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

Abstract

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)xOCH3]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 1H and 13C 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 reveal 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 X‐ray 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.

MOCVD of ZnO Films from Bis(Ketoiminato)Zn(II) Precursors: Structure, Morphology and Optical Properties

“…Synthesis: The preparation of compounds 1 and 2 was carried out according to the recently reported procedure [27]. MOCVD experiments were performed in a custom-built, horizontal, cold-wall reactor [48] using N 2 (6.0) and O 2 (4.5) as carrier and reactive gases, respectively.…”

“…Recently, we reported the synthesis and characterization of two closely related Zn II ketoiminate complexes as potential precursors for the MOCVD of ZnO. [27] [27] Plasma-assisted CVD of ZnO, using the above Zn II -ketoiminates, also revealed the suitability of these compounds for the deposition of ZnO nanostructures with tunable morphological organization. [25] Herein, we report on the analysis of the MOCVD-grown ZnO films using the two bis(ketoiminato) zinc compounds 1 and 2.…”

3,5-Lutidine coordinated zinc(II) aryl carboxylate complexes: Precursors for zinc(II) oxide

“…1 H and 13 C NMR spectra were recorded on an Avance Bruker-300 NMR spectrometer operating at field strengths of 300 and 75Á5 MHz, respectively and chemical shifts are reported relative to tetramethylsilane (TMS) or residual solvent signal. The solid-state crosspolarization magic angle spinning (CP-MAS) 13 C NMR spectra were recorded on a DSX-300 MHz spectrometer and the chemical shifts were referenced with respect to TMS. TOF-MS spectra were recorded on a Micromass LCT KC 455 instrument using electrospray positive ion mode.…”

“…The d C = 176.6 ppm value is assigned to the carbonyl carbon of the monodentate acetate [40,64] and the d C = 181.1 ppm value is assigned to the carbonyl carbon of the monodentate acetate 13 C NMR signals whereas complex 5 revealed only one for the carbonyl carbon as the formerly mentioned complexes possess two crystallographically distinct carbonyl carbon whereas the latter possess only one.…”

“…Hence, there exists a need to synthesize air stable and safe to handle zinc containing precursors that can easily result in the formation of ZnO. Few zinc ketoiminato complexes [13,14] as well as few Lewis base coordinated zinc(II) carboxylate complexes [15][16][17] were also reported to be useful precursors for ZnO .…”