Digital photocorrosion of III-V semiconductors and transition metal dichalcogenides: fundamental and applied research of nanofabrication and molecular interactions at atomic level

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Digital photocorrosion (DIP) is a recently discovered process that my students and I have been exploring for building devices designed to sense electrically charged biomolecules, such as bacteria, present in aqueous environments. This patent-protected application, developed with the support of my 2015-2020 Discovery Grant (DG), takes advantage of both the sub-monolayer controlled photo-dissolution of GaAs/AlGaAs nanoheterostructures in phosphate buffered saline suspensions and the sensitivity of a photoluminescence signal to band bending. The DIP process, a) does not introduce extraneous surface defects, typically observed in laser ablation, magnetron sputtering, plasma etching, or in some conventional wet chemical etching techniques, and b) it could be abruptly terminated by switching off the source of photo-generated carriers, which compares to a self-terminated step of the state-of-the-art atomic layer etching (ALE) technique. These parameters of the DIP process are potentially attractive for trimming material thickness at the atomic level and/or delivering high-quality three-dimensional nanostructures. Technological outcomes of such a development could concern the elusive top-down fabrication of quantum confined III-V nanostructures (e.g., quantum dots or quantum wires), or arbitrary shape monolayers of transition-metal dichalcogenide (TMDC) films that require a robust etching procedure yet to be developed. Thus, building on the success of my previous DG program, I propose to explore DIP (photo-ALE) for an innovative nanostructuring of III-V semiconductor nanoheterostructures and TMDC films. The short-term objective of this program is to establish a) the conditions leading to formation of stoichiometric surfaces of etched binary and ternary III-V materials, and b) initiate the research of photo-ALE of TMDC films. One of the strategically important issues addressed with the program, will concern in situ passivation of the photo-ALE revealed surfaces. This will take advantage of the process carried out entirely in a dedicated photo-flow-cell, assisted with the simultaneously measured photoluminescence (PL) or open-circuit potential. With the spectrally resolvable PL, we will investigate the conditions for achieving 3D quantum confinement in III-V quantum well microstructures and a multilayer to single layer transition in TMDC films. The medium- to long-term objective is to bring the design and fabrication technology of some prototypes of quantum confined III-V devices and TMDC nanodevices closer to a large number of researchers and, thus, contribute to the advancement of an innovative nanofabrication technology of these materials offered at a potentially highly attractive cost.