Abstract
Perpendicularly oriented vinylidene fluoride oligomer thin films with six molecular layers were poled during vacuum evaporation (in situ poling) using a micro-gapped comb-like electrode, and their pyroelectric characteristics were investigated. The extent of polarization achieved with in situ poling performed by applying a low electric field (7.7 MV m−1) is the same as that achieved by conventional post-poling with the application of a high electric field (>100 MV m−1). Despite using a film with a few molecular layers, the in situ poled sensor showed pyroelectric response without the use of an infrared ray absorption layer; voltage sensitivity of 198 V W−1 was obtained, which is much higher than that of the post-poled sensor (∼16 V W−1). The improvement in sensitivity is attributed to the amount of charge injected during the poling treatment.
Highlights
Many sensors around us are generally used to gather information that is referred to as “big data” on work efficiency, safety, security, environment, medicine, industry, agriculture, and social infrastructure.1–4) In the near future, sensor-based big data are expected to bring new business opportunities, leading to better management of smart cities, healthcare services, environmental protection, and disaster monitoring
The extent of polarization achieved with in situ poling performed by applying a low electric field (7.7 MV m−1) is the same as that achieved by conventional post-poling with the application of a high electric field (>100 MV m−1)
Among the different kinds of sensors, pyroelectric infrared sensors are non-contact-type thermal sensors that can detect human body, gas, and abnormal heat generation by receiving infrared rays emitted from humans and heat sources.5–8) In general, pyroelectric sensors are composed of inorganic ferroelectric materials, such as lead zirconate titanate (PZT)
Summary
Many sensors around us are generally used to gather information that is referred to as “big data” on work efficiency, safety, security, environment, medicine, industry, agriculture, and social infrastructure.1–4) In the near future, sensor-based big data are expected to bring new business opportunities, leading to better management of smart cities, healthcare services, environmental protection, and disaster monitoring. Among the different kinds of sensors, pyroelectric infrared sensors are non-contact-type thermal sensors that can detect human body, gas, and abnormal heat generation by receiving infrared rays emitted from humans and heat sources.5–8) In general, pyroelectric sensors are composed of inorganic ferroelectric materials, such as lead zirconate titanate (PZT). Organic ferroelectric materials are one of the promising alternatives to PZT, because of their minimal environmental impact. Vinylidene fluoride (VDF) based organic ferroelectric materials exhibit relatively better ferroelectricity and pyroelectricity among organic ferroelectrics, because they have a large electric dipole moment generated from the difference in electronegativity between the fluorine and hydrogen atoms in the molecule. One of the most commonly used organic ferroelectrics that can be spin-coated to obtain thin films is the polymeric VDF material poly (vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)].11)
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