Nucleation, Pattern Development, and Fidelity in the Photoelectrodeposition of Se-Te Nanostructures

Abstract

The electrochemical growth of Se-Te under polarized illumination results in anisotropic, highly-ordered lamellar nanostructures, tunable by input wavelength. This spontaneous growth occurs at room temperature, in an isotropic solution, with no templating or chemically-directing agents, and with mW-cm-2 illumination intensity with no requirement for coherency. The deposition process is compatible with a wide variety of conductive substrates and can be performed over large areas of unpatterned substrates. However, pattern fidelities in these films are generally low. Improving the potentially broad applicability of this patterning method requires an understanding of pattern development and of factors contributing to the long-range order of films deposited through this phenomenon.Methods of quantifying pattern fidelity have been developed using Fourier-transform (FT) analysis of large-area images of photoelectrodeposited Se-Te films. Nominally identical illumination conditions during the deposition of Se-Te on crystalline (111)-oriented Si substrates doped degenerately with either p- or n-type dopants produced a variation in the morphology of Se-Te films. Films deposited on p+-Si generally displayed much less defective patterns, with a higher degree of anisotropy and a more well-defined pattern period versus films deposited on n+-Si. These results are attributed to the energetics at the dynamic junction formed by growing Se-Te and the Si substrate.Analysis of film morphologies at early levels of mass addition to growth substrates elucidate the mechanism by which junction energetics affect resulting film morphologies. Higher nucleation densities are generally observed under conditions that produced Se-Te films with relatively higher pattern fidelities. Control of pattern fidelity by control of nucleation density, through substrate choice and tuning of applied deposition potential, is demonstrated.