T. A. de Assis, F. D. A. Aarão Reis
We study the effects of time-dependent substrate/film temperature in the deposition of a mesoscopically thick film using a statistical model that accounts for diffusion of adsorbed atoms with coefficients dependent on an activation energy and temperature. For simplicity, a model where only adatoms without lateral neighbors can move is studied by computer simulation, with deposition of typically ${10}^4$ atomic layers and temperature changes up to $30 K$, near or below the room temperature range. Linearly varying and exponentially converging temperature cases are considered. If the temperature decreases during the growth, the global roughness slowly increases at short times, but may show a rapid growth with exponent $\beta >1/2$ after $\sim {10}^3$ monolayers. In the exponentially converging case, the local roughness shows evidence of anomalous scaling, with a large range of the anomalous exponent, and in the linearly decreasing case the local roughness may increase faster than a power law. If the temperature increases during the growth, a non-monotonic evolution of the global roughness may be observed, with a maximum in the linearly increasing case and a sequence of maximum and minimum in the case of exponential convergence to a final temperature. This is explained by the competition of kinetic roughening and the smoothing effect of increasing diffusion coefficients. If some of these features are observed in experiments, our results suggest to investigate the possibility of time varying temperature before relating them to more complex physico-chemical mechanisms.
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http://arxiv.org/abs/1303.5099
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