Synthesis of Tin Nitride SnxNyNanowires by Chemical Vapour Deposition

Tin nitride (Sn(x)N(y)) nanowires have been grown for the first time by chemical vapour deposition on n-type Si(111) and in particular by nitridation of Sn containing NH(4)Cl at 450 degrees C under a steady flow of NH(3). The Sn(x)N(y) nanowires have an average diameter of 200 nm and lengths >/=5 mum and were grown on Si(111) coated with a few nm's of Au. Nitridation of Sn alone, under a flow of NH(3) is not effective and leads to the deposition of Sn droplets on the Au/Si(111) surface which impedes one-dimensional growth over a wide temperature range i.e. 300-800 degrees C. This was overcome by the addition of ammonium chloride (NH(4)Cl) which undergoes sublimation at 338 degrees C thereby releasing NH(3) and HCl which act as dispersants thereby enhancing the vapour pressure of Sn and the one-dimensional growth of Sn(x)N(y) nanowires. In addition to the action of dispersion, Sn reacts with HCl giving SnCl(2) which in turn reacts with NH(3) leading to the formation of Sn(x)N(y) NWs. A first estimate of the band-gap of the Sn(x)N(y) nanowires grown on Si(111) was obtained from optical reflection measurements and found to be approximately 2.6 eV. Finally, intricate assemblies of nanowires were also obtained at lower growth temperatures.