Pulsed DC sputter deposited hydrogenated carbon: an alternative durable infrared optical thin film material

Abstract

This study investigates the feasibility of using hydrogenated carbon thin films deposited by pulsed DC sputtering as an alternative durable optical thin film material for infrared applications. The study focuses on how the mechanical and optical characteristics of the deposited carbon thin films vary with hydrogen content. To precisely control the hydrogen incorporation in the carbon layers, pulsed DC deposition was used in conjunction with a controlled hydrogen generator. This allowed for a methodical investigation of the link between hydrogen content, stresses, transmittance, reflectance, and absorptance. Results of increasing hydrogen content within the carbon films demonstrate a reduction in stress, absorptance and hardness. The hydrogen acts to alleviate the compressive stress levels and mitigate the mechanical durability challenges within the film. Such films have applications in systems that require mechanically robust optical coatings such as antireflection infrared coatings for common infrared substrate materials.