Functional Nanostructures Fabricated by Focused Electron Ion Beam Induced Deposition This thesis constitutes a detailed study of functional nanostructures (ferromagnetic superconducting metallic and semiconducting) fabricated by focused electron ion beam induced deposition techniques. The nanostructures were grown using different precursor materials such as Co2(CO)8 Fe2(CO)9 W(CO)6 (CH3)3Pt(CpCH3) and were characterized by a wide range of techniques. This work reports results obtained for the morphology the microstructure the composition the electrical transport mechanism magnetic and superconducting properties of nanostructures. The results offers exciting prospects in a wide range of applications in nanotechnology and condensed matter physics