2D electron gas 1 2D electron gas (2DEG) 1 Acetone 1 Chemical vapor deposition 1 Electrons 1 Field effect transistors 1 Gold nanoparticles 1 Growth structures 1 High resolution transmission electron microscopy 1 Oxide minerals 1 Oxygen vacancies 1 Sapphire 1 Sb-doped 1 Scalable methods 1 Schottky barrier diodes 1 Square nanostructure Surface electron 1 Surface hydroxyl 1 Tin dioxide 1 Titanium dioxide 1 Two-dimensional surface 1 Vertically aligned 1 X ray photoelectron spectroscopy 1 oxygen vacancies 1 square nanostructures 1 surface hydroxyl 1 tin dioxide 1