Special Issue "Progress in the Characterization of Metal, Dielectric and Semiconducting Optical Thin Films and Coatings"

A special issue of Coatings (ISSN 2079-6412).

Deadline for manuscript submissions: 31 December 2021.

Special Issue Editors

Dr. Olaf Stenzel
Website
Guest Editor
Fraunhofer IOF, Albert-Einstein-Str. 7, 07745 Jena, Germany
Interests: theory and modelling of optical coatings
Dr. Steffen Wilbrandt
Website
Guest Editor
Fraunhofer IOF, Albert-Einstein-Str. 7, 07745 Jena, Germany
Interests: optical coating characterization; in situ spectroscopy, software development

Special Issue Information

Dear Colleagues,

We would like to invite you to submit your work to a Special Issue on “Progress in the Characterization of Metal, Dielectric and Semiconducting Optical Thin Films and Coatings”. Here, thin film and coating characterization is understood as all experimental and theoretical activities that pursue the determination of construction parameters of a coating under investigation. Thus, the characterization of a typical thin film sample could include the clarification of its geometrical construction parameters (surface roughness or film thickness), and typical macroscopic material parameters like optical constants, porosity, average stoichiometry, or density. At a deeper analytical level, it is also the clarification of the crystallinity, energy band structure, internal path length or response times of charge carriers in a sample, which gives us a key to understanding the specifics of light–matter interactions defining the particular optical properties of the investigated sample.

Thin inorganic and organic solid films and their characterization are relevant in semiconductor physics, solar cell development, physical chemistry, optoelectronics, and optical coatings development, to give just a few examples. Growing demands on the performance of optical coatings result in the need for the development and improvement of versatile and accurate coating characterization techniques.

The aim of this Special Issue is to provide a snapshot of the state-of-the-art in optical coating characterization from the extreme ultraviolet (EUV) down to the Terahertz (THz) spectral regions, including metal, semiconducting and dielectric coatings.

In particular, the topics of interest include, but are not limited to

  • Advances in optical coating characterization techniques, including both ex situ and in situ characterization approaches
  • Progress in non-optical characterization techniques
  • Hard- and software developments relevant to coating characterization
  • Measurement of coating properties, reverse search procedures
  • Modelling of coating properties, including ultrathin coatings and island films
  • Structure–property relations
  • Non-linear optical properties of coatings
  • Characterization of coatings for ultrafast optical spectroscopy

Dr. Olaf Stenzel
Dr. Steffen Wilbrandt
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Coatings is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (5 papers)

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Research

Open AccessArticle
Absolute Absorption Measurements in Optical Coatings by Laser Induced Deflection
Coatings 2019, 9(8), 473; https://doi.org/10.3390/coatings9080473 - 27 Jul 2019
Cited by 1
Abstract
Absolute measurement of residual absorption in optical coatings is steadily becoming more important in thin film characterization, in particular with respect to high power laser applications. A summary is given on the current ability of the laser induced deflection (LID) technique to serve [...] Read more.
Absolute measurement of residual absorption in optical coatings is steadily becoming more important in thin film characterization, in particular with respect to high power laser applications. A summary is given on the current ability of the laser induced deflection (LID) technique to serve sensitive photo-thermal absorption measurements combined with reliable absolute calibration based on an electrical heater approach. To account for different measurement requirements, several concepts have been derived to accordingly adapt the original LID concept. Experimental results are presented for prominent UV and deep UV laser wavelengths, covering a variety of factors that critically can influence the absorption properties in optical coatings e.g., deposition process, defects and impurities, intense laser irradiation and surface/interface engineering. The experimental findings demonstrate that by combining high sensitivity with absolute calibration, photo-thermal absorption measurements are able to be a valuable supplement for the characterization of optical thin films and coatings. Full article
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Open AccessFeature PaperArticle
Temperature Dependence of AlF3 Protection on Far-UV Al Mirrors
Coatings 2019, 9(7), 428; https://doi.org/10.3390/coatings9070428 - 05 Jul 2019
Cited by 1
Abstract
More efficient and stable far ultraviolet (FUV) mirrors will enable future space observatories. Traditional FUV mirrors are based on MgF2-protected Al. AlF3 has been identified as a promising substitute for MgF2 to prevent Al oxidation. Hence, the reflectivity, stability, [...] Read more.
More efficient and stable far ultraviolet (FUV) mirrors will enable future space observatories. Traditional FUV mirrors are based on MgF2-protected Al. AlF3 has been identified as a promising substitute for MgF2 to prevent Al oxidation. Hence, the reflectivity, stability, and morphology of AlF3-protected Al mirrors have been investigated as a function of deposition temperature of the AlF3 film. In this work, it is shown how AlF3 deposition temperature is an important parameter whose optimization ultimately yields valuable throughput enhancement and improved endurance to large storage periods. Al films were deposited at room temperature (RT) and AlF3 protective layers were deposited at temperatures ranging from RT to 350 °C. It was found that the optimum AlF3 deposition temperature was between 200 and 250 °C, yielding the largest FUV reflectance and a better stability of the mirrors, which had been stored in a desiccator environment. Increasing AlF3 deposition temperature resulted in an increase in film density, approaching bulk density at 250 °C. The morphology of Al and AlF3 films as a function of AlF3 deposition temperature was also investigated. The increase in the AlF3 deposition temperature resulted in a decrease of both Al and AlF3 surface roughness and in the growth of the grain width at the AlF3 outer surface. It also resulted in a trend for the prevalent (111) planes of Al nanocrystals to orient parallel to the coating surface. Full article
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Open AccessFeature PaperArticle
Optical Characterization of Non-Stoichiometric Silicon Nitride Films Exhibiting Combined Defects
Coatings 2019, 9(7), 416; https://doi.org/10.3390/coatings9070416 - 28 Jun 2019
Cited by 4
Abstract
The study was devoted to optical characterization of non-stoichiometric silicon nitride films prepared by reactive magnetron sputtering in argon-nitrogen atmosphere onto cold (unheated) substrates. It was found that these films exhibit the combination of three defects: optical inhomogeneity (refractive index profile across the [...] Read more.
The study was devoted to optical characterization of non-stoichiometric silicon nitride films prepared by reactive magnetron sputtering in argon-nitrogen atmosphere onto cold (unheated) substrates. It was found that these films exhibit the combination of three defects: optical inhomogeneity (refractive index profile across the films), uniaxial anisotropy with the optical axis perpendicular to the boundaries and random roughness of the upper boundaries. The influence of the uniaxial anisotropy was included into the corresponding formulae of the optical quantities using the matrix formalism and the approximation of the inhomogeneous layer by a multilayer system consisting of large number thin homogeneous layers. The random roughness was described using the scalar diffraction theory. The processing of the experimental data was performed using the multi-sample modification of the least-squares method, in which experimental data of several samples differing in thickness were processed simultaneously. The dielectric response of the silicon nitride films was modeled using the modification of the universal dispersion model, which takes into account absorption processes corresponding to valence-to-conduction band electron transitions, excitonic effects and Urbach tail. The spectroscopic reflectometric and ellipsometric measurements were supplemented by measuring the uniformity of the samples using imaging spectroscopic reflectometry. Full article
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Open AccessArticle
Plasmonic Nanoparticles and Island Films for Solar Energy Harvesting: A Comparative Study of Cu, Al, Ag and Au Performance
Coatings 2019, 9(6), 382; https://doi.org/10.3390/coatings9060382 - 13 Jun 2019
Cited by 5
Abstract
Alternative materials that can potentially replace Au and Ag in plasmonics and broaden its application potential have been actively investigated over the last decade. Cu and Al have been usually overlooked as plasmonic material candidates because they are prone to oxidisation. In this [...] Read more.
Alternative materials that can potentially replace Au and Ag in plasmonics and broaden its application potential have been actively investigated over the last decade. Cu and Al have been usually overlooked as plasmonic material candidates because they are prone to oxidisation. In this work the plasmonic performance of Cu and Al is investigated using numerical simulations of different nanostructures (spheres, cubes, rods and particle dimers) and taking into account the presence of oxidisation. It is shown that geometry can play a dominant role over material properties and the performance of Cu and Al becomes comparable to that of Ag and Au for systems of non-spherical particles and strong electromagnetic coupling among particles. This observation is experimentally confirmed by the fabrication and characterisation of Cu and Al metal island films. Optical characterisation of the samples reveals a comparable performance of these metals to that obtained for Ag and Au and suggests that Cu and Al metal island films can offer an efficient low-cost platform for solar energy harvesting, as shown in water vapour generation proof of concept experiments. Full article
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Open AccessFeature PaperArticle
Spectrophotometric Characterization of Thin Copper and Gold Films Prepared by Electron Beam Evaporation: Thickness Dependence of the Drude Damping Parameter
Coatings 2019, 9(3), 181; https://doi.org/10.3390/coatings9030181 - 09 Mar 2019
Cited by 2
Abstract
Copper and gold films with thicknesses between approximately 10 and 60 nm have been prepared by electron beam evaporation and characterized by spectrophotometry from the near infrared up to the near ultraviolet spectral regions. From near normal incidence transmission and reflection spectra, dispersion [...] Read more.
Copper and gold films with thicknesses between approximately 10 and 60 nm have been prepared by electron beam evaporation and characterized by spectrophotometry from the near infrared up to the near ultraviolet spectral regions. From near normal incidence transmission and reflection spectra, dispersion of optical constants have been determined by means of spectra fits utilizing a merger of the Drude model and the beta-distributed oscillator model. All spectra could be fitted in the full spectral region with a total of seven dispersion parameters. The obtained Drude damping parameters shows a clear trend to increase with decreasing film thickness. This behavior is discussed in the context of additional non-optical characterization results and turned out to be consistent with a simple mean-free path theory. Full article
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