High‐Entropy Liquid Metal Process for Transparent Ultrathin <i>p</i>‐Type Gallium Oxide
Laetitia Bardet, Ali Zavabeti, Amar K. Salih, Dawei Zhang, Mohamed Kilani, Mohammad B. Ghasemian, Anton Tadich, Yunlong Sun, Lucy Johnston, Danyang Wang, Jan Seidel, Francois‐Marie Allioux, Cuong Ton‐That, Jianbo Tang, Kourosh Kalantar‐Zadeh
Abstract
Abstract The naturally self‐limiting oxide formed on the surface of liquid metals can be exfoliated and transferred onto various substrates. This oxide layer with a thickness of a few nanometers is typically highly transparent and can be engineered for applications in large‐area optoelectronics. While the incorporation of solvated elements into the interfacial oxide of post‐transition metal‐based liquid metals is demonstrated for n ‐doping, achieving p ‐doping in such ultrathin oxide layers remains a significant challenge. In this study, the use of dissolved indium (In), platinum (Pt), gold (Au), palladium (Pd), and copper (Cu) in gallium (Ga)‐based alloys is investigated to create a high‐entropy liquid metal system. This allows the exfoliation of a p‐ doped ultrathin oxide layer, predominantly composed of gallium oxide (Ga 2 O 3 ). The incorporation of these post‐transition metals in this high‐entropy system results in their atomic dispersion, with Cu exhibiting limited surface presence. The atomically dispersed Pt, Au, and Pd metals scavenge oxygen during exfoliation at moderate temperatures and release them during cooling down, promoting the emergence of trivalent metallic In in Ga oxide layer. This work presents a novel doping strategy at moderate temperatures to achieve p ‐doped liquid‐metal‐derived ultrathin Ga 2 O 3 layers, which maintain high transparency.