2.16 Technology of large area Cu2SCdS solar cells

Solar energy can be converted in different ways: the most attractive application is the direct conversion of solar radiation to electricity. For large scale application large area photovoltaic devices are necessary. Highly efficient solar cells can be produced on the basis of thin semiconducting films. An automized pilot line production for CdS layers, which are evaporated under high vacuum conditions, and their subsequent treatment to get an encapsulated thin film solar cell, are described. Investigation methods and a theoretical model of the heterojunction are reported.     

Modeling potentiometric sensitivity of conducting polymers

The influence of different polymerization conditions and electrochemical processes provoked by soaking on the potentiometric sensitivity of conducting polymer films is discussed. Poly(pyrrole) doped with hexacyanoferrate(II) is selected as a model polymer. It is shown that, depending on the conditions applied during film deposition and soaking, either anionic or cationic potentiometric responses can be observed and related to the composition of the film. The potentiometric sensitivity of the conducting polymer films is analyzed and interpreted by means of generalized theoretical schema.     

基片与膜厚对硬质薄膜力学性能的影响

采用毫牛力学探针技术的两步压入试验法研究了高速钢和不锈钢基片上不同厚度TiN薄膜的硬度和弹性模量。结果表明 :采用同样工艺制备的TiN薄膜 ,其力学性能随基片类型和膜厚的不同有明显变化。薄膜的硬度和弹性模量随膜厚的增加而提高 ;基体硬度的提高也使薄膜呈现较高的硬度和模量。分析认为薄膜内应力状态的改变是产生这些现象的主要原因。     

Residual stresses in thin polymer films cause rupture and dominate early stages of dewetting

In attempting to reduce the size of functional devices, the thickness of polymer films has reached values even smaller than the diameter of the unperturbed molecule. However, despite enormous efforts for more than a decade, our understanding of the origin of some puzzling properties of such thin films is still not satisfactory and several peculiar observations remain mysterious. For example, under certain conditions, such films show negative expansion coefficients or show undesirable rupture although energetically they are expected to be stable. Here, we demonstrate that many of these extraordinary effects can be related to residual stresses within the film, resulting from the preparation of these films from solution by fast evaporation of the solvent. Consequently, depending on thermal history and ageing time, such films show significant changes even in the glassy state, which we quantify by dewetting experiments and corresponding theoretical studies. Identifying the relevance of frozen-in polymer conformations gives us a handle for manipulating and controlling properties of nanometric thin polymer films.     

Preparation of highly oriented titania nanosheet thin films by electrophoretic deposition

Highly oriented titania nanosheet thin films on Pt substrate were fabricated by electrophoretic deposition. The structure and morphology of thin films formed under a variety of conditions are characterized by X-ray diffraction and field-emission scanning electron microscopy. It was found that the quality of titania nanosheet precursor suspension and electrode potential play crucial roles in the film morphology. After the colloidal suspension is optimized by settling for 2 months, the surface of the deposited film is smooth, and the layered structure is dense and well-organized. Film thickness increases with increasing electrode potential, deposition temperature and deposition time. The delicate balance among the above factors that govern the film quality and thickness should be discerned. The films can exhibit a smooth surface and well-organized layered structure under the optimal deposition conditions.     

Structure and optical properties of InN and InAlN films grown by rf magnetron sputtering

The structure and optical properties of InN and In-rich InAlN films grown by magnetron sputtering were investigated. The XRD results show that these films are highly c-axis oriented. The film morphology and microstructure of these films were observed by AFM and SEM which reveals that the films grown in island growth mode. Optical properties of these films were studied by absorption method. The band gap energy of the InN film grown under substrate temperature of 400 °C is 1.38 eV. By studying the E _g values of InN films deposited under different substrate temperature, the Burstein-Moss effect on band gap of InN was examined. The significant band gap bowing of our In-rich InAlN films was found to be correlated with the In contents. The bowing parameter of 3.68 eV was obtained which is in agreement with previous theoretical predictions.     

Field control of magneto-optic gratings

The Faraday or Kerr rotation of the plane of polarization of light incident on adjacent magnetic domains has opposite sense. Thus light transmitted through a film containing stripe domains or reflected from it is diffracted, as by a grating. The period of such a grating can be controlled by the application of a uniform magnetic field. We report on experimental and theoretical work that explores the range of grating field control under quasistatic conditions, using real films, specifically     

聚丁二酸丁二醇酯及聚丁二酸/己二酸-丁二醇酯在微生物作用下的降解行为

研究了聚丁二酸丁二醇酯(PBS)及其共聚物聚丁二酸/己二酸-丁二醇酯(PBSA)薄膜在可控堆肥条件下的宏观生物降解行为,结果显示,PBS和PBSA薄膜具有良好的生物降解性能,降解过程经历三个阶段:诱导期、加速期和平坦期。对堆肥中的微生物进行分离和筛选,发现杂色曲霉菌对PBS和PBSA的生物降解能力最强。进一步研究PBS和PBSA薄膜在杂色曲霉菌作用下的微观生物降解行为,结果表明,PBSA薄膜比PBS薄膜具有更快的生物降解速率。     

Electron exchange between atomic particle and thin metal island films

The resonant charge transfer between H⁻ ion and thin island films was investigated by the instrumentality of the wave-packet propagation method. Under the fixed island film size the ion level width, which characterizes the efficiency of electron transfer, is found to decrease exponentially with ion-surface distance increase. On the other hand the ion level width shows quantum-size effect when the island film radius is changing. The quantum-size effect can be verified experimentally by measuring the yield of charged atomic particles scattered or sputtered from thin metal island films. The necessary conditions for the quantum-size effect observation are low projectile velocity (under 0.01 a.u.) and small island film radius (under 100 a.u.). The thin island films can be obtained by means of electron stimulated desorption from dielectric surfaces.     

Le superparamagnétisme et l'effet hall de films très minces de nickel déposés et étudiés sous ultra-vide

A very thin film of ferromagnetic material has to be considered as an array of small interacting particles. Such a film is superparamagnetic.Expressions for the Hall resistivity are calculated using a simple model. The results seem to be consistent with experimental data on nickel films, with average thickness below 120 Å, studied under ultrahigh vacuum conditions.     

Microstructural changes in vapour-deposited silver, copper and gold films investigated by internal stress measurements

Structural changes in silver, copper and gold films 100 nm thick evaporated under ultrahigh vacuum conditions were studied by internal stress measurements and by transmission electron microscopy. Tensile stress changes which are not completed until after 5 h for silver and copper and 20 h for gold indicate an increase in the average grain size in these films. The rate of this recrystallization of the film is reduced to about half of its original value when the metal films are coated with a protective layer of MgF₂ immediately after the metal evaporation. When the film recrystallization is not allowed to proceed to completion under vacuum conditions it is again accelerated during exposure of the films to the laboratory atmosphere. From these experiments it can be concluded that the structure of these three metal films as observed using the electron microscope changes from that present at the end of the metal evaporation owing to significant recrystallization. An MgF₂ protective layer can only slow down this recrystallization, not prevent it.     

Thermal Diffusivities of Bilayer Films Deposited on Substrates Characterized Simultaneously by Transient Reflecting Grating Technique

The transient reflecting grating (TRG) technique has been applied to characterize the thermal diffusivities of thin films in trilayered structures. Based on the TRG behavior in the trilayered structures of opaque film/transparent film/substrate, a two-dimensional theoretical model describing the thermal diffusion processes in the trilayed structures is presented and calculated by the finite-element method. The normalized TRG signals decayed with time can be expressed as a triple-exponential function with different time-dependent coefficients. The influences of the thermal properties of the first and second layer films on the TRG signals are calculated and discussed separately. By fitting the theoretical decay curves to the experimental measured data of a series of trilayered structures (Au/ZnO/Si and Al/ZnO/Si with different film thicknesses), the thermal diffusivities of both films in the trilayered structures can be evaluated simultaneously. The results show that the thermal diffusivities of the thin films are strongly dependent on the thickness of the thin films and significantly lower than the corresponding bulk materials, and decay with the decreasing thickness of the films.     

金刚石膜内晶粒尺寸和取向对其热导率的影响

研究了金刚石膜内晶粒尺寸和取向程度对金刚石膜热导率的影响。通过对衬底表面进行不同研磨时间的处理和适当的工艺条件，采用灯丝热解化学气相沉积（ＨＦＣＶＤ）的方法在单晶硅衬底上形成了具有不同晶粒尺寸和不同程度（１００）晶面取向的金刚石膜，并研究了其热导率。结果表明，由大晶粒和较高程度（１００）晶面取向的晶粒构成的金刚石膜具有热导率特性。     

Hartstoffschichten für das Pressen und Prägen von Gläsern bei hohen Temperaturen

Hard and wear resistant coatings for the moulding and embossing of glasses at elevated temperatures Hard and wear resistant coatings of Titanium Aluminium Nitride TiAlN were deposited on various substrates by the application of different reactive deposition processes: RF-magnetron-sputtering, ion beam-sputtering and by the energetic cluster impact (ECI) process. The deposition of the coatings was performed under variation of biasing conditions and of process parameters such as pressures and flow rates of the process gases argon and nitrogen as well as of energies of species hitting the substrate surfaces. The microstructure particularly the growth morphology of several films was investigated by pictures of film cross sections recorded by transmission electron microscopy. Residual intrinsic film stresses were analyzed by measuring deflections of substrates in an interference optical microscope before and after the deposition of the coatings. By heating coated substrates and in-situ observation of deflections at elevated temperatures dependencies of thermally induced stresses on temperatures and variations of intrinsic stresses due to changes within the films could be analyzed and related to microstructure and growth conditions. In the paper specific characteristics of the deposition processes occuring on the scale both of atoms and of clusters which may contain several thousand of atoms are described and related to microstructure, residual stress states and damaging conditions. Different contributions to residual film stresses are analyzed on the base of theoretical considerations taking into account deposition kinetics and thermomecanical properties. The significance of achieved film properties for application, i. e. for the coating of tools for the manufacturing of optical components by moulding and embossing of glasses is discussed.     

Electromagnetic interference shielding characteristics and shielding effectiveness of polyaniline-coated films

The study aims to investigate the electromagnetic interference (EMI) shielding characteristics and shielding effectiveness (SE) of polyaniline (PANI)-coated films. Free-standing films of emeraldine salt were obtained by PANI-emeraldine base with dode-cylbenzensulfonic acid on a polyethylene terephthalate film. The four-point probe method was employed to measure the electrical resistivity for investigating the electromagnetic characteristics of PANI-coated films. In addition, the SE of the PANI-coated films was measured in two different ways: a flanged coaxial shielding effectiveness test and a shielding effectiveness on the testbed having a box-type chamber equipped with instruments for electromagnetic shielding testing under real conditions. The overall SE measured from experiments was also compared with the approximate SE value calculated from a theoretical method. The present study has shown the possibility of utilizing PANI-coated films as EMI shielding/absorption materials.     

Statistical modeling for the optimal deposition of sputteredpiezoelectric films

The quality of sputtered-deposited piezoelectric films used for integrating bulk acoustic wave (BAW) and surface acoustic wave (SAW) devices with semiconductor circuitry depends on several deposition parameters, including substrate temperature, background pressure, gas composition, gas flow rate, and deposition rate. It is desirable to establish the fabrication process based on a selection of the controllable parameter values that optimizes the film quality. It is common practice to perform a number of deposition experiments by varying the controllable parameters to determine the optimal film growth conditions. The films are grown under a number of different conditions within this space and a response parameter related to film performance is measured. Then a multiple linear regression model is fit to the data. By optimizing the fitted response, the best growth conditions can be obtained. This approach is illustrated with data from recent work on the development of very high quality magnetron sputtered aluminum nitride (AlN) films whose acoustic characteristics are like those of epitaxial films grown at considerably higher substrate temperatures. Because the resource cost involved can be high, depending upon the number of deposition runs made, it is desirable to minimize the number of experiments and maximize the amount of information gained from them. A discussion is given on how the statistical theory of experimental design can be used to obtain this goal     

高电压下多孔氧化铝薄膜结构色的制备及分析

多孔氧化铝的微观结构对其光学性能有着显著影响.本文采用高电压制备了普通阳极氧化铝薄膜(单层薄膜)和经高电压表面处理后的光子晶体(多层薄膜),通过理论分析,并结合扫描电镜分别对两种环形氧化铝薄膜建立了微观结构模型图.研究表明:在磷酸电解液中,使用一步阳极氧化方法制备的普通阳极氧化铝多种环形结构色,从中心到边缘结构色逐渐蓝...     

Hydrogen-radical durability of TiO2 thin films for protecting transparent conducting oxide for Si thin film solar cells

Hydrogen-radical durability of TiO₂ thin films has been investigated under conditions for preparing Si thin film solar cells by catalytic chemical vapor deposition method. It is found that the composition and the optical transmittance of TiO₂ films are almost the same before and after hydrogen-radical exposures with a filament temperature at approximately 1700 °C and a H₂ pressure of approximately 133 Pa. The durability of TiO₂ film has also been observed even under the condition with higher hydrogen-radical density under a filament temperature at approximately 1900 °C, in which SnO₂ and ZnO are easily deoxidized. The application of TiO₂ film as a protecting material of transparent conducting oxide film for Si thin film solar cells are discussed by the hydrogen-radical durability and fundamental properties of TiO₂ thin film.     

Crystallization of amorphous antimony films on silver films

The crystallization process in amorphous antimony films 70–330 Å thick evaporated onto silver films 10–150 Å thick which have previously been evaporated onto glass is directly observed through an optical microscope. The conditions under which the crystallization process in the amorphous antimony films is observed are found to be severely limited by the preparation conditions of the silver films. The crystallization can only be observed on silver films thinner than 30–40 Å which have previously been exposed to oxygen or nitrogen gas. The crystallization thickness of amorphous antimony films on these substrates is estimated to be 123-75 Å as the substrate temperature varies from 20 to 80 °C and the activation energy for crystallization to be 0.23-0.30 eV as the film thickness varies from infinity to 200 Å.