P-type nickel cobalt oxide synthetized by chemical bath deposition to applications on thin film transistors

Abstract

This work studies nickel-cobalt oxide (NiCo2O4) thin films synthesized via chemical bath deposition for potential application as p-type active layers in electronic devices. X-ray photoemission electron spectroscopy (XPS) confirms the synthesis of a ternary compound with a stoichiometry of Ni1.04Co1.96O4. The thin film sample exhibiting the closest stoichiometry to the ternary compound has a thickness of approximately 50 nm. Scanning Electron Microscopy (SEM) micrographs indicate an increase in surface porous size corresponding to higher nickel concentrations in the ternary compound. All synthesized NiCo2O4 thin films demonstrate p-type behavior. The lowest resistivity film had a majority carrier concentration of 1×1020 1/cm3, a mobility value of 0.1 cm2/V·s, and a resistivity of 0.1 Ω cm. X-ray diffraction (XRD) studies reveal that the thin films have a type of spinel cubic structure for the phase NiCo2O4. Characteristic spinel bands are observed in the UV–Vis transmittance spectra, and the energy bandgaps of the Ni1.04Co1.96O4 film are estimated to be approximately 3.41 and 2.19 eV using the Tauc method. The thin film with the lowest resistivity was used as an active layer to fabricate a thin-film transistor, displaying typical output curves of a p-channel transistor.