Study On The Optical And Electrical Properties Of Mn-Co(Zn)-Ni-O Films

As a spinel transition metal oxide, Mn-Co-Ni-O has attracted much attention because of the excellent negative temperature coefficient of resistance（NTCR）. The preparation method, device manufacture, electrical, optical and magnetic properties of Mn-Co-Ni-O material have made significant development in recent ten years. Mn-Co-Ni-O material has been widely applied in infrared bolometers, suppression of inrush current, measurement, control, and compensation of temperature. Especially, the material fabricated in the film form shows great potential in the application of uncooled infrared detection. As NiMn₂O4 is an important thermistor material, researchers have been focusing on how to improve the electrical performance of NiMn₂O4 system material. Doping with other elements is an effective method to improve the properties of material. Zn-Ni-Mn-O films have been grown by chemical solution deposition（CSD） method in this dissertation. Traditionally, the Zn-Ni-Mn-O ceramic materials have been fabricated by sintering method at high temperature, and few studies about Zn-Ni-Mn-O films have been reported. The dense and smooth Zn-Ni-Mn-O films prepared by CSD method show good crystallization, which are suitable for the investigation of physical properties, especially the optical property.This dissertation is devoted to investigate the structural, optical and electrical properties of Mn₂-xCo₂xNi1-xO4（MCNO, x=0, 0.25, 0.5, 0.75 and 1） films and Znx Ni1-xMn₂O4（ZNMO, x=0, 0.05, 0.1, 0.15, 0.2 and 0.25） films prepared by CSD method:1. Mn₂-xCo₂xNi1-xO4（x=0, 0.25, 0.5, 0.75 and 1） films have been grown on amorphous Al₂O₃ substrate by CSD method. The structural features and optical property have been studied. It shows that all the MCNO films have pure cubic spinel structure. The XRD peaks shift to higher angle and the lattice constant a decrease with x increasing, which are due to the lattice strain caused by Co substituting. The preferred orientations of MCNO films vary with the increasing of x. The band gap of MCNO films derived from transmission spectrum decreases with the increasing of x.2. The resistivity of MCNO films changes with x increasing by current-voltage（I-V） test at room temperature（RT）. MCNO（x=0.5） has the minimum value of resistivity, which is close to the classical Mn1.56Co0.96Ni0.48O4. The analysis of temperature dependent electrical characteristics shows that all the MCNO films have large TCR（about-4%K-1@295K）. The electrical transport properties of the films fit the variable range hopping（VRH） mode very well. With x increasing, the changes of activation energy E of MCNO films present the identical trend towards the resistivity. And the phase transition temperature has been fitted, which prove the electro-magnetic correlation of the Mn-Co-Ni-O material.3. ZnxNi1-xMn₂O4（x=0, 0.05, 0.1, 0.15, 0.2 and 0.25） films have been grown on amorphous Al₂O₃ and Pt/Ti/SiO2/Si substrates by CSD method. By analysis of XRD patterns, all the films show pure cubic spinel phase. Crystallinity of the ZNMO films on Al₂O₃ substrate has no obvious variation with x increasing. But the diffraction peak intensities of the films on Pt/Ti/SiO2/Si substrate increase with the decreasing of Zn concentration, which is due to the crystal growth and improvement of crystallization. The investigation of temperature dependent electrical characteristics of ZNMO films on Al₂O₃ substrate shows that TCR remain unchanged（about-4.4%K-1@295K）, while the resistivity changes with the increasing of x. The electrical property of NiMn₂O4 film can be improved by doping with a certain amount of Zn without loss of TCR. The optical constants of ZNMO films have been analyzed by spectroscopic ellipsometry measurements in the wavelength range of 300-1100 nm. The changes of the refractive index n and extinction coefficient k caused by Zn substituting are discussed. Additionally, the investigations of the Raman spectra prove that cation configuration and lattice deformation are related to the Zn concentration.