Catalyst-free gallium nitride nanowire nucleation

Extensive research on nanowire devices and applications has unleashed exciting possibilities in a quest for smaller, faster electronic equipment, more sensitive detectors, and new devices that take advantage of the quantum mechanical world. One of the roadblocks to these new technologies is a clear understanding of how nanowires are formed and how to control their growth. Nanowire growths can be grouped in two broad categories: catalytic growths and catalyst-free growths. Catalyst-free nanowire growths are useful in applications where catalyst particles are not desirable.;This thesis deals exclusively with gallium nitride catalyst-free nanowire nucleation and growth mechanisms. GaN nanowires are of particular interest because of GaN's unique optical and electronic properties. This thesis contributes fundamental understanding of the formation mechanisms of catalyst-free GaN nanowire growth through investigations of the matrix from which the nanowires grow and through novel use of the nanowires themselves as a diagnostic of their own growth mechanism. This work shows that nanowire orientation changes as a function of growth temperature and investigates this orientation change in terms of availability of nucleation sites and constituent adatom materials.