Thin Films at Surfaces

A special issue of Surfaces (ISSN 2571-9637).

Deadline for manuscript submissions: closed (28 February 2021) | Viewed by 18340

Special Issue Editors


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Guest Editor
School of Materials, University of Manchester, Manchester M13 9PL, UK
Interests: surface engineering; coatings and thin films; performance and degradation; corrosion; wear; light alloys

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Guest Editor
Dipartimento di Ingegneria ‘E. Ferrari’, Università di Modena e Reggio Emilia, via Vivarelli 10, 41125 Modena, Italy
Interests: optical (Vis-UV) and photoelectron spectroscopies (UV and X-ray); soft X-ray absorption and resonant reflectivity with synchrotron radiation; organic thin film surfaces and interfaces

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Guest Editor
Foundation Fellow at Future Industries Institute, University of South Australia, Mawson Lakes Campus, GPO Box 2471, Adelaide, SA 5001, Australia
Interests: surface forces in soft matter; thin liquid films; bubbles and drops; colloid stability; surfactants; polymers

Special Issue Information

Dear Colleagues,

Many advanced applications in technology rely upon thin and ultrathin films carefully designed, engineered and deposited on the surfaces of solid substrates. Optoelectronic and magnetic devices, nano-electronics and MEMS, biomedical, catalytic and photocatalytic surfaces, tribological, anticorrosion and other protective coatings—to cite just a few examples—are all based on surface films with a thickness ranging from a single atomic layer to several microns, featuring a nanoscale structure and specific properties that provide the desired functionality. Besides this, the emergence of a wide family of new and exotic 2D materials is opening various innovative scenarios and application possibilities. In all these cases, the formation of thin films, their interaction with the substrate material and the external environment as well as the physics and chemistry underpinning film properties require an in-depth fundamental understanding.

The aim of this Special Issue of Surfaces is to offer a broad open-access forum for all groups across the surface science community and gather together a collection of original fundamental, applied research articles and review papers in the context of “Thin Films at Surfaces”. A special emphasis will be given to but not limited by the following topics:

  1. New and emerging thin-film fabrication strategies and techniques that provide tangible benefits in versatility, environmental sustainability, processing efficiency and scalability;
  2. Advanced gas and liquid phase methods for thin-film deposition, self-assembly and epitaxial growth (e.g., assisted with pulsed plasmas, laser or electron beams);
  3. Smart and multifunctional thin-film materials systems with stimuli responsive and adaptive behaviour for demanding applications;
  4. Green, sustainable and bio-compatible thin-film systems and associated fabrication methods;
  5. Advanced thin-film materials, including compositionally and functionally graded nanostructures, superlattices, nanolaminates and 2D materials;
  6. Organic thin films, molecular layers and polymeric systems (e.g., hydrated bio/polymers) with new and enhanced properties;
  7. Advanced characterisation and evaluation techniques for thin-film materials systems that provide a new understanding of relationships between their characteristics (e.g., structural, chemical, topological), protective (e.g., mechanical, tribological, corrosion- and oxidation-resistant) and functional (e.g., electronic, optical, magnetic, biological, catalytic) properties, adhesion and in-service behaviour.

Dr. Aleksey Yerokhin
Prof. Dr. Luca Pasquali
Dr. Marta Krasowska
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 submissions that pass pre-check are 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. Surfaces is an international peer-reviewed open access quarterly 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

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 3956
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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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 3 | Viewed by 3350
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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15 pages, 3648 KiB  
Article
Fluoropolymer Film Formation by Electron Activated Vacuum Deposition
by Kostyantyn Grytsenko, Viachaslau Ksianzou, Yurii Kolomzarov, Peter Lytvyn, Birgit Dietzel and Sigurd Schrader
Surfaces 2021, 4(1), 66-80; https://doi.org/10.3390/surfaces4010009 - 22 Feb 2021
Cited by 6 | Viewed by 3967
Abstract
Polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP) and polychlorotrifluoroethylene (PCTFE) were heated to their decomposition temperature in a high vacuum. The emitted fragments passed an electron cloud, condensed on a substrate and formed fluoropolymer film. Growth rate of PTFE and PHFP films increased up to a [...] Read more.
Polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP) and polychlorotrifluoroethylene (PCTFE) were heated to their decomposition temperature in a high vacuum. The emitted fragments passed an electron cloud, condensed on a substrate and formed fluoropolymer film. Growth rate of PTFE and PHFP films increased up to a factor five in the presence of the electron cloud. Mass spectrometry revealed changes in the mass spectra of fragments generated by thermal decomposition only and formed under electron activation. The observed changes were different for each fluoropolymer. Infrared spectroscopy (IRS) showed that the structure of the films was close to the structure of the bulk polymers. Atomic force microscopy (AFM) has revealed different morphologies of PTFE, PHFP and PCTFE films, suggesting a Volmer–Weber growth mechanism for PTFE and PHFP but a Frank-van der Merwe one for PCTFE. All films were smooth at nanoscale and transparent from ultraviolet to near-infrared region. Additional radio frequency (RF) plasma ignited in the emitted fragments at a low pressure increased mechanical characteristics of the films without losing their optical transparency and smoothness. Full article
(This article belongs to the Special Issue Thin Films at Surfaces)
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11 pages, 3087 KiB  
Article
Synthesis of MoS2 Thin Film by Ionized Jet Deposition: Role of Substrate and Working Parameters
by Amir Ghiami, Melanie Timpel, Andrea Chiappini, Marco Vittorio Nardi and Roberto Verucchi
Surfaces 2020, 3(4), 683-693; https://doi.org/10.3390/surfaces3040045 - 13 Dec 2020
Cited by 4 | Viewed by 3065
Abstract
The lack of scalable synthesis of transition metal dichalcogenides, such as molybdenum disulfide (MoS2), has proved to be a significant bottleneck in realization of fundamental devices and has hindered the commercialization of these materials in technologically relevant applications. In this study, [...] Read more.
The lack of scalable synthesis of transition metal dichalcogenides, such as molybdenum disulfide (MoS2), has proved to be a significant bottleneck in realization of fundamental devices and has hindered the commercialization of these materials in technologically relevant applications. In this study, a cost-efficient and versatile thin-film fabrication technique based on ionized jet deposition (IJD), i.e., a technique potentially providing high processing efficiency and scalability, is used to grow MoS2 thin films on silicon substrates. The operating conditions of IJD were found to influence mainly the ablation efficiency of the target and only slightly the quality of the deposited MoS2 thin film. All as-deposited films show chemical properties typical of MoS2 with an excess of free, elemental sulfur that can be removed by post-deposition annealing at 300–400 °C, which also promotes MoS2 crystallization. The formation of an interface comprised of several silicon oxide species was observed between MoS2 and the silicon substrate, which is suggested to originate from etching and oxidizing processes of dissociated water molecules in the vacuum chamber during growth. The present study paves the way to further design and improve the IJD approach for TMDC-based devices and other relevant technological applications. Full article
(This article belongs to the Special Issue Thin Films at Surfaces)
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15 pages, 4806 KiB  
Article
Atomistic Investigation of Material Deformation Behavior of Polystyrene in Nanoimprint Lithography
by Jahlani Odujole and Salil Desai
Surfaces 2020, 3(4), 649-663; https://doi.org/10.3390/surfaces3040043 - 24 Nov 2020
Cited by 8 | Viewed by 2845
Abstract
This research investigates deformation behavior of polystyrene (PS) as a thermoplastic resist material for the thermal nanoimprint lithography (T-NIL) process. Molecular dynamics modeling was conducted on a PS substrate with dimensions 58 × 65 × 61 Å that was imprinted with a rigid, [...] Read more.
This research investigates deformation behavior of polystyrene (PS) as a thermoplastic resist material for the thermal nanoimprint lithography (T-NIL) process. Molecular dynamics modeling was conducted on a PS substrate with dimensions 58 × 65 × 61 Å that was imprinted with a rigid, spherical indenter. The effect of indenter size, force, and imprinting duration were evaluated in terms of indentation depth, penetration depth, recovery depth, and recovery percentage of the polymer. The results show that the largest indenter, regardless of force, has the most significant impact on deformation behavior. The 40 Å indenter with a 1 µN of force caused the surface molecules to descend to the lowest point compared to the other indenters. An increase in indenter size resulted in higher penetration depth, recovery depth, and recovery percentage. Higher durations of imprint cycle (400 fs) resulted in plastic deformation of the PS material with minimal recovery (4 Å). The results of this research lay the foundation for explaining the effect of several T-NIL process parameters on virgin PS thermoplastic resist material. Full article
(This article belongs to the Special Issue Thin Films at Surfaces)
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