AVS 50th International Symposium
    Thin Films Thursday Sessions
       Session TF-ThM

Paper TF-ThM11
Physical Self-assembly and the Nucleation of 3D Nanostructures by Oblique Angle Deposition@footnote 1@

Thursday, November 6, 2003, 11:40 am, Room 329

Session: Modeling & Fundamentals in Thin Film Deposition
Presenter: T. Karabacak, Rensselaer Polytechnic Institute
Authors: T. Karabacak, Rensselaer Polytechnic Institute
G.-C. Wang, Rensselaer Polytechnic Institute
T.-M. Lu, Rensselaer Polytechnic Institute
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Thin film growth front morphology formed by physical vapor deposition is controlled by many factors including surface diffusion and shadowing effects. Instabilities can occur if shadowing is more dominant compared to other surface effects and can lead to many diverse physically self-assembled 3D nano-size structures@footnote 2,3@ that are otherwise difficult to produce by lithographical techniques. The unique geometrical shapes from a large variety of materials suggest that shadowing effects can be used as an efficient tool to understand and control the growth morphologies by many traditional deposition techniques. In this paper, we explore the fundamental nucleation and growth mechanisms of these structures. Monte Carlo simulations were carried out to predict the island density, island size distribution, and island-island correlation during the initial stages of growth. The results are compared to that obtained by the oblique angle sputter deposited W films imaged by atomic force microscopy and scanning electron microscopy. Isolated islands with quasi-periodic distribution are formed as a natural consequence of the shadowing effect. Isolated columnar structures are shown to grow on these islands and the width w of the columns is predicted to grow as a function of time t in the form of a power law, w ~ t@super p@, where the exponent p is between 0.3 and 0.5. The predicted p is consistent with the experimentally determined exponent values for growth of column widths from a variety of materials such as W, Co, Cu, and Si. @FootnoteText@ @footnote 1@ Work supported by NSF@footnote 2@ Y.-P. Zhao, D.-X. Ye, G.-C. Wang, and T.-M. Lu, "Novel nano-column and nano-flower arrays by glancing angle deposition", Nano Letters 2, 351-354 (2002). @footnote 3@ K. Robbie, M. J. Brett, and A. Lakhtakia, "Chiral sculptured thin films," Nature 384, 616-616 (1996).