【作者】 李宇杰；

【导师】 谢凯；

【作者基本信息】 国防科学技术大学 ， 材料科学与工程， 2010， 博士

【摘要】 光子晶体具有能够调控光子传播的特殊光学特性,成为未来信息产业最有希望的基础材料之一,在光学物理、凝聚态物理、信息工程、新材料等领域引起了广泛关注。Ge作为目前广泛使用的半导体材料,以其为介质制备的Ge反opal和Ge木堆三维光子晶体,整合了半导体的光电特性和和光子晶体的带隙特性,可用作制备具有特定光学效应的光子器件,具有良好的应用前景。本文采用低压化学气相沉积法(LPCVD)和等离子增强化学气相沉积法(PECVD)对opal模板填充Ge,制备出具有较高质量的Ge反opal三维光子晶体薄膜;采用低温和室温PECVD法对高分子木堆填充Ge,制备出高分子-Ge复合木堆。通过理论计算结合实验测试,系统研究了Ge反opal薄膜微观结构状态与宏观反射及透射光学性能之间的关系,进而获得了反opal薄膜光学性能的主要影响因素和调控方法,为Ge反opal光子晶体的实际应用奠定了良好的基础。本文的研究内容与结论包括:1、针对反opal和木堆光子晶体光学性能的研究需求,采用平面波展开法和传输矩阵法对反opal和木堆的光子带隙性能进行了理论计算。获得晶格常数、有效折射率、填充率和入射角度对反opal光子带隙能带和反射系数的影响规律;获得结构参数对木堆光子带隙能带的影响规律。2、针对反opal填充效果的定量表征需求,构建了反opal填充率数值计算的几何结构模型,采用蒙特卡罗法模拟计算,得到了归一化厚度r/d与填充率ff之间的对应关系。3、采用LPCVD法填充Ge制备了Ge反opal。分析了opal结构表层与底层沉积差异的影响因素,通过减小反应速率常数、减小GeH4浓度、增大扩散系数,可减小表层与底层沉积差异。系统研究了工艺参数的影响,实验证明调节反应温度、反应气压和气体流量是调节ff的有效手段,实现了450℃下Ge的致密填充。4、采用PECVD法填充Ge制备了Ge反opal。(1)系统研究了高温PECVD法的反应气压和射频功率对Ge的填充效果的影响。通过提高反应气压,选择适宜的功率范围,实现了550℃下Ge的可控致密填充。(2)系统研究了低温PECVD法的反应温度、气体流量和反应时间对Ge的填充效果的影响。通过选择适宜的射频功率,增大气体流量和反应时间,实现了200℃下Ge的致密填充。(3)研究了室温PECVD法的射频功率对Ge沉积状态的影响,实现了30℃下Ge的沉积。(4)实验证明PECVD过程中,Ge在SiO2微球表面的生长方式为壳层包覆共形生长。5、通过理论计算结合实验测试,系统研究了Ge反opal薄膜微观结构参数与宏观反射光学性能之间的关系。(1)系统研究了晶格常数a和填充率ff对Ge反opal反射光学性能的影响:随着a的增大,带隙反射峰的中心波长和半峰宽均增大。随着ff的增大,带隙反射峰的中心波长和半峰宽增大,band5-band9带反射峰的中心波长反射率增大。通过调节a和ff可有效的调节带隙反射峰位置、半峰宽和中心波长反射率。(2)研究了Ge反opal的变入射角反射光学性能:随着入射角度的增大,带隙发生蓝移,相应带隙反射峰的反射率降低。通过变角度反射光谱研究,证实了Ge反opal存在完全光子带隙。6、研究了Ge反opal薄膜的透射光学性能。(1)实验表明Ge反opal的透射率随波长减小逐渐降低。Band5-band9带所在区域的整体透射率较低,通带与禁带在透射性能上的差异不明显。(2)针对通带透射率低的现象,结合微观结构分析了Ge反opal薄膜中的各种损耗,研究表明损耗主要包括:多晶体Ge导致的吸收损失;结构中的缺陷、不同晶粒取向和空气孔导致的散射损失;薄膜表面漫反射和折射率不同的多界面导致的反射损失。散射损失是反opal整体透射率低的主要原因。(3)研究了增透膜与Ge反opal薄膜复合后的透射光学性能。研究表明:单面镀膜提高了Ge反opal薄膜3～5μm的整体透射率,使带隙与通带的差异明显,对其反射光学性能不产生影响;双面镀膜导致带隙反射峰消失,对光子带隙效应产生不利影响。7、采用毛细微模塑法制备得到两层SU-8木堆和两层PS木堆。采用低温PECVD法得到SU-8-Ge复合木堆;采用室温PECVD法得到PS-Ge复合木堆,烧结去除PS后,得到Ge空心木条有序阵列结构。更多还原

【Abstract】 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.更多还原