Radiative Properties of Thin Films of Common Dielectric Materials in the IR Spectral Range of 1.5–14.2 μm: Application to Infrared Imaging

To measure, map and control temperature, imaging of materials in a thermal furnace routinely utilizes non-contact sensors, such as pyrometers. These pyrometers require a pre-knowledge of the radiative properties of materials in the desired infrared range of wavelengths. In this study, radiative properties of some commonly used thin films of dielectric materials are investigated within the infrared (IR) spectral range of 1.5–14.2 μm. Radiative properties of aluminum oxide (Al₂O₃), silicon dioxide (SiO₂), aluminum nitride (AlN) and silicon nitride (Si₃N₄) have been simulated and compared, utilizing a matrix method of representing the optical properties. The simulated results of the radiative properties show that Si₃N₄ is an excellent choice for the infrared radiation absorbing layer that is currently used in infrared uncooled detectors (microbolometers) because of its optical, mechanical and electrical properties. A case study of the radiative properties of an infrared uncooled microbolometer (Honeywell structure) is presented and discussed in the infrared spectral range of 8–14 μm. The results obtained serve as useful information for the design and fabrication of infrared imaging systems and components such as coatings, detectors, filters, lenses and waveguides.