Investigation On Low-frequency Noise Characteristics Of Mn-Co-Ni-O Thin Film Infrared Detectors

In tasks of space exploration and exploitation,the attitude of the orbitting satellites need to orient in a given direction,or maneuver from the original attitude to another pointing gesture.During these processes,the attitude of the satellite relative to a reference or target azimuth is determinated by calculating the measurement data acquired by the attitude sensor,according to the attitude determination model.The infrared detector,which mades of negative temprature coefficient(NTC)thermistors,is a core optoelectronic device in a satellite attitude sensor.Its performance has significant impact on that of the entire satellite attitude control system.The low-frequency noise is closely related to the internal defects and can be used to characterize the performance of the infrared detectors.Therefore,the study of the low-frequency noise characteristics of the infrared detector helps detecting characteristics of various defects in such devices,and then analyze the impact of potential defects on device performance.The low-frequency noise tesing technology and the low-frequency noise characteristics of infrared detector are systematically studied in this dissertation.Firstly,the realization of the bias circuit,low noise power supply,low noise amplifier,data acquisition technology,noise parameter extraction and data analysis technology was carried out.Then,based on the low-frequency noise characteristics of the infrared detectors and the related noise testing technology,the low-frequency noise testing system for infrared detectors and thermistors was established,respectively.By using these teting system,low-frequency noise characteristics of infrared detector and thermistor under different stresses were studied.The sensitive parameters of low-frequency noise for reliable characterization of infrared detectors were studied and determined.The main works of this dissertation are as follows.(1)The structural characteristics of the thermistor and infrared detector was studied;a bridge bias circuit was designed for simultaneously testing the low-frequency noise of multiple thermistor flakes or infrared detectors without interfering with each other.(2)The low-noise bias voltage supply technology was studied,an ultra-low-noise bias supply based on Ni-Mh battery pack and a low-noise linear series regulator bias supply have been built for long-term noise testing.(3)Low noise amplifier technology was studied,a small,low-power comsumption,low noise preamplifier has been designed.Based on these,a number of sets of multi-channel low-frequency noise test system have been built,effectively reduced the power consumption and the test volume of the system.(4)The structure of the thermistor flake was studied.The mechanism of electric conduction in infrared detector was studied based on a hopping conduction model of spinel.The factors that affect the electric conduction of infrared detectors were decomposed into two parts: grain and grain boundary.The electric conduction model for grain and grain boundary were established,respectively.According to the relationship between electron hopping activation energy in grain,the grain boundary barrier and the resistivity,it has been found that the resistivity at the grain boundaries play a leading role in the resistivity of the infrared detector.(5)The noise mechanism of infrared detector is studied in terms of case sealing,the changing of immersion medium,the degradation of electrode contact,and the defects in the thermistor flake.Reference the metal-insulator-metal(MIM)struct in thick film resistors,combined with conductive mechanism of thermistor flake,the noise model of thermistor flake has been established.The noise mechanism of thermistor flake in grain and grain boundary were studied.It has been found that conduction noise in grain is a basic 1/f noise,and its magnitude is small,and can not be eliminated.The noise result from carrier acrossing the grain boundary barrier has two mechnisms.One is due to the grain boundary barrier Nyquist noise modulate the fluctuation of carriers,and the other is due to the random capture of carriers when their pass through the barrier.Thereby the relationship between noise voltage,the defects in thermistor,interface state density of grain boundary in thermistor,barrier height and the number of traps in the barrier has been established,which laid the foundation for the study of internal defects by the noise of infrared detector.(6)Low-frequency noise of multiple batches of infrared detectors under the stresses of electricity,temperature and radiation has been tested using the built noise test system,and the test results have been analyzed.The noise figure was proposed as a low-frequency parameter for characterizing the reliability of infrared detectors.Test results show that the parameter can accurately estimate the performance of infrared detectors.This provides a means for non-destructive testing and screening of infrared detectors.The works and achievements stated above were partly used in the real production and research already;some of these works are still under further exploration.All the works in this thesis established the experimental and theoretical foundation for further research on reliablity of infrared detectors,and the preparation of high-performance devices.