Optical characterization of the impact of 100 keV protons on the optical properties of ZrO2 films prepared by ALD on fused silica substrates

Atomic layer deposition (ALD)-grown zirconia films underwent irradiation by 100 keV protons at fluences ranging from 1 · 1012 p+/cm2 through 5 · 1014 p+/cm2. The induced structural damage was modeled using the stopping and range of ions in matter (SRIM) and compared with the change of the optical properties characterized by ellipsometry, spectrophotometry, and x-ray reflectometry. Proton-induced contamination of the optical surface due to deposition of a carbon-rich layer was determined. Correct estimation of the substrate damage was shown to be critical for reliable evaluation of the optical constants of the irradiated films. The ellipsometric angle 1 is shown to be sensitive to both the presence of the buried damaged zone in the irradiated substrate and the contamination layer on the surface of the samples. The complex chemistry in carbon-doped zirconia accommodating over-stoichiometric oxygen is discussed, along with the impact of the film composition change on the refractive index of the irradiated films.