Synthesis, crystal structure and vapour pressure studies of novel nickel complex as precursor for NiO coating by metalorganic chemical vapour deposition technique

Abstract

A square planar nickel complex namely bis(N-propyl-3-methylsalicylaldimine)nickel(II) (2) was prepared from its parent compound bis(3-methylsalicylaldehydato)nickel(II) (1) by adding n-propylamine in a methanol medium. The TG/DTA analysis of the resultant Schiff's base complex 2 in the solid phase was evaluated in an inert N2 environment at atmospheric pressure. Complex 2 was completely volatile giving nil residue at 335 °C in a single weight loss step, whereas the complex 1 was found to be non-volatile giving 47% residues till 455 °C. The change in volatility of 2 was brought about by the condensation of n-propylamine with 1 which replaced aldehyde O (-CH=O) with N (-CH=N). The volatile precursor 2 was characterised by single crystal XRD, 1H and 13C NMR, FT-IR, C, H and N elemental analysis and mass spectrometry. The temperature dependence of the saturated vapour pressure and enthalpy of vapourisation (ΔvapH° = 97.9 ± 2.0 kJ mol−1) of the volatile complex 2 was determined by a transpiration TG technique in the temperature range 499–562 K. Subsequently, it was used as a precursor for the deposition of nickel oxide (NiO) thin film on Si(100) substrate by employing plasma assisted metal-organic chemical vapour deposition (PAMOCVD) technique. The nano-crystalline nickel oxide thin films were analysed by XRD and SEM/EDX. X-ray photoelectron spectroscopy (XPS) study confirmed the formation of stoichiometric NiO phase. The band gap of the NiO thin film was found to be 4.31eV exhibiting a blue shift as observed from DRS-UV.