Synthesis and characterization of novel zinc precursors for ZnO thin film deposition by atomic layer deposition†
A novel series of zinc complexes, [EtZn(dab)]2 (1), [EtZn(damb)]2 (2), [EtZn(damp)]2 (3), and [EtZn(dadb)]2 (4), were prepared via single-step substitution. Further, these were analyzed by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, single crystal X-ray diffraction analysis, and thermogravimetric analysis (TGA). The X-ray crystallography analysis revealed that all complexes exist as dimeric structures with distorted tetrahedral geometry having zinc centers that are interconnected via μ2-O bonding of the aminoalkoxy oxygen atom. TGA and thermal analysis of the complexes showed high volatilities and stabilities at sublimation temperatures of 70, 95, 90, and 105 °C at 0.5 Torr for the respective compounds. Precursor 3 was successfully used for ZnO thin film deposition by ALD. A growth rate per cycle (GPC) of 0.125 nm per cycle was obtained at 200 °C and XPS analysis confirmed the growth of highly pure ZnO films without carbon and nitrogen impurities, while XRD analysis revealed the deposition of reasonably crystalline films. Additionally, the high transmittance and wide bandgap of the films are suitable for optoelectronic applications.