Simulations Of The Mechanical Properties Of GaN Nanowire

As a new type of one-dimensional materials, Nanowires has attracted increasing attention. In 2001, Science announced that the semiconductor nanowire-based nano-circuit would be a major breakthrough in human science. Whether a material can be used in human's life depends on the good mechanical properties of this material firstly. Therefore, it is very important to research the basic mechanical properties of nano-materials and nano-devices. With the current rapid development of nanotechnology, Nanostructure semiconductor optoelectronic devices is becoming more and more important in the microelectronics, and a great many study has been made on synthesis and preparation methods of nanostructure semiconductor and devices. But kinds of defects exsit in nanostructure semiconductor made in laboratories in different degrees, which affect the mechanical properties of nanostructure semiconductor. Many researchers neglected the influence of such defects, which cause some differences between theoretical predication and experimental results on mechanical properties of nanostructure semiconductor. To research the effects of defects on mechanical properties of nanostructure semiconductor, it requires investigation in its structure on atomic and molecular scale to find out the discrepancies.In this thesis, classical molecular dynamics method were carried out to investigate the effects of temperature,size,surface defects,random vacancy and different grain boundary (IDB, IDB*, GB-I, GB-II) on the mechanical properties of wurtzite GaN nanowires. It was found that the effect of temperature on young's modulus of gallium nitride (GaN) nanowires was very small, but it had conspicuous influence on critical stress. As the temperature increases, young's modulus of gallium nitride (GaN) nanowires reduced. As the size increase, the young'modulus increased accordingly. With the concentration of random vacancy or surface defects increase, the young's modulus decreases. But at the same level of concentration, the impact of random vacancy on young's modulus is greater than that of surface defects. The grain boundary at which the interface was normal to the axial direction of a nanowire (GB-1, GB-II) did not significantly affect the Young's moduli of the nanowire. However, the inversion domain grain boundaries with and without wrong bonds (IDB, IDB*) may significantly lower the Young moduli of the GaN nanowire. In addition, the inversion domain grain boundaries affect the critical stress of GaN nanowires more than the grain boundary at which the interface was normal to the axial direction of the nanowire.