Preparation And Optical Properties Study Of Germanium Inverse Opal Three Dimensional Photonic Crystal Film

Photonic crystal became one of the promising basic materials because of their unique properties in terms of light propagation. It caused extensive concern in numerous fields such as optics physics, condensed state physics and information technology. Germanium (Ge) is a most popular semiconductor material. Ge inverse opal and Ge woodpile three dimensional photonic crystal based on Ge medium have the photoelectricity characteristic and photonic band gap effect. These two kinds of photonic crystal could be used for preparing photo devices with special optical effect, possessing a well application foreground.In this thesis Ge inverse opal three dimensional photonic crystals film with high quality were prepared by LPCVD and PECVD methods to filling Ge inside opal templates. Macromolecule-Ge composite woodpile was prepared by low temperature and room temperature PECVD methods to filling Ge inside macromolecule woodpile templates. By combining theoretical calculation with experiment testing, the relationship between the microstructure state of Ge inverse opal and the macroscopic optical properties of reflection and transmission had been investigated systematically. Then the mainly influencing factors and control methods of inverse opal film'optical properties. These would lay substantial foundation for the implementation of Ge inverse opal. The main contents and conclusion are as follows:1. Aiming at the optical properties study demand of inverse opal and woodpile, the photonic band gap (PBG) theoretical properties of the inverse opal and woodpile calculated by Plane Wave Expansion Method and Transfer Matrix Method. The effect law of lattice constant, effective refractive index, filling fraction (ff) and incidence angle to the optical properties of the inverse opal had been investigated respectively. The effect law of structure parameter to woodpile PBG structure had been investigated too.2. Aiming at the quantitative measuring demand of filling effect, the geometry calculation model of filling fraction were established. By Monte Carlo simulation, the relationship between r/d and ff were obtained.3. By LPCVD method Ge inverse opal were prepared. The difference between surface and bottom of opal templates would be reduced by decreasing reaction rate, decreasing GeH4 concentration, increasing diffusion coefficient. The technological parameters were investigated systematically. Filling fraction could be adjustment by controlling the reaction temperature, the reaction pressure and the gas flux. The compact filling was carry out at 450℃4. By PECVD method Ge inverse opal were prepared. (1) In the high temperature PECVD processing, the effects of the reaction pressure and the radio frequency power to filling effect were investigated systematically. The controlled compact filling was carry out at 550℃by increasing the reaction pressure, choosing the suitable radio frequency power. (2) In the low temperature PECVD processing, the effects of the reaction temperature, the gas flux and the reaction time to filling effect were investigated systematically. The compact filling was carry out at 200℃by choosing the suitable radio frequency power, increasing the gas flux and the reaction time. (3) The depositing technology of Ge at room temperature by PECVD method had been investigated. The effects of the radio frequency power to Ge deposition were investigated. Ge deposition was carry out at 30℃. (4) In the PECVD processing, Growth mode of Ge film at the surface of SiO2 microsphere is conformal growth as a cover film.5. By combining theoretical calculation with experiment testing, the relationship between the microstructure parameters of Ge inverse opal film and the macroscopic reflectance optical properties had been investigated systematically. The effects of lattice constant (a) and filling fraction (ff) to the reflectance optical properties of Ge inverse opal film were investigated systematically. Along with the increasing of a, the gap center wavelength and full width at half-maximum of PBG reflection peaks increased. Along with the increasing of ff, the gap center wavelength and full width at half-maximum of PBG reflection peaks increased, the reflectivity of band5-band9 gap reflection peaks increased. By controlling a and ff, the gap center wavelength, full width at half-maximum and reflectivity of PBG reflection peaks would be adjusted effectively. (2) The reflectance optical properties of Ge inverse opal with different incident angles had been investigated. Along with the increasing of incident angles the center wavelength of PBG reflection peaks was blue shift, and the reflectivity of PBG reflection peaks decreased. The result approved that Ge inverse opal possesses the complete photonic bandgap.6. The transmission optical properties of Ge inverse opal had been investigated. (1) The transmissivity of Ge inverse opal gradually decreased along with the decreasing of wavelength. The transmissivity difference between passband and forbidden band are not evident, due to the low transmissivity at the area of band5-band9 gap. (2) Aiming the low transmissivity of passband, transmission optical loss of Ge inverse opal film was analyzed by integrating the loss with its microstructure. The study showed that the loss included the absorption loss of polycrystalline Ge; the scattering loss of macroscopic and microscopic defects, different grain orientation, air pore; the diffuse reflection loss on the film surface and the interfaces reflection loss at different index interface. The main reason of the low transmissivity of inverse opal is the scattering loss. (3) The transmission optical properties of the composite film combining anti-reflection (AR) film with Ge inverse opal film had been investigated. After one-sided coating AR film, the transmittivity increased at the area of 3～5μm, the difference of passband and forbidden band was obvious, the reflectance optical properties kept constant. After two-sided coating AR film, the PBG reflectivity peak disappeared; it is disadvantageous to the photonic band gap. After one-sided coating anti-reflection film, the transmission optical properties of the multiplex film including anti-reflection film and Ge inverse opal film was studied. The transmittivity of Ge inverse opal is increased at 3～5μm. The transmittivity of forbidden band and passband are both increased, the difference between them is obvious. After two-sided coating anti-reflection film, there were many void reflectivity peaks in the reflectance spectrum. The reflectivity peak of photonic band gap disappeared; Two-sided AR film is disadvantageous to the photonic band gap.7. Two layers SU-8 woodpile and two layers PS woodpile were prepared by micromolding in capillaries method. By low temperature PECVD method, SU-8-Ge composite woodpile was prepared. By room temperature PECVD method, PS-Ge composite woodpile was prepared. Ge hollow logs ordered arrays were prepared after wiping off PS by sintering.