High temperature gradient nanogap-Pirani micro-sensor with maximum sensitivity around atmospheric pressure

This letter describes and discusses the design and testing of an effcient nanogap Pirani micro-sensor for pressure measurements in a wide range with a maximum sensitivity around atmospheric pressure. The structure combines a substrate-free heated wire and mechanical support using silicon oxide micro-bridges allowing both a constant nanoscale gap between the wire and the substrate and a 1 mm long and 3 µm wide wire. The high aspect ratio of wire provides a uniform heating profile along the wire and contributes to low pressure detection. At the opposite, both the nanoscale gap and the short wire length between two micro-bridges contributes to shift the high pressure limit. Tested between 10 kPa and 800 kPa, the sensor presents a wide measurement range, not fully reached by the experiments, with a maximum of sensitivity close to the atmospheric pressure and performances with up to 38 %/dec sensitivity when operation in constant temperature mode with an overheat of 20 °C.