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Advanced Thin Films and 2D Materials: Mechanism, Fabrication, Characterization and Application

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Keywords
Published Papers

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Thin Films and Interfaces".

Deadline for manuscript submissions: closed (10 February 2024) | Viewed by 6418

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Special Issue Editors

Dr. Sebastiano Vasi

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Guest Editor

Department of Mathematics and Computer Sciences, Physical Sciences and Earth Sciences (MIFT), University of Messina, Viale Ferdinando Stagno d’Alcontres 31, 98166 Messina, Italy
Interests: condensed matter physics; optics and photonics; spectroscopy; food science; biophysics; environmental physics; big data and IoT; artificial intelligence; materials; solar cells; sustainability; sensors; instrumentation
Special Issues, Collections and Topics in MDPI journals

Dr. Ulderico Wanderlingh

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Guest Editor

MIFT Department, University of Messina, Viale Ferdinando Stagno d’Alcontres 31, 98166 Messina, Italy
Interests: optical spectroscopy; X-ray diffraction; neutron spectroscopy; biophysics; biomaterials; biomembrane; biosensors; soft matter; IoT

Special Issue Information

Dear Colleagues,

Recently, thin films, and in particular, two-dimensional (2D) materials, have been extensively studied because of their peculiar chemical and physical properties and applications in the fields of solar cells, energy harvesting and energy conversion, electronics and optoelectronics, biomedicine, sensing, diagnostic, spintronics, and so on. Today, it is possible to synthesize and process a wide range of materials, including, for example, metal chalcogenides and carbon-based compounds, allowing for the development of new technologies, with recent advances in deposition techniques. Furthermore, characterization techniques used to investigate several properties of these materials, such as electrical, thermal, plasmonic, optical, and mechanical properties, are of considerable importance to facilitate their use for specific applications.

The aim of this Special Issue is to provide a global view on advanced thin film and 2D materials, contributing novel information on the state-of-art and current research. In particular, this Special Issue will collect original research papers and review articles that present:

Mechanisms and/or concepts regarding the fabrication and chemical-physical properties of thin film and 2D materials and describing their potential impacts;
Recent advances in the synthesis and characterization of thin film and 2D materials;
Applications of these materials as solar cells, sensors, supercapacitors, and other optoelectronic devices.

In this frame, the understanding of chemical and physical properties of thin films and 2D materials, how to control them, and the study of their interactions and applications are the targets of this Special Issue.

Dr. Sebastiano Vasi
Dr. Ulderico Wanderlingh
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. Materials is an international peer-reviewed open access semimonthly 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 2600 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.

Keywords

thin films
2D materials
mechanisms and synthesis
thin films characterization
2D materials characterization
energy application
biomedical application
miscellaneous application

Published Papers (7 papers)

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Research

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16 pages, 4390 KiB

Open AccessArticle

Multifunctional Superamphiphobic Coating Based on Fluorinated TiO₂ toward Effective Anti-Corrosion

by Xiao Huang, Xinghua Gao, Xin Wang, Hongfei Shang and Shujun Zhou

Materials 2024, 17(10), 2203; https://doi.org/10.3390/ma17102203 - 8 May 2024

Viewed by 132

Abstract

The application of superamphiphobic coatings improves the surface’s ability to repel fluids, thereby greatly enhancing its various functions, including anti-fouling, anti-corrosion, anti-icing, anti-bacterial, and self-cleaning properties. This maximizes the material’s potential for industrial applications. This work utilized the agglomeration phenomenon exhibited by nano-spherical titanium dioxide (TiO₂) particles to fabricate 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) modified TiO₂ (TiO₂@fluoroPOS) fillers with low surface energy. This was achieved through the in-situ formation of protective armor on the surface of the agglomerates using the sol-gel method and fluorination modification. Polyvinylidene fluoride-tetrafluoropropylene (PVDF-HFP) and TiO₂@fluoroPOS fillers were combined using a spraying technique to prepare P/TiO₂@fluoroPOS coatings with superamphiphobicity. Relying on the abundance of papillae, micropores, and other tiny spaces on the surface, the coating can capture a stable air film and reject a variety of liquids. When the coatings were immersed in solutions of 2 mol/L HCl, NaCl, and NaOH for a duration of 12 h, they retained their exceptional superamphiphobic properties. Owing to the combined influence of the armor structure and the organic binder, the coating exhibited good liquid repellency during water jetting and sandpaper abrasion tests. Furthermore, the coating has shown exceptional efficacy in terms of its ability to be anti-icing, anti-waxing, and self-cleaning. Full article

(This article belongs to the Special Issue Advanced Thin Films and 2D Materials: Mechanism, Fabrication, Characterization and Application)

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12 pages, 362 KiB

Open AccessArticle

Theoretical Study of the Phonon and Electrical Conductivity Properties of Pure and Sr-Doped LaMnO₃ Thin Films

by Angel T. Apostolov, Iliana N. Apostolova and Julia Mihailowa Wesselinowa

Materials 2024, 17(9), 1995; https://doi.org/10.3390/ma17091995 - 25 Apr 2024

Viewed by 217

Abstract

The film thickness, temperature, substrate and doping dependence of the phonon energy

ω

and damping

γ

, as well as the electrical conductivity, of pure and Sr-doped LaMnO₃ thin films near the phase transition temperature

T_{N}

are investigated using a microscopic [...] Read more.

The film thickness, temperature, substrate and doping dependence of the phonon energy

ω

and damping

γ

, as well as the electrical conductivity, of pure and Sr-doped LaMnO₃ thin films near the phase transition temperature

T_{N}

are investigated using a microscopic model and the Green’s function technique. Due to the strong spin–phonon interaction, there appears a kink at

T_{N}

in the temperature dependence of

ω (T)

and

γ (T)

. The softening and hardening of the

ω

= 495 cm⁻¹ (A_1g) and

ω

= 614 cm⁻¹ (B_2g) modes is explained by the different sign of the anharmonic spin–phonon interaction constant R. The damping increases with T for both cases because it is proportional to

R^{2}

ω

decreases whereas

γ

increases with an increasing Sr concentration. This is due to the strain caused by the difference between the ionic radii of the La and Sr ions. The film thickness dependence is also considered.

ω

and

γ

increase strongly with the decreasing film thickness. The electrical conductivity is enhanced after the doping of the LMO thin films with Sr, which could be used for energy storage applications. The observed results are in good qualitative agreement with the experimental data. Full article

(This article belongs to the Special Issue Advanced Thin Films and 2D Materials: Mechanism, Fabrication, Characterization and Application)

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11 pages, 4021 KiB

Open AccessArticle

Hexagonal Boron Nitride as an Intermediate Layer for Gallium Nitride Epitaxial Growth in Near-Ultraviolet Light-Emitting Diodes

by Ah-Hyun Park and Tae-Hoon Seo

Materials 2023, 16(22), 7216; https://doi.org/10.3390/ma16227216 - 17 Nov 2023

Viewed by 890

Abstract

We introduce the development of gallium nitride (GaN) layers by employing graphene and hexagonal boron nitride (h-BN) as intermediary substrates. This study demonstrated the successful growth of GaN with a uniformly smooth surface morphology on h-BN. In order to evaluate the crystallinity of GaN grown on h-BN, a comparison was conducted with GaN grown on a sapphire substrate. Photoluminescence spectroscopy and X-ray diffraction confirmed that the crystallinity of GaN deposited on h-BN was inferior to that of GaN grown on conventional GaN. To validate the practical applicability of the GaN layer grown on h-BN, we subsequently grew an NUV-LED structure and fabricated a device that operated well in optoelectrical performance experiments. Our findings validate the potential usefulness of h-BN to be a substrate in the direct growth of a GaN layer. Full article

(This article belongs to the Special Issue Advanced Thin Films and 2D Materials: Mechanism, Fabrication, Characterization and Application)

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11 pages, 2303 KiB

Open AccessEditor’s ChoiceArticle

Tailoring the Structure and Properties of Epitaxial Europium Tellurides on Si(100) through Substrate Temperature Control

by Fan Yu, Xiaodong Qiu, Jinming Zhou, Lin Huang, Bin Yang, Junming Liu, Di Wu, Gan Wang and Yi Zhang

Materials 2023, 16(22), 7093; https://doi.org/10.3390/ma16227093 - 9 Nov 2023

Viewed by 787

Abstract

In this study, we improved the growth procedure of EuTe and realized the epitaxial growth of EuTe₄. Our research demonstrated a selective growth of both EuTe and EuTe₄ on Si(100) substrates using the molecular beam epitaxy (MBE) technique and reveals that the substrate temperature plays a crucial role in determining the structural phase of the grown films: EuTe can be obtained at a substrate temperature of 220 °C while lowering down the temperature to 205 °C leads to the formation of EuTe₄. A comparative analysis of the transmittance spectra of these two films manifested that EuTe is a semiconductor, whereas EuTe₄ exhibits charge density wave (CDW) behavior at room temperature. The magnetic measurements displayed the antiferromagnetic nature in EuTe and EuTe₄, with Néel temperatures of 10.5 and 7.1 K, respectively. Our findings highlight the potential for controllable growth of EuTe and EuTe₄ thin films, providing a platform for further exploration of magnetism and CDW phenomena in rare earth tellurides. Full article

(This article belongs to the Special Issue Advanced Thin Films and 2D Materials: Mechanism, Fabrication, Characterization and Application)

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14 pages, 4886 KiB

Open AccessArticle

Asymmetric TMO–Metal–TMO Structure for Enhanced Efficiency and Long-Term Stability of Si-Based Heterojunction Solar Cells

by Yoon-Chae Jung, Young-Jin Yu, Yu-Kyung Kim, Jin Hee Lee, Jung Hwa Seo and Jea-Young Choi

Materials 2023, 16(16), 5550; https://doi.org/10.3390/ma16165550 - 9 Aug 2023

Viewed by 929

Abstract

In this study, we fabricated Si-based heterojunction solar cells (HSCs) with an asymmetric TMO–metal–TMO (TMT) structure using both MoO₃ and V₂O₅ as the hole-selective contacts. Our HSCs offer enhanced long-term stability and effective passivation for crystal defects on the Si sur-face. We analyzed the oxygen vacancy state and surface morphology of the MoO₃- and V₂O₅-TMO thin films using X-ray photoelectron spectroscopy and atomic force microscopy to investigate their passivation characteristics for Si surface defects. From the measured minority carrier lifetime, V₂O₅ revealed a highly improved lifetime (590 μs) compared to that of MoO₃ (122.3 μs). In addition, we evaluated the long-term stability of each TMO thin film to improve the operation stability of the HSCs. We deposited different types of TMOs as the top- and bottom-TMO layers and assessed the effect of the thickness of each TMO layer. The fabricated asymmetric TMT/Si HSCs showed noticeable improvements in efficiency (7.57%) compared to 6.29% for the conventional symmetric structure which used the same TMO material for both the top and bottom layers. Furthermore, in terms of long-term stability, the asymmetric TMT/Si HSCs demonstrated an efficiency that was 250% higher than that of symmetric TMT/Si HSCs, as determined via power conversion efficiency degradation over 2000 h which is mainly attributed by the lower oxygen vacancy of the top-TMO, V₂O₅. These results suggest that the asymmetric TMT structure is a promising approach for the fabrication of low-cost and high-efficiency Si-based HSCs with enhanced long-term stability. Full article

(This article belongs to the Special Issue Advanced Thin Films and 2D Materials: Mechanism, Fabrication, Characterization and Application)

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15 pages, 9859 KiB

Open AccessArticle

Atomic Layer Deposition of Titanium Oxide-Based Films for Semiconductor Applications—Effects of Precursor and Operating Conditions

by Vladyslav Matkivskyi, Oskari Leiviskä, Sigurd Wenner, Hanchen Liu, Ville Vähänissi, Hele Savin, Marisa Di Sabatino and Gabriella Tranell

Materials 2023, 16(16), 5522; https://doi.org/10.3390/ma16165522 - 8 Aug 2023

Viewed by 1242

Abstract

Two widely used atomic layer deposition precursors, Tetrakis (dimethylamido) titanium (TDMA-Ti) and titanium tetrachloride (TiCl₄), were investigated for use in the deposition of TiOx-based thin films as a passivating contact material for solar cells. This study revealed that both precursors are suited to similar deposition temperatures (150 °C). Post-deposition annealing plays a major role in optimising the titanium oxide (TiO_x) film passivation properties, improving minority carrier lifetime (τ_eff) by more than 200 µs. Aluminium oxide deposited together with titanium oxide (AlO_y/TiO_x) reduced the sheet resistance by 40% compared with pure TiO_x. It was also revealed that the passivation quality of the (AlO_y/TiO_x) stack depends on the precursor and ratio of AlO_y to TiO_x deposition cycles. Full article

(This article belongs to the Special Issue Advanced Thin Films and 2D Materials: Mechanism, Fabrication, Characterization and Application)

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Review

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27 pages, 2997 KiB

Open AccessEditor’s ChoiceReview

Optical Second Harmonic Generation on LaAlO₃/SrTiO₃ Interfaces: A Review

by Andrea Rubano and Domenico Paparo

Materials 2023, 16(12), 4337; https://doi.org/10.3390/ma16124337 - 12 Jun 2023

Cited by 2 | Viewed by 1468

Abstract

As we approach the limits of semiconductor technology, the development of new materials and technologies for the new era in electronics is compelling. Among others, perovskite oxide hetero-structures are anticipated to be the best candidates. As in the case of semiconductors, the interface between two given materials can have, and often has, very different properties, compared to the corresponding bulk compounds. Perovskite oxides show spectacular interfacial properties due to the the rearrangement of charges, spins, orbitals and the lattice structure itself, at the interface. Lanthanum aluminate and Strontium titanate hetero-structures (LaAlO

_{3}

/SrTiO

_{3}

) can be regarded as a prototype of this wider class of interfaces. Both bulk compounds are plain and (relatively) simple wide-bandgap insulators. Despite this, a conductive two-dimensional electron gas (2DEG) is formed right at the interface when a LaAlO

_{3}

thickness of

n \geq 4

unit cells is deposited on a SrTiO

_{3}

substrate. The 2DEG is quite thin, being confined in only one or at least very few mono-layers at the interface, on the SrTiO

_{3}

side. A very intense and long-lasting study was triggered by this surprising discovery. Many questions regarding the origin and characteristics of the two-dimensional electron gas have been (partially) addressed, others are still open. In particular, this includes the interfacial electronic band structure, the transverse plane spatial homogeneity of the samples and the ultrafast dynamics of the confined carriers. Among a very long list of experimental techniques which have been exploited to study these types of interfaces (ARPES, XPS, AFM, PFM, …and many others), optical Second Harmonic Generation (SHG) was found to be suitable for investigating these types of buried interfaces, thanks to its extreme and selective interface-only sensitivity. The SHG technique has made its contribution to the research in this field in a variety of different and important aspects. In this work we will give a bird’s eye view of the currently available research on this topic and try to sketch out its future perspectives. Full article

(This article belongs to the Special Issue Advanced Thin Films and 2D Materials: Mechanism, Fabrication, Characterization and Application)

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