We report the self-assembled growth of Ge islands of different shapes and sizes on p-Si (001) by r.f. magnetron sputtering by varying the r.f. power, growth temperature and postdeposition annealing condition. The well known Stranski-Krastanov growth mechanism due to lattice mismatch between Si & Ge leads to the formation of Ge islands, similar to a more sophisticated MBE growth, albeit at a much higher pressure in our study. Ge nanocrystals embedded in SiO2 matrix have also been grown. Optical properties of nanocrystals exhibiting visible luminescence at room temperature are presented.