Electronic Structure Of SiC/AlN Core/shell Nanowires And Gd-doped ZnO Nanowires: A First-principles Study

One-dimensional semiconductor nanowires have attracted much attention in recent years.Because of their unique electrical and optical properties, semiconductor nanowires play animportant role in the fields of optoelectronics, device miniaturization, and so on. However,pure semiconductor nanowires can hardly satisfy the growing requirements of electronic andoptoelectronic systems. The electrical and optical properties of nanowires can be tuned bymodulating the nanowires radially and doping the impurity elements. The electrical andmagnetic properties of nanowires rely on the intrinsic structure. It is necessary to explore theeffects of the above factors on the optoelectronic and electrical properties in specialapplications of nanowires. In this thesis, we performed first principle calculations to study thestructural stability and the electronic properties of SiC/AlN core/shell nanowires as well as themagnetic coupling properties of Gd-doped ZnO nanowires. The results are as follows.(1) The structural stabilities and electronic properties of saturated and unsaturatedSiC/AlN core/shell nanowires (CSNWs) along [0001] direction are investigated usingfirst-principles calculations with density functional theory. Our calculations demonstrate thatthick AlN shell and small ratio of SiC core make the SiC/AlN CSNWs more stable. The bandgaps decrease with the increasing of CSNWs diameters. After passivation on the surface, typeof SiC/AlN heterostructure changes and the mobility can be improved by increase theCSNWs diameter and the SiC core ratio. These results provide an effective way to modulatethe electronic properties of SiC/AlN structure, which is useful for fabrication and applicationof CSNWs.(2) In the Gd-doped ZnO nanowires, the coupling between the nearest two Gd atoms isferromagnetic, and the ferromagnetic phase becomes more stable when extra electrons areintroduced. These results can be used to explain the ferromagnetism properties of Gd-dopedZnO nanowires.