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Structural characterization of diamond-like carbon films for ultracold neutron applications

Untersuchung der Struktur von diamantähnlichen Kohlenstoff-Dünnschichten für Anwendungen mit ultrakalten Neutronen
: Atchison, F.; Brys, T.; Daum, M.; Fierlinger, P.; Foelske, A.; Gupta, A.; Henneck, R.; Heule, S.; Kasprzak, M.; Kirch, K.; Kötz, R.; Kuzniak, M.; Lippert, T.; Meyer, C.F.; Nolting, F.; Pichlmaier, A.; Schneider, D.; Schultrich, B.; Siemroth, P.; Straumann, U.


Diamond and Related Materials 16 (2007), No.2, pp.334-341
ISSN: 0925-9635
Journal Article
Fraunhofer IWS ()
diamantähnlicher Kohlenstoff; Dünnschicht; anorganischer Überzug; Neutron; Schichtdicke; Oberflächenanalyse; Elektronenkonfiguration

Hydrogen-free DLC (diamond-like carbon) films were produced by vacuum arc deposition for use as wall coating material in UCN (ultracold neutron) applications. The sp(exp 3) fraction, the main quality factor for DLC used in UCN applications, was varied from 0.4 to 0.9, the coating thickness between 10 nm and 120 nm. The samples were characterized by using XANES (X-ray absorption near-edge spectroscopy), XPS (X-ray induced photoelectron spectroscopy), LAwave (laser induced surface acoustic waves), cold neutron reflectometry and Raman spectroscopy at visible excitation wavelength. Reasonable agreement between the different results for film thicknesses below 20 nm was observed. For larger thickness, it was found that the surface-sensitive methods XPS and XANES yield smaller sp(exp 3) fractions (by up to 20 %) than the bulk-sensitive LAwave, being consistent with the assumption of a lower-density surface layer on a nominal-density bulk layer.