Growth and Erosion of Thin Solid Films

Abstract

Thin films that are grown by the process of sputtering are, by and large, quite unlike the smooth, featureless structures that one might expect. In general, these films have a complicated surface morphology and an extended network of grooves and voids in their interiors. Such features can have a profound effect on the physical properties of a thin film. The surface irregularities and the bulk defects are the result of a growth instability due to competitive shadowing, an effect that also plays a role in geological processes such as erosion. For amorphous thin films, the shadow instability can be described by a remarkably simple model, which can be shown to reproduce many important observed characteristics of thin film morphology.

Stochastic growth equations and reparametrization invariance

“…These studies are relevant to a variety of experimental situations including biological growth (Eden, 1958), the propagation of flame fronts (Sivashinsky, 1977(Sivashinsky, , 1979, fluid flow in porous media Martys et al, 1991) and atomic deposition processes (Tu and Harris,1991;Messier and Yehoda, 1985;Bales et al 1990;Tang et al 1990) such as the technologically important molecular beam epitaxy (MBE). On a more fundamental level, some of these processes are prototype of far-from-equilibrium physics without a Hamiltonian formulation (Hohenberg and Halperin, 1977).…”

Surface roughening during plasma-enhanced chemical-vapor deposition of hydrogenated amorphous silicon on crystal silicon substrates

“…Theoretical studies based on the models developed in the 1950s by Herring 6 and Mullins 7 have been expanded to include a variety of additional effects including shadowing and diffusion barriers. 8 Fractal scaling models have been suggested as a way to model growth surfaces with varying success, and Monte Carlo computer simulations allow a variety of model surfaces to be calculated from a set of simple growth models and parameters. 9 Unfortunately, experimental studies of even the simplest homoepitaxial growth systems reveals a complexity beyond current physical models.…”

Nonlinear evolution of surface morphology under shadowing

“…As shown in Fig. 1a and b, the surface shows a grassy topology at early times, which is indicative for geometrical shadowing effects [1,3]. However, shortly after that, cusps develop.…”

“…These cusps are larger structures taking over the smaller ones ( Fig. 1c and d) as expected for shadowing where taller surface features block incoming flux from reaching lower lying areas of the surface [1,3]. However as β > 1 another roughening mechanism which is synchronized to shadowing must be present or the nonlinearity redistributes the spectral power already deposited on the surface and additional roughens the surface by means of this process.…”

“…The primary nonlocal effect is the shadowing effect [3,[7][8][9][10][11], where taller surface features block incoming flux from reaching lower lying areas of the surface. The shadowing effect is active because the incoming flux has an angular distribution.…”