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16 pages, 9080 KiB

Open AccessArticle

High-Quality Spherical Silver Alloy Powder for Laser Powder Bed Fusion Using Plasma Rotating Electrode Process

by Hao Li, Shenghuan Zhang, Qiaoyu Chen, Zhaoyang Du, Xingyu Chen, Xiaodan Chen, Shiyi Zhou, Shuwen Mei, Linda Ke, Qinglei Sun, Zuowei Yin, Jie Yin and Zheng Li

Micromachines 2024, 15(3), 396; https://doi.org/10.3390/mi15030396 - 14 Mar 2024

Viewed by 750

Abstract

The plasma rotating electrode process (PREP) is an ideal method for the preparation of metal powders such as nickel-based, titanium-based, and iron-based alloys due to its low material loss and good degree of sphericity. However, the preparation of silver alloy powder by PREP [...] Read more.

The plasma rotating electrode process (PREP) is an ideal method for the preparation of metal powders such as nickel-based, titanium-based, and iron-based alloys due to its low material loss and good degree of sphericity. However, the preparation of silver alloy powder by PREP remains challenging. The low hardness of the mould casting silver alloy leads to the bending of the electrode rod when subjected to high-speed rotation during PREP. The mould casting silver electrode rod can only be used in low-speed rotation, which has a negative effect on particle refinement. This study employed continuous casting (CC) to improve the surface hardness of S800 Ag (30.30% higher than mould casting), which enables a high rotation speed of up to 37,000 revolutions per minute, and silver alloy powder with an average sphericity of 0.98 (5.56% higher than gas atomisation) and a sphericity ratio of 97.67% (36.28% higher than gas atomisation) has been successfully prepared. The dense S800 Ag was successfully fabricated by laser powder bed fusion (LPBF), which proved the feasibility of preparing high-quality powder by the “CC + PREP” method. The samples fabricated by LPBF have a Vickers hardness of up to 271.20 HV (3.66 times that of mould casting), leading to a notable enhancement in the strength of S800 Ag. In comparison to GA, the S800 Ag powder prepared by “CC + PREP” exhibits greater sphericity, a higher sphericity ratio and less satellite powder, which lays the foundation for dense LPBF S800 Ag fabrication. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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12 pages, 3769 KiB

Open AccessArticle

A Fast Transient Response Capacitor-Less LDO with Transient Enhancement Technology

by Chufan Chen, Mengyuan Sun, Leiyi Wang, Teng Huang and Min Xu

Micromachines 2024, 15(3), 299; https://doi.org/10.3390/mi15030299 - 22 Feb 2024

Viewed by 819

Abstract

This paper proposes a fast transient load response capacitor-less low-dropout regulator (CL-LDO) for digital analog hybrid circuits in the 180 nm process, capable of converting input voltages from 1.2 V to 1.8 V into an output voltage of 1 V. The design incorporates [...] Read more.

This paper proposes a fast transient load response capacitor-less low-dropout regulator (CL-LDO) for digital analog hybrid circuits in the 180 nm process, capable of converting input voltages from 1.2 V to 1.8 V into an output voltage of 1 V. The design incorporates a rail-to-rail input and push–pull output (RIPO) amplifier to enhance the gain while satisfying the requirement for low power consumption. A super source follower buffer (SSFB) with internal stability is introduced to ensure loop stability. The proposed structure ensures the steady-state performance of the LDO without an on-chip capacitor. The auxiliary circuit, or transient enhancement circuit, does not compromise the steady-state stability and effectively enhances the transient performance during sudden load current steps. The proposed LDO consumes a quiescent current of 47 µA and achieves 25 µV/mA load regulation with a load current ranging from 0 to 20 mA. The simulation results demonstrate that a settling time of 0.2 µs is achieved for load steps ranging from 0 mA to 20 mA, while a settling time of 0.5 µs is attained for load steps ranging from 20 mA to 0 mA, with an edge time of 0.1 µs. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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19 pages, 10764 KiB

Open AccessArticle

The Printability, Microstructure, and Mechanical Properties of Fe_80−xMn_xCo₁₀Cr₁₀ High-Entropy Alloys Fabricated by Laser Powder Bed Fusion Additive Manufacturing

by Kai Li, Vyacheslav Trofimov, Changjun Han, Gaoling Hu, Zhi Dong, Yujin Zou, Zaichi Wang, Fubao Yan, Zhiqiang Fu and Yongqiang Yang

Micromachines 2024, 15(1), 123; https://doi.org/10.3390/mi15010123 - 11 Jan 2024

Viewed by 841

Abstract

This work investigated the effect of Fe/Mn ratio on the microstructure and mechanical properties of non-equimolar Fe_80−xMn_xCo₁₀Cr₁₀ (x = 30% and 50%) high-entropy alloys (HEAs) fabricated by laser powder bed fusion (LPBF) additive manufacturing. [...] Read more.

This work investigated the effect of Fe/Mn ratio on the microstructure and mechanical properties of non-equimolar Fe_80−xMn_xCo₁₀Cr₁₀ (x = 30% and 50%) high-entropy alloys (HEAs) fabricated by laser powder bed fusion (LPBF) additive manufacturing. Process optimization was conducted to achieve fully dense Fe₃₀Mn₅₀Co₁₀Cr₁₀ and Fe₅₀Mn₃₀Co₁₀Cr₁₀ HEAs using a volumetric energy density of 105.82 J·mm⁻³. The LPBF-printed Fe₃₀Mn₅₀Co₁₀Cr₁₀ HEA exhibited a single face-centered cubic (FCC) phase, while the Fe₅₀Mn₃₀Co₁₀Cr₁₀ HEA featured a hexagonal close-packed (HCP) phase within the FCC matrix. Notably, the fraction of HCP phase in the Fe₅₀Mn₃₀Co₁₀Cr₁₀ HEAs increased from 0.94 to 28.10%, with the deformation strain ranging from 0 to 20%. The single-phase Fe₃₀Mn₅₀Co₁₀Cr₁₀ HEA demonstrated a remarkable combination of high yield strength (580.65 MPa) and elongation (32.5%), which surpassed those achieved in the FeMnCoCr HEA system. Comparatively, the dual-phase Fe₅₀Mn₃₀Co₁₀Cr₁₀ HEA exhibited inferior yield strength (487.60 MPa) and elongation (22.3%). However, it displayed superior ultimate tensile strength (744.90 MPa) compared to that in the Fe₃₀Mn₅₀Co₁₀Cr₁₀ HEA (687.70 MPa). The presence of FCC/HCP interfaces obtained in the Fe₅₀Mn₃₀Co₁₀Cr₁₀ HEA resulted in stress concentration and crack expansion, thereby leading to reduced ductility but enhanced resistance against grain slip deformation. Consequently, these interfaces facilitated an earlier attainment of yield limit point and contributed to increased ultimate tensile strength in the Fe₅₀Mn₃₀Co₁₀Cr₁₀ HEA. These findings provide valuable insights into the microstructure evolution and mechanical behavior of LPBF-printed metastable FeMnCoCr HEAs. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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22 pages, 10047 KiB

Open AccessArticle

Simulation and Experimental Study of Non-Resonant Vibration-Assisted Lapping of SiCp/Al

by Huibo Zhao, Yan Gu, Yuan Xi, Xingbao Fu, Yinghuan Gao, Jiali Wang, Lue Xie and Guangyu Liang

Micromachines 2024, 15(1), 113; https://doi.org/10.3390/mi15010113 - 09 Jan 2024

Viewed by 752

Abstract

SiCp/Al is a difficult-to-machine material that makes it easy to produce surface defects during machining, and researchers focus on reducing the surface defects. Vibration-assisted machining technology is considered an effective method to reduce surface defects by changing the trajectory and contact mode of [...] Read more.

SiCp/Al is a difficult-to-machine material that makes it easy to produce surface defects during machining, and researchers focus on reducing the surface defects. Vibration-assisted machining technology is considered an effective method to reduce surface defects by changing the trajectory and contact mode of the abrasive. Aiming at the problem of SiCp/Al processing technology, a vibration-assisted lapping device (VLD) is designed, and elliptical motion is synthesized by a set of parallel symmetrical displacement output mechanisms. The working parameters of the device were tested by simulation and experiment, and the lapping performance was verified. Then, the effects of removal characteristics and process parameters on surface roughness and lapping force were analyzed by simulation and experiment. Simulation and experimental results show that frequency and amplitude that are too low or too high are not conducive to the advantages of NVL. The best surface quality was 54 nm, obtained at A = 8 μm and f = 850 Hz. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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16 pages, 4689 KiB

Open AccessArticle

Investigation of Gallium Arsenide Deformation Anisotropy during Nanopolishing via Molecular Dynamics Simulation

by Bo Zhao, Xifeng Gao, Jiansheng Pan, Huan Liu and Pengyue Zhao

Micromachines 2024, 15(1), 110; https://doi.org/10.3390/mi15010110 - 08 Jan 2024

Viewed by 743

Abstract

Crystal orientation significantly influences deformation during nanopolishing due to crystal anisotropy. In this work, molecular dynamics (MD) simulations were employed to examine the process of surface generation and subsurface damage. We conducted analyses of surface morphology, mechanical response, and amorphization in various crystal [...] Read more.

Crystal orientation significantly influences deformation during nanopolishing due to crystal anisotropy. In this work, molecular dynamics (MD) simulations were employed to examine the process of surface generation and subsurface damage. We conducted analyses of surface morphology, mechanical response, and amorphization in various crystal orientations to elucidate the impact of crystal orientation on deformation and amorphization severity. Additionally, we investigated the concentration of residual stress and temperature. This work unveils the underlying deformation mechanism and enhances our comprehension of the anisotropic deformation in gallium arsenide during the nanogrinding process. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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14 pages, 8585 KiB

Open AccessArticle

Surface-Wetting Characteristics of DLP-Based 3D Printing Outcomes under Various Printing Conditions for Microfluidic Device Fabrication

by Jeon-Woong Kang, Jinpyo Jeon, Jun-Young Lee, Jun-Hyeong Jeon and Jiwoo Hong

Micromachines 2024, 15(1), 61; https://doi.org/10.3390/mi15010061 - 28 Dec 2023

Viewed by 1135

Abstract

In recent times, the utilization of three-dimensional (3D) printing technology, particularly a variant using digital light processing (DLP), has gained increasing fascination in the realm of microfluidic research because it has proven advantageous and expedient for constructing microscale 3D structures. The surface wetting [...] Read more.

In recent times, the utilization of three-dimensional (3D) printing technology, particularly a variant using digital light processing (DLP), has gained increasing fascination in the realm of microfluidic research because it has proven advantageous and expedient for constructing microscale 3D structures. The surface wetting characteristics (e.g., contact angle and contact angle hysteresis) of 3D-printed microstructures are crucial factors influencing the operational effectiveness of 3D-printed microfluidic devices. Therefore, this study systematically examines the surface wetting characteristics of DLP-based 3D printing objects, focusing on various printing conditions such as lamination (or layer) thickness and direction. We preferentially examine the impact of lamination thickness on the surface roughness of 3D-printed structures through a quantitative assessment using a confocal laser scanning microscope. The influence of lamination thicknesses and lamination direction on the contact angle and contact angle hysteresis of both aqueous and oil droplets on the surfaces of 3D-printed outputs is then quantified. Finally, the performance of a DLP 3D-printed microfluidic device under various printing conditions is assessed. Current research indicates a connection between printing parameters, surface roughness, wetting properties, and capillary movement in 3D-printed microchannels. This correlation will greatly aid in the progress of microfluidic devices produced using DLP-based 3D printing technology. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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13 pages, 4955 KiB

Open AccessArticle

A Fast Transient Adaptive On-Time Controlled BUCK Converter with Dual Modulation

by Mengyuan Sun, Chufan Chen, Leiyi Wang, Xinling Xie, Yuhang Wang and Min Xu

Micromachines 2023, 14(10), 1868; https://doi.org/10.3390/mi14101868 - 29 Sep 2023

Viewed by 1019

Abstract

This paper proposed a fully integrated adaptive on-time (AOT) controlled buck converter with fast load transient. An adaptive on-time generator is presented to stabilize the output frequency. To enhance the light load efficiency, the converter could transfer from the pulse width modulation (PWM) [...] Read more.

This paper proposed a fully integrated adaptive on-time (AOT) controlled buck converter with fast load transient. An adaptive on-time generator is presented to stabilize the output frequency. To enhance the light load efficiency, the converter could transfer from the pulse width modulation (PWM) to pulse skip modulation (PSM) as the load current decreases. The buck converter can switch between these two modulation modes adaptively with the assistance of a zero current detection circuit. Implemented in the TSMC 0.18 µm BCD (BiCMOS/DMOS) process, the proposed buck converter works with an input voltage ranging from 5.5 to 15 V, an output voltage ranging from 0.5 to 5 V, and an output load ranging up to 5 A. The experimental results show that based on the dual modulation adaptive on-time controlled mode, the transient recovery time from light to heavy load and from heavy load to light load is 13 µs and 15 µs, respectively. An overshot voltage of 57 mV and an undershot voltage of 53 mV are also achieved. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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19 pages, 4082 KiB

Open AccessArticle

Z-Increments Online Supervisory System Based on Machine Vision for Laser Solid Forming

by Junhua Wang, Junfei Xu, Yan Lu, Tancheng Xie, Jianjun Peng and Junliang Chen

Micromachines 2023, 14(8), 1558; https://doi.org/10.3390/mi14081558 - 04 Aug 2023

Viewed by 886

Abstract

An improper Z-increment in laser solid forming can result in fluctuations in the off-focus amount during the manufacturing procedure, thereby exerting an influence on the precision and quality of the fabricated component. To solve this problem, this study proposes a closed-loop control system [...] Read more.

An improper Z-increment in laser solid forming can result in fluctuations in the off-focus amount during the manufacturing procedure, thereby exerting an influence on the precision and quality of the fabricated component. To solve this problem, this study proposes a closed-loop control system for a Z-increment based on machine vision monitoring. Real-time monitoring of the precise cladding height is accomplished by constructing a paraxial monitoring system, utilizing edge detection technology and an inverse perspective transformation model. This system enables the continuous assessment of the cladding height, which serves as a control signal for the regulation of the Z-increments in real-time. This ensures the maintenance of a constant off-focus amount throughout the manufacturing process. The experimental findings indicate that the proposed approach yields a maximum relative error of 1.664% in determining the cladding layer height, thereby enabling accurate detection of this parameter. Moreover, the real-time adjustment of the Z-increment quantities results in reduced standard deviations of individual cladding layer heights, and the height of the cladding layer increases. This proactive adjustment significantly enhances the stability of the manufacturing process and improves the utilization of powder material. This study can, therefore, provide effective guidance for process control and product optimization in laser solid forming. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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10 pages, 9365 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Non-Buffer Epi-AlGaN/GaN on SiC for High-Performance Depletion-Mode MIS-HEMTs Fabrication

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

Micromachines 2023, 14(8), 1523; https://doi.org/10.3390/mi14081523 - 29 Jul 2023

Viewed by 965

Abstract

A systematic study of epi-AlGaN/GaN on a SiC substrate was conducted through a comprehensive analysis of material properties and device performance. In this novel epitaxial design, an AlGaN/GaN channel layer was grown directly on the AlN nucleation layer, without the conventional doped thick [...] Read more.

A systematic study of epi-AlGaN/GaN on a SiC substrate was conducted through a comprehensive analysis of material properties and device performance. In this novel epitaxial design, an AlGaN/GaN channel layer was grown directly on the AlN nucleation layer, without the conventional doped thick buffer layer. Compared to the conventional epi-structures on the SiC and Si substrates, the non-buffer epi-AlGaN/GaN structure had a better crystalline quality and surface morphology, with reliable control of growth stress. Hall measurements showed that the novel structure exhibited comparable transport properties to the conventional epi-structure on the SiC substrate, regardless of the buffer layer. Furthermore, almost unchanged carrier distribution from room temperature to 150 °C indicated excellent two-dimensional electron gas (2DEG) confinement due to the pulling effect of the conduction band from the nucleation layer as a back-barrier. High-performance depletion-mode MIS-HEMTs were demonstrated with on-resistance of 5.84 Ω·mm and an output current of 1002 mA/mm. The dynamic characteristics showed a much smaller decrease in the saturation current (only ~7%), with a quiescent drain bias of 40 V, which was strong evidence of less electron trapping owing to the high-quality non-buffer AlGaN/GaN epitaxial growth. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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8 pages, 3540 KiB

Open AccessFeature PaperEditor’s ChoiceCommunication

Improving Performance of Al₂O₃/AlN/GaN MIS HEMTs via In Situ N₂ Plasma Annealing

by Mengyuan Sun, Luyu Wang, Penghao Zhang and Kun Chen

Micromachines 2023, 14(6), 1100; https://doi.org/10.3390/mi14061100 - 23 May 2023

Viewed by 1360

Abstract

A novel monocrystalline AlN interfacial layer formation method is proposed to improve the device performance of the fully recessed-gate Al₂O₃/AlN/GaN Metal-Insulator-Semiconductor High Electron Mobility Transistors (MIS-HEMTs), which is achieved by plasma-enhanced atomic layer deposition (PEALD) and in situ N [...] Read more.

A novel monocrystalline AlN interfacial layer formation method is proposed to improve the device performance of the fully recessed-gate Al₂O₃/AlN/GaN Metal-Insulator-Semiconductor High Electron Mobility Transistors (MIS-HEMTs), which is achieved by plasma-enhanced atomic layer deposition (PEALD) and in situ N₂ plasma annealing (NPA). Compared with the traditional RTA method, the NPA process not only avoids the device damage caused by high temperatures but also obtains a high-quality AlN monocrystalline film that avoids natural oxidation by in situ growth. As a contrast with the conventional PELAD amorphous AlN, C-V results indicated a significantly lower interface density of states (D_it) in a MIS C-V characterization, which could be attributed to the polarization effect induced by the AlN crystal from the X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM) characterizations. The proposed method could reduce the subthreshold swing, and the Al₂O₃/AlN/GaN MIS-HEMTs were significantly enhanced with ~38% lower on-resistance at V_g = 10 V. What is more, in situ NPA provides a more stable threshold voltage (V_th) after a long gate stress time, and ΔV_th is inhibited by about 40 mV under V_g,stress = 10 V for 1000 s, showing great potential for improving Al₂O₃/AlN/GaN MIS-HEMT gate reliability. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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13 pages, 5147 KiB

Open AccessArticle

Investigation into Photolithography Process of FPCB with 18 µm Line Pitch

by Ke Sun, Gai Wu, Kang Liang, Bin Sun and Jian Wang

Micromachines 2023, 14(5), 1020; https://doi.org/10.3390/mi14051020 - 10 May 2023

Viewed by 1410

Abstract

Due to the widespread application of flexible printed circuit boards (FPCBs), attention is increasing being paid to photolithography simulation with the continuous development of ultraviolet (UV) photolithography manufacturing. This study investigates the exposure process of an FPCB with an 18 µm line pitch. [...] Read more.

Due to the widespread application of flexible printed circuit boards (FPCBs), attention is increasing being paid to photolithography simulation with the continuous development of ultraviolet (UV) photolithography manufacturing. This study investigates the exposure process of an FPCB with an 18 µm line pitch. Using the finite difference time domain method, the light intensity distribution was calculated to predict the profiles of the developed photoresist. Moreover, the parameters of incident light intensity, air gap, and types of media that significantly influence the profile quality were studied. Using the process parameters obtained by photolithography simulation, FPCB samples with an 18 µm line pitch were successfully prepared. The results show that a higher incident light intensity and a smaller air gap result in a larger photoresisst profile. Better profile quality was obtained when water was used as the medium. The reliability of the simulation model was validated by comparing the profiles of the developed photoresist via four experimental samples. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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10 pages, 2217 KiB

Open AccessArticle

Simulation and Experimental Validation of a Pressurized Filling Method for Neutron Absorption Grating

by Eryong Han, Kuanqiang Zhang, Lijuan Chen, Chenfei Guo, Ying Xiong, Yong Guan, Yangchao Tian and Gang Liu

Micromachines 2023, 14(5), 1016; https://doi.org/10.3390/mi14051016 - 09 May 2023

Cited by 1 | Viewed by 1115

Abstract

The absorption grating is a critical component of neutron phase contrast imaging technology, and its quality directly influences the sensitivity of the imaging system. Gadolinium (Gd) is a preferred neutron absorption material due to its high absorption coefficient, but its use in micro-nanofabrication [...] Read more.

The absorption grating is a critical component of neutron phase contrast imaging technology, and its quality directly influences the sensitivity of the imaging system. Gadolinium (Gd) is a preferred neutron absorption material due to its high absorption coefficient, but its use in micro-nanofabrication poses significant challenges. In this study, we employed the particle filling method to fabricate neutron absorption gratings, and a pressurized filling method was introduced to enhance the filling rate. The filling rate was determined by the pressure on the surface of the particles, and the results demonstrate that the pressurized filling method can significantly increase the filling rate. Meanwhile, we investigated the effects of different pressures, groove widths, and Young’s modulus of the material on the particle filling rate through simulations. The results indicate that higher pressure and wider grating grooves lead to a significant increase in particle filling rate, and the pressurized filling method can be utilized to fabricate large-size grating and produce uniformly filled absorption gratings. To further improve the efficiency of the pressurized filling method, we proposed a process optimization approach, resulting in a significant improvement in the fabrication efficiency. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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15 pages, 5551 KiB

Open AccessArticle

Plotter Cut Stencil Masks for the Deposition of Organic and Inorganic Materials and a New Rapid, Cost Effective Technique for Antimicrobial Evaluations

by Andre Childs, Jorge Pereira, Charles M. Didier, Aliyah Baksh, Isaac Johnson, Jorge Manrique Castro, Edwin Davidson, Swadeshmukul Santra and Swaminathan Rajaraman

Micromachines 2023, 14(1), 14; https://doi.org/10.3390/mi14010014 - 21 Dec 2022

Cited by 1 | Viewed by 1979

Abstract

Plotter cutters in stencil mask prototyping are underutilized but have several advantages over traditional MEMS techniques. In this paper we investigate the use of a conventional plotter cutter as a highly effective benchtop tool for the rapid prototyping of stencil masks in the [...] Read more.

Plotter cutters in stencil mask prototyping are underutilized but have several advantages over traditional MEMS techniques. In this paper we investigate the use of a conventional plotter cutter as a highly effective benchtop tool for the rapid prototyping of stencil masks in the sub-250 μm range and characterize patterned layers of organic/inorganic materials. Furthermore, we show a new diagnostic monitoring application for use in healthcare, and a potential replacement of the Standard Kirby-Bauer Diffusion Antibiotic Resistance tests was developed and tested on both Escherichia coli and Xanthomonas alfalfae as pathogens with Oxytetracycline, Streptomycin and Kanamycin. We show that the reduction in area required for the minimum inhibitory concentration tests; allow for three times the number of tests to be performed within the same nutrient agar Petri dish, demonstrated both theoretically and experimentally resulting in correlations of R ≈ 0.96 and 0.985, respectively for both pathogens. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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14 pages, 4533 KiB

Open AccessArticle

Microextrusion Printing of Multilayer Hierarchically Organized Planar Nanostructures Based on NiO, (CeO₂)_0.8(Sm₂O₃)_0.2 and La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ

by Tatiana L. Simonenko, Nikolay P. Simonenko, Philipp Yu. Gorobtsov, Elizaveta P. Simonenko and Nikolay T. Kuznetsov

Micromachines 2023, 14(1), 3; https://doi.org/10.3390/mi14010003 - 20 Dec 2022

Cited by 5 | Viewed by 1692

Abstract

In this paper, NiO, La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) and (CeO₂)_0.8(Sm₂O₃)_0.2 (SDC) nanopowders with different microstructures were obtained using hydrothermal and glycol–citrate methods. The microstructural features of the [...] Read more.

In this paper, NiO, La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) and (CeO₂)_0.8(Sm₂O₃)_0.2 (SDC) nanopowders with different microstructures were obtained using hydrothermal and glycol–citrate methods. The microstructural features of the powders were examined using scanning electron microscopy (SEM). The obtained oxide powders were used to form functional inks for the sequential microextrusion printing of NiO-SDC, SDC and LSCF-SDC coatings with resulting three-layer structures of (NiO-SDC)/SDC/(LSCF-SDC) composition. The crystal structures of these layers were studied using an X-ray diffraction analysis, and the microstructures were studied using atomic force microscopy. Scanning capacitance microscopy was employed to build maps of capacitance gradient distribution over the surface of the oxide layers, and Kelvin probe force microscopy was utilized to map surface potential distribution and to estimate the work function values of the studied oxide layers. Using SEM and an energy-dispersive X-ray microanalysis, the cross-sectional area of the formed three-layer structure was analyzed—the interfacial boundary and the chemical element distribution over the surface of the cross-section were investigated. Using impedance spectroscopy, the temperature dependence of the electrical conductivity was also determined for the printed three-layer nanostructure. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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14 pages, 5102 KiB

Open AccessArticle

Polishing Performance and Removal Mechanism of Core-Shell Structured Diamond/SiO₂ Abrasives on Sapphire Wafer

by Guangen Zhao, Yongchao Xu, Qianting Wang, Jun Liu, Youji Zhan and Bingsan Chen

Micromachines 2022, 13(12), 2160; https://doi.org/10.3390/mi13122160 - 07 Dec 2022

Cited by 2 | Viewed by 1397

Abstract

Corrosive and toxic solutions are normally employed to polish sapphire wafers, which easily cause environmental pollution. Applying green polishing techniques to obtain an ultrasmooth sapphire surface that is scratch-free and has low damage at high polishing efficiency is a great challenge. In this [...] Read more.

Corrosive and toxic solutions are normally employed to polish sapphire wafers, which easily cause environmental pollution. Applying green polishing techniques to obtain an ultrasmooth sapphire surface that is scratch-free and has low damage at high polishing efficiency is a great challenge. In this paper, novel diamond/SiO₂ composite abrasives were successfully synthesized by a simplified sol-gel strategy. The prepared composite abrasives were used in the semi-fixed polishing technology of sapphire wafers, where the polishing slurry contains only deionized water and no other chemicals during the whole polishing process, effectively avoiding environmental pollution. The experimental results showed that diamond/SiO₂ composite abrasives exhibited excellent polishing performance, along with a 27.2% decrease in surface roughness, and the material removal rate was increased by more than 8.8% compared with pure diamond. Furthermore, through characterizations of polished sapphire surfaces and wear debris, the chemical action mechanism of composite abrasives was investigated, which confirmed the solid-state reaction between the SiO₂ shell and the sapphire surface. Finally, applying the elastic-plastic contact model revealed that the reduction of indentation depth and the synergistic effect of chemical corrosion and mechanical removal are the keys to improving polishing performance. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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6 pages, 1050 KiB

Open AccessArticle

Source/Drain Trimming Process to Improve Gate-All-Around Nanosheet Transistors Switching Performance and Enable More Stacks of Nanosheets

by Kun Chen, Jingwen Yang, Tao Liu, Dawei Wang, Min Xu, Chunlei Wu, Chen Wang, Saisheng Xu, David Wei Zhang and Wenchao Liu

Micromachines 2022, 13(7), 1080; https://doi.org/10.3390/mi13071080 - 08 Jul 2022

Viewed by 2036

Abstract

A new S/D trimming process was proposed to significantly reduce the parasitic RC of gate-all-around (GAA) nanosheet transistors (NS-FETs) while retaining the channel stress from epitaxy S/D stressors at most. With optimized S/D trimming, the 7-stage ring oscillator (RO) gained up to 27.8% [...] Read more.

A new S/D trimming process was proposed to significantly reduce the parasitic RC of gate-all-around (GAA) nanosheet transistors (NS-FETs) while retaining the channel stress from epitaxy S/D stressors at most. With optimized S/D trimming, the 7-stage ring oscillator (RO) gained up to 27.8% improvement of delay with the same power consumption, for a 3-layer stacked GAA NS-FETs. Furthermore, the proposed S/D trimming technology could enable more than 4-layer vertical stacking of nanosheets for GAA technology extension beyond 3 nm CMOS technology. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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9 pages, 3879 KiB

Open AccessCommunication

A High-Performance MEMS Accelerometer with an Improved TGV Process of Low Cost

by Yingchun Fu, Guowei Han, Jiebin Gu, Yongmei Zhao, Jin Ning, Zhenyu Wei, Fuhua Yang and Chaowei Si

Micromachines 2022, 13(7), 1071; https://doi.org/10.3390/mi13071071 - 05 Jul 2022

Cited by 4 | Viewed by 1705

Abstract

High-performance MEMS accelerometers usually use a pendulum structure with a larger mass. Although the performance of the device is guaranteed, the manufacturing cost is high. This paper proposes a method of fabricating high-performance MEMS accelerometers with a TGV process, which can reduce the [...] Read more.

High-performance MEMS accelerometers usually use a pendulum structure with a larger mass. Although the performance of the device is guaranteed, the manufacturing cost is high. This paper proposes a method of fabricating high-performance MEMS accelerometers with a TGV process, which can reduce the manufacturing cost and ensure the low-noise characteristics of the device. The TGV processing relies on laser drilling, the metal filling in the hole is based on the casting mold and CMP, and the packaging adopts the three-layer anodic bonding process. Moreover, for the first time, the casting mold process is introduced to the preparation of MEMS devices. In terms of structural design, the stopper uses distributed comb electrodes for overload displacement suppression, and the gas released by the packaging method provides excellent mechanical damping characteristics. The prepared accelerometer has an anti-overload capability of 10,000 g, the noise density is less than 0.001°/√Hz, and it has ultra-high performance in tilt measurement. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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14 pages, 5435 KiB

Open AccessArticle

Design and Fabrication of Silicon-Blazed Gratings for Near-Infrared Scanning Grating Micromirror

by Sinong Zha, Dongling Li, Quan Wen, Ying Zhou and Haomiao Zhang

Micromachines 2022, 13(7), 1000; https://doi.org/10.3390/mi13071000 - 25 Jun 2022

Cited by 2 | Viewed by 2715

Abstract

Blazed gratings are the critical dispersion elements in spectral analysis instruments, whose performance depends on structural parameters and topography of the grating groove. In this paper, high diffraction efficiency silicon-blazed grating working at 800–2500 nm has been designed and fabricated. By diffraction theory [...] Read more.

Blazed gratings are the critical dispersion elements in spectral analysis instruments, whose performance depends on structural parameters and topography of the grating groove. In this paper, high diffraction efficiency silicon-blazed grating working at 800–2500 nm has been designed and fabricated. By diffraction theory analysis and simulation optimization based on the accurate boundary integral equation method, the blaze angle and grating constant are determined to be 8.8° and 4 μm, respectively. The diffraction efficiency is greater than 33.23% in the spectral range of 800–2500 nm and reach the maximum value of 85.62% at the blaze wavelength of 1180 nm. The effect of platform and fillet on diffraction efficiency is analyzed, and the formation rule and elimination method of the platform are studied. The blazed gratings are fabricated by anisotropic wet etching process using tilted (111) silicon substrate. The platform is minished by controlling etching time and oxidation sharpening process. The fillet radius of the fabricated grating is 50 nm, the blaze angle is 7.4°, and the surface roughness is 0.477 nm. Finally, the blazed grating is integrated in scanning micromirror to form scanning grating micromirror by MEMS fabrication technology, which can realize both optical splitting and scanning. The testing results show that the scanning grating micromirror has high diffraction efficiency in the spectral range of 810–2500 nm for the potential near-infrared spectrometer application. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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14 pages, 5348 KiB

Open AccessArticle

Development of a Fault Detection Instrument for Fiber Bragg Grating Sensing System on Airplane

by Cuicui Du, Deren Kong and Chundong Xu

Micromachines 2022, 13(6), 882; https://doi.org/10.3390/mi13060882 - 31 May 2022

Cited by 2 | Viewed by 1517

Abstract

This study develops a fault detection device for the fiber Bragg grating (FBG) sensing system and a fault detection method to realize the rapid detection of the FBG sensing system on airplanes. According to the distribution of FBG sensors on airplanes, the FBG [...] Read more.

This study develops a fault detection device for the fiber Bragg grating (FBG) sensing system and a fault detection method to realize the rapid detection of the FBG sensing system on airplanes. According to the distribution of FBG sensors on airplanes, the FBG sensing system is built based on wavelength division multiplexing (WDM) and space division multiplexing (SDM) technologies. Furthermore, the hardware and software of the fault detection device and the relevant FBG demodulator are studied in detail. Additionally, in view of the similar features of the healthy FBG sensor in the same measuring point, a rapid fault diagnosis method based on a synthetical anomaly index is proposed. The features (light intensity I, signal length L, standard deviation of original sample

σ

and energy value in time-domain P) of FBG sensors are extracted. The aggregation center value of the above feature values is obtained through the loop iteration method. Furthermore, the separation degrees of features are calculated and then form the synthetical anomaly index so as to make an effective diagnosis of the state of the FBG sensor. Finally, the designed fault detection instrument and proposed fault detection method are used to monitor the 25 FBG sensors on the airplane, the results indicated that three faulty and two abnormal FBG sensors on the airplane are identified, showing the effectiveness of the proposed fault detection method. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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8 pages, 7336 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

High Selectivity, Low Damage ICP Etching of p-GaN over AlGaN for Normally-off p-GaN HEMTs Application

by Penghao Zhang, Luyu Wang, Kaiyue Zhu, Yannan Yang, Rong Fan, Maolin Pan, Saisheng Xu, Min Xu, Chen Wang, Chunlei Wu and David Wei Zhang

Micromachines 2022, 13(4), 589; https://doi.org/10.3390/mi13040589 - 09 Apr 2022

Cited by 6 | Viewed by 3171

Abstract

A systematic study of the selective etching of p-GaN over AlGaN was carried out using a BCl₃/SF₆ inductively coupled plasma (ICP) process. Compared to similar chemistry, a record high etch selectivity of 41:1 with a p-GaN etch rate [...] Read more.

A systematic study of the selective etching of p-GaN over AlGaN was carried out using a BCl₃/SF₆ inductively coupled plasma (ICP) process. Compared to similar chemistry, a record high etch selectivity of 41:1 with a p-GaN etch rate of 3.4 nm/min was realized by optimizing the SF₆ concentration, chamber pressure, ICP and bias power. The surface morphology after p-GaN etching was characterized by AFM for both selective and nonselective processes, showing the exposed AlGaN surface RMS values of 0.43 nm and 0.99 nm, respectively. MIS-capacitor devices fabricated on the AlGaN surface with ALD-Al₂O₃ as the gate dielectric after p-GaN etch showed the significant benefit of BCl₃/SF₆ selective etch process. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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14 pages, 6810 KiB

Open AccessArticle

Experimental Study on Diesel Engine Emission Characteristics Based on Different Exhaust Pipe Coating Schemes

by Keqin Zhao, Diming Lou, Yunhua Zhang, Liang Fang and Yuanzhi Tang

Micromachines 2021, 12(10), 1155; https://doi.org/10.3390/mi12101155 - 25 Sep 2021

Cited by 1 | Viewed by 1639

Abstract

The thermal insulation performance of exhaust pipes coated with various materials (basalt and glass fiber materials) under different braiding forms (sleeve, winding and felt types) and the effects on the emission characteristics of diesel engines were experimentally studied through engine bench tests. The [...] Read more.

The thermal insulation performance of exhaust pipes coated with various materials (basalt and glass fiber materials) under different braiding forms (sleeve, winding and felt types) and the effects on the emission characteristics of diesel engines were experimentally studied through engine bench tests. The results indicated that the thermal insulation performance of basalt fiber was higher than that of glass fiber, and more notably advantageous at the early stage of the diesel engine idle cold phase. The average temperature drop during the first 600 s of the basalt felt (BF) pipe was 2.6 °C smaller than that of the glass fiber felt (GF) pipe. Comparing the different braiding forms, the temperature decrease in the felt-type braided material was 2.6 °C and 2.9 °C smaller than that in the sleeve- and winding-type braided materials, respectively. The basalt material was better than the glass fiber material regarding the gaseous pollutant emission reduction performance, especially in the idling cold phase of diesel engines. The NO_x conversion rate of the BF pipe was 7.4% higher than that of the GF pipe, and the hydrocarbon (HC) conversion rate was 2.3% higher than that of the GF pipe, while the CO conversion rate during the first 100 s was 24.5% higher than that of the GF pipe. However, the particulate matter emissions were not notably different. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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Review

Jump to: Research

29 pages, 8077 KiB

Open AccessReview

Radiation Synthesis of High-Temperature Wide-Bandgap Ceramics

by Victor Lisitsyn, Aida Tulegenova, Mikhail Golkovski, Elena Polisadova, Liudmila Lisitsyna, Dossymkhan Mussakhanov and Gulnur Alpyssova

Micromachines 2023, 14(12), 2193; https://doi.org/10.3390/mi14122193 - 30 Nov 2023

Viewed by 729

Abstract

This paper presents the results of ceramic synthesis in the field of a powerful flux of high-energy electrons on powder mixtures. The synthesis is carried out via the direct exposure of the radiation flux to a mixture with high speed (up to 10 [...] Read more.

This paper presents the results of ceramic synthesis in the field of a powerful flux of high-energy electrons on powder mixtures. The synthesis is carried out via the direct exposure of the radiation flux to a mixture with high speed (up to 10 g/s) and efficiency without the use of any methods or means for stimulation. These synthesis qualities provide the opportunity to optimize compositions and conditions in a short time while maintaining the purity of the ceramics. The possibility of synthesizing ceramics from powders of metal oxides and fluorides (MgF₂, BaF₂, WO₃, Ga₂O₃, Al₂O₃, Y₂O₃, ZrO₂, MgO) and complex compounds from their stoichiometric mixtures (Y₃Al₃O₁₂, Y₃Al_xGa_(5-x) O₁₂, MgAl₂O₄, ZnAl₂O₄, MgWO₄, ZnWO₄, Ba_xMg_(2-x) F₄), including activators, is demonstrated. The ceramics synthesized in the field of high-energy electron flux have a structure and luminescence properties similar to those obtained by other methods, such as thermal methods. The results of studying the processes of energy transfer of the electron beam mixture, quantitative assessments of the distribution of absorbed energy, and the dissipation of this energy are presented. The optimal conditions for beam treatment of the mixture during synthesis are determined. It is shown that the efficiency of radiation synthesis of ceramics depends on the particle dispersion of the initial powders. Powders with particle sizes of 1–10 µm, uniform for the synthesis of ceramics of complex compositions, are optimal. A hypothesis is put forward that ionization processes, resulting in the radiolysis of particles and the exchange of elements in the ion–electron plasma, dominate in the formation of new structural phases during radiation synthesis. Full article

(This article belongs to the Special Issue Advanced Micro- and Nano-Manufacturing Technologies)

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