Thin film pyroelectric boosts thermal sensors
Researchers at MIT have developed a technique to produce ultra-thin pyroelectric films for room temperature thermal sensing.
Building thin pyroelectric films is hard, but this gives more sensitivity for thermal sensors. The researchers at MIT have developed a technique to both build single crytal perovskite layers 10nm thick and lift them off
The mass production of these ultrathin complex oxide membranes has been hindered by the challenging requirement of inserting an artificial release layer between the epilayers and substrates.
The film could enable lighter, more portable, and highly accurate far-infrared (IR) sensing devices, with potential applications for night-vision eyewear and autonomous driving in foggy conditions without the need for bulky cooling elements.
The technique achieves atomic precision lift-off of ultrathin membranes without artificial release layers. Rather than using a graphene release layer, the researchers found that certain pyroelectric material, called PMN-PT, did not require an intermediate layer assist in order to separate from its substrate. Growing PMN-PT directly on a single-crystalline substrate, the researchers could then remove the grown film, with no rips or tears to its delicate lattice.
“It worked surprisingly well,” said Xinyuan Zhang, a graduate student in MIT’s Department of Materials Science and Engineering (DMSE). “We found the peeled film is atomically smooth.”
The team fabricated multiple ultrathin films of PMN-PT, each about 10nm thin, peeling them off and transferring them onto a small chip to form an array of 100 ultrathin heat-sensing pixels, each about 60 square microns.
The films were exposed to ever-slighter changes in temperature and found the pixels were highly sensitive to small changes across the far-infrared spectrum and demonstrated a record-high pyroelectric coefficient of 1.76 × 10−2 C m−2 K−1. This comes from the low thickness and the freestanding nature and offers an approach to manufacturing cooling-free detectors that can cover the full far-infrared spectrum, marking a notable advancement in detector technology.
Plasmonics to boost pyroelectric-based hyperspectral sensing
“This film considerably reduces weight and cost, making it lightweight, portable, and easier to integrate,” said Zhang. “For example, it could be directly worn on glasses.”
The sensitivity of the pyroelectric array is comparable to that of state-of-the-art night-vision devices that use photodiodes. This suggests that the films could be incorporated into small, lightweight, and portable devices for various applications that require different infrared regions. For instance, when integrated into autonomous vehicle platforms, the films could enable cars to identify pedestrians and vehicles in complete darkness or in foggy and rainy conditions.
The film could also be used in gas sensors for real-time and on-site environmental monitoring, helping detect pollutants. In electronics, they could monitor heat changes in semiconductor chips to catch early signs of malfunctioning elements.
“We envision that our ultrathin films could be made into high-performance night-vision goggles, considering its broad-spectrum infrared sensitivity at room-temperature, which allows for a lightweight design without a cooling system,” Zhang says. “To turn this into a night-vision system, a functional device array should be integrated with readout circuitry. Furthermore, testing in varied environmental conditions is essential for practical applications.”
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