Investigation On The Mn-Co-Ni-O Films And Uncooled Infrared Detectors

Mn-Co-Ni-O spinel is a kind of transition metal oxides, which has excellent negative temperature coefficient of resistance and great application in civilian and military fields, including thermal infrared detectors, temperature sensor, remote sensing detection, night vision, and so on. These call for the use of films and detectors which have higher performance. Fast response, high sensitivity and the focal plane array device are the main direction of uncooled infrared detector. This thesis mainly researches on the preparation process of Mn-Co-Ni-O film devices, device performance and the infrared thermal imaging experiment based on the Mn-Co-Ni-O film prepared by chemical solution deposition. Optically immersed Mn-Co-Ni-O film detectors with high index of refraction Ge lenses are fabricated to improve the performance of detectors. The characteristics of immersed detectors are investigated. This thesis also studies the influence of sputtering process parameters on the structure, morphology and electrical properties of Mn-Co-Ni-O film. The electronic band structure and pulse laser response characteristics of films are also investigated. The main context and novel points are as follows.1. Temperature-dependent transmission spectra of Mn1.56Co0.96Ni0.48O4(MCNO) films on Al2O3 substrate are measured in 1.5-5.5 μm wavelength range. A dispersion relation that combines Lorentz oscillator model and Cauchy model is successfully adopted to obtain the optical constants of MCNO films. An absorption peak at around 0.8 eV which corresponds to the center energy of Lorentz oscillator is found. The regularity of temperature dependent peak position shows that above the magnetic transition temperature(～200 K) the peak position varies slightly, while below this temperature it varies more obviously. This phenomenon can be explained by the fact that the buildup of magnetic order leads to the localized electron states gradually withdrawing from the Hubbard band gap.2. MCNO film detectors are fabricated to evaluate the performance on infrared detection. It exhibits a responsivity of 330 V/W, detectivity of 0.6×108 cm?Hz1/2/W, and time constant of 19 ms at 30 Hz and ±15 V. The feasibility of MCNO films is demonstrated to be used for uncooled bolometric applications by thermal imaging.3. We describe the design and fabrication of front-incident and back-incident optically immersed detectors with Ge hemispherical lens using the MCNO films prepared by chemical solution deposition. The characteristics of immersed bolometer operated at room temperature are investigated. It is found that the performance of the immersed detectors is significantly enhanced. The front-incident immersed detector exhibits a responsivity of 4.5×103 V/W, detectivity of 8.3×108 cm?Hz0.5/W, and time constant of 18 ms. The back-incident immersed detector exhibits a responsivity of 3.2×103 V/W, detectivity of 9.2×108 cm?Hz1/2/W, and time constant of 7.3 ms. The results demonstrate that the feasibility of optically immersed structure can be used to uncooled infrared bolometric applications.4. High quality of MCNO nanofilms are prepared by sputtering deposition using the target sintering from acetate precursors. Excellent performance of MCNO nanofilms is demonstrated, combining for the high temperature coefficient of resistance, moderate resistivity, and lower noise. The films show an intrinsic recombination with a much faster rate of the order of a microsecond for the laser-pumped carriers, which is ~3 orders of magnitude lower compared with that of the ceramic material. The experiment of ultraviolet photoelectron spectroscopy shows that the electronic band structure of MCNO films is indeed of N-type nature. The results offer a vital avenue for exploiting new applications in modern oxide electronics and optoelectronics.5. We initially research the process parameters of high performance MCNO films prepared by magnetron sputtering, and study the effects of the sputtering atmosphere, sputtering power, substrate temperature and annealing process on the structure, morphology and electrical properties of MCNO films. The experimental results can lay the foundation for the development of focal plane array device.