. Hermon M. Schieber R. B. James E. Y. Lee N. Yang A. J. Antolak D. H. Morse C. Hackett E. Tarver N. N. P. Kolesnikov Yu N. Ivanov V. Komar M. S. Goorsky H. Yoon 《Journal of Electronic Materials》1999,28(6):688-694
Sandia National Laboratories (SNL) is leading an effort to evaluate vertical high pressure Bridgman (VHPB) Cd1−xZnxTe (CZT) crystals grown in the former Soviet Union (FSU) (Ukraine and Russia), in order to study the parameters limiting the
crystal quality and the radiation detector performance. The stoichiometry of the CZT crystals, with 0.04<x<0.25, has been
determined by methods such as proton-induced x-ray emission (PIXE), x-ray diffraction (XRD), microprobe analysis and laser
ablation ICP mass spectroscopy (LA-ICP/MS). Other methods such as triaxial double crystal x-ray diffraction (TADXRD), infrared
transmission spectroscopy (IR), atomic force microscopy (AFM), thermoelectric emission spectroscopy (TEES) and laser induced
transient charge technique (TCT) were also used to evaluate the material properties. We have measured the zinc distribution
in a CZT ingot along the axial direction and also its homogeneity. The (Cd+Zn)/Te average ratio measured on the Ukraine crystals
was 1.2, compared to the ratio of 0.9–1.06 on the Russian ingots. The IR transmission showed highly decorated grain boundaries
with precipitates and hollow bubbles. Microprobe elemental analysis and LA-ICP/MS showed carbon precipitates in the CZT bulk
and carbon deposits along grain boundaries. The higher concentration of impurities and the imperfect crystallinity lead to
shorter electron and hole lifetimes in the range of 0.5–2 and 0.1 μs, respectively, compared to 3–20 and 1–7 μs measured on
U.S. spectrometer grade CZT detectors. These results are consistent with the lower resistivity and worse crystalline perfection
of these crystals, compared to U.S.-grown CZT. However, recently grown CZT from FSU exhibited better detector performance
and good response to alpha particles. 相似文献