Combined deposition of optical interference coatings and wear resistant Diamond Like Carbon (DLC) in a novel box coater

Abstract

Diamond Like Carbon (DLC) is the preferred material for the termination layer in optical interference coatings using infrared (IR) materials since it enhances the environmental stability of the otherwise typically soft substrate and coating materials used in IR. In the state of the art processes, the coating with the infrared materials is deposited in a box coater, then the substrates are transferred and loaded into a separate deposition machine where the DLC layer is then deposited. In the novel box coater presented in this article, the DLC and IR (or dielectric) processes can be run consecutively in the same machine. We will discuss the implementation of the DLC process, then we show how the DLC process was optimized using in-situ stress and broadband optical measurements as well as ex-situ characterization of the adhesion, hardness and abrasion. The resulting single layer DLC films have perfect adhesion to silicon, germanium, glass and antireflection coatings. Furthermore, they are hard and scratch resistant, pass the wiper test and are virtually absorption-free in the 3-5μm and 8-12μm wavelength ranges. We will show the results for adhesion, abrasion and spectral performance of a wideband antireflection coating for 3-5μm including a DLC termination layer.