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Abstract:
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The sensors which measure physical quantities by sensing them as thermal quantities and then converting the thermal signals into electrical signals are called thermal sensors . One such type of thermal sensor is a pyroelectric infrared sensor . Thermal sensors are not popular mainly because they are slow devices , and they have low sensitivity when compared to photon detectors . One major advantage of thermal detectors over photon detectors is that they can operate at room temperature . This is one of the main motivations for this research . The aim of the thesis is to design an uncooled , high detectivity pyroelectric infrared detector . The high detectivity is obtained by reducing the thermal conductivity from the sensor to the substrate or the heat sink . Pyroelectricity is defined as the change in polarization with corresponding change in temperature . Lead calcium titanate (PCT ) is a material which is a ferroelectric perovskite . It has a very high pyroelectric co -efficient , high dielectric constant and if deposited in a proper ratio could yield a very high pyroelectric response in the range of 6 x106 V /W . The thermal conductance between the sensor and the substrate using the proposed design is found to be as low as 9 .51x10 -9 W /K , less than the radiative thermal conductance 3 .69x10 -7 W /K . Two kinds of absorber designs are proposed with this detector . The efficiency of the design and the directivity of the top surface of the infrared sensor are found to have 55° field of view on both sides . Various fabrication methods for fabricating the device have been discussed in detail and the best methods have been mentioned in comparison over the other types . The development of the absorber and its application in the detection mechanism is discussed in detail . |