Researchers from Autonomous University of Barcelona developed a thermoelectric microsensor based on ultrathin suspended silicon films
Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation. Thermal detectors depend on the temperature increase produced by the absorbed radiation and can be used for detection in a broad spectral range. A photo detector has a p–n junction that converts light photons into current. Photodiodes and photo transistors are a few examples of photo detectors. Solar cells convert some of the light energy absorbed into electrical energy. Photosensors converts light to electrical signal and their response is proportional to the power in the beam.
Now, a team of researchers from Autonomous University of Barcelona and Institute of Microelectronics of Barcelona developed a thermoelectric microsensor. The team used a silicon-on-insulator (SOI) wafer to micro-fabricate the device. The device depends on an array of ultrathin single-crystalline n- and p-type thermoelectric legs to generate the output voltage. Finite element modeling was used to obtain the real temperature gradients applied to the thermoelectric legs. A central silicon free-standing membrane was connected and supported to the bulk silicon frame with thermoelectric silicon legs. The output voltage has a linear dependence with the input power, which allows the use of microsensor as a photosensor.
A relationship between the average temperature measured by the platinum grid and the average temperature at the hot junction of the thermoelectric silicon legs was established. The graphs reported increase in temperature and change in temperature profiles, owing to the incident radiation. Moreover, the shape of the temperature distribution changed when different wavelengths were used. The decrease in the thickness of silicon thermopiles led to reduced thermal conductance and heat capacity. This in turn increased the thermal insulation capacity of the membrane. The thermoelectric device was therefore, able to detect at very small temperature differences. The research was published in the journal MDPI Sensors on March 22, 2019.
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