Thermal Design of a Schiff Base Cobalt(II) Precursor: Thermal Stability, Volatility, and Thin Film Deposition of Nanocrystalline Co3O4 by Plasma-Assisted MOCVD

초록

Bis(N-1,1-dimethylpropyl-3-methoxysalicylaldimine)cobalt(II) (B) is a square-planar cobalt complex synthesized by reacting n-tert-pentylamine with its parent compound, bis(3-methoxysalicylaldehydato)cobalt(II) (A), in a solution of methanol. The solid-state Schiff base complex B was analyzed using TG/DTA in an inert nitrogen (N2) atmosphere under atmospheric pressure. Complex A was determined to be nonvolatile, leaving 30% residue up to 598°C. In contrast, Complex B was fully volatile, with only 2% residue remaining at 325°C, following a single weight loss step. The condensation of n-tert-pentylamine with Complex A, replacing the aldehyde oxygen (-CH=O) with an imine nitrogen (-CH=N), resulted in a significant change in the volatility of Complex B. The volatile precursor B was characterized using FTIR spectroscopy, mass spectrometry, and elemental analysis such as carbon, nitrogen, and hydrogen. A transpiration TG method was utilized to examine the temperature dependence of the saturated vapor pressure and enthalpy of vaporization (∆vapHo = 88.42 ± 0.05 kJ mol−1) of volatile complex B in the temperature range of 473–555 K. This molecule was used as a precursor to build a thin layer of cobalt oxide (Co3O4) on a Si(100) substrate using plasma-assisted metal–organic chemical vapor deposition. XRD, SEM/EDS, elemental mapping, and XPS were utilized to examine the nanocrystalline Co3O4 thin films. The optical band gap was evaluated to be 2.29 eV based on analysis using the Kubelka–Munk function. © 2026 John Wiley & Sons Ltd.

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