TFT's and Solar Cells on Flexible Substrates Using Microwave-Deposited Silicon

采用微波电子回旋共振（MECR）化学气相沉积技术制备了高质量的纳米晶硅（nc-Si）薄膜，并将其应用于薄膜晶体管（TFT）和异质结太阳能电池。 现场残余气体分析仪（RGA）将监测该过程并实现可重现的条件。最近的工作已经给出了3 cm 2/V-s的非晶（a-Si：H）膜的场效应迁移率，而通常的值为1 cm 2/V-s，并且迄今为止已经用nc-Si膜实现了超过15 cm 2/V-s。沉积期间的氢稀释（HD）和光子辅助（PA）允许沉积期间的较低衬底温度。MECR工艺将衬底放置在远离等离子体的地方，以避免等离子体损坏。到目前为止，TFT已经相当好地使用氧化物涂覆的Si、石英、玻璃和塑料基板。该工艺易于转移到各种衬底上，性能损失很小。考虑到智力价值，采用HD和PA的MECR工艺将致力于在250 ℃的温度下在较低成本的塑料上获得高质量的Si膜。TFT的栅极的氧化物形成将在200 ℃的温度下进行。薄膜分析将利用高分辨率透射电子显微镜、原子力显微镜、二次离子质谱和其他方法。掠入射X射线散射将评估衬底-膜界面，以最大限度地减少异质界面处的载流子复合，并将结果与深能级瞬态光谱相关。 较小的栅极尺寸，使用电子束图案产生在康奈尔大学和一个新的系统将安装在布法罗，将提供更好的价值的场效应流动性和更好的设备。全硅异质结太阳能电池将利用硅晶片或薄膜上的MECR沉积的a-Si：H和nc-Si，以实现比普通电池高得多的电流，这是由于层中的带隙差异。通过改进薄膜界面，过去10.5%的效率值应提高到15%。关于更广泛的影响问题，研究生将与另一名获得NASA空间赠款支持的研究生和另一名兼职助教进行交流。 一名本科生和一名少数民族高中生在大学BEAM项目的支持下，也将参与该项目。将鼓励少数民族和妇女参加。研究任务和教育课程将相互联系，从项目中受益。这项工作还将与康奈尔大学的纳米制造，布鲁克海文的GIXS工作，在布法罗的团队建立新的电子束系统，NREL的材料和光伏测量，纽约州立大学在斯托尼布鲁克的建模和技术专长，和Taitech公司。用于测量。技术转让机制已在大学内建立。

High-quality nanocrystalline silicon (nc-Si) films will be deposited by microwave electron cyclotron resonance (MECR) chemical vapor deposition with application to thin film transistors (TFT's) and heterojunction solar cells. An in-situ residual gas analyzer (RGA) will monitor the process and achieve reproducible conditions. Recent work has given a field effect mobility of amorphous (a-Si:H) films of 3 cm2/V-s compared to the usual values of 1 cm2/V-s and over 15 cm2/V-s has been achieved so far with nc-Si films. Hydrogen dilution (HD) and photon assist (PA) during deposition permit lower substrate temperatures during deposition. The MECR process places the substrate away from the plasma to avoid plasma damage. Thus far, TFT's have been quite good using oxide-coated Si, quartz, glass and plastic substrates. The process transfers readily to a variety of substrates with little loss in performance.Concerning intellectual merit, the MECR process with HD and PA will be devoted to achieve high quality Si films at temperatures 250 C on lower cost plastics. Oxide formation for the gate of TFT's will be done at temperatures 200 C. Film analysis will utilize high resolution transmission electron microscopy, atomic force microscopy, secondary ion mass spectroscopy and other methods. Grazing incidence X-ray scattering will evaluate substrate-film interfaces to minimize carrier recombination at hetero-interfaces and results correlated with deep level transient spectroscopy. Smaller gate dimensions , using e-beam pattern generation at Cornell University and a new system to be installed in Buffalo, will give much better values of field effect mobility and better devices. The all Si heterojunction solar cell will utilize MECR-deposited a-Si:H and nc-Si on a Si wafer or thin film to achieve much higher currents than with normal cells due to the bandgap difference in the layers. Past efficiency values of 10.5% should be increased to 15% by improved films interfaces. Concerning broader impact issues, the graduate student will interface with another graduate student supported on a NASA Space Grant and another supported part-time as a teaching assistant. An undergraduate student and a minority high school student, with support from the University's BEAM program, will also work on the project. Minorities and women will be encouraged to participate. Research tasks and educational courses will be linked to mutually benefit from the project. This work will also interface with Cornell University for nano-fabrication, Brookhaven for GIXS work , the team in Buffalo setting up the new e-beam system, NREL for materials and photovoltaic measurements, SUNY at Stony Brook for modeling and technical expertise, and Taitech, Inc. for measurements. Technology transfer mechanisms are in place at the university.