Fabrication of germanium inverse opal three-dimensional photonic crystal by low temperature plasma enhanced chemical vapour deposition techniques and optical properties

Abstract

By the solvent vaporization convection self-assembly method, silica colloidal crystal template was prepared. At 200℃, using GeH4 as the precursor gas, plasma enhanced chemical vapour deposition method was then used to fill the high refractive index material germanium, and germanium inverse opal photonic crystal was obtained. At the temperature lower than the temperature of thermal decomposition, GeH4 filling of germanium is realized. The morphology, composition, and optical property of the resulting samples were characterized by scanning electron microscopy, X-ray diffraction and Fourier transform microscopic IR spectroscopy. Results show that of germanium is amorphous, it is transformed into polycrystalline state by annealing. The germanium is homogeneously distributed inside the voids of silica template. The reflective spectrum of the sample has remarkable optical reflective peaks and shows the photonic band gap effects. The center wavelength of the photonic band gap lies in 1650nm and 2640nm. There is good agreement between the measured spectra and the calculated band structure. Germanium was also deposited on the SU-8 film, this shows that the SU-8 photoresist can with stand the deposition temperature. Low temperature deposition method decreases the deposition temperature. So this method can use macromolecule materials as templates. Thus the three-dimensional photonic crystal with more kinds of structure can be obtained by single-inversion procedure.