Roughness and light scattering of ion-beam-sputtered fluoride coatings for 193 nm

Abstract

Scattering characteristics of multilayer fluoride coatings for 193 nm deposited by ion beam sputtering and the related interfacial roughnesses are investigated. Quarter-and half-wave stacks of MgF 2 and LaF 3 with increasing thickness are deposited onto CaF 2 and fused silica and are systematically characterized. Roughness measurements carried out by atomic force microscopy reveal the evolution of the power spectral densities of the interfaces with coating thickness. Backward-scattering measurements are presented, and the results are compared with theoretical predictions that use different models for the statistical correlation of interfacial roughnesses.

Enhanced characterization of niobium surface topography

“…In contrast, PSD data obtained from electropolished materials typically do not exhibit straight lines on a log/log plot but display two regions of strong curvature, as will be seen later. More generally, the PSD of a niobium surface prepared by various methods can be fruitfully decomposed into contributions from each of these types of models [22,26,[35][36][37]:…”

Extending the capabilities of scanning probe microscopy for microroughness analysis in surface engineering

“…The first two parameters (K, scaling factor; n, slope 1) correspond to the fractal model (adequate for most substrates). They are similar for the three samples, although the substrate and coating material of sample C differ from 23 It seems that gold tends to form slightly smoother coatings than titanium nitride and k corr is a measure of the grain size. Both coatings have a grain size of ¾40-50 nm.…”

“…A more detailed description of our approach of the combined-model PSD can be found in Ref. 23. Figure 5 shows an example of this fitting procedure.…”

Procedure to characterize microroughness of optical thin films: application to ion-beam-sputtered vacuum-ultraviolet coatings

“…However, it has been observed that several coatings show the formation of superstructures uniformly distributed along the surface. 23,24 This induces a local maximum in the lower frequencies of the PSD that cannot be described satisfactorily by any of the previous models. An example is represented by the PSD of Fig.…”

“…The results of this study have been published elsewhere. 23,24 Table 2 summarizes the produced designs, where the thickness units are optical quarter-waves and the design wavelength is 193 nm. MgF 2 and LaF 3 were used as the low-and high-index materials, respectively.…”