Characterization of Carbon-Contaminated B4C-Coated Optics after Chemically Selective Cleaning with Low-Pressure RF Plasma

Abstract

Boron carbide (B4C) is one of the few materials that is expected to be most resilient with respect to the extremely high brilliance of the photon beam generated by free electron lasers (FELs) and is thus of considerable interest for optical applications in this field. However, as in the case of many other optics operated at light source facilities, B4C-coated optics are subject to ubiquitous carbon contaminations. Carbon contaminations represent a serious issue for the operation of FEL beamlines due to severe reduction of photon flux, beam coherence, creation of destructive interference, and scattering losses. A variety of B4C cleaning technologies were developed at different laboratories with varying success. We present a study regarding the low-pressure RF plasma cleaning of carbon contaminated B4C test samples via inductively coupled O2/Ar, H2/Ar, and pure O2 RF plasma produced following previous studies using the same ibss GV10x downstream plasma source. Results regarding the chemistry, morphology as well as other aspects of the B4C optical coating before and after the plasma cleaning are reported. We conclude that among the above plasma processes only plasma based on pure O2 feedstock gas exhibits the required chemical selectivity for maintaining the integrity of the B4C optical coatings.

Broadband Superabsorber Operating at 1500 °C Using Dielectric Bilayers

“…However, due to the presence of characteristic peaks for B 4 C (Figure a,b) and AlN (Figure d,e), the surface oxide layer for both samples must be less than 10 nm thick prior to high-temperature treatment, given the limited surface penetration depth of XPS . Both samples undergo further surface oxidation as a result of high-temperature operation, with a final top oxide layer of at least 10 nm, confirmed by the disappearance of the C–B peaks for the B 4 C-coated sample (Figure c,d) , and by the shift of the Al peak for the pure AlN substrate (Figure f) . These data reveal the high preference of the samples for oxidation.…”

Plasma Cleaning of Hydrocarbon and Carbon Contaminated Surfaces of Accelerator Components

“…However, the cleaning efficiency declines with the distance from the source, due to the loss of active plasma species. Studies evaluating the cleaning rates of carbon-based contaminants as a function of RF powers and distances from the plasma source have been performed for small chambers or surfaces [4,5]. In this study we present the cleaning of large accelerator vessels and a first approach in modeling the transport of the active plasma species with COMSOL multiphysics.…”

Reaction analysis and the removal mechanism of organic contaminants in plasma cleaning: a molecular dynamics simulation

“…For instance, plasma containing halogens can effectively etch tin fragments, 17 and the presence of argon in an oxygen plasma induces surface sputtering on optical materials and increases surface roughness. 18 Reactive oxygen species (ROS) possess potent oxidizing properties and are commonly utilized as the principal reactive agents in cleaning processes. 19 Nitrogen exhibits relatively lower cleaning efficacy and is not prone to inducing significant surface roughness or diffuse reflectance alterations.…”