Long rectangular islands of β-Ga2O3 on CoGa(001)—studied by electron energy loss spectroscopy and scanning tunneling microscopy

At 700 K, the oxidation with 1 L ${\mathrm{O}}_{\mathrm{2}}$ of CoGa(001) was investigated by means of high-resolution electron energy loss spectroscopy (EELS), low-energy electron diffraction, Auger electron spectroscopy, and scanning tunneling microscopy (STM). Oxidation with 1 L ${\mathrm{O}}_{\mathrm{2}}$ at 700 K leads to the formation of long, rectangular islands of $\mathrm{\beta -}{\mathrm{Ga}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ oriented in the [100] and [010] directions of the substrate. EEL spectra of the islands of $\mathrm{\beta -}{\mathrm{Ga}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ show intense Fuchs–Kliewer (FK) modes at 305, 455, 645, and $\text{780\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}}.$ The $\mathrm{\beta -}{\mathrm{Ga}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ islands are well ordered and show a $\text{(2×1)}$ structure with two domains, oriented perpendicular to each other. The two-dimensional lattice parameters of $\mathrm{\beta -}{\mathrm{Ga}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ are determined to be $\text{a=2.8±0.1\hspace{0.17em}Å}$ and $\text{b=5.8±0.1\hspace{0.17em}Å.}$