金刚石线锯切割多晶硅片的气相刻蚀制绒研究（英文）

采用气相刻蚀制绒法研究金刚石线锯切割多晶硅片制绒.加热体积比1:3、总体积400mL的HF-HNO3酸混合溶液到90℃,使酸混合溶液受热产生气相,利用气相对金刚石线锯切割多晶硅片表面进行制绒.结果表明,制绒15min之后,硅片表面的切割纹被完全去除;小腐蚀坑密布硅片表面,尺寸小于1μm,而传统湿法酸制绒所形成的腐蚀坑尺寸大于10μm.气相刻蚀后的金刚石线锯切割多晶硅片表面的微观粗糙度比传统酸混液制绒后的金刚石线锯切割多晶硅片表面的微观粗糙度高3倍多.气相制绒效果明显,并仅有12.11%的低反射率.     

金刚石线锯切割多晶硅片的气相制绒研究

采用气相制绒方法对金刚石切割多晶硅片进行表面制绒.2g硅加到HF-HNO3-H2O(400mL,体积比为6:3:1)的酸混合溶液中在室温下反应产生气相,利用气相对金刚石切割多晶硅片表面进行制绒研究.制绒4min时,硅片表面的切割纹被完全去除、大坑套小坑的蜂窝状蚀坑密布硅片表面,减反效果显著,反射率低至19.51%.气相制绒后的金刚石切割多晶硅片表面的微观粗糙度比传统酸混合溶液制绒后的高约20%.     

金刚石线锯切割多晶硅片表面特性与酸刻蚀制绒问题

为解决金刚石切割多晶硅片与常规HF-HNO3-H2O混合酸湿法制绒技术不兼容的问题,对金刚石切割多晶硅片的表面特性和大幅度提高混合酸溶液中HF的比例进行了刻蚀制绒实验.结果表明,金刚石线切割多晶硅片表面存在约33%的光滑条带区域,其余为与砂浆切割硅片表面相近的粗糙崩坑区域;这些光滑区域使得金刚石切割多晶硅片表面光反射率比砂浆切割多晶硅片高3%~4%;而且光滑区域在富HNO3和富HF的HF-HNO3-H2O混合酸溶液中均较难于腐蚀,使其刻蚀制绒后反射率比砂浆切割多晶硅片低1%~2%,制绒后的金刚石切割多晶硅片反射率比制绒后的砂浆切割多晶硅片高4%~6%,不能满足太阳电池生产要求.富HNO3和富HF两种酸刻蚀体系,均不能解决金刚石切割多晶硅片的制绒问题.     

多晶硅片反应离子刻蚀制绒后扩散工艺的匹配性

研究了多晶硅片在反应离子刻蚀制绒后与扩散工艺的匹配性.在相同的扩散工艺下,反应离子刻蚀制绒后硅片的方块电阻值比酸制绒工艺硅片的方块电阻值高3～11 Ω/□,而且其方块电阻不均匀度值约为普通酸制绒工艺硅片的方块电阻不均匀度值的80％.测试了反应离子刻蚀制绒后多晶硅太阳能电池的外量子效率,其外量子效率在340～1 000 nm波段范围与酸制绒多晶硅太阳能电池相比提高了约10％.对反应离子刻蚀制绒电池的电性能进行了分析,提出了与反应离子刻蚀制绒工艺匹配的高方阻扩散工艺.通过优化调整扩散工艺气体中的小氮和干氧流量,获得了在80 Ω/口方块电阻下,反应离子刻蚀制绒多晶硅电池的光电转换效率提升至17.51％,相对于酸制绒多晶硅电池的光电转换效率提高了0.5％.     

多晶硅表面酸腐蚀制备绒面研究

采用各向同性腐蚀法制备多晶硅绒面,腐蚀液为HF和HNO3的混合溶液,缓和剂为NaH2PO4.2H2O溶液.利用SEM、AFM和紫外分光光度计对硅片绒面进行检测和分析,初步探讨了酸腐蚀机理.结果表明:采用NaH2PO4.2H2O溶液作为缓和剂,腐蚀后的硅片表面具有均匀的腐蚀坑,表面陷光效果较好,通过优化各种参量,反应速度可以控制在2 μm/min左右,适合工业生产的要求.在富HF时,硅片表面易形成尖锐边缘的腐蚀坑,出现或多或少的小孔,反射率最低可达16.5%～17.5%|在富HNO3时,硅片表面易形成腐蚀坑较浅、尺寸偏大的气泡状绒面或光面,反射率较高.     

多晶硅表面酸腐蚀制备绒面研究

采用各向同性腐蚀法制备多晶硅绒面,腐蚀液为HF和HNO2的混合溶液,缓和剂为NaH2PO.2H2O溶液.利用SEM、AFM和紫外分光光度计对硅片绒面进行检测和分析,初步探讨了酸腐蚀机理.结果表明:采用NaH2PO4.2H2O溶液作为缓和剂,腐蚀后的硅片表面具有均匀的腐蚀坑,表面陷光效果较好,通过优化各种参量,反应速度可...     

表面钝化对多晶硅绒面形貌的影响

多晶硅表面制绒技术是太阳能光伏产业亟待突破的一个关键技术.本文根据多晶硅强酸制绒的基本原理,提出了表面活性剂钝化多晶硅表面以降低硅原子与酸反应速度从而改善多晶硅绒面形貌的方法.实验研究了不同含量的添加剂对酸液刻蚀多晶硅绒面形貌的影响,用扫描电镜观察对应的绒面结构,用积分反射仪测量其绒面的表面反射率.实验结果表明:加入活性剂后酸液能使多晶硅表面陷阱坑分布更加均匀,并且能有效消除产生漏电流的缺陷性深沟槽,样品表面反射率比较低,其表面反射率降低到21.5%.与传统酸液腐蚀的多晶硅绒面结构相比,陷阱坑密度明显增加,这种方法在多晶硅太阳电池的生产中是有价值的.     

多晶硅表面织构化新工艺的研究

先后采用电化学腐蚀法和化学酸腐蚀法腐蚀多晶硅,用于制备高效率多晶硅太阳电池.首先将多晶硅片在HF和CH3 CH2 OH体积比为1:2的溶液中进行电化学预腐蚀,具体研究不同电流密度对多晶硅绒面形貌的影响;然后采用化学酸腐蚀法进行二次腐蚀,去除多晶硅表面的疏松结构,得到高性能的多晶硅绒面.使用扫描电镜观察多晶硅表面腐蚀形貌...     

一种基于四甲基氢氧化铵溶液蒸汽的新型硅刻蚀方法

在微机电技术中,利用刻蚀方法对硅进行体结构加工是一步重要的工艺程序. 本文提出了一种基于四甲基氢氧化铵的新型刻蚀方法,四甲基氢氧化铵刻蚀溶液被加热到沸点,单晶硅片置于刻蚀液面的上方,通过刻蚀溶液的蒸汽实现对硅片的各向异性气相刻蚀,此方法并不依赖于昂贵的传统干法刻蚀真空设备. 相比于传统湿法刻蚀,本文提出的刻蚀方法具有若干优点,例如低粗糙度、高刻蚀速率和高均匀性,刻蚀速率和表面粗糙度分别可达到2.13 μm/min和1.02 nm. 同时,在背腔刻蚀工艺中,在硅片非刻蚀面上的隔膜结构和Al基图形可被完好无损地保存下来. 最后,本文提出了一种可能的刻蚀机理说明观察到的实验现象. 与传统湿法刻蚀不同,在本文的气相刻蚀中,由于刻蚀溶液的蒸发过程,刻蚀表面将形成一层薄的水汽层,四甲基氢氧化铵刻蚀剂的离化和刻蚀反应均在这一层中进行,这有助于H₂气泡的快速脱附,以及反应界面分子交换速率的提升.     

CVD金刚石中的氮对等离子体刻蚀的影响

采用非对称磁镜场电子回旋共振等离子体分别对沉积过程中掺氮和未掺氮的化学气相沉积金刚石膜进行了刻蚀研究, 结果表明: 掺氮制备的金刚石膜的刻蚀主要集中在晶棱处, 经过4h刻蚀后其表面粗糙度由刻蚀前的4.761 μm下降至3.701 μm, 刻蚀对金刚石膜的表面粗糙度的影响较小; 而未掺氮制备的金刚石膜的刻蚀表现为晶面的均匀刻蚀, 晶粒坍塌,刻蚀4h后其表面粗糙度由刻蚀前的3.061 μm下降至1.083 μm. 刻蚀导致表面粗糙度显著降低. 上述差别的主要原因在于金刚石膜沉积过程中掺氮导致氮缺陷在金刚石晶棱处富集, 晶棱处电子发射加强, 引导离子向晶棱运动并产生刻蚀, 从而加剧晶棱的刻蚀. 而未掺氮金刚石膜,其缺陷相对较少且分布较均匀 ,刻蚀时整体呈现为 (111) 晶面被均匀刻蚀继而晶粒坍塌的现象. 关键词： 掺氮 金刚石膜 刻蚀 非对称磁镜场     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.