Formation of Uniform Germanium Islands on Silicon Substrate Using Nickel as Catalyst by Thermal Evaporation Method

Uniform germanium islands (GIs) were grown on Si (100) using a nickel layer as catalyst through the physical vapor deposition of germanium (Ge) powder at 1000°C at different deposition times. Prior to the deposition of Ge layer, nickel (Ni) catalyst was deposited on silicon substrates via radio frequency magnetron sputtering technique. Scanning electron microscopy results showed that the increase in deposition time resulted in a variation in surface morphology. Energy dispersive X-ray spectrometer analysis found that the GI samples composed of Ni element indicating the role of Ni in uniform Ge islands formation. The X-ray diffraction pattern spectra revealed that the GIs exhibited a Ge cubic structure and the intensity of Ge peaks varies with deposition time. In-plane strain indicated that the strain caused by the substrate is tensile and changed to compressive strain at the longer deposition time. The Raman spectra exhibited a red shift in the Ge-Ge peak, compared with the bulk Ge, as a result of compressive strain of the GIs. Fourier transform infrared spectrum analysis also indicated that the optical band gap Eg values of GIs can be varied by deposition time.