多晶硅表面绒面的制备及优化

本论文依据多晶硅结构的特点,对多晶硅表面绒面的制备进行研究并优化制绒工艺。酸绒面的制备可以改善多晶硅表面减反射效果。在合适的反应条件下用酸腐蚀的方法可以在硅片上制备出减反射效果良好的绒面,并且工艺简单、成本低,适合于工业的实际生产和应用。连续生产过程中不断添加一定比例的腐蚀液会使多晶硅片在一个相当长的范围内达到稳定的制绒效果。并且通过控制腐蚀深度可以得到好的短路电流,进而增大电池的光电转换效率。     

多晶硅太阳电池表面绒面制备工艺优化

采用各向同性腐蚀法制备多晶硅绒面,利用正交实验法研究了不同腐蚀液配方中的HNO3、HF和缓和剂NaH2PO4·2H2O的含量对多晶硅太阳电池绒面的反射率和腐蚀速度的影响。结果表明:NaH2PO4.2 H2O溶液对腐蚀速度有着显著的影响,其次为HF溶液和HNO3溶液;对于反射率来说,其影响因素的重要性主次顺序为HF溶液、HNO3溶液、NaH2PO4·2 H2O缓和剂。在本实验条件下,最佳的酸腐蚀混合液配方为HF∶HNO3∶NaH2PO4.2 H2O=9∶1∶7,在该工艺条件下,制备的硅片绒面腐蚀坑较为均匀,反射率为17%左右。     

多晶酸制绒添加剂对硅片绒面的影响

在HNO3-HF制绒体系中加入添加剂,对硅片进行制绒,并对制绒后的硅片进行了表面形貌分析和光学性能表征。腐蚀深度结果显示,不同种类的添加剂对腐蚀速率作用不同;硅片表面反射率测试结果显示,所用添加剂对改善制绒后表面光学均匀性有积极作用。通过对添加剂组分配方的优化,在不改变制绒工艺条件的基础上制得腐蚀深度3.5~4.5μm、表面反射率20%~21%的多晶硅片,有望使现有产线制绒效果得到改善。     

倒金字塔型多晶黑硅的制备、表征及性能研究

金刚线切多晶硅片具有加工效率高、硅片厚度薄以及无需添加SiC微粉等研磨浆料的特点,成为了一种新兴的硅片切割技术。然而传统酸制绒工艺很难对金刚线切多晶硅片起到很好的制绒效果,限制了其在实际生产中的推广。多晶硅表面的陷光结构对其转换效率具有重要影响,但多晶电池表面纳米级别孔洞绒面结构会导致很高的载流子复合损失。通过含有HF/NH_4F/H_2O_2及其他弱碱性物质的混合溶液对硅片表面的纳米级孔洞结构进行修饰,更改反应时间,得到了多组具有微米级规则倒金字塔结构的黑硅多晶电池。对不同倒金字塔结构的黑硅样品进行表征并测试其实际性能,得到了最优的反应时间为240 s。     

表面织构化对于多晶硅太阳电池性能的影响

表面织构化作为太阳电池生产工艺的起始工序,对于转换效率的影响至关重要.在HF-HNO3-H2O腐蚀溶液体系下,通过调整腐蚀时间制备了三种典型的多晶硅织构化表面,并利用扫描电子显微镜(SEM)和光电转换效率测试仪(IPCE)对其表面形貌和反射率特性进行表征分析.结果表明:低反射率的织构化表面并未获得更高的转换效率,而在HF-HNO3-H2O腐蚀溶液体系下,腐蚀100 s制备得到的“蠕虫状”的腐蚀坑分布均匀,反射率约为26％;且可以很好匹配太阳电池生产工艺中的后续工序,制备得到的太阳电池效率为16.68％,VOC和JSC分别为623 mV和34.55mA/cm2.该织构化方案已在25 MW多晶硅太阳电池生产线上实施,绒面质量得到保证,不增加工艺难度和生产成本,适合于工业生产.     

添加剂对单晶硅太阳电池表面织构化的影响

在传统的氢氧化钾/水/乙醇制绒体系中添加酸类(酒石酸,硼酸)、表面活性剂(甲基纤维素、十二烷基磺酸钠、聚乙二醇PEG400)等添加剂,研究了添加剂含量对制绒面形貌和反射率的影响。研究表明,制绒液中酒石酸质量浓度为400×10-6时制绒效果最好,硅片反射率降低到原始硅片的55.48%;混合添加100×10-6酒石酸、200×10-6硼酸的制绒效果更加明显,反射率达到原始硅片的40.81%。而在酒石酸/硼酸混合体系中添加质量分数为0.2%的表面活性剂PEG400时制绒效果较好,硅片反射率降低为原始硅片反射率的40.45%。     

硅的腐蚀溶液

本文阐述了HNO_3—HF—H_2SO_4—HAC四元素硅片腐蚀的方法,研究了各组份对硅和钼腐蚀的影响。结果表明,该溶液对钼的腐蚀仅为常用腐蚀溶液的5％以下,对硅的腐蚀可以适当调整。采用该工艺,可获得光滑、平整的镜表面和节省腐蚀溶液,降低成本。     

酸腐多晶硅太阳电池表面织构的研究

多晶硅太阳电池是目前光伏发展的主要趋势,而缺乏有效的表面织构的方法是多晶硅太阳电池发展的一个瓶颈.采用酸腐多晶硅片的方法获得各向同性的表面织构.酸腐蚀液选取HF-HNO3混合溶液并用H2SO4进行改良.分别利用扫描电镜(SEM)和光谱响应系统分析了腐蚀后多晶硅片的表面形貌和反射率.结果表明,酸腐多晶硅表面分布均匀的蠕虫状腐蚀坑,反射率很低,在PECVD SiNx减反射膜后反射率大大下降.     

纳米线超小绒面太阳电池的改进研究

多晶硅太阳电池由于晶向不一致,存在反射率较高的问题,因此,降低多晶硅太阳电池的反射率成为提高多晶硅太阳电池性能的最有效手段之一。利用硝酸银溶液作为腐蚀液,对多晶硅的表面进行处理,使得多晶硅片表面的反射率在可见光波段降低到5%左右,同时探索了利用氮化硅作为保护层,避免腐蚀液对多晶硅片背面造成损伤的方法。最后,对利用此方法制备多晶硅绒面存在的问题进行了分析,并提出了下一步的改进方案。     

单晶硅太阳能电池前表而化学腐蚀研究

制绒工艺是晶硅太阳能电池产业化研究的重要方向之一。本文对德国Rena公司的湿法腐蚀制绒设备进行了工艺流程的简要概括,在产业化环境中对硅片表面的化学处理工艺进行了研究。通过研究分析,自制的GP溶液能有效的降低溶液表面张力并改善单晶硅片表面的浸润效果;湿法腐蚀后,硅片表面绒面结构清晰,金字塔形状均匀,底座大小在2～3μm左右;由腐蚀深度变化曲线分析可知,各腐蚀槽腐蚀深度值92％都集中在7．5～8．5之间,接近最优化腐蚀深度,碎片率低于5‰。     

Novel 3D PZT thin film structure for micromechanics

In this work, fabrication and properties of 3-dimensional structures coated with piezoelectric Pb(Zr,Ti)O₃ (PZT) thin films have been studied in order to improve the piezoelectric coupling into the third dimension. Calotte layers have been chosen as demonstration devices. The base diameters range from 40 to 120 μm, the height varies between 10 to 40 μm. A dynamic, in-situ co-sputtering process allowing for in-situ growth was applied. Micromoulds were formed by wet etching in silicon. The etchant was a HNA solution (HF, HNO₃, CH₃COOH) on a silicon dioxide mask. Calottes were obtained with the desired geometry and smooth surface state after few minutes etching time, and the use of chemical mechanical polishing (CMP). After deposition of the PZT membrane, deep silicon dry etching was then used to liberate the calotte layer. The dielectric constant and loss tangent of the calotte capacitors amounted to 830 and 5%, respectively (10 kHz). The fundamental resonance frequencies varied between 2.5 and 16.5 MHz, and were found to be inversely proportional to the base area of the calotte, the proportionality factor being 0.08 Hz m².     

纳米多孔硅可控制备研究

采用了自制双槽和电化学腐蚀法在不同电阻率的硅片上制备出表面平整度很好的纳米多孔硅层,利用场发射扫描电子显微镜对多孔硅的微观形貌进行了分析表征。实验表明多孔硅的孔径、孔隙率和厚度随电化学腐蚀的电流密度和腐蚀时间增加而增加,且电解液中HF(40%)和无水乙醇(99.7%)的配比很趋近时,多孔硅的孔洞分布均匀性越好。在电阻率为0.01~0.02Ω·cm的P型硅片上制备的纳米多孔硅其效果相比其他电阻率的要好。     

Effects of Substrate Bias on the Diamond Nanostructure by Reactive Ion Etching

Abstract

Dense and uniform diamond nanocone arrays on titanium substrate were constructed by using bias-assisted reactive ion etching (RIE) of diamond films in a microwave plasma chemical vapor deposition (MPCVD) system. A hydrogen/argon mixture was employed as work gas with ratio of 3/1. The formation of nanocone structure was generated the lengthways physical bombardment/sputtering by argon ions, and selective chemical reaction of graphite and disordered carbons by hydrogen atoms and ions. The structure, size, and density depended on the substrate bias. The surface morphology of diamond film and nanostructures were characterized by field emission scanning electron microscope (FESME), and the composition of diamond film and nanostructures were characterized by Raman spectra. The Stopping and Range of Trons in Matter (SRIM) software was used to simulate the bombardment effect of the diamond film on different Ar⁺ ion incident angles during the etching process. The experimental results showed substrate bias at ?180?V and ?210?V was beneficial to the formation of high density, small size and sharp nanocones, meanwhile larger bias contributed to the formation of large size nanocones. Besides, as-prepared nanocones still maintained significant diamond phase.     

等离子体表面改性玻璃纤维增强的环氧树脂性能研究

本文基于水轮发电机定子绝缘材料的性能,采用介质阻挡放电在空气中大气压下对无碱玻璃纤维进行表面改性实验,考察改性时间对玻璃纤维表面形貌及化学组成成分变化的影响。其次,用不同处理时间下的玻璃纤维掺杂双酚A型环氧树脂,并制备成复合材料,分别测试了复合材料的拉伸、弯曲等力学参数,对比分析低温等离子体改性时间对复合材料力学性能的影响。实验结果表明,经等离子体处理180s后,玻璃纤维表面出现许多刻蚀坑,并且引入了O-C=O含氧官能团,O-C=O基团含量从未处理的0%上升到7.9%,而复合材料的拉伸、弯曲强度也分别提高了30.97%、37.5%。分析表明,低温等离子体的化学刻蚀作用引起的玻璃纤维表面形貌的变化,以及表层极性基团的引入,是玻璃纤维表面活化处理中的主导过程。采用等离子体表面活化后的玻璃纤维增强环氧树脂,可以使复合材料的力学性能得到显著提高。     

Asymmetrical single-mode silica waveguide deposited by PECVD

Silicon oxynitride (SiON) layer and SiO₂ buffer layer were deposited on silicon wafers by PECVD technique using SiH₄, N₂O and N₂. The refractive index of SiON films measured at a wavelength of 1552 nm using a prism coupler, could be continuously varied from 1.4480 to 1.4508. Optical planar waveguides with a thickness of 6 μm and a refractive index contrast (Δn) of 0.36% have been obtained. In addition, etching experiments were performed using ICP dry etching equipment on thick SiON films grown on Si substrates covered with a thick SiO₂ buffer layer. In order to measure optical properties, a polarization maintaining single-mode fiber was used for the input and a microscope objective for the output at 1.55 μ m. A low-loss and low propagation SiON-based waveguide was fabricated with easily adjustable refractive index of core layer.     

All-silicon bistable micromechanical fiber switch based on advancedbulk micromachining

Bulk silicon micromachining is used to fabricate bistable optical fiber switches. The switches are based on a silicon device consisting of an actuator for fiber movement and a V-groove fiber clamp for bistable operation. The complete mechanical structures including thermal actuators are etched into standard 〈100〉 silicon wafers using anisotropic wet etching in KOH. While switching is caused by asymmetric thermal expansion of a U-shaped silicon cantilever, the fiber clamp is driven by the bimaterial effect. The efficient process technology allows a low cost batch fabrication of these devices. The switches exhibit an insertion loss <1 dB and a crosstalk of <-60 dB using standard single-mode fibers. A switching power below 1 W is required during switching     

金属锂电极在KOH碱性溶液中的腐蚀研究(Ⅰ)

通过测试不同温度、浓度的KOH电解液对金属锂腐蚀反应的影响,研究了金属锂在碱性电解液中的腐蚀行为,拟合出金属锂腐蚀速度随KOH电解液浓度的变化关系。在此基础上,分析计算了金属锂在碱性电解液中的腐蚀反应动力学参数,获得了该体系腐蚀过程的重要动力学数据,包括金属锂腐蚀反应的活化能Ea、腐蚀反应速度常数kcorr、腐蚀反应动力学方程指前因子,以及溶液中H2O的活度与KOH浓度之间的关系等。分析了金属锂腐蚀反应的控制步骤及其主要动力学参数,结果发现H2O在金属锂表面的阴极还原是整个腐蚀过程的速度控制步骤。