Crystal Structures of GaN Nanodots by Nitrogen Plasma Treatment on Ga Metal Droplets

Abstract

Gallium nitride (GaN) is one of important functional materials for optoelectronics and electronics. GaN exists both in equilibrium wurtzite and metastable zinc-blende structural phases. The zinc-blende GaN has superior electronic and optical properties over wurtzite one. In this report, GaN nanodots can be fabricated by Ga metal droplets in ultra-high vacuum and then nitridation by nitrogen plasma. The size, shape, density, and crystal structure of GaN nanodots can be characterized by transmission electron microscopy. The growth parameters, such as pre-nitridation treatment on Si surface, substrate temperature, and plasma nitridation time, affect the crystal structure of GaN nanodots. Higher thermal energy could provide the driving force for the phase transformation of GaN nanodots from zinc-blende to wurtzite structures. Metastable zinc-blende GaN nanodots can be synthesized by the surface modification of Si (111) by nitrogen plasma, i.e., the pre-nitridation treatment is done at a lower growth temperature. This is because the pre-nitridation process can provide a nitrogen-terminal surface for the following Ga droplet formation and a nitrogen-rich condition for the formation of GaN nanodots during droplet epitaxy. The pre-nitridation of Si substrates, the formation of a thin SiN x layer, could inhibit the phase transformation of GaN nanodots from zinc-blende to wurtzite phases. The pre-nitridation treatment also affects the dot size, density, and surface roughness of samples.

Inhomogeneity-mediated systematic reduction of the Schottky barrier in a Au/GaN nanorod film interface

“…During the growth of nanostructures in the MBE, surface morphology and its evolution were observed with in situ RHEED analysis. The patterns shown in figure 1(a) correspond to the high-density nanorod samples (Nano1 and Nano1 * ) and semicircular arc-like RHEED patterns are expected to arise only from nanorods [47][48][49][50]. As the nanorod density decreases for the Nano2 and Nano2 * samples, the GaN film underneath is exposed and, for this kind of structure, an electron beam would not only get diffracted from the nanorods but also the GaN thin film.…”

Plasmas Processes Applied on Metals and Alloys

“…The crystal structures of GaN nanodots produced by nitrogen plasma treatment on Ga metal droplets were investigated. The formation of a thin SiN x layer could inhibit the phase transformation of GaN nanodots from a zinc-blende phase to a wurtzite phase [8]. Al 2 O 3 coatings were prepared on Ti-45Al-8.5Nb alloys via cathodic plasma electrolysis deposition.…”