Deformation and material removal in a nanoscale multi-layer thin film solar panel using nanoscratch

Amorphous Si thin film solar panels are multi-layer structures consisting of nanometric layers of hard and brittle materials. The deformation and material removal characteristics of the panel cross-section were investigated using nano-mechanical testing. Nanoindentation and nanoscratching were performed using indenters of various geometries at a range of loads. Atomic force microscopy and electron microscopy were used to study the resulting deformation structures and mechanisms. Plastic deformation of the brittle layers was observed below a critical scratch depth, where material removal occurred without fracture. The critical depth was found to be dependent on indenter geometry and material properties. The indenter tip with the smallest included angle resulted in the greatest scratch depths and material removal. The increased scratching speed also improved the removal efficiency. The results of this work can be applied to develop the ductile regime machining process for thin film solar panels.     

Large deformation of thin films and layered flat panels: effects of gravity

A general theory is presented for the large deformation of thin films and layered flat panels in which gravitational forces have a marked influence on the evolution of curvature, shape and instability. Isotropic, linear elastic deformation is considered with small strains and moderate rotations. The thermomechanical properties of the layered material are allowed to vary through the panel thickness so as to derive a general result for multilayers and graded materials. Explicit analytical expressions are derived for the critical curvature and the critical “effective load” at which curvature bifurcation occurs. The analysis considers square, circular and rectangular panels that are simply supported at three points, with the thin film on the panel facing either up or down. A boundary layer analysis is presented for rectangular panels specifically to examine the effect of panel shape on curvature evolution and geometric stability. Computational simulations involving full three-dimensional hyperelastic formulations with large rotations and two-dimensional hyper elastic formulations with moderate rotations were used to assess the validity of the analytical results. Systematic experiments on the large deformation characteristics of flat glass panels with and without silicon nitride thin film deposits were carried out to check the predictive capabilities of the theory. The trends predicted by the theory and its quantitative predictions of bifurcation with and without thin film deposits on the panels were found to be in reasonable agreements with experiments. The limits of the solutions of the present theory for the special case of thin films on substrates with only mismatch strains are shown to converge to prior analytical results. Furthermore, the theory is shown to capture the experimental trends observed during large deformation in thin-film/substrate systems in the absence of gravitational effects.     

脉冲激光沉积及硒化法制备Cu(In,Ga)Se2薄膜研究

采用脉冲激光沉积和硒化后热处理的方法在石英衬底上制备Cu(In,Ga)Se2（简写为CIGS）薄膜,研究脉冲激光沉积（PLD）技术在制备CIGS薄膜太阳能电池材料上的应用,分析了不同预制层沉积顺序及厚度对CIGS薄膜组织结构、表面形貌、成分以及光学性能的影响。实验结果表明：(1)利用PLD技术及后硒化处理的工艺,制得的CIGS太阳能电池吸收层具有纯相和高结晶度等特性;(2)CuGa/In金属预制层的叠层顺序和叠层数、硒化退火温度对薄膜的结晶质量、晶粒尺寸、成分都具有重要的影响,其中叠层顺序影响最为明显;(3)样品均表现出对可见光区具有透射率低和吸收系数高的光学特性。本工作为制备性能优良的CIGS太阳能电池吸收层,提供了一个新颖的工艺手段。     

Yield surface of polycrystalline thin films as revealed by non-equibiaxial loadings at small deformation

A biaxial device developed at DiffAbs beamline of the SOLEIL synchrotron facility has been employed to determine the applied strains in film–substrate composites using both X-ray diffraction and digital image correlation measurements. Such an experimental combination is used for the first time to determine the yield surface of a polycrystalline thin film deposited on a polyimide substrate. In situ biaxial tensile tests under different biaxial planar load ratios were performed on W/Cu nanocomposite thin films deposited on flexible substrates. The effect of loading path on the yield stress of W/Cu nanocomposites is presented by considering a large range of proportional loadings. By comparing experimental results with theoretical models, this study reveals the brittle behaviour of W/Cu nanocomposite thin films at small deformations.     

太阳热反射隔热彩色涂料的制备及隔热性能

目的从色彩三原色理论出发,制备隔热性能优异的太阳热反射隔热彩色涂料。方法将复合钛红、钴蓝、钛铬黄、镍钛黄和铬绿颜料复配为颜料,硅溶胶偶联苯丙复合乳液为成膜基料,制备了紫色、蓝色、橙色和绿色太阳热反射隔热彩色涂料。用扫描电子显微镜和电子探针对颜料微观结构和元素进行定量检测,用紫外/可见/近红外分光光度计探究颜料的反射特性、涂膜反射特性和污染处理后涂膜太阳光反射比降低率。分别从涂膜试板背面隔热温差和涂膜试板对箱体中心的辐射热流降低率两个方面,衡量太阳热反射隔热彩色涂料的隔热效果。结果紫色、蓝色、橙色和绿色4种太阳热反射隔热彩色涂膜的太阳光反射比均在0.5000以上,分别为0.6287、0.5433、0.7594和0.6991,涂膜污染后的太阳光反射比降低率均满足相关标准≤15%的要求。涂膜试板背面隔热温差均在3℃以上,涂膜试板对箱体中心的辐射热流降低率均在10%以上,隔热降温性能显著。结论采用色彩三原色理论选择合适的红外反射颜料,可制备出隔热性能优异的太阳热反射隔热彩色涂料。     

Effect of porous silicon layer on the performance of Si/oxide photovoltaic and photoelectrochemical cells

Photovoltaic and photoelectrochemical systems were prepared by the formation of a thin porous film on silicon. The porous silicon layer was formed on the top of a clean oxide free silicon wafer surface by anodic etching in HF/H₂O/C₂H₅OH mixture (2:1:1). The silicon was then covered by an oxide film (tin oxide, ITO or titanium oxide). The oxide films were prepared by the spray/pyrolysis technique which enables doping of the oxide film by different atoms like In, Ru or Sb during the spray process. Doping of SnO₂ or TiO₂ films with Ru atoms improves the surface characteristics of the oxide film which improves the solar conversion efficiency.The prepared solar cells are stable against environmental attack due to the presence of the stable oxide film. It gives relatively high short circuit currents (I_sc), due to the presence of the porous silicon layer, which leads to the recorded high conversion efficiency. Although the open-circuit potential (V_oc) and fill factor (FF) were not affected by the thickness of the porous silicon film, the short circuit current was found to be sensitive to this thickness. An optimum thickness of the porous film and also the oxide layer is required to optimize the solar cell efficiency. The results represent a promising system for the application of porous silicon layers in solar energy converters. The use of porous silicon instead of silicon single crystals in solar cell fabrication and the optimization of the solar conversion efficiency will lead to the reduction of the cost as an important factor and also the increase of the solar cell efficiency making use of the large area of the porous structures.     

预沉积ZnO薄膜对ZnO−MoS2/ZnO复合涂层结构与性能影响

目的 通过优化原子层沉积工艺获取不同厚度ZnO薄膜,研究ZnO薄膜晶体取向对ZnO?MoS2涂层生长结构的影响,获得具有优异摩擦学性能的ZnO?MoS2/ZnO复合涂层。方法 采用原子层沉积法在不锈钢基体上预沉积不同厚度的ZnO薄膜,再用射频磁控溅射技术继续沉积ZnO?MoS2涂层,制备ZnO?MoS2/ZnO固体润滑复合涂层。结果 X射线衍射分析发现,预沉积ZnO薄膜有诱导后续ZnO?MoS2涂层沉积生长的作用,预沉积100 nm厚ZnO薄膜的ZnO?MoS2/ZnO复合涂层显示出宽化的MoS2 (002)馒头峰,其截面形貌显示为致密的体型结构,获得的摩擦因数最低(0.08),纳米硬度最高(2.33 GPa),硬度/模量比显示该复合涂层的耐磨损性能得到提升;X射线光电子能谱分析结果表明,复合涂层表面游离S与空气中水发生反应程度大约为原子数分数5%,显示复合涂层耐湿性能较好;基于原子层沉积ZnO薄膜生长及其对后续ZnO?MoS2涂层生长的影响分析,提出了ZnO?MoS2/ZnO复合涂层磨损模型,阐明了ZnO薄膜对复合涂层结构及摩擦学性能的影响,并以该模型解释了200 nm厚 ZnO薄膜上沉积ZnO?MoS2涂层出现的摩擦因数由高到低的变化趋势及最终磨损失效现象。结论 合适的原子层沉积制备的ZnO薄膜有利于MoS2 (002)取向生长,可有效提升ZnO?MoS2/ZnO复合涂层的摩擦学性能;控制ZnO薄膜厚度,可实现ZnO薄膜与基底及ZnO?MoS2层间界面之间的优化结合,以制得具有较好摩擦学性能及使用寿命的ZnO?MoS2/ZnO复合涂层。     

ELID grinding and tribological characteristics of TiAlN film

This paper presents the results of electrolytic in-process dressing (ELID) grinding experiments performed on TiAlN film and characterization of the tribological characteristics of the produced films. In advanced films coated by physical vapor deposition, such as CrN and TiAlN, the low surface roughness required for attaining superior tribological characteristics is difficult to attain by use of only a coating process. ELID of grinding wheels improves wheel performance, enabling the attainment of specular finishes on brittle materials, with surface roughness on the nanometer scale (4 to 6 nm). In the present study, high-quality TiAlN film surfaces were fabricated by the ELID technique, typically achieving a surface roughness of around Ra 0.0024 μm by employment of a SD#30,000 wheel. Scanning electron microscopy reveals that ELID improved the finish, as indicated by the shape of grinding marks. Chemical element analysis by an energy-dispersed x-ray diffraction system suggests that ELID grinding formed an oxide layer in the machined surface of TiAlN film. Therefore, in addition to the highly smooth surface, an oxide layer formed by ELID grinding imparts superior tribological properties to ELID-ground TiAlN film.     

A study on the thermal conductivity measurements of Cu thin films utilizing temperature distribution

Thin film type materials are widely used in high-tech industries including electronics, photonics and even machine tools. Often, knowledge of the thermal properties of thin films is needed to assess reliability through thermal stress analysis when the thin film type materials are applied to functional electronic parts. Only a few methods have been developed for thermal conductivity measurement of a thin film on a substrate. In this study Cu thin films were processed on the borosilicate glass substrate of prismatic bar shape using sputtering. Two Cu coated surfaces of specimens were brought into contact to maintain the insulated boundary conditions. The temperature distributions were measured from the back surface of the substrate using radiation thermometry. The thermal conductivities of the Cu thin films were measured and found to be much lower than those of bulk materials. The measured thermal conductivities were found to be closely related to the microstructures of the Cu thin films.     

低频机械谱术测量薄膜切变模量及微量油膜探测

描述了工作在共振和次共振模式下的低频机械波谱仪的基本原理．主要介绍了研究金属衬底上薄膜的物理性质的两种方法：第一种方法，用于测量沉积在钼丝上的TiN／Ti(C，N)多层膜的切变模量和内耗；第二种方法，用于探测钢片表面微量油膜的存在．尽管这两种技术有着各自不同的应用目的及对象，但它们均源自能够导致机械能损耗的表面效应。     

Preparation and optical properties of Nb-NbN multilayer films as solar selective absorptive coatings

Based on the cermet double layer structure, Nb-NbN multi-layer films for solar selective coatings were deposited by direct current reactive magnetron sputtering. The Nb/Nb-NbN/Al2O3 trilayered structure was deposited on a stainless steel (SS) substrate by using a single niobium target. The expected components were adjusted by changing the gas flowing ratios of Ar: N2. The Al2O3 antireflective layer on the top of the film was produced by r. f. magnetron sputtering using Al2O3 ceramic target. A solar absorptivity of 0.94 and a normal emissivity of 0.16 at room temperature have been achieved for the coating. Thermal vacuum aging to the samples was carried out at 350 and 500 ℃ for 1 h. The results show a good thermal stability. Microstructure and its dependence on temperature of the Nb, NbN and Nb-NbN single layers were investigated, respectively.     

图形化固体薄膜技术及其摩擦学性能的研究进展

固体薄膜技术可以用于显著提高材料的摩擦学性能,表面图形化技术则通过在部件表面制备预先设计的图形来改善摩擦副的接触和润滑行为。近年来,人们尝试将表面图形化技术和固体薄膜技术相结合,出现了一类称之为图形化薄膜的技术。研究表明:在很多情况下,与单纯的完整薄膜或图形化表面相比,图形化薄膜能够同时发挥薄膜的强化作用和图形化改变摩擦界面行为的作用,在改善和提高摩擦学性能方面具有综合优势。文中总结了图形化薄膜技术方面的研究工作;介绍了图形化薄膜的制备技术、分类、摩擦学性能以及应用;分析讨论了图形化薄膜的作用机理;并展望了图形化薄膜的发展前景。     

Synthesis of Cr-Al2O3 Cermet Selective Surfaces Coated by SnO2 Thin Film by Air Plasma Spraying

High efficient Cr-Al2O3 cermet selective surfaces coated by sol-gel SnO2 thin film for high-temperature application were synthesized by air plasma spraying(APS),followed further heat and polish treatment.The phase composition and micro morphology of coating samples were characterized by X-ray diffractions(XRD),scanning electron microscope(SEM)and roughmeter respectively.The solar absorptance(α)and thermal emittance(ε)were determined by optical spectrum instrument.The results show that Cr-Al2O3 cermet coating has a high absorptivity nearly 0.90.But unfortunately,the emissivity of these coatings is nearly 0.50 because of the big thickness and coarse surface prepared by APS technique.However,once coated SnO2 thin film,the composite coatings exhibit excellent selective absorbing property of α=0.89 and ε=0.12.Thus,SnO2 thin film plays a significant role in decreasing the emissivity of coatings as antireflection layer.And furthermore,the optical performance shows that more metal content and smooth surface are favorable for the selective absorbing property.Moreover,the coatings have excellent bond strength with stainless steel substrate and thermal shock resistance at high temperature.     

Solar energy-conversion processes in organic solar cells

Organic semiconducting materials have demonstrated attractive light-absorption and photocurrent-generation functions due to their delocalized π electrons as well as intra-molecular and inter-molecular charge separation processes. On the other hand, organic semiconducting materials have easy property tuning, are mechanically flexible, and have large-area thin film formation properties. As a result, organic materials have become potential candidates in solar energy applications. This article will review critical energy-conversion processes in organic solar cells with the focus on singlet and triplet photovoltaic responses.     

硅基微磁通门非晶Fe96Nb4铁芯薄膜的研究

采用磁控溅射法制备一种适合用于硅基微磁通门的新型非晶Fe96Nb4软磁铁芯薄膜,并利用X射线衍射仪、扫描电子显微镜、振动样品磁强计测试薄膜的相组成、表面形貌、和磁滞回线,用双铁芯磁通门探头线圈对制作的铁芯薄膜进行试验.结果表明:随制备温度的升高,薄膜的缺陷明显减小,软磁性能显著改善.基片温度为630 K时制作的硅基Fe96Nb4铁芯薄膜的性能适合用于微磁通门铁芯材料.     

Concepts for the design of advanced nanoscale PVD multilayer protective thin films

Technological challenges in future surface engineering applications demand continuously new material solutions offering superior properties and performance. Concepts for the design of such advanced multifunctional materials can be systematically evolved and verified by means of physical vapour deposition. The classical multilayer coating concept today is well established and widely used for the design of protective thin films for wear and tribological applications. It has proven great potential for the development of novel thin film materials with tailored properties. In the past decade, the emerging new class of nanoscale coatings has offered to the material scientists an even more powerful toolbox for the engineering thin film design through a combination of the multilayer concept with new nano-coatings. Some examples are the use and integration of low friction carbon-based nanocomposites in advanced multilayer structures or the stabilization of a specific coating in another structure in a nanolaminated multilayer composite. This paper reviews the latest developments in hard, wear-resistant thin films based on the multilayer coating concept. It describes the integration of nanocrystalline, amorphous and nanocrystalline/amorphous composite materials in multilayers and covers various phenomena such as the superlattice effect, stabilization of materials in another, foreign structure, and effects related to coherent and epitaxial growth. Innovative concepts for future, smart multilayer designs based on an extremely fine structural ordering at the nanoscale are presented as well.     

Structural and optical properties of tellurium films obtained by chemical vapor deposition（CVD）

1 Introduction Te thin films have been extensively used in various technological areas, especially in microelectronic devices such as gas sensor [1?3], optical information storage [4] and other applications [5?7]. All these applications are due to remark…     

联氨浓度对化学水浴沉积ZnS薄膜性能的影响

利用化学水浴法(CBD)在硫酸锌、氨水、联氨、硫脲的沉积体系下制备CIGS太阳能电池的ZnS缓冲层薄膜,研究了联氨浓度对缓冲层ZnS薄膜的生长过程、晶体结构及物理性能的影响。结果表明,联氨浓度能够显著影响ZnS薄膜的生长速度,联氨浓度越高,薄膜厚度越大,薄膜的致密性也随之提高;联氨浓度对薄膜的结晶性影响较小,CBD法制备的ZnS薄膜均为非晶薄膜;制备的ZnS薄膜有较高的透过率,禁带宽度为3.85 eV左右,能够使更多短波、高能量光子透过缓冲层到达CIGS吸收层,从而提高电池性能。     

离子束辅助沉积法制备重掺N氧化铈提高其可见光吸收性能

氧化铈是一种潜在的可见光催化材料,但是如何实现在氧化铈晶格内的N掺杂是阻碍其发展的主要原因。本研究中,我们采用离子束辅助沉积法制备了N掺杂的氧化铈薄膜材料,采用该方法实现了对氧化铈薄膜的高含量N掺杂,N含量可高达25%,远远高于采用传统方法制备的氮掺杂氧化铈。N 1s的高分辨谱显示,掺杂的N替代了氧化铈中的O而实现了N在氧化铈晶格中的掺杂。XRD结果显示,氧化铈薄膜在生长过程中,N离子的轰击并没有改变氧化铈的晶体结果,但是改变了氧化铈薄膜表面形貌,从SEM结果上可以看出氧化铈表面颗粒变得细小,薄膜表面变得光滑。紫外可见吸收光谱结果显示,随着掺N量的增加,氧化铈的光吸收发生红移。     

Analytical model to determine the critical feed per edge for ductile-brittle transition in milling process of brittle materials

Brittle materials like glass are considered difficult-to-machine because of their high tendency towards brittle fracture during machining. The technological challenge in machining such brittle materials is to achieve material removal by plastic deformation rather than characteristic brittle fracture. In ductile mode machining, the material is removed predominantly by plastic deformation and any cracks produced due to possible fracture in the cutting zone are prevented from extending into the machined surface. This is achieved by selecting an appropriate cutting tool and suitable machining parameters. In ductile machining by milling process, fracture induced cracks are diverted away from final machined surface by selecting a suitable feed per edge less than a critical threshold value. Hence determination of critical feed per edge is of paramount importance to achieve ductile mode machining by milling process. This paper presents an analytical model based on fracture mechanics principles to predict the critical feed per edge in milling process of glass. The size and orientation of cracks originating from brittle fracture during machining have been quantified by using indentation test results and the critical value of feed per edge has been determined analytically as a function of intrinsic materials properties governing brittle fracture and plastic deformation. Furthermore, an equivalent tool included angle has been suggested for machining operation as against the indenter included angle to correlate the indentation and machining test results with improved degree of accuracy. Experimental results validated the proposed model fairly accurately. It has been established that if the longest cracks oriented in radial direction to the cutting edge trajectory are prevented from reaching the final machined surface by selecting a feed per edge less than or equal to a critical value, a crack-free machined surface can be achieved.