Photoluminescence of Surface Modified Silicon Carbide Nanowires
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Photoluminescence of Surface Modified Silicon Carbide Nanowires Polite D. Stewart1,2, Ryan Rich1 A. Nemashkalo1 and T. W. Zerda1 1 Physics Department, Texas Christian University, Fort Worth, TX 76129 USA 2 Southern University, Baton Rouge, LA 70813, USA ABSTRACT SiC nanowires were produced from carbon nanotubes and nanosize silicon powder in a tube furnace at temperatures between 1100oC and 1350oC. SiC nanowires had average diameter of 30 nm and very narrow size distribution. The surface of the SiC nanowires is covered by an amorphous layer composed of amorphous SiC and various carbon and silicon compounds. The objective of the research was to modify the surface structure of the SiC nanowires, a step necessary for future surface functionalization. The acid etched nanowires were analyzed using FTIR, TEM, x-ray diffraction, and photoluminescence. The concentration of Si-Ox groups in untreated specimens was estimated to account for 1% of the total mass of a 2 nm thick amorphous layer wrapping around all structures. After treatment in HF this concentration was negligibly small. TEM images show that after treatment the amorphous layer was removed but the diameter of the core remained unchanged. The surface was roughened and multiple pits formed on that surface. X-ray line broadening analysis indicates a significant contribution due to stress caused by dislocations and planar faults. After acid etching line narrowing was observed and attributed to stress reduction and elimination of the smallest wires. The photoluminescence signal from as received samples was very weak but increased greatly after acid treatment, indicating that the signal is related to surface defects. Measurements at low temperatures, 8 K, showed peaks due to point and planar defects. INTRODUCTION One-dimensional semiconductor nanomaterials deserve special attention, because they play a crucial role as building blocks of future molecular electronic applications.[1] SiC in the one-dimensional form, such as nanowires, nanotubes, nanorods, or nanowhiskers, possesses even more attractive attributes than in the bulk structure. Attempts to use SiC nanowires for nanoelectronic and optoelectronic device applications have been reported.[2] Hardness and tensile strength of SiC nanowires are greater than in the case of the larger SiC whiskers.[3,4] Therefore they may be applied as reinforcement to monolithic ceramics in order to improve fracture tolerance and toughness of the composites.[5-7] SiC nanowires have already been obtained by various methods, such as the sol-gel process, catalytic chemical vapor deposition, vapor-liquid-solid growth mechanism, reaction between carbon nanotubes (CNT) and SiO vapor at high temperatures, reaction between CNT and liquid or vapor Si, and others [7,8]. The major goal in all these techniques is the control of the desired parameters, such as grain size, nanowire diameter and length, and concentrations of various defects. Certain defect structures strongly affect the mechanical and electronic properties and are critical for the fu
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