Seed/Catalyst-Free Growth of Gallium-Based Compound Materials on Graphene on Insulator by Electrochemical Deposition at Room Temperature

We report the growth of gallium-based compounds, i.e., gallium oxynitride (GaON) and gallium oxide (Ga(2)O(3)) on multilayer graphene (MLG) on insulator using a mixture of ammonium nitrate (NH(4)NO(3)) and gallium nitrate (Ga(NO(3))(3)) by electrochemical deposition (ECD) method at room temperature (RT) for the first time. The controlling parameters of current density and electrolyte molarity were found to greatly influence the properties of the grown structures. The thicknesses of the deposited structures increase with the current density since it increases the chemical reaction rates. The layers grown at low molarities of both solutions basically show grain-like layer with cracking structures and dominated by both Ga(2)O(3) and GaON. Such cracking structures seem to diminish with the increases of molarities of one of the solutions. It is speculated that the increase of current density and ions in the solutions helps to promote the growth at the area with uneven thicknesses of graphene. When the molarity of Ga(NO(3))(3) is increased while keeping the molarity of NH(4)NO(3) at the lowest value of 2.5 M, the grown structures are basically dominated by the Ga(2)O(3) structure. On the other hand, when the molarity of NH(4)NO(3) is increased while keeping the molarity of Ga(NO(3))(3) at the lowest value of 0.8 M, the GaON structure seems to dominate where their cubic and hexagonal arrangements are coexisting. It was found that when the molarities of Ga(NO(3))(3) are at the high level of 7.5 M, the grown structures tend to be dominated by Ga(2)O(3) even though the molarity of NH(4)NO(3) is made equal or higher than the molarity of Ga(NO(3))(3). When the grown structure is dominated by the Ga(2)O(3) structure, the deposition process became slow or unstable, resulting to the formation of thin layer. When the molarity of Ga(NO(3))(3) is increased to 15 M, the nanocluster-like structures were formed instead of continuous thin film structure. This study seems to successfully provide the conditions in growing either GaON-dominated or Ga(2)O(3)-dominated structure by a simple and low-cost ECD. The next possible routes to convert the grown GaON-dominated structure to either single-crystalline GaN or Ga(2)O(3) as well as Ga(2)O(3)-dominated structure to single-crystalline Ga(2)O(3) structure have been discussed.