As a wide bandgap (II-VI) semiconductor, zinc selenide’s (ZnSe) transparency in the mid-infrared region makes zinc selenide-supported self-assembled monolayers (SAMs) ideal for functionalizing optoelectronic devices. Although ZnSe’s native oxide layer is conducive to forming SAMs, modifying the thickness and species of oxide layers allows for the deposition of denser, lower defect, more technologically relevant SAMs. In this study we demonstrate how the thickness and species of oxide layers can be optimized for the formation of sufficiently low-defect SAMs by varying the chemical surface treatment (UV-ozone cleaning, hydrochloric acid etch, ammonium hydroxide etch) and time allotted for oxide layer regeneration (0, 24, 42,168 hours). To this end, the native oxide layer was stripped from optically polished ZnSe substrates using a chemical etch and allowed to regenerate for a given period of time before SAM deposition. Resultant SAMs were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, contact angle analysis and atomic force microscopy. We correlate the increasing hydrophobicity of etched ZnSe substrates over time with the growth of oxide layers characterized in XPS. We demonstrate that while thiolate head groups have an optimal affinity for the native oxide layer, the native layer inhibits the growth of SAMs for alternate head groups (ex. carboxylic acid) which have a higher affinity for etched substrates.

Interfacial impact of oxides for zinc selenide-supported self-assembled monolayers

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.