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Functional Micro-/Nanostructures: Advanced Fabrication and Application

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A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanofabrication and Nanomanufacturing".

Deadline for manuscript submissions: closed (31 January 2024) | Viewed by 13865

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Dr. Guanhua Zhang

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Guest Editor

College of Mechanical and Vehicle Engineering, Hunan University, Changsha 410082, China
Interests: functional micro/nanostructure fabrication and application; miniature energy storage devices; flexible electronics; electromagnetic shielding

Dr. Peng Cao

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Guest Editor

Department of Chemical and Materials Engineering, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
Interests: light metals; powder metallurgy; energy-related materials; glass ceramics
Special Issues, Collections and Topics in MDPI journals

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Dear Colleagues,

Micro/nanofunctional structures have shown promising applications in many fields, such as energy, catalysis, the environment, optoelectronics, and microelectromechanical systems (MEMS), due to their excellent physicochemical properties. In the past few decades, intensive efforts have been devoted to developing micro-/nanofunctional structures from 0D to 3D, which feature a superior surface-to-volume ratio, extraordinary electronic properties, and intriguing electrochemical activity.

Currently, one of the challenges in the field of international research on micro/nanofunctional structures is how to achieve precise design and selective control synthesis of the structure of micro- and nanostructured units in order to obtain novel functions and applications. Additionally, the relationships between the role of micro/nanofunctional structures and the enhanced performance of the devices are still not clear.

This Special Issue aims to present recent progress in novel micro-/nanostructure design, fabrication, advanced characterization techniques, and functional device applications. The format of articles includes full papers, communications, and reviews. Potential topics include but are not limited to:

Design and processing of novel micro/nanofunctional structures;
Advanced characterization of micro/nanofunctional structures;
Electrochemical energy conversion and storage applications;
Multifunctional optoelectronic device applications;
Environmental catalysis applications;
Microelectromechanical system applications;
Highly efficient electromagnetic shielding applications.

Dr. Guanhua Zhang
Dr. Peng Cao
Guest Editors

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Keywords

micro-/nanofunctional structures
design and fabrication
advanced characterization techniques
functional device application

Published Papers (11 papers)

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Research

11 pages, 2696 KiB

Open AccessArticle

Interfacial Polarization Control Engineering and Ferroelectric PZT/Graphene Heterostructure Integrated Application

by Kaixi Bi, Shuqi Han, Jialiang Chen, Xiaoxue Bi, Xiangyu Yang, Liya Niu and Linyu Mei

Nanomaterials 2024, 14(5), 432; https://doi.org/10.3390/nano14050432 - 27 Feb 2024

Viewed by 693

Abstract

Integration and miniaturization are the inevitable trends in the development of electronic devices. PZT and graphene are typical ferroelectric and carbon-based materials, respectively, which have been widely used in various fields. Achieving high-quality PZT/graphene heterogeneous integration and systematically studying its electrical properties is of great significance. In this work, we reported the characterization of a PZT film based on the sol–gel method. Additionally, the thickness of the PZT film was pushed to the limit size (~100 nm) by optimizing the process. The test results, including the remnant and leakage current, show that the PZT film is a reliable and suitable platform for further graphene-integrated applications. The non-destructive regulation of the electrical properties of graphene has been studied based on a domain-polarized substrate and strain-polarized substrate. The domain structures in the PZT film exhibit different geometric structures with ~0.3 V surface potential. The I–V output curves of graphene integrated on the surface of the PZT film exhibited obvious rectification characteristics because of p/n-doping tuned by an interfacial polarized electric field. In contrast, a ~100 nm thick PZT film makes it easy to acquire a larger strain gradient for flexural potential. The tested results also show a rectification phenomenon, which is similar to domain polarization substrate regulation. Considering the difficulty of measuring the flexural potential, the work might provide a new approach to assessing the flexural polarized regulation effect. A thinner ferroelectric film/graphene heterojunction and the polarized regulation of graphene will provide a platform for promoting low-dimension film-integrated applications. Full article

(This article belongs to the Special Issue Functional Micro-/Nanostructures: Advanced Fabrication and Application)

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13 pages, 3979 KiB

Open AccessArticle

Highly Sensitive Paper-Based Force Sensors with Natural Micro-Nanostructure Sensitive Element

by Haozhe Zhang, Yuyu Ren, Junwen Zhu, Yanshen Jia, Qiang Liu and Xing Yang

Nanomaterials 2024, 14(4), 358; https://doi.org/10.3390/nano14040358 - 14 Feb 2024

Viewed by 682

Abstract

Flexible paper-based force sensors have garnered significant attention for their important potential applications in healthcare wearables, portable electronics, etc. However, most studies have only used paper as the flexible substrate for sensors, not fully exploiting the potential of paper’s micro-nanostructure for sensing. This article proposes a novel approach where paper serves both as the sensitive element and the flexible substrate of force sensors. Under external mechanical forces, the micro-nanostructure of the conductive-treated paper will change, leading to significant changes in the related electrical output and thus enabling sensing. To demonstrate the feasibility and universality of this new method, the article takes paper-based capacitive pressure sensors and paper-based resistive strain sensors as examples, detailing their fabrication processes, constructing sensing principle models based on the micro-nanostructure of paper materials, and testing their main sensing performance. For the capacitive paper-based pressure sensor, it achieves a high sensitivity of 1.623 kPa⁻¹, a fast response time of 240 ms, and a minimum pressure resolution of 4.1 Pa. As for the resistive paper-based strain sensor, it achieves a high sensitivity of 72 and a fast response time of 300 ms. The proposed new method offers advantages such as high sensitivity, simplicity in the fabrication process, environmental friendliness, and cost-effectiveness, providing new insights into the research of flexible force sensors. Full article

(This article belongs to the Special Issue Functional Micro-/Nanostructures: Advanced Fabrication and Application)

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17 pages, 33157 KiB

Open AccessArticle

Research on Fabrication of Phononic Crystal Soft-Supported Graphene Resonator

by Xiande Zheng, Ying Liu, Jiapeng Zhen, Jing Qiu and Guanjun Liu

Nanomaterials 2024, 14(2), 130; https://doi.org/10.3390/nano14020130 - 05 Jan 2024

Viewed by 705

Abstract

In aviation, aerospace, and other fields, nanomechanical resonators could offer excellent sensing performance. Among these, graphene resonators, as a new sensitive unit, are expected to offer very high mass and force sensitivity due to their extremely thin thickness. However, at present, the quality factor of graphene resonators at room temperature is generally low, which limits the performance improvement and further application of graphene resonators. Enhancing the quality factor of graphene resonators has emerged as a pressing research concern. In a previous study, we have proposed a new mechanism to reduce the energy dissipation of graphene resonators by utilizing phononic crystal soft-supported structures. We verified its feasibility through theoretical analysis and simulations. This article focuses on the fabrication of a phononic crystal soft-supported graphene resonator. In order to address the issues of easy fracture, deformation, and low success rate in the fabrication of phononic crystal soft-supported graphene resonators, we have studied key processes for graphene suspension release and focused ion beam etching. Through parameter optimization, finally, we have obtained phononic crystal soft-supported graphene resonators with varying cycles and pore sizes. Finally, we designed an optical excitation and detection platform based on Fabry–Pérot interference principle and explored the impact of laser power and spot size on phononic crystal soft-supported graphene resonators. Full article

(This article belongs to the Special Issue Functional Micro-/Nanostructures: Advanced Fabrication and Application)

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10 pages, 2709 KiB

Open AccessArticle

Formation of Multiscale Pattern Structures by Combined Patterning of Nanotransfer Printing and Laser Micromachining

by Tae Wan Park, Young Lim Kang, Eun Bin Kang, Seungmin Kim, Yu Na Kim and Woon Ik Park

Nanomaterials 2023, 13(16), 2327; https://doi.org/10.3390/nano13162327 - 13 Aug 2023

Viewed by 1167

Abstract

Various lithography techniques have been widely used for the fabrication of next-generation device applications. Micro/nanoscale pattern structures formed by lithographic methods significantly improve the performance capabilities of the devices. Here, we introduce a novel method that combines the patterning of nanotransfer printing (nTP) and laser micromachining to fabricate multiscale pattern structures on a wide range of scales. Prior to the formation of various nano-in-micro-in-millimeter (NMM) patterns, the nTP process is employed to obtain periodic nanoscale patterns on the target substrates. Then, an optimum laser-based patterning that effectively engraves various nanopatterned surfaces, in this case, spin-cast soft polymer film, rigid polymer film, a stainless still plate, and a Si substrate, is established. We demonstrate the formation of well-defined square and dot-shaped multiscale NMM-patterned structures by the combined patterning method of nTP and laser processes. Furthermore, we present the generation of unusual text-shaped NMM pattern structures on colorless polyimide (CPI) film, showing optically excellent rainbow luminescence based on the configuration of multiscale patterns from nanoscale to milliscale. We expect that this combined patterning strategy will be extendable to other nano-to-micro fabrication processes for application to various nano/microdevices with complex multiscale pattern geometries. Full article

(This article belongs to the Special Issue Functional Micro-/Nanostructures: Advanced Fabrication and Application)

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7 pages, 4921 KiB

Open AccessCommunication

A Novel Atomic-Level Post-Etch-Surface-Reinforcement Process for High-Performance p-GaN Gate HEMTs Fabrication

by Luyu Wang, Penghao Zhang, Kaiyue Zhu, Qiang Wang, Maolin Pan, Xin Sun, Ziqiang Huang, Kun Chen, Yannan Yang, Xinling Xie, Hai Huang, Xin Hu, Saisheng Xu, Chunlei Wu, Chen Wang, Min Xu and David Wei Zhang

Nanomaterials 2023, 13(16), 2275; https://doi.org/10.3390/nano13162275 - 08 Aug 2023

Cited by 1 | Viewed by 1055

Abstract

A novel atomic-level post-etch-surface-reinforcement (PESR) process is developed to recover the p-GaN etching induced damage region for high performance p-GaN gate HEMTs fabrication. This process is composed of a self-limited surface modification step with O₂ plasma, following by an oxide removal step with BCl₃ plasma. With PESR process, the AlGaN surface morphology after p-GaN etching was comparable to the as-epitaxial level by AFM characterization, and the AlGaN lattice crystallization was also recovered which was measured in a confocal Raman system. The electrical measurement further confirmed the significant improvement of AlGaN surface quality, with one-order of magnitude lower surface leakage in a metal-semiconductor (MS) Schottky-diode and 6 times lower interface density of states (D_it) in a MIS C-V characterization. The XPS analysis of Al₂O₃/AlGaN showed that the p-GaN etching induced F-byproduct and Ga-oxide was well removed and suppressed by PESR process. Finally, the developed PESR process was successfully integrated in p-GaN gate HEMTs fabrication, and the device performance was significantly enhanced with ~20% lower of on-resistance and ~25% less of current collapse at V_ds,Q bias of 40 V, showing great potential of leverage p-GaN gate HEMTs reliability. Full article

(This article belongs to the Special Issue Functional Micro-/Nanostructures: Advanced Fabrication and Application)

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12 pages, 5777 KiB

Open AccessArticle

Thermally Conductive and Electrically Insulating Epoxy Composites Filled with Network-like Alumina In Situ Coated Graphene

by Ruicong Lv, Haichang Guo, Lei Kang, Akbar Bashir, Liucheng Ren, Hongyu Niu and Shulin Bai

Nanomaterials 2023, 13(15), 2243; https://doi.org/10.3390/nano13152243 - 03 Aug 2023

Cited by 1 | Viewed by 980

Abstract

With the rapid development of the electronics industry, there is a growing demand for packaging materials that possess both high thermal conductivity (TC) and low electrical conductivity (EC). However, traditional insulating fillers such as boron nitride, aluminum nitride, and alumina (Al₂O₃) have relatively low intrinsic TC. When graphene, which exhibits both superhigh TC and EC, is used as a filler to fill epoxy resin, the TC of blends can be much higher than that of blends containing more traditional fillers. However, the high EC of graphene limits its application in cases where electrical insulation is required. To address this challenge, a method for coating graphene sheets with an in situ grown Al₂O₃ layer has been proposed for the fabrication of epoxy-based composites with both high TC and low EC. In the presence of a cationic surfactant, a dense Al₂O₃ layer with a network structure can be formed on the surface of graphene sheets. When the total content of Al₂O₃ and graphene mixed filler reached 30 wt%, the TC of the epoxy composite reached 0.97 W m⁻¹ K⁻¹, while the EC remained above 10¹¹ Ω·cm. Finite element simulations accurately predicted TC and EC values in accordance with experimental results. This material, with its combination of high TC and good insulation properties, exhibits excellent potential for microelectronic packaging applications. Full article

(This article belongs to the Special Issue Functional Micro-/Nanostructures: Advanced Fabrication and Application)

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11 pages, 2682 KiB

Open AccessArticle

Nanoelectromechanical Temperature Sensor Based on Piezoresistive Properties of Suspended Graphene Film

by Shuqi Han, Siyuan Zhou, Linyu Mei, Miaoli Guo, Huiyi Zhang, Qiannan Li, Shuai Zhang, Yaokai Niu, Yan Zhuang, Wenping Geng, Kaixi Bi and Xiujian Chou

Nanomaterials 2023, 13(6), 1103; https://doi.org/10.3390/nano13061103 - 19 Mar 2023

Cited by 2 | Viewed by 1574

Abstract

The substrate impurities scattering will lead to unstable temperature-sensitive behavior and poor linearity in graphene temperature sensors. And this can be weakened by suspending the graphene structure. Herein, we report a graphene temperature sensing structure, with suspended graphene membranes fabricated on the cavity and non-cavity SiO₂/Si substrate, using monolayer, few-layer, and multilayer graphene. The results show that the sensor provides direct electrical readout from temperature to resistance transduction by the nano piezoresistive effect in graphene. And the cavity structure can weaken the substrate impurity scattering and thermal resistance effect, which results in better sensitivity and wide-range temperature sensing. In addition, monolayer graphene is almost no temperature sensitivity. And the few-layer graphene temperature sensitivity, lower than that of the multilayer graphene cavity structure (3.50%/°C), is 1.07%/°C. This work demonstrates that piezoresistive in suspended graphene membranes can effectively enhance the sensitivity and widen the temperature sensor range in NEMS temperature sensors. Full article

(This article belongs to the Special Issue Functional Micro-/Nanostructures: Advanced Fabrication and Application)

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11 pages, 2083 KiB

Open AccessArticle

Controllable Patterning of Metallic Photonic Crystals for Waveguide–Plasmon Interaction

by Yuanhai Lin, Deqing Che, Wenjie Hao, Yifei Dong, Heng Guo, Junsheng Wang and Xinping Zhang

Nanomaterials 2023, 13(4), 629; https://doi.org/10.3390/nano13040629 - 05 Feb 2023

Cited by 1 | Viewed by 1437

Abstract

Waveguide–plasmon polaritons sustained in metallic photonic crystal slabs show fascinating properties, such as narrow bandwidth and ultrafast dynamics crucial for biosensing, light emitting, and ultrafast switching. However, the patterning of metallic photonic crystals using electron beam lithography is challenging in terms of high efficiency, large area coverage, and cost control. This paper describes a controllable patterning technique for the fabrication of an Ag grating structure on an indium–tin oxide (ITO) slab that enables strong photon–plasmon interaction to obtain waveguide–plasmon polaritons. The Ag grating consisting of self-assembled silver nanoparticles (NPs) exhibits polarization-independent properties for the excitation of the hybrid waveguide–plasmon mode. The Ag NP grating can also be annealed at high temperature to form a continuous nanoline grating that supports the hybrid waveguide–plasmon mode only under transverse magnetic (TM) polarization. We tuned the morphology and the periodicity of the Ag grating through the concentration of silver salt and the photoresist template, respectively, to manipulate the strong coupling between the plasmon and the waveguide modes of different orders. Full article

(This article belongs to the Special Issue Functional Micro-/Nanostructures: Advanced Fabrication and Application)

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15 pages, 5039 KiB

Open AccessArticle

In Situ Growth of Nickel–Cobalt Metal Organic Frameworks Guided by a Nickel–Molybdenum Layered Double Hydroxide with Two-Dimensional Nanosheets Forming Flower-Like Struc-Tures for High-Performance Supercapacitors

by Cheng Cheng, Yongjin Zou, Fen Xu, Cuili Xiang and Lixian Sun

Nanomaterials 2023, 13(3), 581; https://doi.org/10.3390/nano13030581 - 31 Jan 2023

Cited by 5 | Viewed by 1511

Abstract

Metal organic frameworks (MOFs) are a kind of porous coordination polymer supported by organic ligands with metal ions as connection points. They have a controlled structure and porosity and a significant specific surface area, and can be used as functional linkers or sacrificial templates. However, long diffusion pathways, low conductivity, low cycling stability, and the presence of few exposed active sites limit the direct application of MOFs in energy storage applications. The targeted design of MOFs has the potential to overcome these limitations. This study proposes a facile method to grow and immobilize MOFs on layered double hydroxides through an in situ design. The proposed method imparts not only enhanced conductivity and cycling stability, but also provides additional active sites with excellent specific capacitance properties due to the interconnectivity of MOF nanoparticles and layered double hydroxide (LDH) nanosheets. Due to this favorable heterojunction hook, the NiMo-LDH@NiCo-MOF composite exhibits a large specific capacitance of 1536 F·g⁻¹ at 1 A·g⁻¹. In addition, the assembled NiMo-LDH@NiCo-MOF//AC asymmetric supercapacitor can achieve a high-energy density value of 60.2 Wh·kg⁻¹ at a power density of 797 W·kg⁻¹, indicating promising applications. Full article

(This article belongs to the Special Issue Functional Micro-/Nanostructures: Advanced Fabrication and Application)

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12 pages, 3738 KiB

Open AccessArticle

Thermal-Assisted Laser Fabrication of Broadband Ultralow Reflectance Surface by Combining Marangoni Flow with In Situ Deposition

by Jingbo Yin, Huangping Yan, Rui Zhou, Yuanzhe Li and Anna He

Nanomaterials 2023, 13(3), 480; https://doi.org/10.3390/nano13030480 - 25 Jan 2023

Cited by 1 | Viewed by 1685

Abstract

Functional surfaces with broadband ultralow optical reflectance have many potential applications in the fields of enhancing solar energy utilization, stray light shielding, infrared stealth, and so on. To fabricate broadband anti-reflection surfaces with low cost, high quality, and more controllability, a strategy of preparing multi-scale structures by thermal-assisted nanosecond laser was proposed. This strategy combines laser ablation with Marangoni flow of molten materials and in situ deposition of nanoparticles. The thermal-assisted strategy increases the depth to width ratio of the anti-reflection structures. The average reflectance of laser-textured TC4 (Ti-6Al-4V) surface is as low as 1.71% in the wavelength range of 200–2250 nm and 7.8% in the 2500–25,000 nm. The ultra-low reflectance surface has a significantly enhanced photothermal conversion performance. Meanwhile, the anti-reflection effect can be extended to the mid-infrared band, which has potential stealth application prospect. This synergetic manufacturing strategy has wide adaptability of materials, which provides new paths for the preparation of broadband ultralow reflectance surface. Moreover, this thermal-assisted laser fabrication strategy is prospective in the preparation of other functional micro-nano structures. Full article

(This article belongs to the Special Issue Functional Micro-/Nanostructures: Advanced Fabrication and Application)

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14 pages, 3545 KiB

Open AccessEditor’s ChoiceArticle

K_xCo_1.5−0.5xFe(CN)₆/rGO with Dual−Active Sodium Ion Storage Site as Superior Anode for Sodium Ion Battery

by Gang Zhou, Mincong Fan, Lei Wang, Xianglin Li, Danqing Liu and Feng Gao

Nanomaterials 2023, 13(2), 264; https://doi.org/10.3390/nano13020264 - 07 Jan 2023

Viewed by 1607

Abstract

The unique and open large frame structures of prussian blue analogues (PBA) enables it for accommodating a large number of cations (Na⁺, K⁺, Ca²⁺, etc.), thus, PBA are considered as promising electrode materials for the rechargeable battery. However, due to the chemical composition, there are still many alkaline metal ions in the gap within the framework, which puts multivalent metals in PBA in a low valence state and affects the sodium storage performance. To improve the valence of metal ions in PBA materials, precursors prepared by co−precipitation method and hydrothermal method are used to synthesis K_xCo_1.5−0.5xFe(CN)₆ through further chemical oxidation. Through the introducing of reduced graphene oxide (rGO) with excellent conductivity by a simple physical mixing method, the cycle stability and rate performance of the PBA material can be further improved. The K_0.5Co_1.2Fe(CN)₆·2H₂O/rGO anode prepared with 2 h hydrothermal time and further chemical oxidation, named as KCoHCP−H2−EK/rGO, exhibits a super electrochemical performance, delivering initial charge/discharge capacities of 846.7/1445.0 mAh·g⁻¹, and a capacity retention of 58.2% after 100 cycles at a current density of 100 mA·g⁻¹. The KCoHCP−H2−EK/rGO outstanding electrochemical behaviors are attributed to the unique dual−active site structure properties and the improved surface conductance of materials by rGO components. Full article

(This article belongs to the Special Issue Functional Micro-/Nanostructures: Advanced Fabrication and Application)

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