Volatile, Monomeric, and Fluorine-Free Precursors for the Metal Organic Chemical Vapor Deposition of Zinc Oxide

Two new bis(ketoiminato)zinc(II) compounds that show excellent precursor properties for the chemical vapor deposition (CVD) of zinc oxide materials are presented. The synthesis of the ketoiminato zinc complexes [Zn{[(CH2)(x)-OCH3]NC(CH3)=C(H)C(CH3)=O}(2)] (1: x = 2; 2: x = 3) is straightforward and can easily be scaled up. Compounds 1 and 2 were analyzed by H-1 and C-13 NMR spectroscopy, elemental analysis, single-crystal X-ray diffraction analysis, and electron ionization mass spectrometry. The compounds exist as monomers with a distorted tetrahedral zinc center. Thermogravimetric studies, sublimation, and solubility tests re-veal very promising properties for metal organic CVD related applications. Preliminary metal organic CVD experiments with the use of compound 1 were performed as a screening for the suitability of the new bis(ketoiminato)zinc complexes as precursors for the growth of ZnO thin films in the presence of oxygen. The films were characterized by Xray diffraction, scanning electron microscopy, energy dispersive analysis of X-ray, and Rutherford backscattering measurements. The as-deposited ZnO films were stoichiometric; the crystalline films exhibited strong preferred orientation along the c-axis.