Si3N4-TiN loaded carbon coating with porous structure as broadband light superabsorber for uncooled IR sensors

Abstract

A carbon nanoparticles (CNP), Si3N4 and TiN nanoparticles loaded porous structure carbon microparticles (CMP) coating (CMP/CNP-Si3N4-TiN) as broadband light superabsorber is proposed for the infrared absorber layer of uncooled infrared sensor with high sensitivity in the 3–5 μm and 8–14 μm atmospheric windows, which is suited for use as non-dispersive infrared (NDIR) gas sensors and non-contact infrared thermometers. The CMP, Si3N4 and TiN nanoparticles were added in sequence to the nanocarbon-based ink, and then prepared into a broadband light superabsorber coating by high voltage electrostatic spraying. Scanning electron microscopy (SEM) micrographs showed that the framework of porous coating was made up of a large number of charged CMP which repel each other during high voltage electrostatic spraying and that the CNP in the initial ink, Si3N4 and TiN nanoparticles reunited with the CMP together commendably. The experimental results and corresponding analyses illustrated that the distinctive CMP porous structure with arbitrary sizes and random spatial positions created guided mode for manipulation of incident light waves and almost completely absorbed the photons of light over wide range of wavelengths. The CNP, Si3N4 and TiN nanoparticles can provide multiple reflections and scatterings, which made the light propagation path increase, resulting in an extensive absorption enhancement. Benefited from the synergetic effect of CMP, CNP, Si3N4 and TiN, the CMP/CNP-Si3N4-TiN coating exhibited 93.8% and 92.6% absorption at 3–5 μm and 8–14 μm, respectively. Finally, the modified thermopile infrared (IR) sensor with CMP/CNP-Si3N4-TiN coating presented output voltage amplitudes of 1170 mV, which was 62.5% higher than that of the reference thermopile IR sensor.