等离子体刻蚀对CdTe太阳电池性能的影响

采用不同干法腐蚀条件下的CdTe薄膜制成器件, 通过I-V、C-V和光谱响应等测试 了电池性能参数。结果表明,溅 射时间太短和功率太小时不能完全去除氧化层,溅射时间过长和功率过高会对薄膜表面造成 损伤, 影响器件性能。 通 过选择器件性能较好的电池、 找出适合等离子束溅 射工艺的条件,所制成的电池转化效率 达 到10.99%;而湿法腐蚀所 制成器件的转化效率为 10.26%。由此可以认为,等离子束轰击溅射的 腐蚀方法较湿法腐蚀更适用于CdTe太阳电池的制备。     

脉冲Nd:YAG激光烧蚀金属Cu产生等离子体发光羽的研究

通过在不同的环境气压下拍摄Nd：YAG脉冲激光烧蚀金属Cu诱导发光的发光羽,提出了发光羽的分区模型．并用之定性地解释了所观察的现象,认为不同烧蚀区域的发光机理不同。     

激光等离子体烧蚀推力的机理研究

随着航天空航空天技术的发展,激光等离子体推进受到了人们的普遍关注.基于激光与物质相互作用产生等离子体的空间分布,本文从微观、宏观和简化模型推导了碳靶的烧蚀压与激光强度的幂函数关系,幂指数分别是0.60493、2/3和2/3.实验测得碳靶的最大偏移量与激光能量的幂函数关系,幂指数为0.61936.实验与微观模型的幂指数相...     

Excimer Laser Etching Process of CdTe Crystals for Formation of Deep Vertical Trenches

Deep isolation trenches with high aspect ratio were formed on CdTe crystals using the excimer laser etching technique. Vertical trenches 80-μm deep and 55-μm wide were formed in 5 min by irradiating a laser on the CdTe crystal through a contact-type metal mask in vacuum. Surface chemistry of the laser-irradiated CdTe crystal was examined by Auger electron spectroscopy (AES), scanning electron microscopy (SEM), and photoluminescence (PL) to determine the extent of laser-induced damage. It was found that the damaged layer remains confined to the thin surface layer in the submicron range, which could be easily removed by a light Br-methanol etch.     

Antireflective structures in CdTe and CdZnTe surfaces by ECR plasma etching

A rigorous coupled-wave analysis procedure has been used to design structures which can be embedded in Cd(Zn)Te surfaces to make them antireflective in the 8–14 m spectral region. Gray scale lithography was used to produce these patterns in photoresist layers. High fidelity transfer of patterns into Cd(Zn)Te surfaces was accomplished by utilizing an electron cyclotron resonance plasma with etch selectivity values in the range of 6.7–13.3. Transmission values at patterned surfaces were measured to be as high as 99.3%.     

Transient plasma shielding effects during pulsed laser ablation of materials

The absorption of laser energy by the plasma during pulsed laser deposition of thin films has been analyzed theoretically. The amount of laser energy absorbed in the plasma termed as the “plasma shielding factor” is a function of the incident laser wavelength, and time dependent plasma dimensions and electron density. Due to time varying parameters, a quantitative analysis of the plasma absorption is difficult. A model which takes into account the absorption of laser energy by the plasma has been developed. In this model, the time-dependent plasma dimension is replaced by the time dependent ablation depth. Using simulated absorption coefficient values, the ablation characteristics of silicon and high T_c superconductors are computed and compared with experimental results. The plasma shielding factor was found to vary approximately linearly with absorbed laser energy. The calculations also showed that the plasma shielding was strongly dependent on the laser fluence but varies very weakly with the simulated plasma absorption coefficient values. Experimental results on plume shielding showed good agreement with the calculations.     

CO2与Nd:YAG脉冲激光锡等离子体羽辉膨胀特性的研究

为了研究激光光源对极紫外(EUV)等离子体碎屑的影响,采用脉冲Nd:YAG激光与CO2激光激发Sn产生等离子体,基于直接成像法,研究了等离子体羽辉在低气压中的膨胀特性。通过确定等离子体边界,计算出各个角度的等离子体羽辉膨胀边界随时间的变化规律,以及运动动能随运动路径的变化规律。结果表明,气压为10Pa时,在相同激光能量密度(2.5106mJ/cm2)的条件下,CO2脉冲激光作用锡靶产生EUV的等离子体动能小于Nd:YAG脉冲激光作用锡靶产生的等离子体动能;在减缓离子碎屑的研究中,CO2脉冲激光作为EUV的产生光源要优于Nd:YAG脉冲激光。这一结果对研究激光等离子体的应用是有帮助的。     

超快激光制备PMMA微流道机理及工艺研究

由于传统加工方法不能解决PMMA微流道的加工质量不好和效率低的问题,本文对超快激光直写PMMA制备微流道的烧蚀机理和工艺参数进行了研究。根据实验分析不同的激光功率、加工速度和加工次数对微流道的宽度和横截面的影响规律,利用超快激光加工系统制备微流道,并采用超景深三维显微镜观测微流道的表面形貌。实验结果表明,当超快激光的加工速度为20 mm/s时,激光功率为1.5 W时,制备的微流道的宽度较小、宽度趋势比较平稳;当超快激光作用PMMA的次数一样,由于加工速度逐渐增加,制备的微流道其宽度和激光的加工速度保持线性增加。当加工速度越大时,微流道的宽度较小、且壁面趋势相对平缓,而当加工速度一定,超快激光的输出功率在1.5 W时,微流道内壁区域不易出现残渣堆积和气泡隆起现象。本文通过优化超快激光加工系统的工艺参数,从而加工出尺寸精度高、表面光滑、宽度为20~90 μm的微流道芯片。     

Optical properties of undoped and iodine-doped CdTe

A comprehensive study of the properties of undoped and iodine-doped CdTe structures by photoluminescence (PL) and photoreflectance (PR) is reported. Undoped bulk CdTe and iodine-doped CdTe layers grown by metalorganic molecular beam epitaxy on (lOO)-oriented CdTe and (211)B-oriented GaAs substrates with electron concentrations ranging from 10¹⁴ to mid-10¹⁸ cm^-3 were included in this study. Lineshape modeling of 80KPL and PR spectra indicated the presence of both free exciton and donor-hole transitions at the higher doping levels. Strong PL and PR signals were also observed at room temperature. If only a single transition is considered for the analysis of the 300K spectra, the PL emission peak and the PR transition energy both exhibit a strong dependence on electron concentration for doped layers. However, lineshape modeling of the room-temperature spectra indicated the presence of multiple transitions consisting of free exciton and direct band-to-band transitions. The use of two transitions resulted in a constant value of bandgap over the entire range of conductivities studied. A strong correlation remained between the broadening of the PR and PL spectra and excess carrier concentration N_D-N_A. In addition, the E₁ transition energy measured by PR was found to vary dramatically with growth conditions.     

金属表面激光烧蚀的发射光谱分析

时间和空间分辨发射光谱方法被用来研究短脉冲（５ｎｓ）激光烧蚀钛靶过程中产生的等离子体羽。通过测量其中钛原子和离子的发射光谱，计算了等离子体羽的膨胀速度，讨论了钛原子和一价离子密度的时间分布和时间演化以及激光参数的影响。     

Influence of space charge on lux-ampere characteristics of high-resistivity CdTe

The concentrations of defects forming at near-midgap level in high-resistivity CdTe were estimated on the basis of room-temperature lux-ampere characteristics. A simple model explaining their sublinear dependence based on the presence of discrete levels near the midgap is presented. It is shown that accumulation of space charge in the sample can explain the observed experimental data. Theoretical calculations show that a maximum concentration of the midgap level leading to the observed slope α of lux-ampere characteristic, I_ph=C×I^α, is less than 10¹³ cm⁻³ for a wide range of capture cross sections of electrons and holes. This result supports models that assume formation of a high-resisitivity state with a minimum deep-level doping.     

激光烧蚀过程中冲量耦合系数的研究

首先分析了激光烧蚀过程中,对冲量耦合系数大小有影响的因素,然后利用简化的物理模型,对激光聚焦后直接烧蚀固体靶的情况进行了理论分析,并应用数值计算重点讨论了激光能量在靶物质中的不同分布对冲量耦合系数的影响。结果说明:能量的分布不是影响冲量耦合系数的主要方面,而靶物质材料和靶结构对冲量耦合系数会有较大影响。     

Chemical Interaction of CdTe and CdZnTe with Aqueous Solutions of H2O2-HI-Tartaric Acid

An iodine-based etching system, H₂O₂-HI-tartaric acid, was tested on CdTe samples with (110), (100), (111)A, and (111)B orientations. The etching rate of CdTe was shown to depend on the sample orientation, ratio of etchant composition components, temperature, and rotation speed of the disc. A study of the chemical composition and structure of the (211)B Cd_1−x Zn _x Te surfaces etched under different conditions was carried out. X-ray photoelectron spectroscopy (XPS) measurements showed that a nearly stoichiometric surface was achieved after heating of the etched surface in vacuum. Reflection high-energy electron diffraction (RHEED) measurements revealed a very good single-crystalline surface layer in samples etched with HI-based solutions as compared with bromine-methanol treatment.     

强激光加载真空中铝靶冲量耦合的数值模拟

为了获得强激光加载真空中铝靶的冲量耦合系数,利用激光体烧蚀模型,采用流体力学理论和1维Lagrange有限差分的计算方法,对真空条件下不同激光参量时气化物质对靶产生冲量的过程进行了数值模拟,模拟计算结果与实验测量结果、Phipps定标关系符合得较好。结果表明,在等离子体条件下,冲量耦合系数随着激光功率密度的增大而减小。     

排气方式及工艺参数对等离子体刻蚀a-Si均一性的影响

本文对在等离子体刻蚀工艺中,功率、压强、气体比例重要参数对a-Si刻蚀均一性的影响进行了研究。采用PECVD成膜、RIE等离子体刻蚀,并通过台阶仪和光谱膜厚测定仪对膜厚进行表征。结果表明压强在10~15Pa,功率在5 500~6 500 W的参数区间,a-Si刻蚀均一性波动不大,适合工业化生产。a-Si刻蚀速率及刻蚀均一性对气体比例较为敏感,SF6∶HCl=800∶2 800mL/min时a-Si刻蚀均一性为最佳。四角排气方式对维持等离子体浓度作用明显,有利于刻蚀均一性的提升。四周排气方式会破坏等离子体浓度进而破坏a-Si刻蚀的均一性。     

Chemical Etching of CdTe in Aqueous Solutions of H<Subscript>2</Subscript>O<Subscript>2</Subscript>-HI-Citric Acid

An iodine-based etching system, H₂O₂-HI-citric acid, has been developed and tested on CdTe samples with orientations (111)A, (111)B, (110), and (100). The etching velocity of CdTe was shown to depend on sample orientation and other etching conditions. The surface roughness was comparable with that of the surfaces after Br-methanol treatment. A comparative study of the chemical composition of the (211)B CdZnTe surfaces etched under different conditions was performed. X-ray photoelectron spectroscopy (XPS) measurements showed that all treated surfaces of CdZnTe samples are enriched with Te. The HI-based treatment seems to be more acceptable than the Br-methanol treatment in terms of elimination of Te oxides from the surface, however.     

准分子激光化学反应淀积硫化物薄膜

提出了一种新的激光光化学三元反应体系，用于制备硫化铅薄膜。应用吸收光谱、扫描电镜和Ｘ射线光电子能谱等测试手段研究了膜的性质和组成，指出了该方法淀积硫化物薄膜的可行性。     

Contamination of silicon and oxidized silicon wafers during plasma etching

Neutron activation analysis has been used to study the type and level of contamination of silicon and oxidized silicon wafers exposed to various plasmas used in silicon device processing. Silicon wafers exposed to plasmas in a reactor previously used to remove SiN passivation layers from Au metallized wafers were found to be heavily contaminated with Au (up to ∼10¹⁴ atoms/cm²). Au contamination of oxidized silicon wafers similarly treated was two to three orders of magnitude smaller regardless of whether SiO₂ etched faster or slower than Si in the plasmas used. Wet chemical cleaning of contaminated Si subsequent to plasma exposure was relatively ineffective in removing residual Au. This is interpreted as indicating indiffusion of Au during plasma exposure of Si. Exposure to a polymer forming plasma reduced the level of Au contamination of Si by nearly two orders of magnitude due to effective “sealing” of reactor surfaces by polymer film. Further, the level of contamination of Si was observed to decrease by over two orders of magnitude with usage time of the reactor during a 300-day time period when no Au containing materials were introduced into the reactor.     

利用碳糊成膜法改进CdTe太阳电池背处理工艺

提出一种新型的制备Cd％太阳电池背接触方法。利用碳糊成膜法,将含Cu、Te的CdCl2浆状悬浊液涂覆在CdTe表面,只进行一次后退火,X射线衍射（XRD）、二次质子谱（SIMS）测试发现,就能同时达到CdCl2后处理的作用、形成CuxTe的缓冲层和降低背接触势垒的目的。实验结果表明。本文方法将传统的CdCl2后处理和形...     

In-situ ellipsometric measurements of the MBE growth of CdTe/HgTe and CdTe/ZnTe superlattices

Phase modulated ellipsometric data recorded during molecular beam epitaxial growth of CdTe/HgTe and CdTe/ZnTe superlattices on (100) and (211)B oriented Cd_0.96Zn_0.04Te and GaAs substrates are presented. The measurements provide a continuous monitor of the growth process, thickness, growth rate, compositional data, and evidence of interdiffusion in CdTe/HgTe superlattices at elevated temperatures. The thickness measurements are independent of growth kinetics and surface orientation and agree well with those obtained from x-ray diffraction and reflection high energy electron diffraction. Ellipsometry shows that the incorporation of Hg in CdTe is significantly higher on (100) oriented surfaces than on (211)B oriented surfaces. Fine structure in the data from CdTe/ZnTe superlattices may be associated with a surface reconstruction during deposition of each CdTe layer. The experimental results for CdTe/HgTe superlattices compare well with results of thin film multi-layer calculations. The general applicability of ellipsometry as an in-situ analytical technique for epitaxial growth of a range of semiconductor superlattices is discussed.