Experiments On Double-Tip STM And Calculations Of Electric Characteristics Of Specific Nano-Structures

The research in the thesis could be divided into three parts, namely, the construction of a double-tip scanning tunneling microscopy(STM), the analysis of conductance of quantum point contact in STM, and simulation of electric field distribution of carbon nanotubes(CNTs) array .First, a double-tip STM was constructed based on a specially designed electric control system, and a method for double tip aligned was suggested. With this double-tip STM, the I-V and I-Z curves of the tunneling junction built up with two tungsten tips were measured.Second, the conductance of quantum point contact in STM was calculated by modal matching and scattering matrices method. The results showed that the conductance of the nano-structures formed during quantum point contact in STM was quantized. The quantization phenomenon becomes more obvious as the radius and cone angle of the nano-structures decreases. The quantitative behavior could be observed more easily with semiconductors than with metals.Third, the electric field distribution and electric field enhancement factor of CNTs array in a carbon nanotubes field emission display(CNT-FED) were calculated. The effect of the length, diameter and separation of the CNTs to the electric field and electric field enhancement factor was studied. As the numerical results show, when the separation between CNTs reach three times of the length of CNT, the screen effect is negligible, the intensity of electric field and electric field enhancement factor increase linearly with the length of CNT. When the diameter of CNT is small, the electric field and electric field enhancement factor decrease rapidly with the diameter.