Robust and Electrically Conductive ZnO Thin Films and Nanostructures: Their Applications in Thermally and Chemically Harsh Environments

"Harsh electronics", which are designed to operate under harsh environments, have garnered significant attention to collect various physical and chemical information in surroundings toward the Internet of Things era. Among various electronic materials and structures, ZnO thin films, which consist of an abundant resource, have been intensively investigated because of their unique electrical and optical properties. However, ZnO thin films have been regarded as chemically nonresistive to harsh environments (e.g., high temperatures, high humidity, and acidic and basic conditions). Herein, we present recent progress and advances in electrically conductive ZnO thin films and nanostructures for applications in harsh electronics. First, various fabrication methods and progresses for achieving high-quality ZnO nanomaterials are introduced. Subsequently, previously reported approaches for enhancing the reliability and stability of ZnO nanostructures in harsh electronics are compared. Strategies for fabricating robust ZnO materials and ZnO-based electronics are discussed on the basis of several proposed mechanisms. Finally, we describe the current limitation, perspective, and outlook for future developments of ZnO nanostructures for use in harsh electronics.