The Role Of The Dislocations In The Growth Of Nanowires

The growth mechanism research of one dimensional nanomaterials is the fundamental of growth control, structure and properties. Screw dislocation driven growth mechanism is important which was put forward in the 1950 s to explain the one dimensional growth of crystal. However, the screw dislocation in the nanowire could not be confirmed under the limited experimental conditions at that time. Due to the development of experimental technology, the screw dislocation driven growth mechanism has been widely concerned after 2008. This work focuses on the role of dislocations in the growth of Cu O and Zn S nanowires. The main contents of this paper are as follows:Firstly, Cu O nanowires were prepared by the thermal oxidation method. The effect of temperature and cooling mode on the growth of Cu O nanowires was studied. Few Cu O nanowires were obtained in the air cooling sample after heating at 600?, while a large-scale Cu O nanowires were observed in sample cooling in furnace from 600?. Besides, there are many nanowires in the air cooling sample after heating at 400?.It could be concluded that the growth temperature of Cu O nanowires is no higher than 400?. Cu O layer got growth when the temperature is higher than 400?, and the growth of Cu O nanowires was mainly occurred at lower temperature. These results could be understood by the diffusion of Cu ions in the oxidation layer.Second, the electron microscope analysis of nanowires showed that the copper oxide nanowires were multiple twin structure. It was found that there was a screw dislocation in the growth direction of the nanowire, and the vector of screw dislocation is [110] direction. The stress and defects in the copper oxidation process lead to the generation of multiple twin structure. The stress in the multiple twin structure leads to the generation of screw dislocations in the nanowires. The screw dislocation drives the one dimensional growth.Third, the twins and stacking faults in the Zn S nanowires were analyzed. The growth direction of Zn S nanowires is changed from the [01-10] direction to the [0001] direction by the stacking faults. On the other hand, the twins can also change the growth direction of the nanowires without the change of crystal orientation. It is considered that partial dislocations in the Zn S nanowires have a contribution to the onedimensional growth. The outcrop of partial dislocations provides a step which drives the one-dimensional growth of the crystal similar to the screw dislocation.