In-Situ grown carbon nanotubes for enhanced CO₂ detection in non-dispersive-infra-red system

Non-dispersive-infra-red (NDIR) sensors are believed to be one of the most selective and robust solutions for CO₂ detection, though cost prohibits their broader integration. In this paper we propose a commercially viable silicon-on-insulator (SOI) complementary metal-oxide (CMOS) micro-electro-mechanical (MEMS) technology for an IR thermal emitter. For the first time, vertically aligned multi walled carbon nanotubes (VA-MWCNTs) are suggested as a possible coating for the enhancement of the emission intensity of the optical source of a NDIR system. VA-MWCNTs have been grown in situ by chemical vapour deposition (CVD) exclusively on the heater area. Optical microscopy, scanning electron microscopy and Raman spectroscopy have been used to verify the quality of the VA-MWCNTs growth. The CNT-coated emitter demonstrated an increased response to CO₂ of approx. 60%. Furthermore, we show that the VA-MWCNTs are stable up to temperatures of 500°C for up to 100 hours.