Influence of evaporation rate and chamber pressure on the FUV reflectance and physical characteristics of aluminum films

Optimizing the growth conditions of Al mirrors for superconducting nanowire single-photon detectors

“…This indicates that the density of spikes depends on the time required for the formation of a monolayer (monolayer formation time). It describes the time required to cover the sample surface by residual substances present in the deposition chamber [33]. At higher deposition rates, the amount of impurities incorporated into the layer decreases, resulting in lower stress and fewer spikes.…”

Electron beam-generated plasmas in NF3 environments for the passivation of UV/O/IR mirrors

“…The line ratio technique was used to measure ratio of excited atomic F, undergoing the 2𝑠 2 2𝑝 4 ( 𝑃 3 )3𝑝 → 2𝑠 2 2𝑝 4 ( 𝑃 3 )3𝑠 (703.7 nm) transition, to excited Ar undergoing the 3𝑠 2 3𝑝 5 ( 𝑃 2 1/2 °)4𝑝 → 3𝑠 2 3𝑝 5 ( 𝑃 2 1/2 °)4𝑠 (750.4 nm) transition, and then calculate the density of ground state F in the system based on the known density of the ground state Ar population. Further details on this method and its application in electron beam generated plasmas can be found in previous work by Boris et al [29].…”

“…Al protected with MgF2 has been used in a number of flight missions with Hubble Space Telescope (HST) [2] being one of the most prominent. Al/MgF2 systems are environmentally stable, with low surface roughness and high reflectance at >120 nm, and have been produced without the need of elevated substrate temperatures or post annealing [3]. This coating technology is considered TRL 9, has extended flight heritage, and would be a safe choice for HWO.…”

“…This is a process-related issue, which is driven by the coating configuration and the deposition chamber geometry associated to the process. This issue is further amplified by the necessity of using very high deposition rates for both the Al and the fluoride layer, since there is a direct correlation between rate and optical quality [3]. The utilization of high deposition rates complicates the use of substrate rotation systems or planetary systems.…”

Preparation of enhanced Al/MgF2 vacuum ultraviolet reflective coatings using electron-beam evaporation

“…Quijada et al studied the impact of resistive evaporation process conditions on the VUV reflectance of Al/MgF2 coatings. However, the reflectance data they presented exhibited significant fluctuations with the deposition rate, indicating difficulties in achieving stable control over the evaporation state and coating performance [8].…”