Deposition,opto-electronic and structural characterization of polymorphous silicon thin films to be applied in a solar cell structure

In this study we analyze the optoelectronic properties and structural characterization of hydrogenated polymorphous silicon thin films as a function of the deposition parameters. The films were grown by plasma enhanced chemical vapor deposition (PECVD) using a gas mixture of argon (Ar), hydrogen (H₂) and dichlorosilane (SiH₂Cl₂). High-resolution transmission electron microscopy images and Raman measurements confirmed the existence of very different internal structures (crystalline fractions from 12% to 54%) depending on the growth parameters. Variations of as much as one order of magnitude were observed in both the photoconductivity and effective absorption coefficient between the samples deposited with different dichlorosilane/hydrogen flow rate ratios. The optical and transport properties of these films depend strongly on their structural characteristics, in particular the average size and densities of silicon nanocrystals embedded in the amorphous silicon matrix. From these results we propose an intrinsic polymorphous silicon bandgap grading thin film to be applied in a p–i–n junction solar cell structure. The different parts of the solar cell structure were proposed based on the experimental optoelectronic properties of the pm-Si:H thin films studied in this work.     

Deposition of thin film silicon using the pulsed PECVD and HWCVD techniques

We report on the use of pulsed plasma-enhanced chemical vapor deposition (P-PECVD) technique and show that “state-of-the-art” amorphous silicon (a-Si:H) materials and solar cells can be produced at a deposition rate of up to 15 Å/s using a modulation frequency in the range 1–100 kHz. The approach has also been developed to deposit materials and devices onto large area, 30 cm×40 cm, substrates with thickness uniformity (<5%), and gas utilization rate (>25%). We have developed a new “hot wire” chemical vapor deposition (HWCVD) method and report that our new filament material, graphite, has so far shown no appreciable degradation even after deposition of 500 μm of amorphous silicon. We report that this technique can produce “state-of-the-art” a-Si:H and that a solar cell of p/i/n configuration exhibited an initial efficiency approaching 9%. The use of microcrystalline silicon (μc-Si) materials to produce low-cost stable solar cells is gaining considerable attention. We show that both of these techniques can produce thin film μc-Si, dependent on process conditions, with 1 1 1 and/or 2 2 0 orientations and with a grain size of approx. 500 A. Inclusion of these types of materials into a solar cell configuration will be discussed.     

多晶硅太阳电池用SiN薄膜的研究进展

SiN薄膜因为具有良好的减反射性质和钝化作用，已经越来越广泛地应用于多晶硅太阳电池的制造工艺中，介绍了SiN薄膜在硅太阳电池中的性质，制备方法等研究现状，同时提出了存在的问题并展望了今后的发展趋势。     

PECVD法制备低介电常数含氟碳膜研究

采用PECVD法制备了低介电常数薄膜a-C：F，研究了薄膜沉积速率与温度及射频功率的关系，测量了不同沉积条件下薄膜的介电常数，并用FTIR分析了薄膜的化学结构及成分，发现薄膜沉积速率与沉积条件密切相关，其介电性与其化学结构以及沉积条件密切相关。     

富氧氮氧化硅薄膜退火的研究

利用红外吸收(IR)谱和X射线光电子谱(XPS)对富氧氮氧化硅(oxygen-rich SiOxNy)及其在600、750和900℃下退火后样品的微结构进行了研究.实验中除观察到N、H的释放外,首次发现退火会导致SiOxNy中O的释放,同时还发现退火温度不同,H、O、N元素的释放量以及微结构的变化都不相同,根据这些现象,提出了5个化学反应过程并予以解释.     

A simple diborane-degradation model for controlling p-type doping of microcrystalline silicon

The preparation of p-type amorphous- or microcrystalline silicon often requires the use of a gas mixture containing diborane. Whereas the concentration of this gas in the process chamber is critical for the determination of the doping level, and thus of the properties, of resulting films, it is in practice very difficult to have a proper control of such a concentration owing to the degradation of diborane in the cylinder by polymerisation. The main consequence is a significant lack of reproducibility of results. The present paper analyses the problem and its practical influence, describes a simple diborane-degradation model, proposes certain approaches based thereon and shows experimental results illustrating the validity of the procedures suggested. It is finally concluded that the application of this simple model is a straightforward and effective way to control diborane doping level in p-type amorphous- or microcrystalline silicon.     

PECVD方法用于梯度薄膜材料的研究

本文研究了ＰＥＣＶＤ方法制备Ｓｉ－Ｏ－Ｍ系梯度薄膜材料，并运用计算机控制技术成功地制备了涂层折射率随膜深成正弦波形式连续变化的Ｒｕｇａｔｅ单通带滤波器样品。结果表明，采用ＰＥＣＶＤ方法可以制备性能上乘、结构复杂的梯度薄膜材料，ＰＥＣＶＤ方法在研究、开发高级光学涂层领域有着宽广的应用前景。     

Adhesion studies of diamond-like carbon films deposited on Ti6Al4V substrate with a silicon interlayer

Diamond-like carbon (DLC) films have proven quite advantageous in many tribological applications due to their low friction coefficient, their extreme hardness, and more recently their high adherence on different substrate materials. However, for many applications, DLC films as thick as 2 μm are required, which cause high residual stress. In order to overcome this problem, this study observed the behavior of different thicknesses of silicon interlayer between DLC films and Ti6Al4V substrates. The study also analyzed the relation of growth parameters to the mechanical properties of DLC films. Silicon and DLC films were grown by using a rf-PECVD at 13.56 MHz with silane and methane atmospheres, respectively. The contribution of an interlayer thickness to the adhesion between the DLC films and Ti6Al4V substrate was evaluated by using a micro-scratch technique. The hardness and friction coefficient were evaluated by using microindentation and lateral force microscopy (LFM), respectively. Raman scattering spectroscopy was used to characterize the film quality. A correlation was found between the intrinsic stress and adhesion of DLC film and the parameters of the silicon interlayer growth. The addition of a silicon interlayer successfully reduced intrinsic stress of the films, even as measured by using a perfilometry technique.     

TFT有源矩阵α－Si∶H薄膜PECVD淀积工艺研究

分析了α－Ｓｉ∶Ｈ薄膜的质量和厚度对α－Ｓｉ∶ＨＴＦＴ关键性指标的影响，深入、详细地讨论了其ＰＥＣＶＤ淀积工艺，并在实验的基础上确定了最佳淀积工艺参数，从而获得了高性能的７５ｍｍ３７２×２７６像素α－Ｓｉ∶ＨＴＦＴ有源矩阵     

a-C:F:H films prepared by PECVD

Fluorinated amorphous hydrogenated a-C:F:H carbon thin films were deposited using radio frequency plasma enhanced chemical vapor deposition(RF-PECVD) reactor with CF4 and CH4 as source gases and were annealed in a N2 atmosphere. The properties of these films were evaluated by FTIR spectrometry, UV-VIS spectrophotometry and single-wavelength spectroscopic ellipsometry. A correspondence relativity connection between the deposition rate and technology was found. The chemical bonding structures and the content of CHx and CFx in the films are transformed and the optical band gap decreases monotonically with increasing temperature after annealing.The dielectric constant is increased with decreasing content of F in the films and the optical band gap is decreased with decreasing the content of H in the film.