Controlling the infrared optical properties of rf-sputtered NiO films for applications of infrared window

• This paper introduces an AR coating of infrared window, by using NiO film.
• NiO films were coated on a Si wafer by rf-sputtering method in Ar and O2 mixed gas.
• The transmittance of the Si wafer was increased after NiO coating, and annealing.
• Increased transmittance after annealing can be ascribed to the reduction in defects.

In this paper, we will focus on an IR transmittance enhancement technique from the window material point of view by using metal oxides, especially nickel oxide (NiO). At first, anti-reflection (AR) coatings were modeled by using the optical properties of NiO films. The transmittance of the model was predicted using Swanepoel’s model and verified with NiO film prepared by rf magnetron sputtering. Also, post-deposition annealing was performed and was found to change the optical properties of the NiO film. Therefore, we analyzed the annealing effect on the IR optical properties of the NiO film. Furthermore, we confirmed the durability of the NiO film and verified the possibility of this material being used in infrared optics.