Research

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11 pages, 1430 KiB

Open AccessArticle

Ambipolar to Unipolar Conversion in C₇₀/Ferrocene Nanosheet Field-Effect Transistors

by Dorra Mahdaoui, Chika Hirata, Kahori Nagaoka, Kun’ichi Miyazawa, Kazuko Fujii, Toshihiro Ando, Manef Abderrabba, Osamu Ito, Shinjiro Yagyu, Yubin Liu, Yoshiyuki Nakajima, Kazuhito Tsukagoshi and Takatsugu Wakahara

Nanomaterials 2023, 13(17), 2469; https://doi.org/10.3390/nano13172469 - 01 Sep 2023

Viewed by 892

Abstract

Organic cocrystals, which are assembled by noncovalent intermolecular interactions, have garnered intense interest due to their remarkable chemicophysical properties and practical applications. One notable feature, namely, the charge transfer (CT) interactions within the cocrystals, not only facilitates the formation of an ordered supramolecular [...] Read more.

Organic cocrystals, which are assembled by noncovalent intermolecular interactions, have garnered intense interest due to their remarkable chemicophysical properties and practical applications. One notable feature, namely, the charge transfer (CT) interactions within the cocrystals, not only facilitates the formation of an ordered supramolecular network but also endows them with desirable semiconductor characteristics. Here, we present the intriguing ambipolar CT properties exhibited by nanosheets composed of single cocrystals of C₇₀/ferrocene (C₇₀/Fc). When heated to 150 °C, the initially ambipolar monoclinic C₇₀/Fc nanosheet-based field-effect transistors (FETs) were transformed into n-type face-centered cubic (fcc) C₇₀ nanosheet-based FETs owing to the elimination of Fc. This thermally induced alteration in the crystal structure was accompanied by an irreversible switching of the semiconducting behavior of the device; thus, the device transitions from ambipolar to unipolar. Importantly, the C₇₀/Fc nanosheet-based FETs were also found to be much more thermally stable than the previously reported C₆₀/Fc nanosheet-based FETs. Furthermore, we conducted visible/near-infrared diffuse reflectance and photoemission yield spectroscopies to investigate the crucial role played by Fc in modulating the CT characteristics. This study provides valuable insights into the overall functionality of these nanosheet structures. Full article

(This article belongs to the Special Issue Semiconductor Nanomaterials: Growth, Characterization and Optoelectronic Application)

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12 pages, 5570 KiB

Open AccessArticle

Synthesis and Physical Characteristics of Undoped and Potassium-Doped Cubic Tungsten Trioxide Nanowires through Thermal Evaporation

by Po-Heng Sung, Hsi-Kai Yen, Shu-Meng Yang and Kuo-Chang Lu

Nanomaterials 2023, 13(7), 1197; https://doi.org/10.3390/nano13071197 - 27 Mar 2023

Cited by 1 | Viewed by 1248

Abstract

We report an efficient method to synthesize undoped and K-doped rare cubic tungsten trioxide nanowires through the thermal evaporation of WO₃ powder without a catalyst. The WO₃ nanowires are reproducible and stable with a low-cost growth process. The thermal evaporation processing [...] Read more.

We report an efficient method to synthesize undoped and K-doped rare cubic tungsten trioxide nanowires through the thermal evaporation of WO₃ powder without a catalyst. The WO₃ nanowires are reproducible and stable with a low-cost growth process. The thermal evaporation processing was conducted in a three-zone horizontal tube furnace over a temperature range of 550–850 °C, where multiple substrates were placed at different temperature zones. The processing parameters, including pressure, temperature, type of gas, and flow rate, were varied and studied in terms of their influence on the morphology, aspect ratio and density of the nanowires. The morphologies of the products were observed with scanning electron microscopy. High resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction studies were conducted to further identify the chemical composition, crystal structure and growth direction of the nanostructures. Additionally, the growth mechanism has been proposed. Furthermore, we investigated the potassium doping effect on the physical properties of the nanostructures. Photoluminescence measurements show that there were shorter emission bands at 360 nm and 410 nm. Field emission measurements show that the doping effect significantly reduced the turn-on electric field and increased the enhancement factor. Furthermore, as compared with related previous research, the K-doped WO₃ nanowires synthesized in this study exhibited excellent field emission properties, including a superior field enhancement factor and turn-on electric field. The study reveals the potential of WO₃ nanowires in promising applications for sensors, field emitters and light-emitting diodes. Full article

(This article belongs to the Special Issue Semiconductor Nanomaterials: Growth, Characterization and Optoelectronic Application)

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18 pages, 5824 KiB

Open AccessArticle

Synthesis and Deposition of Silver Nanowires on Porous Silicon as an Ultraviolet Light Photodetector

by Anas A. M. Alqanoo, Naser M. Ahmed, Md. R. Hashim, Munirah A. Almessiere, Sofyan A. Taya, Ahmed Alsadig, Osamah A. Aldaghri and Khalid Hassan Ibnaouf

Nanomaterials 2023, 13(2), 353; https://doi.org/10.3390/nano13020353 - 15 Jan 2023

Cited by 4 | Viewed by 1857

Abstract

The applications of silver nanowires (AgNWs) are clearly relevant to their purity and morphology. Therefore, the synthesis parameters should be precisely adjusted in order to obtain AgNWs with a high aspect ratio. Consequently, controlling the reaction time versus the reaction temperature of the [...] Read more.

The applications of silver nanowires (AgNWs) are clearly relevant to their purity and morphology. Therefore, the synthesis parameters should be precisely adjusted in order to obtain AgNWs with a high aspect ratio. Consequently, controlling the reaction time versus the reaction temperature of the AgNWs is crucial to synthesize AgNWs with a high crystallinity and is important in fabricating optoelectronic devices. In this work, we tracked the morphological alterations of AgNWs during the growth process in order to determine the optimal reaction time and temperature. Thus, here, the UV–Vis absorption spectra were used to investigate how the reaction time varies with the temperature. The reaction was conducted at five different temperatures, 140–180 °C. As a result, an equation was developed to describe the relationship between them and to calculate the reaction time at any given reaction temperature. It was observed that the average diameter of the NWs was temperature-dependent and had a minimum value of 23 nm at a reaction temperature of 150 °C. A significant purification technique was conducted for the final product at a reaction temperature of 150 °C with two different speeds in the centrifuge to remove the heavy and light by-products. Based on these qualities, a AgNWs-based porous Si (AgNWs/P-Si) device was fabricated, and current-time pulsing was achieved using an ultra-violet (UV) irradiation of a 375 nm wavelength at four bias voltages of 1 V, 2 V, 3 V, and 4 V. We obtained a high level of sensitivity and detectivity with the values of 2247.49% and 2.89

\times

10¹² Jones, respectively. The photocurrent increased from the μA range in the P-Si to the mA range in the AgNWs/P-Si photodetector due to the featured surface plasmon resonance of the AgNWs compared to the other metals. Full article

(This article belongs to the Special Issue Semiconductor Nanomaterials: Growth, Characterization and Optoelectronic Application)

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12 pages, 425 KiB

Open AccessArticle

Magnetic, Phonon and Optical Properties of Transition Metal and Rare Earth Ion Doped ZnS Nanoparticles

by Iliana Apostolova, Angel Apostolov and Julia Wesselinowa

Nanomaterials 2023, 13(1), 79; https://doi.org/10.3390/nano13010079 - 23 Dec 2022

Cited by 2 | Viewed by 1305

Abstract

The surface, size and ion doping effects on the magnetic, phonon and optical properties of ZnS nanoparticles are studied based on the s-d model including spin-phonon and Coulomb interaction, and using a Green’s function theory. The changes of the properties are explained on [...] Read more.

The surface, size and ion doping effects on the magnetic, phonon and optical properties of ZnS nanoparticles are studied based on the s-d model including spin-phonon and Coulomb interaction, and using a Green’s function theory. The changes of the properties are explained on a microscopic level, due to the different radii between the doping and host ions, which cause different strains—compressive or tensile, and change the exchange interaction constants in our model. The magnetization increases with increasing small transition metal (TM) and rare earth (RE) doping concentration. For larger TM dopants the magnetization decreases. The phonon energies increase with increasing TM, whereas they decrease by RE ions. The phonon damping increases for all doping ions. The changes of the band gap energy with different ion doping concentration is also studied. Band gap changes in doped semiconductors could be due as a result of exchange, s-d, Coulomb and electron-phonon interactions. We have tried to clarify the discrepancies which are reported in the literature in the magnetization and the band gap energy. Full article

(This article belongs to the Special Issue Semiconductor Nanomaterials: Growth, Characterization and Optoelectronic Application)

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11 pages, 3588 KiB

Open AccessArticle

Numerical Study of GaP Nanowires: Individual and Coupled Optical Waveguides and Resonant Phenomena

by Maria A. Anikina, Prithu Roy, Svetlana A. Kadinskaya, Alexey Kuznetsov, Valeriy M. Kondratev and Alexey D. Bolshakov

Nanomaterials 2023, 13(1), 56; https://doi.org/10.3390/nano13010056 - 23 Dec 2022

Cited by 2 | Viewed by 1673

Abstract

The development of novel nanophotonic devices and circuits necessitates studies of optical phenomena in nanoscale structures. Catalyzed semiconductor nanowires are known for their unique properties including high crystallinity and silicon compatibility making them the perfect platform for optoelectronics and nanophotonics. In this work, [...] Read more.

The development of novel nanophotonic devices and circuits necessitates studies of optical phenomena in nanoscale structures. Catalyzed semiconductor nanowires are known for their unique properties including high crystallinity and silicon compatibility making them the perfect platform for optoelectronics and nanophotonics. In this work, we explore numerically optical properties of gallium phosphide nanowires governed by their dimensions and study waveguiding, coupling between the two wires and resonant field confinement to unveil nanoscale phenomena paving the way for the fabrication of the integrated optical circuits. Photonic coupling between the two adjacent nanowires is studied in detail to demonstrate good tolerance of the coupling to the distance between the two aligned wires providing losses not exceeding 30% for the gap of 100 nm. The dependence of this coupling is investigated with the wires placed nearby varying their relative position. It is found that due to the resonant properties of a nanowire acting as a Fabry–Perot cavity, two coupled wires represent an attractive system for control over the optical signal processing governed by the signal interference. We explore size-dependent plasmonic behaviors of the metallic Ga nanoparticle enabling GaP nanowire as an antenna-waveguide hybrid system. We demonstrate numerically that variation of the structure dimensions allows the nearfield tailoring. As such, we explore GaP NWs as a versatile platform for integrated photonic circuits. Full article

(This article belongs to the Special Issue Semiconductor Nanomaterials: Growth, Characterization and Optoelectronic Application)

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9 pages, 1062 KiB

Open AccessArticle

Balancing the Number of Quantum Wells in HgCdTe/CdHgTe Heterostructures for Mid-Infrared Lasing

by Mikhail A. Fadeev, Alexander A. Dubinov, Anna A. Razova, Arina A. Yantser, Vladimir V. Utochkin, Vladimir V. Rumyantsev, Vladimir Ya. Aleshkin, Vladimir I. Gavrilenko, Nikolai N. Mikhailov, Sergey A. Dvoretsky and Sergey V. Morozov

Nanomaterials 2022, 12(24), 4398; https://doi.org/10.3390/nano12244398 - 09 Dec 2022

Cited by 2 | Viewed by 1101

Abstract

HgCdTe-based heterostructures with quantum wells (QWs) are a promising material for semiconductor lasers in the atmospheric transparency window (3–5 μm) thanks to the possibility of suppressing Auger recombination due to the no-parabolic law of carrier dispersion. In this work, we analyze the thresholds [...] Read more.

HgCdTe-based heterostructures with quantum wells (QWs) are a promising material for semiconductor lasers in the atmospheric transparency window (3–5 μm) thanks to the possibility of suppressing Auger recombination due to the no-parabolic law of carrier dispersion. In this work, we analyze the thresholds of stimulated emission (SE) under optical pumping from heterostructures with a different number of QWs in the active region of the structure. Total losses in structures are determined from the comparison of thresholds for the different number of QWs in the active region. It is shown that, thanks to the increased modal gain, a higher number of QWs results in lower threshold pumping intensity and, consequently, higher temperature of SE. These results indicate that improvements to the modal gain can result in a moderate uplift in the temperature of SE from mid-infrared HgCdTe-based heterostructures. On the other hand, at a high enough QW count threshold, the intensity no longer depends on the number of the QWs and is determined by the transparency concentration of a single QW. Full article

(This article belongs to the Special Issue Semiconductor Nanomaterials: Growth, Characterization and Optoelectronic Application)

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11 pages, 1959 KiB

Open AccessFeature PaperArticle

Copper-Arsenic-Sulfide Thin-Films from Local Raw Materials Deposited via RF Co-Sputtering for Photovoltaics

by Pedro Centeno, Miguel Alexandre, Filipe Neves, Elvira Fortunato, Rodrigo Martins, Hugo Águas and Manuel J. Mendes

Nanomaterials 2022, 12(19), 3268; https://doi.org/10.3390/nano12193268 - 20 Sep 2022

Cited by 1 | Viewed by 1946

Abstract

The inexorable increase of energy demand and the efficiency bottleneck of monocrystalline silicon solar cell technology is promoting the research and development of alternative photovoltaic materials. Copper-arsenic-sulfide (CAS) compounds are still rather unexplored in the literature, yet they have been regarded as promising [...] Read more.

The inexorable increase of energy demand and the efficiency bottleneck of monocrystalline silicon solar cell technology is promoting the research and development of alternative photovoltaic materials. Copper-arsenic-sulfide (CAS) compounds are still rather unexplored in the literature, yet they have been regarded as promising candidates for use as p-type absorber in solar cells, owing to their broad raw material availability, suitable bandgap and high absorption coefficient. Here, a comprehensive study is presented on the structural and optoelectronic properties of CAS thin-films deposited via radio-frequency magnetron co-sputtering, using a commercial Cu target together with a Cu-As-S target with material obtained from local resources, specifically from mines in the Portuguese region of the Iberian Pyrite Belt. Raman and X-ray diffraction analysis confirm that the use of two targets results in films with pronounced stoichiometry gradients, suggesting a transition from amorphous CAS compounds to crystalline djurleite (Cu₃₁S₁₆), with the increasing proximity to the Cu target. Resistivity values from 4.7 mΩ·cm to 17.4 Ω·cm are obtained, being the lowest resistive films, those with pronounced sub-bandgap free-carrier absorption. The bandgap values range from 2.20 to 2.65 eV, indicating promising application as wide-bandgap semiconductors in third-generation (e.g., multi-junction) photovoltaic devices. Full article

(This article belongs to the Special Issue Semiconductor Nanomaterials: Growth, Characterization and Optoelectronic Application)

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16 pages, 3877 KiB

Open AccessArticle

Efficient and Facile Synthetic Route of MoO₃:MoS₂ Hybrid Thin Layer via Oxidative Reaction of MoS₂ Nanoflakes

by Hind Lamkaouane, Hajar Ftouhi, Mireille Richard-Plouet, Nicolas Gautier, Nicolas Stephant, Mimoun Zazoui, Mohammed Addou, Linda Cattin, Jean Christian Bernède, Yamina Mir and Guy Louarn

Nanomaterials 2022, 12(18), 3171; https://doi.org/10.3390/nano12183171 - 13 Sep 2022

Cited by 8 | Viewed by 1958

Abstract

In the present study, MoO₃:MoS₂ hybrid thin layers have been synthesized through partial oxidation of MoS₂. We have demonstrated that the reaction requires darkness conditions to decrease the oxidation rate, thus obtaining the hybrid, MoO₃:MoS₂ [...] Read more.

In the present study, MoO₃:MoS₂ hybrid thin layers have been synthesized through partial oxidation of MoS₂. We have demonstrated that the reaction requires darkness conditions to decrease the oxidation rate, thus obtaining the hybrid, MoO₃:MoS₂. A simple liquid-phase exfoliation (LPE) is carried out to achieve homogenous MoS₂ nanoflakes and high reproducibility of the results after MoS₂ oxidation. XPS analyses reveal the presence of MoO₃, MoS₂, and MoOxSy in the hybrid layer. These results are also confirmed by X-ray diffraction and high-resolution TEM. Optical absorbance reveals that the absorption peaks of the MoO₃:MoS₂ hybrid are slightly redshifted with the appearance of absorption peaks in the near-infrared region due to the defects created after the oxidation reaction. The composition and atomic percentages of each component in the hybrid layer as a function of reaction time have also been reported to give perspective guides for improving electronic and optoelectronic devices based on 2D-MoS₂. Full article

(This article belongs to the Special Issue Semiconductor Nanomaterials: Growth, Characterization and Optoelectronic Application)

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13 pages, 2642 KiB

Open AccessArticle

Compact Ga₂O₃ Thin Films Deposited by Plasma Enhanced Atomic Layer Deposition at Low Temperature

by Yue Yang, Xiao-Ying Zhang, Chen Wang, Fang-Bin Ren, Run-Feng Zhu, Chia-Hsun Hsu, Wan-Yu Wu, Dong-Sing Wuu, Peng Gao, Yu-Jiao Ruan, Shui-Yang Lien and Wen-Zhang Zhu

Nanomaterials 2022, 12(9), 1510; https://doi.org/10.3390/nano12091510 - 29 Apr 2022

Cited by 12 | Viewed by 2448

Abstract

Amorphous Gallium oxide (Ga₂O₃) thin films were grown by plasma-enhanced atomic layer deposition using O₂ plasma as reactant and trimethylgallium as a gallium source. The growth rate of the Ga₂O₃ films was about 0.6 Å/cycle [...] Read more.

Amorphous Gallium oxide (Ga₂O₃) thin films were grown by plasma-enhanced atomic layer deposition using O₂ plasma as reactant and trimethylgallium as a gallium source. The growth rate of the Ga₂O₃ films was about 0.6 Å/cycle and was acquired at a temperature ranging from 80 to 250 °C. The investigation of transmittance and the adsorption edge of Ga₂O₃ films prepared on sapphire substrates showed that the band gap energy gradually decreases from 5.04 to 4.76 eV with the increasing temperature. X-ray photoelectron spectroscopy (XPS) analysis indicated that all the Ga₂O₃ thin films showed a good stoichiometric ratio, and the atomic ratio of Ga/O was close to 0.7. According to XPS analysis, the proportion of Ga³⁺ and lattice oxygen increases with the increase in temperature resulting in denser films. By analyzing the film density from X-ray reflectivity and by a refractive index curve, it was found that the higher temperature, the denser the film. Atomic force microscopic analysis showed that the surface roughness values increased from 0.091 to 0.187 nm with the increasing substrate temperature. X-ray diffraction and transmission electron microscopy investigation showed that Ga₂O₃ films grown at temperatures from 80 to 200 °C were amorphous, and the Ga₂O₃ film grown at 250 °C was slightly crystalline with some nanocrystalline structures. Full article

(This article belongs to the Special Issue Semiconductor Nanomaterials: Growth, Characterization and Optoelectronic Application)

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Review

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31 pages, 11483 KiB

Open AccessReview

Gallium Oxide Nanostructures: A Review of Synthesis, Properties and Applications

by Nishant Singh Jamwal and Amirkianoosh Kiani

Nanomaterials 2022, 12(12), 2061; https://doi.org/10.3390/nano12122061 - 15 Jun 2022

Cited by 36 | Viewed by 6212

Abstract

Gallium oxide, as an emerging semiconductor, has attracted a lot of attention among researchers due to its high band gap (4.8 eV) and a high critical field with the value of 8 MV/cm. This paper presents a review on different chemical and physical [...] Read more.

Gallium oxide, as an emerging semiconductor, has attracted a lot of attention among researchers due to its high band gap (4.8 eV) and a high critical field with the value of 8 MV/cm. This paper presents a review on different chemical and physical techniques for synthesis of nanostructured β-gallium oxide, as well as its properties and applications. The polymorphs of Ga₂O₃ are highlighted and discussed along with their transformation state to β-Ga₂O₃. Different processes of synthesis of thin films, nanostructures and bulk gallium oxide are reviewed. The electrical and optical properties of β-gallium oxide are also highlighted, based on the synthesis methods, and the techniques for tuning its optical and electrical properties compared. Based on this information, the current, and the possible future, applications for β-Ga₂O₃ nanostructures are discussed. Full article

(This article belongs to the Special Issue Semiconductor Nanomaterials: Growth, Characterization and Optoelectronic Application)

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