Growth and characteristics of a novel two-dimensional oxide GaO

Since the emergence of graphene in 2004, numerous two-dimensional (2D) materials have been experimentally and/or theoretically confirmed to exist in a stable state, with the continuous discovery of new materials. We herein report on the controllable growth and characteristics of a novel 2D material, namely GaO. By depositing an atomic layer of Ga on an Au(111) single-crystal surface through electron-beam evaporation and subsequent oxidization, a monolayer (ML) gallium oxide 1 ML-GaO/Au(111) is obtained. Its elemental composition and structural symmetry were characterized using x-ray photoelectron spectroscopy, low-energy electron diffraction, and atomic-resolution scanning tunneling microscopy (STM). Subsequently, through cyclic deposition of Ga followed by oxidation, an ultrathin film with an equivalent coverage of 11 ML-GaO/Au(111) was achieved. Phonon spectrum calculations based on first-principles reveal the dynamical stability of this novel 2D GaO structure. Furthermore, theoretical simulation results are consistent with experimental STM observations, confirming the atomic structure of this 2D GaO material. The theoretical calculations further reveal an indirect bandgap of about 3.12 eV, and a very high electron mobility between 5348.34 and 5606.76 cm 2 ·V −1 ·s −1 for this 2D GaO.