Abstract
A methodology is proposed for designing a multi-frequency band pyroelectric sensor which can detect subjects with various frequencies or velocities. A structure with dual pyroelectric layers, consisting of a thinner sputtered ZnO layer and a thicker aerosol ZnO layer, proved helpful in the development of the proposed sensor. The thinner sputtered ZnO layer with a small thermal capacity and a rapid response accomplishes a high-frequency sensing task, while the thicker aerosol ZnO layer with a large thermal capacity and a tardy response is responsible for low-frequency sensing tasks. A multi-frequency band pyroelectric sensor is successfully designed, analyzed and fabricated in the present study. The range of the multi-frequency sensing can be estimated by means of the proposed design and analysis to match the thicknesses of the sputtered and the aerosol ZnO layers. The fabricated multi-frequency band pyroelectric sensor with a 1 μm thick sputtered ZnO layer and a 20 μm thick aerosol ZnO layer can sense a frequency band from 4000 to 40,000 Hz without tardy response and low voltage responsivity.
Highlights
Pyroelectricity, which is electric current generation from time-dependent temperature fluctuations, is useful in many applications, such as pollution monitoring, hot image detectors, intruder alarms, gas analysis and temperature sensors
The principle of thin-film pyroelectric sensors is based on the pyroelectric effect, namely converting the heat transfer rates to the corresponding electrical signal
The thickness of the sputtered ZnO layer was named as TPZ
Summary
Pyroelectricity, which is electric current generation from time-dependent temperature fluctuations, is useful in many applications, such as pollution monitoring, hot image detectors, intruder alarms, gas analysis and temperature sensors. Thin-film pyroelectric sensors have many advantages, such as facile integration with on-chip circuitry, uncooled detection, room-temperature operation, speed, lower system costs, portability and a wide spectral response with high sensitivity [1,2,3]. The principle of thin-film pyroelectric sensors is based on the pyroelectric effect, namely converting the heat transfer rates to the corresponding electrical signal. The pyroelectric effect is the property of selected dielectric materials with polar point symmetry, which show a spontaneous electrical polarization as a function of temperature. A change in the temperature of the material with respect to time (thermal fluctuations) causes a correspondent variation in the induced charge, thereby producing a pyroelectric current.
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