Temperature And Illumination On The Growth And Electrical Properties Of Silicon Nanowires

One-dimensional nanostructured materials are attracting more and more attention due to their uniques physical, chemical, mechanical, electronic, magnetic, optics and etc properties. Among them, Silicon nanowires have been regarded as one of the most potential building blocks for future micro-nano electronic devices due to their special semiconducting properties.So far lots of methods had been established to form the silicon nanowires. In this thesis, the metal (Ag)-assisted Galvanic Displacement, which is a facile and mild process for forming the silicon nanowires, had been chosen. A new formation mechanism for metal (Ag)-assisted Galvanic Displacement had been proposed. In term of the Galvanic Displacement for Silicon nanowires growth, two different formation mechanisms had been proposed. The major controversy was focused on the position of reduced silver particles. In other words, do these particles exist on the top of the nanowires or droped into the bottom by weight of themselves? We used the double-sided polished silicon wafers to form the silicon nanowires on both sides. Since the results showed that the growth rates of silicon nanowires on both sides were almost identical, it is concluded that the reduced silver should be on the top of the nanowires.Based on the discovered the formation mechanisms of silicon nanowires and the influential factor, we used the best parameters,35mM silver nitrate,20%HF and 60 mins reaction time, to study the effect of the temperature and light on the formation of the silicon nanowires by the Galvanic Displacement. We studied the influence of light illumination on the growth length and the temperature effect on the growth length and the surface morphology of formed silicon nanowires. The influence of temperature on the growth length of the the silicon nanowires were also formulated. All these can provid the references of the rapid, accurate growth of silicon nanowires, which had fixed length and ordered arrangement. In this thesis, the perfect order nano-wire arrays up to 400μm long, had been made, which basically achieved ultimate limition of the Galvanic Displacement. Then they can be used as the starting materials for the sensors based on the big aspect ratio and multil devices integrated on single nano-wire.The electrochemical experiment of single nano-wire displayed that the electrochemical properties of nano-wire formed by the Galvanic Displacement was stable. The resistivity increased with increasing of temperature among 30-130℃. The single nano-wire was more sensitive to the light illumination due to the big surface to volume rate. In the condition of the light, the current increased more 30-50 percent than that in the condition of the darkness. And the photocurrent would increase with increasing of ectric-field intensity.