| Autor: |
Brandt, I. S., Zoldan, V. C., Stenger, V., Plá Cid, C. C., Pasa, A. A., Oliveira, T. J., Aarão Reis, F. D. A. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 2015, Vol. 118 Issue 14, p145303-1-145303-10, 10p, 1 Color Photograph, 1 Diagram, 7 Graphs |
| Abstrakt: |
Cuprous oxide (Cu2O) films from 25 nm to 1500 nm were electrodeposited on n-Si(100) and Ni/n-Si(100) substrates from aqueous solution at room temperature. X-ray diffraction and transmission electron microscopy imaging show that the Cu2O structure and morphology are strongly affected by the substrate choice, with V shape and U shape columnar growth on n-Si(100) and Ni/n-Si(100), respectively. Atomic force microscopy reveals the presence of rounded grains at the surface in both cases. Anomalous and normal roughening are observed in films grown on n-Si and Ni, respectively, but estimates of scaling exponents are not conclusive. On the other hand, the distributions of local heights, roughness, and extremal heights show good agreement with those of the fourth order linear stochastic equation of Mullins and Herring (MH). Thus, surface dynamics in both systems is dominated by diffusion of adsorbed molecules, with no large scale effect of possible inhomogeneities in mass flux from the solution or in reaction and adsorption rates. In growth on n-Si substrates, the noise amplitude of the MH equation increases in time as t0.8, while the coefficient of the curvature-related term is time-independent. Step edge energy barriers restrict the mass flux across grain boundaries, thus a broad size distribution of initial grains leads to coarsening of the larger ones. This explains their V shape in the thickest films and establishes a connection with the anomalous roughening. These effects are reduced in films grown on Ni/n-Si, which initially have much larger grains with narrower size distributions and, consequently, smaller fluctuations in coarse grained growth rates. Thus, despite the relevance of electrochemical conditions for Cu2O films to grow and their influence on crystallographic orientation, large scale surface features are determined by physical properties of the material and its interactions with the substrate, with a universal microscopic dynamics similar to vapor deposition. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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