Structural and Optical Properties of Strained Gallium Nitride Nanowires
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Structural and Optical Properties of Strained Gallium Nitride Nanowires Hee Won Seo, Seung Yong Bae, Jeunghee Park, Department of Chemistry, Korea University, Jochiwon 339-700 Korea; Hyunik Yang, College of Engineering Science, Hanyang University, Ansan 425-791 Korea; Kwang Soo Park, Sangsig Kim, Department of Electric and Electronic engineering, Korea University, Seoul 136-701 Korea * Corresponding Authors: [email protected] ABSTRACT Bulk-quantity single crystalline wurtzite gallium nitride nanowires with a mean diameter of 25 nm were synthesized on silicon substrate using a catalyst-assisted reaction of gallium and gallium nitride mixture with ammonia. They exhibit a strong and broad photoluminescence in the energy range of 2.9-3.6 eV with no yellow band. X-ray diffraction and Raman scattering data suggest that the nanowires would experience biaxial compressive stresses in the inward radial direction and the induced tensile uniaxial stresses in the wire axis. The blue photoluminescence would originate from the recombination of the bound excitons under the compressive and tensile stresses. INTODUCTION Gallium nitride (GaN) material has been the subject of intense research for UV or blue emitters, detectors, high-speed field-effect transistors, and high-temperature microelectronic devices.[1-3] Recently, one-dimensional GaN nanostructure, GaN nanowire (GaN-NW), has attracted much attention because of its potential for new visible and UV optoelectronic applications. A number of research groups showed many successful syntheses of cylindrical GaN-NWs using various methods such as arc discharge,[4] laser ablation,[5] sublimation,[6] pyrolysis,[7] chemical vapor deposition (CVD).[8,9] Here we report a bulk-quantity growth of GaN-NWs with well-defined diameters using a new CVD route and study on their unique optical properties. EXPERIMENTAL DETAILS About 0.5 g of Ga metal (99.999 %, Aldrich) and GaN powder (99.99+ %, Aldrich) with about 1:1 mole ratio was put in a quartz boat placed inside of a quartz tube reactor. Iron (Fe) nanoparticles were deposited on a silicon substrate using the laser photodissociation of Fe(CO)5 at 266 nm. The size of iron nanoparticles was 8-10 nm. The substrate was transferred at a distance of about 10 cm away from the quartz boat. NH3 gas was introduced into the quartz tube at a rate of 200 sccm. The temperature of Ga source was set at 1050 °C and that of the substrate was approximately 950 °C. The growth time was 2 hours. The size and structure of the products were examined by scanning electron microscopy (SEM, Hitachi S-4300), transmission electron microscopy (TEM, Jeol JEM-2010), selected-area electron diffraction (SAED), and X-ray powder diffraction (XRD, Philips X’PERT MPD). Raman scattering spectra were taken using a 514.5 nm argon ion laser. The temperature-dependent photoluminescence (PL) has been conducted in the range 8-300 K. The excitation source was 325 nm line from a helium-cadmium (He-Cd) laser. K7.1.1 Downloaded from https://www.cambridge.org/core. Columbia University Lib
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