Remote thermal sensing and imaging is currently one of the most prominent technological fields. It is raising a lot of industrial interest as its market value is expected to grow beyond $10 billion/year by 2020. Remote thermal sensing and imaging finds applications in fundamental research, industrial quality control, future communication networks (THz based), military, isolation in housing, smart buildings, etc. The most used approach for the required sensors is bolometers, which are uncooled radiation heat sensors. The route for improved performance is enhanced absorption of thermal radiation, improved thermal isolation, reduced thermal mass, increased sensitivity of thermal transduction and reduced noise. However, even though the route is clear, bolometer technology has stagnated over the last decade.
FUTBOL aims to cause a paradigm shift in bolometer technology by making use of suspended devices made of atomically thin single crystalline sheets of material, 2D materials, to create a novel sensor with unseen resolution and measuring speed. Indeed, 2D materials are an attractive alternative to traditional bolometer materials. Their extreme aspect ratio allows for excellent thermal isolation, low areal mass density results in microscopic thermal mass and electrostatically tunable properties allows active tuning of temperature sensitivity and absorption of thermal radiation. The working principle of the 2D materials based bolometer is as follows: Absorbed thermal radiation heats up the suspended sheet, which can be monitored by measuring the induced change in the resonance frequency or electrical resistance. A schematic of the bolometer concept can be seen in the figure.
Realization of the suggested 2D material based bolometer will contribute to the need for better, faster and cheaper bolometers. Existing applications will benefit from improve technology and new applications will emerge. For instance, thermal imaging sensors complements LIDAR, RADAR and ultrasonic scanners used in self-driving cars.
The main objective of the FUTBOL project was to fabricate and characterize 2D material based bolometers.
At the end of the FUTBOL project, we have successfully fabricated graphene based bolometers. The measured relative frequency change per absorbed microwatt is 0.7% which is comparable to state of the art resonating radiation sensors. The minimum detectable power was estimated to be 1.4 nW. By exchanging graphene with e.g. WSe2 we expected this value can be improved with orders of magnitude and be beyond state-of-the-art.
