Ultrathin Freestanding MoSiN Nanocomposite Membranes as Efficient High‐Temperature Mid‐Infrared Thermal Emitters

ABSTRACT A novel ultrathin freestanding MoSiN nanocomposite membrane, comprising intermetallic and dielectric phases, demonstrates strong potential as a stable and efficient mid‐infrared emitter for gas sensing under extreme thermal conditions. This study develops and investigates ultrathin MoSiN freestanding membranes, focusing on their structural, optical and thermal properties to evaluate their potential to serve as efficient, low‐power and stable mid‐IR emitters for miniaturized and reliable gas sensors. A 12 nm‐thick freestanding MoSiN membrane with lateral dimensions of 10 mm × 10 mm was fabricated with a supporting frame. Reducing the membrane thickness lowers thermal mass, minimizing power consumption and enabling faster heating and cooling for enhanced thermal response. Structural analysis reveals a unique microstructure comprising intermetallic phases (Mo 5 Si 3 , MoSi 2 ) that coexist with an oxygen‐diffused silicon nitride dielectric phase. The intermetallic phases provide free carriers for mid‐infrared absorption, while the dielectric phase enhances mechanical stability and thermal endurance. The membrane exhibits metal‐like emissivity (0.41) and maintains structural integrity up to 900°C. Repeated thermal cycling under pulsed heating demonstrates excellent temperature control, high repeatability, and rapid radiative cooling, confirming its suitability for high‐temperature sensing. This combination of structural, optical, and thermal attributes positions MoSiN membranes as promising candidates for next‐generation gas Microheater, emissivity, free carrier absorption, freestanding membrane, mid infrareddetection technologies.