High reflectance ta-C coatings in the extreme ultraviolet

Abstract

The extreme ultraviolet (EUV) reflectance of amorphous tetrahedrally coordinated carbon films (ta-C) prepared by filtered cathodic vacuum arc was measured in the 30-188-nm range at near normal incidence. The measured reflectance of films grown with average ion energies in the ~70-140-eV range was significantly larger than the reflectance of a C film grown with average ion energy of ~20 eV and of C films deposited by sputtering or evaporation. The difference is attributed to a large proportion of sp 3 atom bonding in the ta-C film. This high reflectance is obtained for films deposited onto room-temperature substrates. The reflectance of ta-C films is higher than the standard singlelayer coating materials in the EUV spectral range below 130 nm. A selfconsistent set of optical constants of ta-C films was obtained with the Kramers-Krönig analysis using ellipsometry measurements in the 190-950 nm range and the EUV reflectance measurements. These optical constants allowed calculating the EUV reflectance of ta-C films at grazing incidence for applications such as free electron laser mirrors. 5962-5963 (1994). 9. G. F. Jacobus, R. P. Madden, and L. R. Canfield, "Reflecting films of platinum for the vacuum ultraviolet," J.Opt. Soc. Am. 53(9), 1084-1088 (1963). 10. W. R. Hunter, D. W. Angel, and G. Hass, "Optical properties of evaporated platinum films in the vacuum ultraviolet from 220 Å to 150 Å," J. Opt. Soc. Am. 69(12), 1695-1699 (1979). 11. G. Hass, G. F. Jacobus, and W. R. Hunter, "Optical properties of evaporated iridium in the vacuum ultraviolet from 500 Å to 2000 Å," J. Opt. Soc. Am. 57(6), 758-762 (1967). 12. J. T. Cox, G. Hass, J. B. Ramsey, and W. R. Hunter, "Reflectance and optical constants of evaporated osmium in the vacuum ultraviolet from 300 to 2000 Å," J. Opt. Soc. Am. 63(4), 435-438 (1973 Robertson, "Density, sp 3 fraction, and cross-sectional structure of amorphous carbon films determined by x-ray reflectivity and electron energy-loss spectroscopy," Phys. Rev. B 62(16), 11089-11103 (2000). 32. F. Xiong, Y. Y. Wang, and R. P. H. Chang, "Complex dielectric function of amorphous diamond films deposited by pulsed-excimer-laser ablation of graphite," Phys. Rev. B Condens. Matter 48(11), 8016-8023 (1993). 33. S. Waidmann, M. Knupfer, J. Fink, B. Kleinsorge, and J. Robertson, "Electronic structure studies of undoped and nitrogen-doped tetrahedral amorphous carbon using high-resolution electron energy-loss spectroscopy," J.

Raman Spectroscopy of Amorphous Carbon Films Modified by Single‐Pulse Irradiation of Nanosecond and Femtosecond Lasers

“…Optical properties of the ta‐C film were calculated with following values of refractive index n and extinction coefficient k at wavelengths of 800 and 248 nm: n = 2.50 and 2.75; k = 0.03 and 0.28, respectively . Larruquert et al presented value of k = 0.015 for thin (less than 100 nm) ta‐C films at wavelength of 800 nm. In Ref.…”

“…The penetration depth of the probe Raman laser radiation in amorphous carbon is rather differing from initial film. For amorphous carbon (glassy carbon) this value is about 60 nm and for ta‐C film – 1500 nm, which are calculated from the values of n and k for both materials at the wavelength of 514.5 nm . So the signal in Raman spectra can be collected from the depth varying in the range from 60 to 1500 nm depending on the degree of clusters crystallization induced by the laser action on the film.…”

“…We assume that the difference in swelling height and structure of modified by fs and ns pulses material is mainly an effect of the heat diffusion. In case of nanosecond pulses, the heat diffusion length ( χτ ) 1/2 = 140 nm is larger than the absorption depth 1/ α = 70 nm . Thus, the heat transfer into the sample interior during ns pulse action makes the laser‐heated layer significantly thicker.…”

Free Electron Laser Measurement of Liquid Carbon Reflectivity in the Extreme Ultraviolet

“…The real and imaginary optical constants corresponding to refractive index n and extinction coefficient k from an amorphous film are shown in Figure 3 [27]. Over the 20-45 nm range, the extinction coefficient (k) increases monotonically and the refractive index (n) decreases.…”

Direct optical excitation of dark plasmons for hot electron generation

“…5-7. The amorphous carbon was implemented by using the experimental data of Larruquert et al 38 A gold slab with a thickness of 200 nm was added for the simulation of the layers over a gold substrate, as shown in Fig. 9.…”