Synthesis and Characterization of Large‐Area Nanometer‐Thin β‐Ga2O3 Films from Oxide Printing of Liquid Metal Gallium

Abstract

Herein, wafer‐scale Ga2O3 films are shown, which are synthesized by oxide printing of liquid metal Ga on SiO2/Si and sapphire substrates. This process enables highly uniform ≈2 nm‐thick films over ≫1 mm2 areas. The physical properties of these films (as‐deposited and after annealing in ambient conditions) are investigated. X‐ray photoelectron spectroscopy indicates that the as‐prepared films contain significant fractions (up to 8% wt) of Ga metal residue, which completely converts to Ga2O3 after annealing. Results from Raman spectroscopy confirm the presence of β‐phase in annealed samples. Transmission electron microscopy images indicate that the films are composed of polycrystalline domains. Photoluminescence is observed in all samples, depicting the typical spectrum of Ga2O3 with four emission bands. After annealing, the luminescence intensity increases across all samples, which is attributed to an enhancement in crystallinity. Also, the relative intensity of the blue emission decreases after annealing, which is consistent with a transition from bluish to greenish color in the films. This observation is associated with a change in defect population upon annealing. Overall, these results demonstrate that oxide printing of liquid metal gallium is a simple process that, upon annealing of the resulting films, leads to nanometer‐thin β‐Ga2O3 films over wafer‐scale areas.