The Fabrication And Application Of Silicon Microstructural Material

In recent years, the preparation and application of the microstructural materials, especially the microstructural semiconductors, have attracted more and more attention in the field of physics,chemical,material,electronics and etc.. The microsturctural and the micro-devices will initialize a new technology revolution in the 21st century.In this thesis, the preparations of one-dimensional and two-dimensional silicon microstructural materials, on the one hand, one-dimensional oxidized porous silicon photonic crystal were investigated firstly. The formation mechanisms and the preparation methods of one-dimensional oxidized porous silicon photonic crystal were studied deeply. Based on a large number of experimental a series of optimality conditions in experiment were obtained. The islands array of 1D porous silicon photonic crystal reflector for far infrared image detector was realized. On the other hand, Silicon microchannel (Si-MCP) thin film with high surface to volume ratio has been fabricated by conventional microelectronics technology. The technology of electroless plating nickel on Si-MCP and their potential application such as electrochemical supercapacitors, directed methanol fuel cells (DMFCs), biosensor and bio-fuel cells were studied deeply. Some innovative progresses had been achieved in the application in uncoolled infrared sensor based on 1D porous silicon photonic crystal reflector islands array, but the fabrication of Ni-Pd/Si-MCP electrode and their application in DMFCs and biosensor as well as bio-fuel cells were the key innovative content of this thesis. The mainly works are listed as following:The mechanism and the related theory of one dimensional porous silicon photonic crystal had been analyzed. Then in combination with the principle of silicon electrochemical etching and the software of Matlab, the parameters were proposed for the formation of one dimensional porous silicon photonic crystal.The most optimized parameters, such as current density, HF concentration, the type of substrate, the formation temperature, the RTO time and temperature were obtained by a serial of experiment. Then through the transfer-matrix method (TMM) designed, the porous silicon photonic crystals with the PBG gap ranging in mid 5,6,7μm were formatted. Considering device application of photonic crystal for uncoolled infrared sensors, concerns must be taken on the following issues. One was the cool part and the interconnections doesn't need thermal insulator. Moreover, when fabricated large area Photonic crystal layers for sensor, the mechanical properties must had better stability. But the experimental results show that if increase the layers to enhance the optical properties, the surface of the photonic crystal will crack. More importance the interconnection between each unit was difficulty during application in devices. So the localization islands array of photonic crystal area was fabricated which PBG gap ranging in mid 12μm. Fourier transform infrared spectroscopy (FTIR) was applied to check the difference before and after oxidation, contrast and comparison with simulation. It is found that the center wavelength was shifted to short. When the incidence angle reaches 50°, it still had a wide bandwidth which proves to be a good reflective mirror within wide incidence angles (50°) for far-infrared wavelength.In this part, the fabrication process and the equipment of MCP were introduced briefly by the combination of lithography and electrochemical etching technology. From SEM images, it is clearly that the connective film is composed of a regular cube array with silicon walls between them. Both the length and width of the silicon MCP can be varied by choosing the etching time, enchant and temperature. In our experiments, the distance between each cube is about 1μm, the side length of each cube is about 5μm, and the depth can reach about 250μm. There are little impurities in each channel. Then the optimum conditions of electroless plating nickel films on Si-MCP were studied. The feasibility of Electrochemical Supercapacitors based on NiO/Si-MCP nanocomposite was discussed. The fabricated high surface to volume ratio silicon microchannel plates were modified by electroless plating Ni and Ni-Pd technology, the morphologies of the Ni/Si-MCP and Ni-Pd/Si-MCP composites were studied by SEM. The compositions of them were determined by EDS, and the catalytic abilities were obtained by a LK3200A electrochemical workstation (Tianjin, China).It is found that the 3D structure constitutes a proton conductive path from the catalysts to electrolyte membranes thereby playing an important role in the performance of the DMFCs and glucose biosensors or bio-fuel cells. Besides the good electronic conductivity, the silicon MCP had well-ordered channels that bode well for facile molecular transport of the reactants and products enhancing molecular conversion. The high volume to surface ratio increases the reaction area, and so more catalyst nanoparticles can be deposited onto the electrode surface resulting in the high surface reactivity. So this new catalyst supported by the silicon MCP electrode can significantly enhance the electrode kinetics.In conclusion, the silicon micorstuctural materials of one-dimensional oxidized porous silicon photonic crystal and silicon microchannel plates can be formed by electrochemical method under normal conditions. Their good performance make some potential cells and sensor application like direct methanol fuel cells and glucose biosensor.