Suspended 1D nanoheaters for ultralow-power thermal conductivity detector-type gas sensors fabricated via a simple four-step wafer-scale process

Abstract

Thermal conductivity detector (TCD)-type gas sensors detect gases by measuring the change in resistance of a Joule heater, influenced by the surrounding gas environment. TCD-type sensors are extensively employed for high-concentration gas detection and gas analysis in gas chromatography due to their wide measuring range and fast response to various gases. However, conventional TCD devices rely on complex and environmentally harmful fabrication methods to build micro/nano-sized suspended 1D heater architecture necessary for improved sensitivity and power efficiency. In this study, we present a simple four-step wafer-scale fabrication method-photolithography, pyrolysis, photolithography, and metallization-for producing suspended 1D nanoheaters via selective metal deposition on a suspended carbon nanogrid backbone. The unique suspended 1D architecture, featuring a high surface-to-volume ratio and minimized thermal mass, significantly enhances power efficiency and gas sensitivity. The ultrasmall 1D architecture (width: similar to 450 nm, thickness: similar to 800 nm) achieves ultrafast heating/cooling. This fast-switching capability enables facile duty cycling operation (0.1 % duty cycle at 50 Hz), resulting in an exceptionally low power consumption of similar to 300 nW-comparable to state-of-the-art nanoheaters fabricated by more elaborate methods. Under duty-cycled operation, the fabricated TCD-type gas sensor demonstrates high sensitivity across a wide gas concentration range (He: 1-5 %, H-2: 1-20 %, Ar: 1-100 %).