Maskless Photoelectrochemical Fabrication of Anisotropic Three-Dimensional Nanostructured Semiconductors

Binary and ternary IV-VI and II-VI semiconductor materials were photoelectrochemically deposited from aqueous precursors, yielding highly periodic nanostructured films over macroscopic square centimeter areas despite the absence of any templating agents or lithographic steps. Electro-/chemical modification was performed following deposition to tune the elemental stoichiometry of the deposits without a concomitant loss in structure fidelity nor crystallinity. The morphology of these features was controlled by the optical inputs to the deposition: extremely anisotropic lamellar-type features formed spontaneously under the presence of linearly polarized light and the periodicity of the features scaled with illumination wavelength. The deposition process was simulated using a two-step iterative model which included a finite-difference time domain method to model light absorption and a Monte Carlo method to model mass addition; these simulations matched the experimentally observed morphologies. This approach offers a method by which highly nanostructured materials that are of interest for photon-harvesting applications can be deposited in a manner that allows for self-optimization in order to maximize light absorption. This work demonstrates that photoelectrochemical deposition can be utilized to provide rapid, template-free fabrication of 3D semiconductor nanopatterns over macroscale areas for a variety of material systems. Extension of this technique to group IV materials is underway.