Formation of arrays of gallium nitride nanorods within mesoporous silica SBA-15

We report the first formation of arrays of GaN nanorods inside the nanoscale channels of mesoporous silica SBA-15. GaCl3 dissolved in toluene was incorporated into the methyl group-functionalized SBA-15 powder. The pore surfaces functionalized with methyl groups should facilitate the impregnation with GaCl3. Formation of GaN nanorod arrays within SBA-15 was carried out by heating the powder to 700 degrees C for 3 h under nitrogen atmosphere, followed by ammonolysis at 900 degrees C for 5 h. epsilon-Ga2O3, an unusual phase for Ga2O3, formed after the first thermal process and was converted into wurtzite GaN during ammonolysis. The final products have been characterized by FT-IR spectra, powder XRD patterns, TEM images and SAED patterns, EDS analysis, and nitrogen adsorption-desorption isotherm measurements to confirm the presence of GaN nanostructures. The nanorods are 6-7.5 nm in diameter, and can be a few hundreds of a nanometer in length to exhibit nanowire structure. Free-standing GaN nanorod arrays were revealed upon removal of the silica framework with HF solution. Optical characterization of the isolated GaN nanorod arrays shows a strong and sharp near band-edge emission at 375 nm, and two phonon-assisted donor-acceptor peaks at 395 and 415 nm. A broad but weak emission in the region of 335-360 nm due to the quantum confinement effect of short nanorods was observed.