Nanometric Al2O3 Layers Obtained from Liquid Metals: Implications for Sensing Devices

Nanomaterials, and in particular nanolayers, are of importance in the fields of electronics, biomedical devices, and sensors. It is thus crucial to develop sustainable ways to obtain these nanomaterials and fully characterize their potential in view of these applications. In this work, the microstructure and chemical composition of Al2O3 oxide layers obtained by exfoliation from liquid metals are investigated. The method allows nanometric oxide layers to be obtained at low temperatures, without excessive waste, as the base alloy can be reused in the process. Metal oxide layers were deposited on different substrates, including glass, Si, and SiO2. The Al2O3 oxide was obtained from two liquid metal compositions (GaAleut and Ga-30 at% Al) in order to understand the influence of the composition of the base alloy on the final product. The contact angle between the alloys and substrates was measured using the static sessile drop method. The layers were characterized using AFM and TEM. Moreover, the chemical composition was assessed using XPS. The samples consist of alpha-Al2O3 nanocrystallites embedded in an amorphous oxide layer, with similar to 20 to 30 nm nanodroplets of metallic gallium. The nanometric oxide layers obtained within the frame of this work have the potential to be used in gas sensors upon further research.