Optically Manipulated Bottom-up Growth of Nanopatterned Semiconductor Films

Abstract

Bottom-up growth of macroscale Se-Te alloy films displaying nanoscale patterning with significant periodic order was effected via photoelectrochemical deposition. The exact nature of the optical excitation was the determinant of the features sizes, periodicities, anisotropies, and orientations of the nanoscale pattern. Use of linearly polarized light resulted in highly-anisotropic lamellar morphologies with the long axes of the patterns aligned along the E-field vector and increasing the complexity of the polarization input resulted in a concomitant increase in pattern complexity. 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. Additionally, 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 probabalistic 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.