低温加热对碲镉汞表面组分的影响

碲镉汞(Hg_(1-x)Cd_xTe)是一种禁带宽度可调的三元系窄禁带半导体,选择适当Hg/Cd比的材料,可满意地制造出其响应波段从近红外延伸到远红外的各种Hg_(1-x)Cd_xTe红外探测器。由于汞具有容易挥发的特性,因而它给器件的制造带来了许多麻烦。近年来,人们对Hg_(1-x)Cd_xTe表面以及它与介质之间的界面发生了很大兴趣。人们已研     

碲镉汞阳极硫化膜界面的光电子能谱研究

用电子能谱方法研究了Hg_(1-x)Cd_xTe样品在0.1M的Na_2S·9H_2O+乙二醇溶液中形成的阳极硫化膜,结果表明界面上汞的含量较高,介质膜含氧;但在0.1M的Na_2S·9H_2O+NaOH+乙二醇溶液中形成的阳极硫化膜几乎不含氧,介质膜的主要成分是CdS,且含有较多的Hg和Te。结果表明,碲镉汞表面的含水硫化可以获得同无水硫化、无水多硫化和含水多硫化钝化表面基本一致的介质膜,从而实现了含水硫化钝化碲镉汞表面。     

MOCVD法生长HgCdTe／CdTe／GaAs多层异质结材料工艺和性能研究

本文简述MOCVD法生长HgCdTe晶膜的优点。采用变通的多层互扩散工艺生长了HgCdTe/GaAs外延片。研究了生长HgCdTe生长速率与衬底温度的关系,DETe和DMCd源分压对生长速率的影响,Hg_(1-x)Cd_xTe中x值与汞源温度的关系,当汞源温度固定时,Hg_(1-x)Cd_xTe中x值与气体流速V的关系。并采用多种方法分析HgCdTe外延片的表面形貌,结晶性,界面和缺陷,Te、Cd、Hg、Ga、As的截面分布,组份和其均匀性,光电性能等。测得HgCdTe和缓冲层CdTe的FWHM为450弧度秒,界面平坦、清晰,过度层约0.12μm。生长x值为0.1～0.8mol,均匀性△X=0.008。典型样品的性能,在77K电子浓度为1.4×10~(16)cm~(-3),迁移率为7.4×10~4cm~2/v·s,透射率为42％。     

垂直浸渍液相外延Hg1—xCdxTe的生长及性能

本文报导采用汞回流垂直浸渍液相外延方法,在CdTe或CdZnTe(111)面的衬底上生长Hg_(1-x)Cd_xTe单晶,其厚度为20μm,面积为1.5×2cm~2,组分x从0.18到0.7,组分均匀性Δx≈0.001。样品经热处理以后,x=0.2的n型样品电子浓度n≈1×10~(15)cm~(-3),电子迁移率μ≈10~5cm~2/v·s,p型样品空穴浓度p≈2×10~(16)cm~(-3),空穴迁移率μ≈300cm~2/v·s,双晶衍射显示样品的半峰宽为90arc sec,X光貌相分析表明外延层晶体结构优良。样品的红外光谱测量,电学参数测量以及载流子寿命测量表明样品具有优良的光电性质。     

碲镉汞材料及工艺控制的分析方法

随着碲镉汞红外器件的小型化、高品质化和性能的提高,对原材料的纯度、器件工艺质量控制方法提出了更高的要求。就分析方法而言,不仅要求有高的定量分析精度,同时要求分析方法对杂质元素的分析范围广(多元素分析)、元素的探测灵敏度高。对器件工艺控制分析来说,除了基体元素成分、杂质元素的定量分析外,还要求分析方法能在横向和纵向分析,并有相当的空间分辨率。就上述要求给出了碲镉汞材料提纯、CMT(碲镉汞,Cd(?)Hg(?)Te)晶体生长及器件工艺控制分析的主要分析技术方法、特点及其进展。讨论了基体元素定量分析的精度,痕量元素定量分析的能力、灵敏度及其进行深度剖面分析的深度分辨率。     

两类典型的低温应用红外探测材料研究

红外探测器件是现代军用武器装备目标识别的核心构件,而红外探测材料的性能将直接影响器件的性能水平。综述了两类典型的低温应用红外探测材料研究进展,以红外探测材料研究和应用的尺度为分类标准,分别对微米尺度的窄带隙直接半导体碲镉汞和基于量子效应的四种低维材料进行了介绍,并指出了当前红外探测材料研究存在的问题和发展的方向。     

中波碲镉汞边缘接触不对称MIS结构的低频噪声

对两种不同结构的中波碲镉汞光导红外探测器件的噪声进行了测量,发现叠层结构器件的低频噪声比具有简单结构器件的大。针对叠层结构,提出了用来分析噪声的边缘接触不对称MIS结构模型。分析表明,叠层电极下的碲镉汞表面在偏置电压作用下,容易出现耗尽层是低频噪声增加的主要原因。     

碲镉汞晶体辐射损伤的分析电镜研究

用分析电子显微镜观察了碲镉汞晶体的显微结构。发现在大剂量电子辐射下,显微结构有较强的损伤。进一步用 X线能谱分析和高分辨电子显微术研究表明,大剂量电子辐射引起了碲镉汞晶体的超结构、叠栅、无序化和 Hg 含量减少。     

Cd_xZn_(1-x)Se_yS_(1-y)量子点/PVDF纳米复合薄膜的制备与性能研究

以聚偏氟乙烯(PVDF)作为Cd_xZn_(1-x)Se_yS_(1-y)量子点微封装材料,利用简易刮涂法工艺成功制备出大面积、高稳定性的Cd_xZn_(1-x)Se_yS_(1-y)量子点/PVDF纳米复合薄膜,同时对该纳米复合薄膜的结构、形貌及光学性能进行表征和分析,并进一步研究纳米复合薄膜的水热稳定性。研究结果表明,使用刮涂工艺制备的Cd_xZn_(1-x)Se_yS_(1-y)量子点/PVDF纳米复合薄膜仍然保持优良的荧光光致发光特性,利用该工艺能够实现大面积8 cm×15 cm Cd_xZn_(1-x)Se_yS_(1-y)量子点/PVDF纳米复合薄膜制备,该薄膜在紫外灯照射下发出明亮红光。通过PVDF和Cd_xZn_(1-x)Se_yS_(1-y)量子点的复合,将得到的复合薄膜在沸水中沸煮240min发光性能基本不会发生变化,具备超高的稳定性。     

PECVD法生长的氧化锡薄膜的结构与性能研究

非化学计量的二氧化锡是一种 n 型半导体材料,具有良好的光电特性。本文用等离子增强化学气相沉积(PECVD)法生长 SnO_(2-x)薄膜,并进行了生长条件与其结构和性能的研究。结果表明:不同的淀积条件,可以获得从多晶到非晶态不同结构、化学稳定性良好、可见光透射率高、具有不同电导率的 SnO_(2-x)薄膜材料。     

Some recent advances in bulk growth of mercury cadmium telluride crystals

The inherent metallurgical problems associated with the HgTe/CdTe pseudobinary alloy system render the standard crystal growth processes inapplicable to the preparation of mercury cadmium telluride crystals for infrared detector applications. A variety of rather nonconventional techniques have been developed to overcome these problems. Two such techniques, viz. asymmetrical Bridgman and horizontal casting for solid-state recrystallization, developed at Solid State Physics Laboratory for the bulk growth of mercury cadmium telluride crystals are reviewed in this communication. Due to the poor thermal conductivity of mercury cadmium telluride melts and solids, and the use of thick-walled quartz ampuoles, it is extremely difficult to obtain a flat solid-liquid interface during Bridgman growth of this material. The technique of asymmetrical Bridgman has been successful in overcoming this problem to a great extent. Solid-state recrystallization has been widely accepted as one of the most successful techniques for obtaining large quantities of acceptable-quality mercury cadmium telluride crystals for infrared detector applications. This is a two-step process—the melt is first quenched to obtain a good cast, which is then subjected to a grain-growth annealing. The horizontal casting procedure developed for solid state recrystallization growth has been successful in improving the overall quality and yield of bulk mercury cadmium telluride crystals.     

Protein‐Directed Synthesis of NIR‐Emitting,Tunable HgS Quantum Dots and their Applications in Metal‐Ion Sensing

The development of luminescent mercury sulfide quantum dots (HgS QDs) through the bio‐mineralization process has remained unexplored. Herein, a simple, two‐step route for the synthesis of HgS quantum dots in bovine serum albumin (BSA) is reported. The QDs are characterized by UV–vis spectroscopy, Fourier transform infrared (FT‐IR) spectroscopy, luminescence, Raman spectroscopy, transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), circular dichroism (CD), energy dispersive X‐ray analysis (EDX), and picosecond‐resolved optical spectroscopy. Formation of various sizes of QDs is observed by modifying the conditions suitably. The QDs also show tunable luminescence over the 680–800 nm spectral regions, with a quantum yield of 4–5%. The as‐prepared QDs can serve as selective sensor materials for Hg(II) and Cu(II), based on selective luminescence quenching. The quenching mechanism is found to be based on Dexter energy transfer and photoinduced electron transfer for Hg(II) and Cu(II), respectively. The simple synthesis route of protein‐capped HgS QDs would provide additional impetus to explore applications for these materials.     

Sequencing Batch Reactor (SBR) for the removal of Hg2+ and Cd2+ from synthetic petrochemical factory wastewater

Petrochemical factories which manufacture vinyl chloride monomer and poly vinyl chloride (PVC) are among the largest industries which produce wastewater contains mercury and cadmium. The objective of this research is to evaluate the performance of a lab-scale Sequencing Batch Reactor (SBR) to treat a synthetic petrochemical wastewater containing mercury and cadmium. After acclimatization of the system which lasted 60 days, the SBR was introduced to mercury and cadmium in low concentrations which then was increased gradually to 9.03±0.02 mg/L Hg and 15.52±0.02 mg/L Cd until day 110. The SBR performance was assessed by measuring Chemical Oxygen Demand, Total and Volatile Suspended Solids as well as Sludge Volume Index. At maximum concentrations of the heavy metals, the SBR was able to remove 76-90% of Hg(2+) and 96-98% of Cd(2+). The COD removal efficiency and MLVSS (microorganism population) in the SBR was affected by mercury and cadmium concentrations in influent. Different species of microorganisms such as Rhodospirilium-like bacteria, Gomphonema-like algae, and sulfate reducing-like bacteria were identified in the system. While COD removal efficiency and MLVSS concentration declined during addition of heavy metals, the appreciable performance of SBR in removal of Hg(2+) and Cd(2+) implies that the removal in SBR was not only a biological process, but also by the biosorption process of the sludge.     

Assembly and Study of Different Mercury Cells with Known Impurity Content and Isotopic Composition

The “Centro Español de Metrología” is carrying out a project to improve the knowledge of the influence of impurities and isotopic composition on the temperature of the mercury triple point. High-purity mercury from the Almaden mine (stated purity of 99.9998%) was further purified by vacuum distillation. Three mercury fractions, the original mercury from Almaden and two distilled fractions, were characterized in terms of both impurities and isotopic composition and used to measure the mercury triple point. The original mercury sample contained silver at 560 ng · g^?1 as the main impurity while the impurity levels were much lower (silver < 1 ng · g^?1) in the two distilled fractions. The isotopic composition of the distilled fractions showed delta values, expressed as $1,000\times(^{198/202}{\rm Hg}_{\rm sample}-^{198/202}\,{\rm Hg}_{\rm reference})/^{198/202}{\rm Hg}_{\rm reference}The “Centro Espa?ol de Metrología” is carrying out a project to improve the knowledge of the influence of impurities and isotopic composition on the temperature of the mercury triple point. High-purity mercury from the Almaden mine (stated purity of 99.9998%) was further purified by vacuum distillation. Three mercury fractions, the original mercury from Almaden and two distilled fractions, were characterized in terms of both impurities and isotopic composition and used to measure the mercury triple point. The original mercury sample contained silver at 560 ng · g⁻¹ as the main impurity while the impurity levels were much lower (silver < 1 ng · g⁻¹) in the two distilled fractions. The isotopic composition of the distilled fractions showed delta values, expressed as , of 1.37±0.07 (1σ) for the first distilled sample and −1.55±0.03 (1σ) for the second distilled sample with reference to the original Almaden mercury. For the measurement of the mercury triple point, an alcohol stirred bath was used that allowed two cells to be compared nearly simultaneously. It was observed that the presence of the silver impurities in the high-purity mercury modified slightly the mercury triple point while the effect of variations in the isotopic composition can be considered negligible.     

Airborne mercury pollution from a large oil spill accident on the west coast of Korea

Atmospheric mercury pollution was recognized after a large oil spill on the west coast of Korea on 7 December 2007. In this study, the concentrations of gaseous elemental mercury (GEM: Hg(0)) in air were measured both shortly after the oil spill ( approximately 100h) and 1month after the accident near the accident site. When the Hg concentration levels were compared between two seashore sites and two parallel sites offshore, the values tend to decrease further offshore. The unusual rise in Hg concentration levels observed on the seashore area shortly after the accident (mean of 16.4+/-9.85ngm(-3)) dropped dramatically after 1month with active cleanup activities (2.99+/-1.40ngm(-3)). Because of the connection between crude oil and Hg (one of the major impurities), the unusual rise in the atmospheric Hg after the oil spill can be explained by the active evasion of Hg from the spilled crude oil. Although Hg levels determined a few days after the accident did not exceed the reference exposure limits (REL) proposed by several agencies, the early build-up of elemental mercury level due to the oil spill might have exerted certain impacts on the surrounding environments.     

Mechanisms of heavy metal sorption on alkaline clays from Tundulu in Malawi as determined by EXAFS

Chromium(III), copper(II), zinc(II), cadmium(II), mercury(II) and lead(II) cations are among the most common heavy metal pollutants in industrial waste waters. In our continued work on cost effective wastewater heavy metal removal agents and methods using local material, this study examines the interactions of chromium(III), copper(II), zinc(II), cadmium(II), mercury(II) and lead(II) cations with natural mixed clay minerals from Tundulu in Malawi using extended X-ray absorption fine structure (EXAFS) spectroscopy. The mixed clays were previously characterised and found to contain illite, low ordered kaolinite, mixed layer minerals and the non-clay mineral carbonate fluoroapatite with a mean pH(PZC) of 9.63. The EXAFS analyses provided qualitative evidence that oxygen atoms occupy the first coordination shells in all the studied central atoms. The metal species on the clay mineral surfaces seem to be adsorbates and/or precipitates of hydrolysis products. Chromium(III) forms a polynuclear hydrolysis complex on the mineral surface with Cr-O bond and Cr...Cr distances of 2.00 and 3.03 A, respectively, which is indicative of a chain structure with edge sharing CrO(6) octahedra. Copper(II) is bound to phosphate groups on the surface at low pH and has a first shell of coordinated oxygen atoms with Jahn-Teller distortion as revealed by different Cu-O bonds of 1.96 A for the equatorial ones, at 2.30 and 2.65 A for the axial oxygens, and a Cu-P distance at 3.29 A is distinguished as well. Upon treatment at neutral pH copper(I) oxide seems to be the main precipitation product on the clay surface. At neutral pH zinc(II) forms also polynuclear hydrolysis complexes with Zn-O bond and Zn...Zn distances of 2.01 and 3.11A, respectively, which shows the presence of edge sharing ZnO(4) tetrahedra. Cadmium(II) is adsorbed to the clay surfaces as a six-coordinated CdO(6) complex in octahedral fashion, but it is not possible to distinguish if cadmium is hydrated or partly hydrolysed. Mercury(II) is present as linear O-Hg-O units but without any observable Hg...Hg distance at high pH showing that mercury(II) is hydrolysed but not present as mercury(II) oxide. At low pH, linear O-Hg-Hg-O units are present showing that mercury(II) is reduced to mercury(I). No precise chemical environment around the lead(II) could be obtained for the lead(II) treated clays due to formation of different hydrolysis structures with multiple coordination numbers by lead(II) salts on the mixed clays.     

用密度泛函理论研究汞在CeO_2(111)表面的吸附

采用密度泛函理论计算了Hg、HgCl、HgCl_2在CeO_2(111)表面的吸附构型、吸附能和态密度。结果表明,Hg在CeO_2(111)表面属于弱化学吸附。HgCl与CeO_2(111)表面为强化学吸附,是反应的重要中间体。HgCl_2在CeO_2(111)表面是物理吸附,易发生解离,脱除。氯对于汞的吸附和氧化产生较强的影响,这与实验结果相一致。基于计算结果,得到汞在CeO_2(111)表面的反应机理。     

A Novel Method for Determination of the Thermal Diffusivity of Thin Films Using a Modulated CO<Subscript>2</Subscript> Laser

The thermal diffusivity of thin metal films has been measured by combining a fast infrared radiation thermometer with a mercury cadmium telluride (MCT) detector and a CO₂ laser modulated at a radio frequency up to 2 MHz. The laser output beam modulated by an acousto-optic modulator (AOM) is directed to the front surface of the blackened copper thin film (10m thick, 9.5 mm in diameter). The thermal radiation from the back surface of the sample is detected. From the observed phase delay in the detected signal of 0.68 radian to the input laser beam, the thermal diffusivity is determined to be 1.11 × 10^-4m²·s^-1, which agrees well with the value of 0.99 × 10^-4m²·s^-1 calculated from literature results. The method is generally applicable for measurements of thermal properties of nano/micro materials.Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22--27, 2003, Boulder, Colorado, U.S.A.     

Purification of cadmium up to 5N+ by vacuum distillation

Cadmium was refined by vacuum distillation, a technique suitable for low boiling and melting point materials, to remove the heavy and low vapour pressure impurities at ppm level. The detailed analysis of the purified Cd as well as raw Cd was done by ICP-OES techniques for 27 impurity elements. Purification was carried out in an efficient high-yield vacuum distillation system designed and fabricated for purifying 3N+ purity indigenous cadmium to 5N+ (99.999%). Analysis confirmed the reduction of total impurity content from 134 ppm (3N7) for raw Cd to 3 ppm (5N7) upon vacuum distilled Cd. The present study shows that the analysis of impurities such as Fe, Mg and Ca are contributed from environmental effect, whereas impurities such as Pb, Bi, Ag, Ni, Cu, Zn and Tl require adaptation of elemental analysing technique to counter dilution effect. The Hg trace analysis can however be carried out by hydride generation techniques.     

Efficient Mercury Capture Using Functionalized Porous Organic Polymer

The primary challenge in materials design and synthesis is achieving the balance between performance and economy for real‐world application. This issue is addressed by creating a thiol functionalized porous organic polymer (POP) using simple free radical polymerization techniques to prepare a cost‐effective material with a high density of chelating sites designed for mercury capture and therefore environmental remediation. The resulting POP is able to remove aqueous and airborne mercury with uptake capacities of 1216 and 630 mg g^?1, respectively. The material demonstrates rapid kinetics, capable of dropping the mercury concentration from 5 ppm to 1 ppb, lower than the US Environmental Protection Agency's drinking water limit (2 ppb), within 10 min. Furthermore, the material has the added benefits of recyclability, stability in a broad pH range, and selectivity for toxic metals. These results are attributed to the material's physical properties, which include hierarchical porosity, a high density of chelating sites, and the material's robustness, which improve the thiol availability to bind with mercury as determined by X‐ray photoelectron spectroscopy and X‐ray absorption fine structure studies. The work provides promising results for POPs as an economical material for multiple environmental remediation applications.