Characterization of Cu-doped (Ni,Mn)3O4 thin films annealed at low temperatures

Abstract

Negative-temperature coefficient of resistance (NTCR) thin films were prepared from (Ni0.2Mn2.8-xCux)Cl2 (0.010 ≤ x ≤ 0.040) solutions by liquid flow deposition (LFD) method. Influence of the Cu on the structural and electrical properties of the films annealed at °400°C was studied. It was found that the incorporation of copper (Cu) promoted an increase in both the crystallinity and grain size of the films. As Cu level increased, the absolute negative temperature coefficient of resistance (TCR) of the films was slightly decreased from 3.21% to 2.38%K−1. On the other hand, the electrical resistivity (ρ) of the films significantly dropped with an increase of Cu, which was attributed to the improved carrier concentration rather than the enlarged grain size. The best electrical performance with ρ ~ 200 Ωcm was achieved in the film with x = 0.025 at room temperature. We provide the discussion on the conduction mechanism, particularly, for the high conduction behavior of the films via the changes of oxidation states of the manganese.

Keywords

• liquid flow deposition
• thin films
• spinels
• nickel-copper-manganite
• solution process
• ir sensors