Formation of Gallium Nanocrystals on the Sapphire Substrates

Ga nanocrystals were obtained on the sapphire substrates by thermal evaporation method in Ar atmosphere at deposition time of 10, 15 and 20 s. The size, shape and number of Ga nanocrystals were determined by intelligent analysis of SEM images. Ga nanocrystals and microcrystals on the sapphire substrates were condensed in hexagonal and tetragonal forms, close to the crystalline structures of sapphire and Ga. Most Ga nanocrystals at deposition time 10 s were condensed as the plates with hexagonal shape similar to hexagonal shape of R (1 $$\bar {1}$$ 02) structure of sapphire substrates. Ga nanocrystals and microcrystals with tetragonal shape also were observed at deposited time large than 10 s. The increase of deposition time from 10 to 20 s provided the rise of numbers of Ga nanocrystals with the increase of their density on 58% on the substrate surface, and microcrystal sizes from 120 to 300 nm. Gallium oxide (Ga2O3) detected by X-ray phase analysis was formed due to the interaction of surface atoms of Ga nanocrystals and microcrystals with oxygen atoms on the surface of the sapphire substrate (Al2O3). A two-layer structure was found at deposition times of 15 and 20 s that the lower layer consisted of Ga microcrystals grown on sapphire substrates. Second layer of Ga nanocrystals was formed on top surface of first layer microcrystals.