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MOLECULAR BEAM EPITAXIALLY DEPOSITED AMORPHOUS SILICON D. J. LOCKWOOD1, J.-M. BARIBEAU1, M. NOËL2, J. C. ZWINKELS2, B. J. FOGAL3, and S. K. O'LEARY3 1 Institute for Microstructural Sciences, National Research Council of Canada, Ottawa, Ontario, Canada K1A 0R6 2 Institute for National Measurement Standards, National Research Council of Canada, Ottawa, Ontario, Canada K1A 0R6 3 Faculty of Engineering, University of Regina, Regina, Saskatchewan, Canada S4S 0A2 ABSTRACT We have deposited a novel form of amorphous silicon through molecular beam epitaxy in an ultra-high vacuum. In particular, by depositing silicon atoms onto an optical quality fused quartz substrate at room temperature we have obtained a silicon-based material that lacks the periodicity that characterizes crystalline silicon but nevertheless has 98% of the density. Spectroscopic studies reveal that there are only trace amounts of hydrogen and other impurity atoms in this novel form of amorphous silicon, this contrasting dramatically with the case of conventional amorphous silicon. The Raman and optical spectroscopic properties of this form of amorphous silicon are contrasted with those of conventional amorphous silicon and sputtered amorphous silicon, and conclusions, regarding the amount of disorder, are drawn. Finally, the device implications of this novel form of amorphous silicon are discussed. INTRODUCTION Amorphous silicon continues to be the focus of considerable attention owing to its remarkable potential for electron device applications. At present, device-quality amorphous silicon is usually prepared through the plasma decomposition of silane gas [1], the resultant material being a mixture of silicon and hydrogen atoms. It is widely held that the hydrogen atoms that exist within this material are responsible for its favorable electronic properties [2,3]. Unfortunately, these hydrogen atoms are also believed to be responsible for the deterioration in the electronic characteristics that occurs upon exposure to light [4,5,6]. This has encouraged researchers to seek alternate forms of amorphous silicon, which retain the favorable electronic characteristics of conventional amorphous silicon without the large amounts of hydrogen. Recently, for example, Brockhoff et al. [7] prepared amorphous silicon thin-film transistors using hot-wire deposition, the resultant hydrogen content being an order of magnitude lower than that found in conventional amorphous silicon. Molecular beam epitaxy, a technique that is presently being used in crystalline semiconductor epitaxial growth, affords a great deal of control over the deposition process, the thickness, composition, and impurity content of the resultant films being tailored to suit the needs of the specific application under consideration. In this paper, we employ molecular beam epitaxy to deposit thin films of amorphous silicon, with the hope that such a deposition will lead to higher quality amorphous silicon. The primary aim of this study is the determination of the material characteristics of this novel f