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12 pages, 24443 KiB

Open AccessArticle

Peculiarities of the 7 × 7 to 5 × 5 Superstructure Transition during Epitaxial Growth of Germanium on Silicon (111) Surface

by Vladimir V. Dirko, Kirill A. Lozovoy, Andrey P. Kokhanenko, Olzhas I. Kukenov, Alexander G. Korotaev and Alexander V. Voitsekhovskii

Nanomaterials 2023, 13(2), 231; https://doi.org/10.3390/nano13020231 - 04 Jan 2023

Cited by 3 | Viewed by 1329

Abstract

This paper presents the results of studying the processes of epitaxial growth of germanium on silicon with crystallographic orientation (111) in a wide temperature range. The temperature dependences of the duration of the transition stage from the 7 × 7 to 5 × [...] Read more.

This paper presents the results of studying the processes of epitaxial growth of germanium on silicon with crystallographic orientation (111) in a wide temperature range. The temperature dependences of the duration of the transition stage from the 7 × 7 to 5 × 5 superstructure and the values of the critical thickness of the transition from two-dimensional to three-dimensional growth in the range from 250 to 700 °C are determined using the reflection high-energy electron diffraction method. It was shown for the first time that the transition time from the 7 × 7 superstructure to 5 × 5 superstructure depends on the temperature of epitaxial growth. The region of low temperatures of synthesis, which has received insufficient attention so far, is also considered. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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19 pages, 9995 KiB

Open AccessArticle

Plasma-Modified PI Substrate for Highly Reliable Laser-Sintered Copper Films Using Cu₂O Nanoparticles

by Wei-Han Cheng, Ming-Tsang Lee, Kiyokazu Yasuda and Jenn-Ming Song

Nanomaterials 2022, 12(18), 3237; https://doi.org/10.3390/nano12183237 - 18 Sep 2022

Cited by 3 | Viewed by 1463

Abstract

Plasma modification of polyimide (PI) substrates upon which electrical circuits are fabricated by the laser sintering of cuprous oxide nanoparticle pastes was investigated systematically in this study. Surface properties of the PI substrate were investigated by carrying out atomic force microscopy (AFM) and [...] Read more.

Plasma modification of polyimide (PI) substrates upon which electrical circuits are fabricated by the laser sintering of cuprous oxide nanoparticle pastes was investigated systematically in this study. Surface properties of the PI substrate were investigated by carrying out atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Experimental results show that surface characteristics of PI substrates, including surface energy, surface roughness, and surface binding significantly affected the mechanical reliability of the sintered copper structure. Among the plasma gases tested (air, O₂, Ar-5%H₂, and N₂-30%H₂), O₂ plasma caused the roughest PI surface as well as the most C=O and C–OH surface binding resulting in an increased polar component of the surface energy. The combination of all those factors caused superior bending fatigue resistance. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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12 pages, 3784 KiB

Open AccessArticle

Mechanism Understanding for Size Regulation of Silver Nanowires Mediated by Halogen Ions

by Ni Xiao, Yinan Chen, Wei Weng, Xiaopeng Chi, Hang Chen, Ding Tang and Shuiping Zhong

Nanomaterials 2022, 12(15), 2681; https://doi.org/10.3390/nano12152681 - 04 Aug 2022

Cited by 5 | Viewed by 1482

Abstract

The controllable preparation of silver nanowires (AgNWs) with a high aspect ratio is key for enabling their applications on a large scale. Herein, the aspect ratio regulation of AgNWs mediated by halogen ion composition in ethylene glycol system was systematically investigated and the [...] Read more.

The controllable preparation of silver nanowires (AgNWs) with a high aspect ratio is key for enabling their applications on a large scale. Herein, the aspect ratio regulation of AgNWs mediated by halogen ion composition in ethylene glycol system was systematically investigated and the size evolution mechanism is elaborately understood. The co-addition of Br⁻ and Cl⁻ results in AgNWs with the highest aspect ratio of 1031. The surface physicochemical analysis of AgNWs and the density functional theory calculations indicate that the co-addition of Br⁻ and Cl⁻ contributes to the much-enhanced preferential growth of the Ag(111) crystal plane. At the same time, when Cl⁻ and Br⁻ coexist in the solution, the growth of the Ag(100) crystal plane on the AgNWs was restrained compared with that in the single Cl⁻ system. Resultantly, the enhanced growth of Ag(111) and the inhibited growth of Ag(100) contribute to the formation of AgNWs with a higher aspect ratio in the Cl–Br mixed solution. The results can provide new insights for understanding the morphology and size evolution during the AgNWs preparation in ethylene glycol system. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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13 pages, 4244 KiB

Open AccessArticle

Optimization of Piezoresistive Strain Sensors Based on Gold Nanoparticle Deposits on PDMS Substrates for Highly Sensitive Human Pulse Sensing

by Yu-Shun Su, Wei-Rong Yang, Wei-Wun Jheng, Watson Kuo, Shien-Der Tzeng, Kiyokazu Yasuda and Jenn-Ming Song

Nanomaterials 2022, 12(13), 2312; https://doi.org/10.3390/nano12132312 - 05 Jul 2022

Cited by 1 | Viewed by 1452

Abstract

In this study, highly-sensitive piezoresistive strain sensors based on gold nanoparticle thin films deposited on a stretchable PDMS substrate by centrifugation were developed to measure arterial pulse waveform. By controlling carbon chain length of surfactants, pH value and particle density of the colloidal [...] Read more.

In this study, highly-sensitive piezoresistive strain sensors based on gold nanoparticle thin films deposited on a stretchable PDMS substrate by centrifugation were developed to measure arterial pulse waveform. By controlling carbon chain length of surfactants, pH value and particle density of the colloidal solutions, the gauge factors of nanoparticle thin film sensors can be optimized up to 677 in tensile mode and 338 in compressive mode, and the pressure sensitivity up to 350. Low pH and thin nanoparticle films produce positive influences to superior gauge factors. It has been demonstrated that nanoparticle thin film sensors on PDMS substrates were successfully applied to sense arterial pulses in different body positions, including wrist, elbow crease, neck, and chest. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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14 pages, 2915 KiB

Open AccessArticle

Iron Single Atoms Anchored on Nitrogen-Doped Carbon Matrix/Nanotube Hybrid Supports for Excellent Oxygen Reduction Properties

by Yining Jia, Chunjing Shi, Wei Zhang, Wei Xia, Ming Hu, Rong Huang and Ruijuan Qi

Nanomaterials 2022, 12(9), 1593; https://doi.org/10.3390/nano12091593 - 07 May 2022

Cited by 2 | Viewed by 1951

Abstract

Single-atom non-precious metal oxygen reduction reaction (ORR) catalysts have attracted much attention due to their low cost, high selectivity, and high activity. Herein, we successfully prepared iron single atoms anchored on nitrogen-doped carbon matrix/nanotube hybrid supports (FeSA-NC/CNTs) by the pyrolysis of Fe-doped zeolitic [...] Read more.

Single-atom non-precious metal oxygen reduction reaction (ORR) catalysts have attracted much attention due to their low cost, high selectivity, and high activity. Herein, we successfully prepared iron single atoms anchored on nitrogen-doped carbon matrix/nanotube hybrid supports (FeSA-NC/CNTs) by the pyrolysis of Fe-doped zeolitic imidazolate frameworks. The nitrogen-doped carbon matrix/carbon nanotube hybrid supports exhibit a specific surface area of 1626.814 m² g⁻¹, which may facilitate electron transfer and oxygen mass transport within the catalyst and be beneficial to ORR performance. Further electrochemical results revealed that our FeSA-NC/CNTs catalyst exhibited excellent ORR activity (half-wave potential: 0.86 V; kinetic current density: 39.3 mA cm⁻² at 0.8 V), superior to that of commercial Pt/C catalyst (half-wave potential: 0.846 V; kinetic current density: 14.4 mA cm⁻² at 0.8 V). It also has a great stability, which makes it possible to be a valuable non-noble metal electrode material that may replace the latest commercial Pt/C catalyst in the future. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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8 pages, 2663 KiB

Open AccessArticle

Single- and Twin-Photons Emitted from Fiber-Coupled Quantum Dots in a Distributed Bragg Reflector Cavity

by Xiangjun Shang, Shulun Li, Hanqing Liu, Xiangbin Su, Huiming Hao, Deyan Dai, Xiaoming Li, Yuanyuan Li, Yuanfei Gao, Xiuming Dou, Haiqiao Ni and Zhichuan Niu

Nanomaterials 2022, 12(7), 1219; https://doi.org/10.3390/nano12071219 - 05 Apr 2022

Cited by 2 | Viewed by 1644

Abstract

In this work, we develop single-mode fiber devices of an InAs/GaAs quantum dot (QD) by bonding a fiber array with large smooth facet, small core, and small numerical aperture to QDs in a distributed Bragg reflector planar cavity with vertical light extraction that [...] Read more.

In this work, we develop single-mode fiber devices of an InAs/GaAs quantum dot (QD) by bonding a fiber array with large smooth facet, small core, and small numerical aperture to QDs in a distributed Bragg reflector planar cavity with vertical light extraction that prove mode overlap and efficient output for plug-and-play stable use and extensive study. Modulated Si doping as electron reservoir builds electric field and level tunnel coupling to reduce fine-structure splitting (FSS) and populate dominant XX and higher excitons XX⁺ and XXX. Epoxy package thermal stress induces light hole (lh) with various behaviors related to the donor field: lh h₁ confined with more anisotropy shows an additional X_Z line (its space to the traditional X lines reflects the field intensity) and larger FSS; lh h₂ delocalized to wetting layer shows a fast h₂–h₁ decay; lh h₂ confined shows D_3h symmetric higher excitons with slow h₂–h₁ decay and more confined h₁ to raise h₁–h₁ Coulomb interaction. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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8 pages, 3872 KiB

Open AccessArticle

Thickness Dependence of Superconductivity in Layered Topological Superconductor β-PdBi₂

by Huijie Li, Huanhuan Wang, Wenshuai Gao, Zheng Chen, Yuyan Han, Xiangde Zhu and Mingliang Tian

Nanomaterials 2021, 11(11), 2826; https://doi.org/10.3390/nano11112826 - 24 Oct 2021

Cited by 10 | Viewed by 2517

Abstract

We report a systematic study on the thickness-dependent superconductivity and transport properties in exfoliated layered topological superconductor β-PdBi₂. The superconducting transition temperature T_c is found to decrease with the decreasing thickness. Below a critical thickness of 45 nm, the [...] Read more.

We report a systematic study on the thickness-dependent superconductivity and transport properties in exfoliated layered topological superconductor β-PdBi₂. The superconducting transition temperature T_c is found to decrease with the decreasing thickness. Below a critical thickness of 45 nm, the superconductivity is suppressed, but followed by an abrupt resistance jump near T_c, which is in opposite to the behavior in a superconductor. We attribute suppressed T_c to the enhanced disorder as the thickness decreases. The possible physical mechanisms were discussed for the origination of sharply increased resistance in thinner β-PdBi₂ samples. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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12 pages, 4843 KiB

Open AccessArticle

Measurement of Nanometre-Scale Gate Oxide Thicknesses by Energy-Dispersive X-ray Spectroscopy in a Scanning Electron Microscope Combined with Monte Carlo Simulations

by Thomas Walther

Nanomaterials 2021, 11(8), 2117; https://doi.org/10.3390/nano11082117 - 20 Aug 2021

Cited by 2 | Viewed by 2359

Abstract

A procedure based on energy-dispersive X-ray spectroscopy in a scanning electron microscope (SEM-EDXS) is proposed to measure ultra-thin oxide layer thicknesses to atomic scale precision in top-down instead of cross-sectional geometry. The approach is based on modelling the variation of the electron beam [...] Read more.

A procedure based on energy-dispersive X-ray spectroscopy in a scanning electron microscope (SEM-EDXS) is proposed to measure ultra-thin oxide layer thicknesses to atomic scale precision in top-down instead of cross-sectional geometry. The approach is based on modelling the variation of the electron beam penetration depth and hence the depth of X-ray generation in the sample as a function of the acceleration voltage. This has been tested for the simple case of silica on silicon (SiO₂/Si) which can serve as a model system to study gate oxides in metal-on-semiconductor field-effect transistors (MOS-FETs). Two possible implementations exist both of which rely on pairs of measurements to be made: in method A, the wafer piece of interest and a reference sample (here: ultra-clean fused quartz glass for calibration of the effective k-factors of X-ray lines from elements O and Si) are analysed at the same acceleration voltage. In method B, two measurements of the apparent O/Si ratio of the same wafer sample need to be made at different acceleration voltages and from their comparison to simulations the SiO₂ layer thickness of the sample can be inferred. The precision attainable is ultimately shown to be limited by surface contamination during the experiments, as very thin carbonaceous surface layers can alter the results at very low acceleration voltages, while the sensitivity to ultra-thin surface oxides is much reduced at higher acceleration voltages. The optimal operation voltage is estimated to lie in the range of 3–15 kV. Method A has been experimentally verified to work well for test structures of thin oxides on Si-Ge/Si. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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26 pages, 4559 KiB

Open AccessArticle

Approaching Disordered Quantum Dot Systems by Complex Networks with Spatial and Physical-Based Constraints

by Lucas Cuadra and José Carlos Nieto-Borge

Nanomaterials 2021, 11(8), 2056; https://doi.org/10.3390/nano11082056 - 12 Aug 2021

Cited by 3 | Viewed by 1886

Abstract

This paper focuses on modeling a disordered system of quantum dots (QDs) by using complex networks with spatial and physical-based constraints. The first constraint is that, although QDs (=nodes) are randomly distributed in a metric space, they have to fulfill the condition that [...] Read more.

This paper focuses on modeling a disordered system of quantum dots (QDs) by using complex networks with spatial and physical-based constraints. The first constraint is that, although QDs (=nodes) are randomly distributed in a metric space, they have to fulfill the condition that there is a minimum inter-dot distance that cannot be violated (to minimize electron localization). The second constraint arises from our process of weighted link formation, which is consistent with the laws of quantum physics and statistics: it not only takes into account the overlap integrals but also Boltzmann factors to include the fact that an electron can hop from one QD to another with a different energy level. Boltzmann factors and coherence naturally arise from the Lindblad master equation. The weighted adjacency matrix leads to a Laplacian matrix and a time evolution operator that allows the computation of the electron probability distribution and quantum transport efficiency. The results suggest that there is an optimal inter-dot distance that helps reduce electron localization in QD clusters and make the wave function better extended. As a potential application, we provide recommendations for improving QD intermediate-band solar cells. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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13 pages, 3118 KiB

Open AccessArticle

Hybrid Films Based on Bilayer Graphene and Single-Walled Carbon Nanotubes: Simulation of Atomic Structure and Study of Electrically Conductive Properties

by Michael M. Slepchenkov, Pavel V. Barkov and Olga E. Glukhova

Nanomaterials 2021, 11(8), 1934; https://doi.org/10.3390/nano11081934 - 27 Jul 2021

Cited by 8 | Viewed by 2039

Abstract

One of the urgent problems of materials science is the search for the optimal combination of graphene modifications and carbon nanotubes (CNTs) for the formation of layered hybrid material with specified physical properties. High electrical conductivity and stability are one of the main [...] Read more.

One of the urgent problems of materials science is the search for the optimal combination of graphene modifications and carbon nanotubes (CNTs) for the formation of layered hybrid material with specified physical properties. High electrical conductivity and stability are one of the main optimality criteria for a graphene/CNT hybrid structure. This paper presents results of a theoretical and computational study of the peculiarities of the atomic structure and the regularities of current flow in hybrid films based on single-walled carbon nanotubes (SWCNTs) with a diameter of 1.2 nm and bilayer zigzag graphene nanoribbons, where the layers are shifted relative to the other. It is found that the maximum stresses on atoms of hybrid film do not exceed ~0.46 GPa for all considered topological models. It is shown that the electrical conductivity anisotropy takes place in graphene/SWCNT hybrid films at a graphene nanoribbon width of 4 hexagons. In the direction along the extended edge of the graphene nanoribbon, the electrical resistance of graphene/SWCNT hybrid film reaches ~125 kOhm; in the direction along the nanotube axis, the electrical resistance is about 16 kOhm. The prospects for the use of graphene/SWCNT hybrid films in electronics are predicted based on the obtained results. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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10 pages, 5642 KiB

Open AccessArticle

Low-Thermal-Budget Photonic Sintering of Hybrid Pastes Containing Submicron/Nano CuO/Cu₂O Particles

by Po-Hsiang Chiu, Wei-Han Cheng, Ming-Tsang Lee, Kiyokazu Yasuda and Jenn-Ming Song

Nanomaterials 2021, 11(7), 1864; https://doi.org/10.3390/nano11071864 - 20 Jul 2021

Cited by 8 | Viewed by 2179

Abstract

Copper oxide particles of various sizes and constituent phases were used to form conductive circuits by means of photonic sintering. With the assistance of extremely low-energy-density xenon flash pulses (1.34 J/cm²), a mixture of nano/submicron copper oxide particles can be reduced [...] Read more.

Copper oxide particles of various sizes and constituent phases were used to form conductive circuits by means of photonic sintering. With the assistance of extremely low-energy-density xenon flash pulses (1.34 J/cm²), a mixture of nano/submicron copper oxide particles can be reduced in several seconds to form electrical conductive copper films or circuits exhibiting an average thickness of 6 μm without damaging the underlying polymeric substrate, which is quite unique compared to commercial nano-CuO inks whose sintered structure is usually 1 μm or less. A mixture of submicron/nano copper oxide particles with a weight ratio of 3:1 and increasing the fraction of Cu₂O in the copper oxide both decrease the electrical resistivity of the reduced copper. Adding copper formate further improved the continuity of interconnects and, thereby, the electrical conductance. Exposure to three-pulse low-energy-density flashes yields an electrical resistivity of 64.6 μΩ·cm. This study not only shed the possibility to use heat-vulnerate polymers as substrate materials benefiting from extremely low-energy light sources, but also achieved photonic-sintered thick copper films through the adoption of submicron copper oxide particles. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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13 pages, 4558 KiB

Open AccessArticle

Morphology-Controlled Vapor Phase Growth and Characterization of One-Dimensional GaTe Nanowires and Two-Dimensional Nanosheets for Potential Visible-Light Active Photocatalysts

by Li-Chia Tien and Yu-Che Shih

Nanomaterials 2021, 11(3), 778; https://doi.org/10.3390/nano11030778 - 18 Mar 2021

Cited by 6 | Viewed by 2151

Abstract

Gallium telluride (GaTe) one-dimensional (1D) and two-dimensional (2D) materials have drawn much attention for high-performance optoelectronic applications because it possesses a direct bandgap for all thickness. We report the morphology-controlled vapor phase growth of 1D GaTe nanowires and 2D GaTe nanosheets by a [...] Read more.

Gallium telluride (GaTe) one-dimensional (1D) and two-dimensional (2D) materials have drawn much attention for high-performance optoelectronic applications because it possesses a direct bandgap for all thickness. We report the morphology-controlled vapor phase growth of 1D GaTe nanowires and 2D GaTe nanosheets by a simple physical vapor transport (PVT) approach. The surface morphology, crystal structure, phonon vibration modes, and optical property of samples were characterized and studied. The growth temperature is a key synthetic factor to control sample morphology. The 1D GaTe single crystal monoclinic nanowires were synthesized at 550 °C. The strong interlayer interaction and high surface migration of adatoms on c-sapphire enable the assembly of 1D nanowires into 2D nanosheet under 600 °C. Based on the characterization results demonstrated, we propose the van der Waals growth mechanism of 1D nanowires and 2D nanosheets. Moreover, the visible-light photocatalytic activity of 1D nanowires and 2D nanosheets was examined. Both 1D and 2D GaTe nanostructures exhibit visible-light active photocatalytic activity, suggesting that the GaTe nanostructures may be promising materials for visible light photocatalytic applications. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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Review

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44 pages, 4797 KiB

Open AccessReview

A Review on Low-Dimensional Nanomaterials: Nanofabrication, Characterization and Applications

by Paras, Kushal Yadav, Prashant Kumar, Dharmasanam Ravi Teja, Sudipto Chakraborty, Monojit Chakraborty, Soumya Sanjeeb Mohapatra, Abanti Sahoo, Mitch M. C. Chou, Chi-Te Liang and Da-Ren Hang

Nanomaterials 2023, 13(1), 160; https://doi.org/10.3390/nano13010160 - 29 Dec 2022

Cited by 18 | Viewed by 7462

Abstract

The development of modern cutting-edge technology relies heavily on the huge success and advancement of nanotechnology, in which nanomaterials and nanostructures provide the indispensable material cornerstone. Owing to their nanoscale dimensions with possible quantum limit, nanomaterials and nanostructures possess a high surface-to-volume ratio, [...] Read more.

The development of modern cutting-edge technology relies heavily on the huge success and advancement of nanotechnology, in which nanomaterials and nanostructures provide the indispensable material cornerstone. Owing to their nanoscale dimensions with possible quantum limit, nanomaterials and nanostructures possess a high surface-to-volume ratio, rich surface/interface effects, and distinct physical and chemical properties compared with their bulk counterparts, leading to the remarkably expanded horizons of their applications. Depending on their degree of spatial quantization, low-dimensional nanomaterials are generally categorized into nanoparticles (0D); nanorods, nanowires, and nanobelts (1D); and atomically thin layered materials (2D). This review article provides a comprehensive guide to low-dimensional nanomaterials and nanostructures. It begins with the classification of nanomaterials, followed by an inclusive account of nanofabrication and characterization. Both top-down and bottom-up fabrication approaches are discussed in detail. Next, various significant applications of low-dimensional nanomaterials are discussed, such as photonics, sensors, catalysis, energy storage, diverse coatings, and various bioapplications. This article would serve as a quick and facile guide for scientists and engineers working in the field of nanotechnology and nanomaterials. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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