Electrochemical deposition of chalcogenide semiconductor films: InSe and GeTe

Electrodeposition is a low cost, room temperature method for the deposition of semiconductor thin films. Using Electrochemical Atomic Layer Deposition (EALD) and Potential Pulse Atomic Layer Deposition (PPALD), films with atomic layer control can be achieved. By reducing one monolayer of one element onto the substrate, followed by a molecular layer of a second element, films of varying thicknesses can be made. These films can be used in such applications as photoanodes in solar cells or as a phase change material in computer memory. The stoichiometry and smoothness of the films is controlled by the pH of the solution, concentration of precursor, and electrochemical potential in relation to the Nernst equation. Indium Selenide is a 2D layered chalcogenide material with 2 main stoichiometries: InSe and In2Se3, which have different bandgaps. By controlling the electrochemical potentials at which In and Se are deposited and stripped in our sequence, the stoichiometry can be engineered using PPALD. The resulting films were extremely smooth and homogenous with photoactive properties that might make it attractive as a photoanode in a photoelectrochemical cell. Germanium Telluride is another layered chalcogenide, but with promise as a phase change memory material. Due to the small electrochemical potential ranges with which Ge and Te overlap to deposit and strip, fine control of deposition potential and time are necessary. Using feedback from the voltammetry stripping curves, we can start to optimize the conditions for the deposition sequence.

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