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Surfaces, Volume 4, Issue 2 (June 2021) – 5 articles

Cover Story (view full-size image): A tunable conversion of the surface anisotropy from four-fold to two-fold is demonstrated via epitaxial growth of CaF2 (110) stripe arrays on Si(001). A fine control over dimensions and periodicity of the stripe arrays is carried out through a two-stage growth process. Such controllable tuning is supposedly important for the applications in which the striped fluorite surface is used to guide nucleation of the various functional materials grown on top. Study of the shape and in-plane correlation between the fluorite stripes of nanometer size is effectively achieved through the use of grazing-incidence 3D reciprocal space mapping utilizing scattering of X-rays and high-energy electrons. View this paper.
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22 pages, 17100 KiB  
Review
Ionic Systems and Nanomaterials as Antiseptic and Disinfectant Agents for Surface Applications: A Review
by Francisco Faísca, Luis Filipe, Zeljko Petrovski, Miguel M. Santos, Sandra Gago and Luís C. Branco
Surfaces 2021, 4(2), 169-190; https://doi.org/10.3390/surfaces4020016 - 7 Jun 2021
Cited by 3 | Viewed by 3419
Abstract
Antiseptics and disinfectants are extensively used for a variety of topical and hard-surface applications. A wide variety of biocides as active chemical agents is found in these products, including alcohols, phenols, iodine, and chlorine. Many of these active agents demonstrate broad-spectrum antimicrobial activity; [...] Read more.
Antiseptics and disinfectants are extensively used for a variety of topical and hard-surface applications. A wide variety of biocides as active chemical agents is found in these products, including alcohols, phenols, iodine, and chlorine. Many of these active agents demonstrate broad-spectrum antimicrobial activity; however, the mode of action of these agents is not well-documented. This review is focused on several examples of ionic systems based on ionic surfactants and ionic liquids as well as nanomaterials and nanoparticles acting as antiseptics and disinfectants for surfaces. It is important to note that many of these biocides may be used singly or in combination in a variety of products, which vary considerably in activity against microorganisms. Antimicrobial activity can be influenced by several factors such as formulation effects, presence of an organic load, synergy, temperature, dilution, and test method. The most promissory compounds based on ionic systems and nanomaterials published in mainly the last decade is chronologically reported in this review. Full article
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12 pages, 9475 KiB  
Article
Electrodeposition of Cu on PEDOT for a Hybrid Solid-State Electronic Device
by Martina Vizza, Giulio Pappaianni, Walter Giurlani, Andrea Stefani, Roberto Giovanardi, Massimo Innocenti and Claudio Fontanesi
Surfaces 2021, 4(2), 157-168; https://doi.org/10.3390/surfaces4020015 - 24 May 2021
Cited by 7 | Viewed by 3877
Abstract
Conductive polymers are nowadays attracting great attention for their peculiar mechanical, electrical and optical proprieties. In particular, PEDOT can be used in a wide range of innovative applications, from electroluminescent devices to photovoltaics. In this work, the electrochemical deposition of 3,4 ethylenedioxythiophene (EDOT) [...] Read more.
Conductive polymers are nowadays attracting great attention for their peculiar mechanical, electrical and optical proprieties. In particular, PEDOT can be used in a wide range of innovative applications, from electroluminescent devices to photovoltaics. In this work, the electrochemical deposition of 3,4 ethylenedioxythiophene (EDOT) was performed on various substrates (ITO, thin films of gold and palladium on silicon wafers) by means of both potentiostatic and potentiodynamic techniques. This was intended to further expand the applications of electrochemically deposited PEDOT, particularly regarding the preparation of thin films in tight contact with electrode surfaces. This allows one to obtain systems prone to be used as electrodes in stacked devices. Chronoamperometric experiments were performed to study the nucleation and growth process of PEDOT. SEM, ESEM and AFM analysis allowed the characterization of the morphology of the polymeric films obtained. Raman and visible spectroscopy confirmed the high-quality of the coatings on the different substrates. Then, the PEDOT films were used as the base material for the further electrodeposition of a copper layer. In this way, a hybrid electronic device was obtained, by using electrochemical methods only. The high conductivity and ohmic behavior of the device were confirmed over a wide range of frequencies with electrical impedance spectroscopy analysis. Full article
(This article belongs to the Special Issue Thin Films at Surfaces)
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42 pages, 8844 KiB  
Article
Finite Element Analyses of the Modified Strain Gradient Theory Based Kirchhoff Microplates
by Murat Kandaz and Hüsnü Dal
Surfaces 2021, 4(2), 115-156; https://doi.org/10.3390/surfaces4020014 - 14 May 2021
Cited by 3 | Viewed by 3755
Abstract
In this contribution, the variational problem for the Kirchhoff plate based on the modified strain gradient theory (MSGT) is derived, and the Euler-Lagrange equations governing the equation of motion are obtained. The Galerkin-type weak form, upon which the finite element method is constructed, [...] Read more.
In this contribution, the variational problem for the Kirchhoff plate based on the modified strain gradient theory (MSGT) is derived, and the Euler-Lagrange equations governing the equation of motion are obtained. The Galerkin-type weak form, upon which the finite element method is constructed, is derived from the variational problem. The shape functions which satisfy the governing homogeneous partial differential equation are derived as extensions of Adini-Clough-Melosh (ACM) and Bogner-Fox-Schmit (BFS) plate element formulations by introducing additional curvature degrees of freedom (DOF) on each node. Based on the proposed set of shape functions, 20-, 24-, 28- and 32- DOF modified strain gradient theory-based higher-order Kirchhoff microplate element are proposed. The performance of the elements are demonstrated in terms of various tests and representative boundary value problems. Length scale parameters for gold are also proposed based on experiments reported in literature. Full article
(This article belongs to the Special Issue Interfaces in Materials Science and Engineering)
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9 pages, 1728 KiB  
Article
Reactive Dual Magnetron Sputtering: A Fast Method for Preparing Stoichiometric Microcrystalline ZnWO4 Thin Films
by Yannick Hermans, Faraz Mehmood, Kerstin Lakus-Wollny, Jan P. Hofmann, Thomas Mayer and Wolfram Jaegermann
Surfaces 2021, 4(2), 106-114; https://doi.org/10.3390/surfaces4020013 - 27 Apr 2021
Cited by 1 | Viewed by 2877
Abstract
Thin films of ZnWO4, a promising photocatalytic and scintillator material, were deposited for the first time using a reactive dual magnetron sputtering procedure. A ZnO target was operated using an RF signal, and a W target was operated using a DC [...] Read more.
Thin films of ZnWO4, a promising photocatalytic and scintillator material, were deposited for the first time using a reactive dual magnetron sputtering procedure. A ZnO target was operated using an RF signal, and a W target was operated using a DC signal. The power on the ZnO target was changed so that it would match the sputtering rate of the W target operated at 25 W. The effects of the process parameters were characterized using optical spectroscopy, X-ray diffraction, and scanning electron microscopy, including energy dispersive X-ray spectroscopy as well as X-ray photoelectron spectroscopy. It was found that stoichiometric microcrystalline ZnWO4 thin films could be obtained, by operating the ZnO target during the sputtering procedure at a power of 55 W and by post-annealing the resulting thin films for at least 10 h at 600 °C. As FTO coated glass substrates were used, annealing led as well to the incorporation of Na, resulting in n+ doped ZnWO4 thin films. Full article
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9 pages, 1520 KiB  
Article
Controllable CaF2 Nanosized Stripe Arrays on Si(001) Studied by X-ray and Electron Diffraction
by Sergey M. Suturin, Vladimir V. Fedorov, Alexander M. Korovin, Gleb A. Valkovskiy, Masao Tabuchi and Nikolai S. Sokolov
Surfaces 2021, 4(2), 97-105; https://doi.org/10.3390/surfaces4020012 - 6 Apr 2021
Cited by 2 | Viewed by 3290
Abstract
Adding uniaxial in-plane anisotropy to the otherwise four-fold Si(001) surface has for a long time been known to be possible via epitaxial deposition of a single atomic layer of calcium fluoride (CaF2), which forms an array of micron-long (110) oriented parallel [...] Read more.
Adding uniaxial in-plane anisotropy to the otherwise four-fold Si(001) surface has for a long time been known to be possible via epitaxial deposition of a single atomic layer of calcium fluoride (CaF2), which forms an array of micron-long (110) oriented parallel stripes when the substrate temperature during the growth is kept in the range of 700–800 °C. As shown in the present paper, a fine control over dimensions and periodicity of the stripe array is possible through the introduction of a two-stage growth process at which the (110) orientation of the fluorite layer is settled at the high-temperature nucleation stage, while the stripes of controllable dimensions are formed at the second stage. By varying the substrate temperature at the second growth stage in the range of 800–400 °C, the stripe arrays with a periodicity from above 30 nm to below 10 nm can be fabricated with the height variation changing accordingly. Such variability can be of use in the applications in which the striped fluorite surface is used to influence the anisotropy of other functional (e.g., magnetically ordered or organic) materials grown on top. While large CaF2 stripes can be easily characterized by direct space techniques such as atomic force microscopy, the study of the shape and in-plane correlation between the stripes of a much smaller size is most effectively achieved through the use of grazing incidence reciprocal space techniques applied in the present paper. The discussed universal approach to 3D reciprocal space mapping utilizing scattering of X-rays and high-energy electrons offers a complementary way to study samples with arrays of long and narrow one-dimensional stripes at their surface. Full article
(This article belongs to the Special Issue Thin Films at Surfaces)
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