Optical Direction of Morphological Complexity of Periodic Semiconductor Nanoarchitectures Deposited Via Templateless Photeolectrodeposition

Abstract

Electrodeposition of Se-Te alloy films under illumination spontaneously generates nanopatterned films with significant periodic order. The feature sizes, periodicities, anisotropies, and orientations of the nanoscale pattern are a function of the exact nature of the optical excitation. Isotropic morphologies consisting of ordered arrays of nanopores were generated using unpolarized illumination whereas linearly polarized light resulted in highly-anisotropic lamellar morphologies with the long axes of the patterns aligned along the E-field vector. The pattern periodicity was encoded by the illumination spectral profile. A single periodicity in single spatial direction was only generated even with the use of broadband and multimodal spectral profiles and multiple polarization inputs and the periodicity was found to be sensitive to all investigated tuning of such profiles. Structures with nonequal periodicities in the two orthogonal in-plane directions could also be generated and both periodicities could be independently controlled. Additoinally, the anisotropies, subwavelength feature size and periodic nature of the deposits enables the fabrication of optical elements with significant wavelength and polarization discrimination. The nanopatterning process occurred without the use of any type of physical or chemical templating agents: no photomask, patterned substrate nor surfactants/ligands were used to influence the morphology. Modeling of the growth using a combination of full-wave electromagnetic simulations of light absorption and scattering coupled with Monte Carlo simulations of mass addition successfully reproduced the experimentally observed morphologies and indicated that morphology development was a consequence of the fundamental light-matter interactions during growth.