Research

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11 pages, 2834 KiB

Open AccessArticle

Optimization of Layer Transfer and Photolithography for Device Integration of 2D-TMDC

by Amir Ghiami, Tianyishan Sun, Hleb Fiadziushkin, Songyao Tang, Annika Grundmann, Michael Heuken, Holger Kalisch and Andrei Vescan

Crystals 2023, 13(10), 1474; https://doi.org/10.3390/cryst13101474 - 10 Oct 2023

Viewed by 984

Abstract

Extensive research into two-dimensional transition metal dichalcogenides (2D-TMDCs) over the past decade has paved the way for the development of (opto)electronic devices with enhanced performance and novel capabilities. To realize devices based on 2D-TMDC layers, compatible and optimized technologies such as layer transfer [...] Read more.

Extensive research into two-dimensional transition metal dichalcogenides (2D-TMDCs) over the past decade has paved the way for the development of (opto)electronic devices with enhanced performance and novel capabilities. To realize devices based on 2D-TMDC layers, compatible and optimized technologies such as layer transfer and photolithography are required. Challenges arise due to the ultrathin, surface-only nature of 2D layers with weak van der Waals adhesion to their substrate. This might potentially compromise their integrity during transfer and photolithography processes, in which prolonged exposure at usually high temperature to reactive chemicals and strong solvents are conventionally used. In this paper, we show that employing a dry-transfer technique based on thermal release tape (TRT) as an alternative to wet processes based on KOH solution better preserves layer quality. In the succeeding device fabrication process, an optimized photolithography as a cost-effective and widely available method for device patterning is utilized. The introduced photolithography protocol presents a near-perfect yield and reproducibility. To validate our optimized techniques, we fabricated field-effect transistors (FETs) using 2D-MoS₂ layers from metal–organic chemical vapor deposition (MOCVD), wet- and dry-transferred onto SiO₂/Si substrates. Our findings mark a significant stride towards the efficient and industry-compatible utilization of 2D van der Waals materials in device fabrication. Full article

(This article belongs to the Special Issue Advances in Low-Dimensional Materials for Electronics and Sensing Applications)

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17 pages, 4796 KiB

Open AccessArticle

Porous, Tremella-like NiFe₂O₄ with Ultrathin Nanosheets for ppb-Level Toluene Detection

by Yanlin Zhang, Honglong Qu, Cheng Gang, Hongtao Guan, Chengjun Dong and Zongyou Yin

Crystals 2023, 13(6), 865; https://doi.org/10.3390/cryst13060865 - 25 May 2023

Cited by 1 | Viewed by 1231

Abstract

As a typical spinel ferrite, NiFe₂O₄ is suitable for use in gas sensors. Herein, we report the fabrication of porous, tremella-like NiFe₂O₄ assembled using porous, ultrathin nanosheets via the coordination of Ni²⁺ and Fe²⁺ with [...] Read more.

As a typical spinel ferrite, NiFe₂O₄ is suitable for use in gas sensors. Herein, we report the fabrication of porous, tremella-like NiFe₂O₄ assembled using porous, ultrathin nanosheets via the coordination of Ni²⁺ and Fe²⁺ with 1,4-phenylenediboronic acid. The optical band gap of the NiFe₂O₄ is estimated to be about 1.7 eV. Furthermore, the NiFe₂O₄ sensor annealed at 400 °C exhibits a low detection limit of 50 ppb, a fast response/recovery time (11.6 s/41.9 s to 10 ppm toluene), good reproducibility, and long-term stability at 220 °C. The suitable sensing performances can be attributed to the good catalytic activity of NiFe₂O₄ to toluene oxidation. Moreover, the ultrathin nanosheets with porous structures provide a large number of active sites to significantly favor the diffusion and adsorption/desorption of toluene molecules. This current work provides an insight into fabricating NiFe₂O₄ using 1,4-phenylenediboronic acid, which is promising for ppb-level toluene detection. Full article

(This article belongs to the Special Issue Advances in Low-Dimensional Materials for Electronics and Sensing Applications)

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13 pages, 4146 KiB

Open AccessArticle

Novel Mixed-Phase α/γ-Fe₂O₃ Micro-Flower Assembled with Nanosheets for Enhancing Acetone Detection

by Ruonan Tian, Huai Tan, Gang Chen, Hongtao Guan, Chengjun Dong and Zongyou Yin

Crystals 2023, 13(5), 810; https://doi.org/10.3390/cryst13050810 - 13 May 2023

Cited by 1 | Viewed by 1113

Abstract

Although individual γ-Fe₂O₃ and α-Fe₂O₃ have been widely fabricated for gas sensors, their mixed phase of α/γ-Fe₂O₃ might deliver excellent sensing properties. In this study, a facile solvothermal method was used to fabricate Fe-alkoxide. [...] Read more.

Although individual γ-Fe₂O₃ and α-Fe₂O₃ have been widely fabricated for gas sensors, their mixed phase of α/γ-Fe₂O₃ might deliver excellent sensing properties. In this study, a facile solvothermal method was used to fabricate Fe-alkoxide. After thermal treatment, it was converted into γ-Fe₂O₃, α-Fe₂O₃ and their mixed-phase α/γ-Fe₂O₃ with a nanosheets-assembled flower-like structure. We studied the influence of calcination temperature on the phase and sensing properties on acetone detection. The α/γ-Fe₂O₃ which annealed at 400 °C included 18% α-Fe₂O₃ and it exhibited excellent sensing performance towards acetone compared to that of γ-Fe₂O₃ and α-Fe₂O₃. It showed a response of 353 to acetone with a concentration of 200 ppm, and a low limit of detection of 0.5 ppm at 160 °C. In addition, the change in responses with acetone concentration from 50 to 200 ppm shows a good linear relationship. Moreover, this material has good reproducibility and selectivity as well as a fast response time of 22 s and recovery time of 14 s to 200 ppm. Therefore, our mixed phase of α/γ-Fe₂O₃ possesses great prospects for acetone detection. Full article

(This article belongs to the Special Issue Advances in Low-Dimensional Materials for Electronics and Sensing Applications)

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10 pages, 4597 KiB

Open AccessArticle

N-Polar Indium Nitride Quantum Dashes and Quantum Wire-like Structures: MOCVD Growth and Characterization

by Vineeta R. Muthuraj, Wenjian Liu, Henry Collins, Weiyi Li, Robert Hamwey, Steven P. DenBaars, Umesh K. Mishra and Stacia Keller

Crystals 2023, 13(4), 699; https://doi.org/10.3390/cryst13040699 - 19 Apr 2023

Viewed by 1021

Abstract

The electrical properties of InN give it potential for applications in III-nitride electronic devices, and the use of lower-dimensional epitaxial structures could mitigate issues with the high lattice mismatch of InN to GaN (10%). N-polar MOCVD growth of InN was performed to explore [...] Read more.

The electrical properties of InN give it potential for applications in III-nitride electronic devices, and the use of lower-dimensional epitaxial structures could mitigate issues with the high lattice mismatch of InN to GaN (10%). N-polar MOCVD growth of InN was performed to explore the growth parameter space of the horizontal one-dimensional InN quantum wire-like structures on miscut substrates. The InN growth temperature, InN thickness, and NH₃ flow during growth were varied to determine optimal quantum wire segment growth conditions. Quantum wire segment formation was observed through AFM images for N-polar InN samples with a low growth temperature of 540 °C and 1–2 nm of InN. Below 1 nm of InN, quantum dashes formed, and 2-D layers were formed above 2 nm of InN. One-dimensional anisotropy of the electrical conduction of N-polar InN wire-like samples was observed through TLM measurements. The sheet resistances of wire-like samples varied from 10–26 kΩ/□ in the longitudinal direction of the wire segments. The high sheet resistances were attributed to the close proximity of the treading dislocations at the InN/GaN interface and might be lowered by reducing the lattice mismatch of InN wire-like structures with the substrate using high lattice constant base layers such as relaxed InGaN. Full article

(This article belongs to the Special Issue Advances in Low-Dimensional Materials for Electronics and Sensing Applications)

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9 pages, 1983 KiB

Open AccessArticle

Enhanced Ammonia Gas Adsorption through Site-Selective Fluorination of Graphene

by Tianbo Duan, Hu Li, Lakshya Daukiya, Laurent Simon and Klaus Leifer

Crystals 2022, 12(8), 1117; https://doi.org/10.3390/cryst12081117 - 10 Aug 2022

Cited by 3 | Viewed by 1658

Abstract

Graphene has been widely explored as an ideal platform for gas sensing owing to exceptional properties, such as its atom-thin two-dimensional conjugated structure and large specific surface area. Herein, we report that, by introducing covalent C-F bonds via site-selective ion-beam-induced fluorination, graphene sensing [...] Read more.

Graphene has been widely explored as an ideal platform for gas sensing owing to exceptional properties, such as its atom-thin two-dimensional conjugated structure and large specific surface area. Herein, we report that, by introducing covalent C-F bonds via site-selective ion-beam-induced fluorination, graphene sensing response to ammonia gas can be considerably improved due to the enhanced gas adsorption on the surface of fluorinated graphene. The response to the ammonia gas increased by a factor of eight together with the limit of detection approaching 65 ppb. The absorption kinetics between the ammonia gas and fluorinated graphene were analyzed by using the Langmuir isotherm model and the result shows that the enhanced sensitivity is mainly attributed to the strong binding energy of fluorinated graphene to ammonia gas molecules, which is consistent with previous theoretical predictions. Full article

(This article belongs to the Special Issue Advances in Low-Dimensional Materials for Electronics and Sensing Applications)

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9 pages, 2497 KiB

Open AccessArticle

A First-Principles Study on the Structural and Carrier Transport Properties of Inorganic Perovskite CsPbI₃ under Pressure

by Sheng Huang, Mingzhi Jiao, Xi Wang and Xinjian He

Crystals 2022, 12(5), 648; https://doi.org/10.3390/cryst12050648 - 01 May 2022

Cited by 10 | Viewed by 2025

Abstract

Lead halide perovskite has attracted intensive attention for pressure and strain detection. Principally, pressure-induced changes in the structure and resistance of perovskite may bring great potential for developing high-performance piezoresistive pressure sensors. Herein, for the first time, we study the structural changes and [...] Read more.

Lead halide perovskite has attracted intensive attention for pressure and strain detection. Principally, pressure-induced changes in the structure and resistance of perovskite may bring great potential for developing high-performance piezoresistive pressure sensors. Herein, for the first time, we study the structural changes and the hot carrier cooling process of perovskite CsPbI₃ under pressure based on density functional theory and time-dependent density functional theory. The calculation results show that the lattice constant of CsPbI₃ linearly decreases and the time and path of the hot carrier cooling process change apparently under pressure. Meanwhile, the pressure will change the transition dipole moment, and the position of the k-point will not affect the optical properties of perovskite. Subsequently, the electrical conductivity enlarges as the pressure increases due to the change in charge density caused by pressure, which will be helpful for its potential application in the pressure sensors. Full article

(This article belongs to the Special Issue Advances in Low-Dimensional Materials for Electronics and Sensing Applications)

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Review

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18 pages, 2898 KiB

Open AccessReview

Transistor-Based Synaptic Devices for Neuromorphic Computing

by Wen Huang, Huixing Zhang, Zhengjian Lin, Pengjie Hang and Xing’ao Li

Crystals 2024, 14(1), 69; https://doi.org/10.3390/cryst14010069 - 09 Jan 2024

Viewed by 1404

Abstract

Currently, neuromorphic computing is regarded as the most efficient way to solve the von Neumann bottleneck. Transistor-based devices have been considered suitable for emulating synaptic functions in neuromorphic computing due to their synergistic control capabilities on synaptic weight changes. Various low-dimensional inorganic materials [...] Read more.

Currently, neuromorphic computing is regarded as the most efficient way to solve the von Neumann bottleneck. Transistor-based devices have been considered suitable for emulating synaptic functions in neuromorphic computing due to their synergistic control capabilities on synaptic weight changes. Various low-dimensional inorganic materials such as silicon nanomembranes, carbon nanotubes, nanoscale metal oxides, and two-dimensional materials are employed to fabricate transistor-based synaptic devices. Although these transistor-based synaptic devices have progressed in terms of mimicking synaptic functions, their application in neuromorphic computing is still in its early stage. In this review, transistor-based synaptic devices are analyzed by categorizing them into different working mechanisms, and the device fabrication processes and synaptic properties are discussed. Future efforts that could be beneficial to the development of transistor-based synaptic devices in neuromorphic computing are proposed. Full article

(This article belongs to the Special Issue Advances in Low-Dimensional Materials for Electronics and Sensing Applications)

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20 pages, 3227 KiB

Open AccessReview

Advances in the Field of Graphene-Based Composites for Energy–Storage Applications

by Yining Du, Mingyang Wang, Xiaoling Ye, Benqing Liu, Lei Han, Syed Hassan Mujtaba Jafri, Wencheng Liu, Xiaoxiao Zheng, Yafei Ning and Hu Li

Crystals 2023, 13(6), 912; https://doi.org/10.3390/cryst13060912 - 04 Jun 2023

Cited by 7 | Viewed by 2192

Abstract

To meet the growing demand in energy, great efforts have been devoted to improving the performances of energy–storages. Graphene, a remarkable two-dimensional (2D) material, holds immense potential for improving energy–storage performance owing to its exceptional properties, such as a large-specific surface area, remarkable [...] Read more.

To meet the growing demand in energy, great efforts have been devoted to improving the performances of energy–storages. Graphene, a remarkable two-dimensional (2D) material, holds immense potential for improving energy–storage performance owing to its exceptional properties, such as a large-specific surface area, remarkable thermal conductivity, excellent mechanical strength, and high-electronic mobility. This review provides a comprehensive summary of recent research advancements in the application of graphene for energy–storage. Initially, the fundamental properties of graphene are introduced. Subsequently, the latest developments in graphene-based energy–storage, encompassing lithium-ion batteries, sodium-ion batteries, supercapacitors, potassium-ion batteries and aluminum-ion batteries, are summarized. Finally, the challenges associated with graphene-based energy–storage applications are discussed, and the development prospects for this field are outlined. Full article

(This article belongs to the Special Issue Advances in Low-Dimensional Materials for Electronics and Sensing Applications)

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24 pages, 7115 KiB

Open AccessReview

Advanced Algorithms for Low Dimensional Metal Oxides-Based Electronic Nose Application: A Review

by Xi Wang, Yangming Zhou, Zhikai Zhao, Xiujuan Feng, Zhi Wang and Mingzhi Jiao

Crystals 2023, 13(4), 615; https://doi.org/10.3390/cryst13040615 - 03 Apr 2023

Cited by 8 | Viewed by 1539

Abstract

Low-dimensional metal oxides-based electronic noses have been applied in various fields, such as food quality, environmental assessment, coal mine risk prediction, and disease diagnosis. However, the applications of these electronic noses are limited for conditions such as precise safety monitoring because electronic nose [...] Read more.

Low-dimensional metal oxides-based electronic noses have been applied in various fields, such as food quality, environmental assessment, coal mine risk prediction, and disease diagnosis. However, the applications of these electronic noses are limited for conditions such as precise safety monitoring because electronic nose systems have problems such as poor recognition ability of mixed gas signals and sensor drift caused by environmental factors. Advanced algorithms, including classical gas recognition algorithms and neural network-based algorithms, can be good solutions for the key problems. Classical gas recognition methods, such as support vector machines, have been widely applied in electronic nose systems in the past. These methods can provide satisfactory results if the features are selected properly and the types of mixed gas are under five. In many situations, this can be challenging due to the drift of sensor signals. In recent years, neural networks have undergone revolutionary changes in the field of electronic noses, especially convolutional neural networks and recurrent neural networks. This paper reviews the principles and performances of typical gas recognition methods of the electronic nose up to now and compares and analyzes the classical gas recognition methods and the neural network-based gas recognition methods. This work can provide guidance for research in related fields. Full article

(This article belongs to the Special Issue Advances in Low-Dimensional Materials for Electronics and Sensing Applications)

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30 pages, 7317 KiB

Open AccessReview

Advances in Two-Dimensional Materials for Optoelectronics Applications

by Mingyue Zhao, Yurui Hao, Chen Zhang, Rongli Zhai, Benqing Liu, Wencheng Liu, Cong Wang, Syed Hassan Mujtaba Jafri, Aamir Razaq, Raffaello Papadakis, Jiangwei Liu, Xiaoling Ye, Xiaoxiao Zheng and Hu Li

Crystals 2022, 12(8), 1087; https://doi.org/10.3390/cryst12081087 - 04 Aug 2022

Cited by 19 | Viewed by 5774

Abstract

The past one and a half decades have witnessed the tremendous progress of two-dimensional (2D) crystals, including graphene, transition-metal dichalcogenides, black phosphorus, MXenes, hexagonal boron nitride, etc., in a variety of fields. The key to their success is their unique structural, electrical, mechanical [...] Read more.

The past one and a half decades have witnessed the tremendous progress of two-dimensional (2D) crystals, including graphene, transition-metal dichalcogenides, black phosphorus, MXenes, hexagonal boron nitride, etc., in a variety of fields. The key to their success is their unique structural, electrical, mechanical and optical properties. Herein, this paper gives a comprehensive summary on the recent advances in 2D materials for optoelectronic approaches with the emphasis on the morphology and structure, optical properties, synthesis methods, as well as detailed optoelectronic applications. Additionally, the challenges and perspectives in the current development of 2D materials are also summarized and indicated. Therefore, this review can provide a reference for further explorations and innovations of 2D material-based optoelectronics devices. Full article

(This article belongs to the Special Issue Advances in Low-Dimensional Materials for Electronics and Sensing Applications)

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