Preparation Of The Silicon Nanowires And Their Sensor Application

In recent years,the preparation and application of the nanostructured materials, especially the nanostructured semicoducors,have attracted more and more attention in the field of physics,chemicak,meteriah electronics and etc..The nanotechnology and the nano-devices will initialize a new technology revolution in the 21st century.In this thesis,the preparation of a new large-area aligned nanostructured semiconductors,silicon nanowires(SiNWs) were investigated firstly.The patterned silicon nanowires were realized.The electrochemical hydrogen peroxide sensor using SiNWs as the sensing element was investigated.Some innovative progresses had been achieved in the patterning of SiNWs and the electrochemical SiNWs sensors.The mainly works are listed as following:1.Study of the formation mechanism of silicon nanowiresThe surface behavior of the H-terminated silicon in noble metal ions contained HF-based solution had been analysed.According to Galvanic Displacement in combination with the principle of the silicon electrochemical etching,the formation process of silicon nanowire was studied carefully.A new formation mechanism for silicon nanowire was proposed based on Galvanic Displacement.2.Formation of silicon nanowire via Galvanic Displacement.A large area aligned identical silicon nanowires arrays were prepared by Galvanic Displacement under normal conditions(room temperature,1 atm).The prepared materials were characterized by X-Ray Diffraction(XRD),Scanning Electron Microscope(SEM) and Transmission electron microscopy(TEM) to obtain the information on the structural and morphological properties.The parameters which can effect the morphology of silicon nanowires,such as concentrations and reaction time, were analyzed.And the optimized experimental parameters were obtained.The as-prepared SiNWs can be used as the electrode materials for electrochemical biosensor. These results are also confirmed in some degree the formation mechanism of silicon nanowires we proposed.3.Preparation of the patterned silicon nanowires In order to put silicon nanowires into application,the technology to form the silicon nanowires in the pre-defined areas selectively,i.e.,the patterning of silicon nanowire,is necessary.Using a standard photolithography technique and silicon nitride as mask, selective silicon nanowires on the silicon substrate were realized.The formation difference between the patterned SiNWs and the un-patterned ones were explained by dynamics of the reaction.4.Application of silicon nanowires in hydrogen peroxide sensorsThe electrochemical hydrogen peroxide sensor based on SiNWs were investigated. The surface of the prepared silicon nanowires was firstly modified with Prussian Blue(PB) by chemical depositions.The modified Prussian/SiNWs was used as the working electrode for the electrochemical analysis.The capacitance versus actuation voltage,(the C-V curve) is characteristic for the steady state behavior of the Prussian/SiNWs electrode. The electrochemical behaviors of the Prussian blue modified silicon nanowires(PB/SiNWs) electrode in hydrogen peroxide(H₂O₂) solutions were analysed. The results demonstrate that the PB/SiNWs electrodes are potential as the electrochemical biosensor for H₂O₂ detection.In conclusion,the silicon nanowires can be formed by by Galvanic Displacement method under normal conditions.The patterned silicon nanowires will have some potential sensor application like electrochemical sensor.