Annealing effect on the structural, electrical and 1/f noise properties of Mn–Co–Ni–O thin films

Abstract

Thin films of Mn1.4Co1.0Ni0.6O4 (MCN) spinel oxide are grown by radio frequency (RF) magnetron sputtering method on amorphous Al2O3 substrate. We investigate the annealing effect on the micro structural and electrical properties of RF sputtered MCN films. It is found that the crystallinity of MCN film is improved with increasing annealing time at 750 °C, and the annealed films present excellent cubic spinel (220) preferred orientation in X-ray diffraction patterns. Comparing to as-sputtered thin film, the annealed films show a decrease of 60 to 70 % in resistivity at 300 K. The annealed samples with post annealing time longer than 18 min acquire a negative temperature coefficient of resistance of about −3.73 %K−1 and resistivity of about 210–220 Ω cm at 300 K. 1/f noise of MCN films are also studied and the Hooge’s parameters (γ/n) are calculated. After annealing for 18 to 90 min, the γ/n values of the films are on the order of 10−21 cm3, which ranks about two orders lower than that of amorphous silicon.