Journal of Crystal Growth, Vol.316, No.1, 25-29, 2011
Enhanced growth and photoluminescence properties of SnxNy (x > y) nanowires grown by halide chemical vapor deposition
Tin nitride nanowires have been grown by halide chemical vapor deposition via the reaction of Sn with NH4Cl at 425 degrees C under a steady flow of NH3 using small ramp rates <10 degrees C/min, which is critical for obtaining a high yield and uniform distribution of nanowires. Tin nitride nanowires with diameters < 100 nm and lengths of 2-3 mu m were grown on Si and exhibited pronounced peaks in the X-ray diffraction corresponding to Sn rich SnxNy (x > y) with a hexagonal structure, i.e. c = 5.193 angstrom, a = 3.725 angstrom. The excitation of the SnxNy NWs with UV light of lambda =300 nm at T = 300 and 77 K gave a broad photoluminescence (PL) spectrum covering 450-750 nm attributed to optical transitions between shallow and deep traps located within the band gap. These traps are most likely related to surface and nitrogen vacancy states. Time correlated, single photon counting PL measurements taken between 450 and 750 nm, showed that the PL decay has a multi-exponential structure, suggesting the existence of complex, non-radiative relaxation paths with relaxation times that are found to become shorter at smaller wavelengths. Finally no significant differences were observed between the PL spectra of the SnxNy and In doped SnxNy NWs most likely due to the low level of incorporation of In attributed to differences in the ionic radii of In and Sn but also the larger energy and growth temperatures required for the formation of In-N bonds. (C) 2010 Elsevier B.V. All rights reserved.
Keywords:Nanostructures;Chloride vapor phase epitaxy;Nanomaterials;Nitrides;Semiconducting materials