Novel Three-dimensional Sensors Based On Silicon Microchannel Plates

The fabrication and application of three-dimensional materials have attracted tremendous attention. Silicon based three-dimensional materials have become the best choice to fabricate micro-electrochemical sensor and energy device arising from their unique properties in physics and chemistry compared with bulk materials and compatibility with silicon IC technology. This thesis focuses on silicon micro-channel plate prepared by electrochemical etching and the main works are listed as following:First, the method of the fabrication of silicon micro-channel plate by using the photo-electrochemical technology is described. The experimental parameters such as concentration of etchant, illumination, bias voltage and etching temperature are further optimized. Samples of silicon micro-channel plate fabricated under the selected conditions have good surface topography, large active area and high aspect ratio. The micro-channel layer can be separated from substrate automatically. The silicon micro-channel plate could be applied in various fields as novel three-dimensional material.A sensitive amperometric ethanol sensor composed of highly dispersed palladium nanoparticles on the vertically aligned nickel coated silicon microchannel plate (MCP) has been constructed. The morphology of the palladium modified nickel coated silicon MCP electrode was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The performance of the Pd/Ni/Si MCP electrode for the electrochemical detection of ethanol was investigated by cyclic voltammetry and amperometry. The electrode with three dimensional structure shows high catalytic activity towards the oxidation of ethanol in 0.10 M KOH solution. At an applied potential of-0.10 V, the Pd/Ni/Si MCP electrode shows a high sensitivity of 0.992 mA mM-1 cm-2 and the detection limit is 16.8μM. The linear range is up to 60 mM with a linear correlation coefficient of 0.998.It also possesses excellent electrocatalytic properties,rapid response,as well as good stability and repeatability.The OPPy-Pd/silicon MCP electrode fabricated electrochemically boasts a number of advantages such as high sensitivity,good stability,reproducibility,and quick response.Excellent selectivity is rendered by the OPPy film and signals arising from oxidation of common interferences such as UA and AA can be effectively suppressed. At a potential of+0.08 V,good sensitivity of 0.37 mA mM-1 cm-2 and detection limit of 2.06μM are attained. The linear range is up to 24 mM with a linear correlation coefficient of 0.997. Furthermore, the electrode is highly resistant to interfering substances because the effects of common coexisting substances can be effectively eliminated by the OPPy film and the response in the current to interferences on the electrode surface is almost negligible. This novel electrode has great potential application in nonenzymatic detection of glucose.We developed an ethanol fuel cell based on silicon micro-channel plate. The suitable spatial dimension and high porosity in this three-dimensional array can increase the active sites and enhance the mass transfer of reactants or products, thereby accelerating fast electron transfer and improving the catalyst efficiency. The onset potential for ethanol oxidation shifts negatively on Pd/Ni/Si MCP, and the current density peak is higher than that of planar Pd/Ni/Si. These results reveal that the microchannel structure plays an important role in the enhanced activity of ethanol oxidation. The stability of the Pd/Ni/Si MCP is evaluated by chronoamperogram. The electrocatalytic performance of prepared electrode for ethanol oxidation was investigated by varying concentrations of KOH and ethanol in order to understand the mechanism.The electrochemical etching technology can not only be used to prepare silicon-based micro-channel plate, but also be applied to fabricate porous silicon structure with given depth. The three-dimensional p-n junction based on porous silicon structure is formed by diffusion which can be used as novel energy conversion device adopted in high energy physics, clean energy power source and material test. The electrochemical etching process utilizing anodization has been described as a recommendable method to fabricate three-dimensional structure for p-n junction. However, the thickness of sidewall between two adjacent pores in the structure is usually too thin for p-type silicon to accord with technological requirement of following diffusion. In this section, pulse current was employed to manufacture satisfactory microstructure p-type silicon with thick sidewall.The 3D p-n junction based on this novel structure is promising for application in photovoltaic energy conversion and detection. By applying 3D p-n junction in solar cell,photons acquire an opportunity for secondary absorption. Therefore,electrical parameters such as output current and energy conversion efficiency are greatly improved. The feasibility of the theory is proved by the results of Matlab simulations.Furthermore,common fabrication process facilitates their applications both at laboratory and industrial levels, so it is an effective method which can yield higher efficiency without a large number of additional investments.In conclusion,electrodes constructed by silicon-based micro-channel plate have high potential in electrochemical sensors and fuel cells owing to superior electrocatalytic properties and stability.It is of great significance for development of novel integrated device.The three-dimensional p-n junction which is also obtained by electrochemical etching method has laid good foundation for the improvement of solar cell. The works in this thesis provide new entry point for the application of micro electro mechanical system technology in energy source and sensor field. The industrialization of this research with innovative and scientific value will bring huge social and economic benefits.