Controllable Electrochemical Fabrication Of Electrode Pairs With Nano-Scale Gap And SERS Studies

Recently, molecular electronic devices have attracted considerable attention because of their potential application as alternatives to silicon-based semiconductor devices. The investigation on the electron transport through individual molecules is of special importance for the development of molecular devices. The electrode pairs with appropriate gap linked by functional molecules might become a common approach to study single molecular properties. At present several methods for fabricating electrode pairs have been invented, however all these methods are based on nano-/micro-fabrication with the requirements of special equipments and complex process. In this thesis, a new method for fabricating electrode pair was developed based on electrochemical etching, the main results were listed as following:1) A feedback electronic circuit with high sensitivity was developed to control the electrochemical etching by optimizing the parameters of the components. By monitoring the difference between the applied voltage and the certain reference voltage, the applied etching voltage could be removed at the different etching duration. As a consequence, a series of Au electrode pairs with the gap distance ranging from nanometers to several hundreds nanometers were fabricated. The electrode pairs with large gap distance to micrometer were fabricated by electrochemical etching because of its excellent rigid of tungsten. This method might be developed as a simply way for the modeling investigation of the molecular electronic device.2) 1D conducting polymer (PPY, P3HT and PEDOT: PSS) nano structure were fabricated to link the electrode pair gap as a simply model of molecular device. The electronic measurements and Raman spectroscopy were employed to characterize the polymer linked the electrode pair. The results revealed that the electrode pair could be linked by the polymer nanofiber, electron was flowed between the electrode pairs along with the nanofiber, and applied voltage dependent Raman bands of the polymer fiber were observed. 3) 1, 4- benzenedithiol (1, 4- BDT) was served as probing molecule, the SERS effect of electrode pairs with different gap was investigated. The electrode pairs exhibited strong SERS effect when the gap distance was decreased to certain value. It was mainly due to the giant electromagnetic field in the electrode pair nano-scale gap. Moreover, the relationship of the SERS intensities and the angle between polarization of incident excitation line and the gap axis was probed preliminary.