MOCVD of Vertically Aligned ZnO Nanowires Using Bidentate Ether Adducts of Dimethylzinc

The dimethylzinc-bidentate ether adducts [Me2Zn(1,4-dioxane)] (1), [Me2Zn(1,2-dimethoxyethane)] (2) and [Me2Zn(1,4-thioxane)] (3) are used as precursors for the growth of vertically aligned zinc oxide (ZnO) nanowires (NWs) by liquid-injection, metal-organic (MO) CVD. The ZnO NWs are deposited on Si(111) and F-doped SnO2/glass substrates in the absence of a seed catalyst. The precursors (1) and (2) are used to deposit ZnO NWs at substrate temperatures of 450 degrees C and 500 degrees C, whilst higher deposition temperatures of 550-600 degrees C are necessary to obtain ZnO NWs using (3). X-ray diffraction (XRD) data show that the NWs grown from all three adduct precursors are deposited in the wurtzitic ZnO phase. Room-temperature photoluminescence (PL) data for the ZnO NWs grown using (1) and (2) show an intense peak at 3.28 eV due to near band-edge emission with a very low intensity of defect-related green luminescence at 2.42 eV. In contrast, room-temperature PL data for the ZnO NWs deposited using (3) is dominated by deep centre, defect-related emission at 2.42 eV. Auger electron spectroscopy (AES) shows that the ZnO films deposited from (1) and (2) are high purity with no detectable carbon, but the ZnO films grown from (3) are contaminated with sulfur (1 at.-%). Single-crystal X-ray structures show that (1) is polymeric containing bridging 1,4-dioxane ligands while (2) is a monomeric complex featuring a chelating 1,2-dimethoxyethane ligand. The wide [Me-Zn-Me] bond angles in (1) and (2) (152.0(3)degrees and 154.5(2)degrees, respectively) suggest moderately weak [Me2Zn]-ligand interactions. Complex (3) is polymeric and exhibits nearly linear [Me-Zn-Me] bond angles, indicative of much weaker [Me2Zn]-ligand interactions.