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

利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硅薄膜，并将其应用于薄膜晶体管和异质结太阳电池。现场残留气体分析仪(RGA)将监测这一过程，并实现可重现的条件。最近的工作给出了非晶(a-Si：H)薄膜的场效应迁移率为3cm2/V-S，而通常的场效应迁移率为1cm2/V-S，而nc-Si薄膜的场效应迁移率则超过了15cm2/V-S。沉积过程中的氢稀释(HD)和光子辅助(PA)允许在沉积过程中降低衬底温度。MECR工艺将衬底放置在远离等离子体的位置，以避免等离子体损坏。到目前为止，TFT在使用氧化物涂层的硅、石英、玻璃和塑料基板时表现相当好。该工艺很容易转移到各种基板上，性能损失很小。考虑到智力上的优点，采用HD和PA的MECR工艺将致力于在250℃的低成本塑料上获得高质量的硅薄膜。TFT栅极的氧化物形成将在200℃下完成，薄膜分析将利用高分辨率电子显微镜、原子力显微镜、二次离子质谱仪和其他方法。掠入射X射线散射将评估衬底-薄膜界面，以最大限度地减少异质界面上的载流子复合，并与深能级瞬变光谱结果相关联。更小的门尺寸，使用康奈尔大学的电子束图案生成，以及将在布法罗安装的新系统，将提供更好的场效应机动性和更好的设备。全硅异质结太阳电池将利用MECR在硅片或薄膜上沉积的a-Si：H和nc-Si来获得比普通电池高得多的电流，这是由于各层之间的带隙差异。通过改进薄膜界面，应将过去10.5%的效率值提高到15%。关于更广泛的影响问题，研究生将与另一名由NASA太空补助金资助的研究生和另一名作为助教的兼职研究生接触。在该大学BEAM项目的支持下，一名本科生和一名少数民族高中生也将参与该项目。将鼓励少数族裔和妇女参与。研究任务和教育课程将从该项目中互惠互利。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、布法罗的新电子束系统安装团队、材料和光伏测量的NREL、石溪的纽约州立大学的建模和技术专长以及Taitech，Inc.的测量工作相联系。这所大学已经建立了技术转让机制。

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.