Influence of Substrates on the Long-Range Order of Photoelectrodeposited Se-Te Nanostructures

The long-range order of anisotropic phototropic Se-Te films grown electrochemically at room temperature under uniform-intensity, polarized, incoherent, near-IR illumination has been investigated using crystalline (111)-oriented Si substrates doped degenerately with either p- or n-type dopants. Fourier-transform (FT) analysis was performed on large- area images obtained with a scanning electron microscope, and peak shapes in the FT spectra were used to determine the pattern fidelity in the deposited Se-Te films. Under nominally identical illumination conditions, phototropic films grown on p(+)-Si(111) exhibited a higher degree of anisotropy and a more well-defined pattern period than phototropic films grown on n(+)-Si(111). Similar differences in the phototropic Se-Te deposit morphology and pattern fidelity on p(+)-Si versus n(+)-Si were observed when the deposition rate and current densities were controlled for by adjusting the deposition parameters and illumination conditions. The doping-related effects of the Si substrate on the pattern fidelity of the phototropic Se-Te deposits are ascribable to an electrical effect produced by the different interfacial junction energetics between Se-Te and p(+)-Si versus n(+)-Si that influences the dynamic behavior during phototropic growth at the Se-Te/Si interface.