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High Vacuum thermal evaporation was used to grow germanium islands on the silicon substrate covered by silicon oxide. The Ge nano-islands were formed by thermal annealing at different temperatures from 500 °C to 700 °C. Formation of islands was studied by various analytical techniques. The thickness of Ge layer was determined by rutherford backscattering spectroscopy (RBS). Also, combined with channeling technique, the composition and probable contaminants during synthesis processes were investigated. To explore the islands size and shape, both atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) were used. Then the topographical images of surfaces were studied by AFM. The outcome of experimental evaluations of growth mechanism has indicated that with increasing the annealing temperature up to 700 °C, Ge islands were appeared from a uniform layer. Moreover, the statistical assessments of surfaces have shown that the nano-island's sizes can be varied from several hundred nanometers to 30 nm by growing the annealing temperature. The reduction of the size along with an increase of the number of nano-islands after each thermal treatment is a major factor to prohibit us from seeing their clear images in AFM. The possibility of running statistical estimation on islands, instead, is the powerful tool of extracting and probing the distribution and the shape of Ge island's peak in AFM images. [ABSTRACT FROM AUTHOR]