Coalesced nanomorphology, in situ, and ex situ applications of self assembled Gallium droplets grown by metal organic chemical vapor deposition

Abstract

Self assembled Gallium droplets are used as catalyst for epitaxial growth of III–V semiconductor nanowires. Understanding the effect of droplets’ nanostructure on in situ catalysed growth of nanowires is essential. Evolution of MOCVD grown Ga droplets’ self-assembled structure under different growth conditions, therefore, has been studied. The droplet nanomorphology has been explained on the basis of Ostwald-ripening based coalescence growth model. Two major morphologies of Ga droplets have been observed, namely, Valved and Spherical. Where a partial coalescence leads to the formation of valved nanostructures, complete coalescence of droplets give rise to spherical nanomorphology. Droplet morphology has been observed to have significant effect on in situ catalysed growth of GaAs nanowires by MOCVD. Twin and singular nanowires have been grown using valved and spherical Ga droplets, respectively, as catalyst. In addition, Gallium droplets having spherical nanomorphology with average diameter of around 80nm and surface density of about 4×109/cm2 have been subjected to ex situ chemical oxidation to examine their chemical and morphological stability. The scanning electron microscopy of the oxidized sample has confirmed the retention of spherical morphology. The detailed theoretical depth analysis of the photoemission spectrum of the oxidized droplets has revealed the formation of interesting Ga-Ga2O3 core-shell nanostructure within a spherical droplet with a shell thickness of more than 3nm.