Dr. David Necas Profile

Dr. David Necas

at Masaryk Univ

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Author

Publications (5)

Proceedings Article | 26 April 2016 Paper

Optical characterization of SiO2 thin films using universal dispersion model over wide spectral range

Daniel Franta, David Nečas, Ivan Ohlídal, Angelo Giglia

Proceedings Volume 9890, 989014 (2016) https://doi.org/10.1117/12.2227580

KEYWORDS: Silica, Thin films, Thin film devices, Optical constants, Ellipsometry, Spectrophotometry, Ultraviolet radiation, Instrument modeling, Spectral models, Optical properties, Product engineering, Optical components, Refractive index, Absorption, Reflectivity, Data modeling, Infrared spectroscopy, Atomic force microscopy

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Proceedings Article | 24 September 2015 Paper

Possibilities and limitations of imaging spectroscopic reflectometry in optical characterization of thin films

Miloslav Ohlídal, Ivan Ohlidal, David Nečas, Jiří Vodák, Daniel Franta, Pavel Nádaský, František Vižd'a

Proceedings Volume 9628, 96280R (2015) https://doi.org/10.1117/12.2191052

KEYWORDS: Thin films, Intelligence systems, Reflectance spectroscopy, Spectroscopy, Reflectometry, Imaging spectroscopy, Reflectivity, Ellipsometry, CCD cameras, Spectroscopic ellipsometry

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Proceedings Article | 24 September 2015 Paper

Wide spectral range characterization of antireflective coatings and their optimization

Daniel Franta, David Nečas, Ivan Ohlídal, Jiří Jankuj

Proceedings Volume 9628, 96280F (2015) https://doi.org/10.1117/12.2190109

KEYWORDS: Data modeling, Refractive index, Silica, Infrared spectroscopy, Spectroscopy, Ellipsometry, Silicon, Optical coatings, Systems modeling, Instrument modeling

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Proceedings Article | 24 September 2015 Paper

Dispersion model for optical thin films applicable in wide spectral range

Daniel Franta, David Nečas, Ivan Ohlídal, Angelo Giglia

Proceedings Volume 9628, 96281U (2015) https://doi.org/10.1117/12.2190104

KEYWORDS: Absorption, Refractive index, Electronics, Dielectrics, Phonons, Ultraviolet radiation, Europium, Infrared spectroscopy, Spectroscopy, Electrons

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Proceedings Article | 24 September 2015 Paper

Simultaneous determination of optical constants, local thickness, and local roughness of thin films by imaging spectroscopic reflectometry

David Nečas, Ivan Ohlídal, Jiří Vodák, Miloslav Ohlídal, Daniel Franta

Proceedings Volume 9628, 96280C (2015) https://doi.org/10.1117/12.2190091

KEYWORDS: Intelligence systems, Spectroscopy, Reflectance spectroscopy, Imaging spectroscopy, Gallium arsenide, Refractive index, Data processing, Thin films, Spectroscopic ellipsometry, Atomic force microscopy

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A new optical characterization method based on imaging spectroscopic reflectometry (ISR) is presented and illustrated on the characterization of rough non-uniform epitaxial ZnSe films prepared on GaAs substrates. The method allows the determination of all parameters describing the thin films exhibiting boundary roughness and non-uniformity in thickness, i.e. determination of the spectral dependencies of the optical constants, map of local thickness and map of local rms values of heights of the irregularities for the rough boundaries. The local normal reflectance spectra in ISR correspond to small areas (37×37 μm²) on the thin films measured within the spectral range 270{900 nm by pixels of a CCD camera serving as the detector of imaging spectrophotometer constructed in our laboratory. To our experience the small areas corresponding to the pixels are sufficiently small so that the majority of the films can be considered uniform in all parameters within these areas. Boundary roughness is included into the reflectance formulas by means of the scalar diffraction theory (SDT) and the optical constant spectra of the ZnSe films were expressed by the dispersion model based on the parametrization of the joint density of electronic states (PJDOS). In general, there is a correlation between the searched parameters if the individual local reflectance spectra are fitted separately and, therefore, the local reflectance spectra measured for all the pixels are treated simultaneously using so called multi-pixel method in order to remove or reduce this correlation and determine the values of all the parameters with a sufficient accuracy. The results of the optical characterization of the same selected sample of the epitaxial ZnSe thin film obtained using the method presented here and combined method of variable-angle spectroscopic ellipsometry, spectroscopic reflectometry and single-pixel immersion spectroscopic reflectometry are introduced in the contribution as well.

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