Crystallization-dependent structural and optical properties of Mn1.56Co0.96Ni0.48O4 thin films grown by chemical solution deposition on Si (100)

Abstract

Mn1.56Co0.96Ni0.48O4 (MCN) thin films are deposited onto Si (100) substrate under different post-annealing temperatures of 450 °C and 600 °C. As identified by the X-ray diffraction (XRD) and SEM, pronounced difference in crystallinity is observed between the film annealed under 600 °C and 450 °C. Spectroscopic ellipsometry spectra, infrared transmission and reflection spectra are measured to compare and analyze the optical properties of the crystalline and non-crystalline MCN thin films. Ellipsometry measurement demonstrates the n, k spectra in the visible-to-near infrared range (300–1000 nm), indicating three absorption peaks locating at 1.6 eV, 2.6 eV, and above 3.5 eV for the crystallized sample, which corresponds to the charge-transfer (CT) transition involving O2− (2p) and Mn4+ (3d) ions, O2− (2p) to Co2+ (3d) ions, and O2− (2p) and Mn3+ (3d) ions, respectively. Transmittance and reflectance spectra in the near infrared (1.3 µm)-to-far infrared (25 µm) range are also investigated. A two-oscillator model is performed to directly analyze the combined transmission and reflection spectra in the far infrared (400 cm−1–800 cm−1) to acquire the optical constants, where the difference of n, k values of the crystallized and non-crystalline MCN films in reststrahlen band is investigated for the first time.