Ion beam milling of optically polished CaF2 surfaces

Dieter Flamm; Axel Schindler; Marion Berger

doi:10.1117/12.505658

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22 December 2003 Ion beam milling of optically polished CaF₂ surfaces

Dieter Flamm, Axel Schindler, Marion Berger

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Proceedings Volume 5180, Optical Manufacturing and Testing V; (2003) https://doi.org/10.1117/12.505658
Event: Optical Science and Technology, SPIE's 48th Annual Meeting, 2003, San Diego, California, United States

Abstract

Calcium Fluoride roughness evolution caused by ion beam milling has been studied in dependence on the ion milling parameters and different optically polished surfaces, respectively. For polished surfaces with high crystal damage, the roughness is dominated by the uncovering of the sub-surface damage due to the ion beam milling. For smooth surfaces with low damage the roughness is an intrinsic one and the creation of self-organized nanoscale structures can be obtained. Ion milling parameters influence more the intrinsic roughness than the extrinsic. Generally, high ion energies and sputter gases with low atom mass produce rough surfaces. Low ion energies and gases with high mass result in smooth surfaces. Ion bombardment induces a decomposition of CaF₂ in the near surface layer. Surface analytical measurements show that ion sputtering to some extent decompose the CaF₂ surface layer in contrast to the combined action of ion sputtering and low energy electron irradiation. The measured higher VUV absorption after ion milling is caused by the modified sub-surface layer mainly and not by the increased surface roughness.

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Dieter Flamm, Axel Schindler, and Marion Berger "Ion beam milling of optically polished CaF₂ surfaces", Proc. SPIE 5180, Optical Manufacturing and Testing V, (22 December 2003); https://doi.org/10.1117/12.505658

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