This study investigates the growth of GaN nanowires by controlling the surface

diffusion of Ga species on sapphire in a plasma-enhanced chemical vapour

deposition system. Under nitrogen-rich growth conditions, Ga has a tendency to

adsorb on the substrate surface diffusing to nanowires to contribute to their growth.

The significance of surface diffusion on the growth of nanowires was dependent on

the environment of the nanowire on the substrate surface as well as the gas phase

species and compositions. Under nitrogen-rich growth conditions, the growth rate

was strongly dependent on the surface diffusion of gallium, but the addition of 5%

hydrogen in nitrogen plasma instantly diminishes the surface diffusion effect.

Gallium desorbs easily from the surface by reaction with hydrogen. On the other

hand, under gallium-rich growth conditions, nanowire growth was shown to be

dominated by the gas phase deposition, with negligible contribution from surface

diffusion. This was the first study reporting the inhibition of surface diffusion

effects by hydrogen addition, which can be useful in tailoring the growth and

characteristics of nanowires. Without any evidence of direct deposition on the

nanowire surface, gallium and nitrogen were shown to dissolve into the catalyst for

growing the nanowires at 900C.

Controlled Surface Diffusion in Plasma-Enhanced Chemical Vapour Deposition of

GaN Nanowires. W.C.Hou, F.C.N.Hong: Nanotechnology, 2009, 20[5], 055606