New Methods For Preparation Of Ge And GeO₂Materials

1.Contrary to the conventional physical vapor deposition (PVD) under temperature gradients, we carried on a vacuum evaporation under the same temperature(both the Ge evaporation source and the substrates) to fabricate germanium(Ge) films. In this work, attraction between the film and the substrate is the the driving force for film growth. The most interesting result is that films on Ag substrate are oriented growth. It seems to be a cheap method to fabricate Ge films.2. Sol-gel Sn-doped GeO2powders were prepared using GeO2-ammonia aqueous solution as the precursor. The samples were characterized by X-ray diffraction, energy dispersive X-ray spectra, infrared spectra, SEM, UV-vis diffuse reflectance spectra and PL spectra. The results show that the Sn-doped GeO2powder sample consists of double-layered particles and has hexagonal crystalline structure. The addition of Sn to GeO2causes variation of lattices constant and red-shift of infrared absorption spectra. The band gaps of pure GeO2and Sn-doped GeO2were estimated to be5.04and4.51eV, respectively, based on UV-vis diffuse reflectance spectrum analyses. The PL spectra exhibited that Sn-doped GeO2emited ultraviolet light at325nm.3.In our work, CO2laser was used to heat the target and GeO2powders were used as the target materials. The whole process was in N2atmosphere. We got uniform spherical GeO2/Ge nanocomposites, which were100-200nm in size by adapting the laser’s power, the speed of N2current, and the location of the target. TEM images of the particles show that there are some smaller nanoparticles inside of the particle. XRD and EDS analyses of this composite show that this composite is composed of Ge with diamond structure, hexegonal GeO2, and amorphous GeO2. After dissolving this composite with excess alkli aqueous, we got small particles whose sizes were under50nm. XRD analysis shows that these particles are Ge with diamond structure. It indicates that the particle prepared by laser thermal evaporation has a GeO2/Ge core-shell structure. The photoluminescence spectra of GeO2/Ge core-shell structure show that the powders emit a blue light at480nm with the excitation light at365nm, while Ge nanopaticles emit a light at414nm with the excitation light at362nm.