Characterization of ternary (Ni,Co,Mn)3O4 thin films for microbolometer applications

Abstract

A liquid flow deposition (LFD) technique was successfully applied to grow (Ni0.1Mn2.9−xCox)O4 (NMCx, x = 0.015, 0.027, 0.048, 0.065, 0.082, 0.097, 0.119 and 0.145) thin films onto Si wafer substrates at a low temperature (50 °C). The microstructure of the films was studied by field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). X-ray diffraction (XRD) analysis results showed that heat treatment at a temperature of 400 °C leads to the formation of a cubic spinel AB2O4 structure in the films. Measurements of the electrical resistance–temperature (R–T) dependence in a temperature range of 293–373 K revealed a very good negative temperature coefficient of resistance (NTC) characteristic for all annealed films. Films with a very low resistivity (ρ) of 613–831 Ω cm were obtained from solutions when x was varied in a range of 0.065–0.082, without substantially affecting the sensitivity. The difference in the electrical properties of the films was attributed to a valence state shift of manganese in accordance with the Co dopant concentration and this was also confirmed by an X–ray photoelectron spectroscopy (XPS) analysis. On the basis of their high NTC characteristic, low processing temperature, and very low specific resistivity, the NMCx thin films have a promising application in the integrated microbolometer devices.