Synthesis and characterization of novel self-generating liquid MOCVD precursors for thin films of zinc oxide

Three novel Zn(hfa)(2). 2H(2)O . polyether adducts have been prepared through simple procedures with stoichiometric quantities of zinc hydroxide, Hhfa, and polyether. The products have been characterized by elemental analysis, X-ray single-crystal analysis, fast atom bombardment mass spectra, H-1 and F-19 NMR spectra, thermogravimetric (TG;)-differential TG-differential scanning calorimetry (DSC) thermal measurements, and infrared transmittance spectroscopy. An attempt to obtain water-free adduct was unsuccessful even using excess polyethers. X-ray single-crystal data of the Zn(hfa)(2). 2H(2)O . diglyme adduct show that the polyether does not coordinate to the metal center. Nevertheless, metrical data are indicative of bridging interactions involving the oxygen of one coordinated H2O molecule and the three oxygens of the diglyme. Very mild heating (37-51 degrees C) results in liquid compounds that, in turn, can easily be evaporated. Preliminary gas-phase Fourier transform-IR measurements in vacuo suggest that the anhydrous Zn(hfa)(2). diglyme forms upon evaporation due to competing H2O and diglyme ancillary ligation. Deposition experiments, in a low-pressure horizontal hot-wall reactor, on fused SiO2 (quartz) substrates, result in ZnO films. X-ray diffraction measurements provide evidence that they consist of hexagonal (002) and (10l) oriented, crystals. UV-vis spectra show that the transmittance of as deposited films in the visible region is about 90%.