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Micromachines
Volume 14
Issue 11
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Micromachines, Volume 14, Issue 11 (November 2023) – 158 articles

Cover Story (view full-size image): As sensing technology has numerous applications, various materials and patterning methods are used for sensor fabrication. This affects the characteristics and performance of sensors, and research centered specifically on these patterns is necessary for the high integration and high performance of these devices. In this paper, the authors review the patterning techniques used in recently reported sensors, specifically the most widely used capacitive sensors, and their impact on sensor performance. Methods for increasing sensor performance through three-dimensional (3D) structures are also introduced. View this paper
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17 pages, 15441 KiB  
Article
Temperature Cycle Reliability Analysis of an FBAR Filter-Bonded Ceramic Package
by Wenchao Tian, Wenbin Li, Shuaiqi Zhang, Liming Zhou and Heng Wang
Micromachines 2023, 14(11), 2132; https://doi.org/10.3390/mi14112132 - 20 Nov 2023
Viewed by 942
Abstract
On the background that the operating frequency of electronic devices tends to the radio frequency (RF) segment, a film bulk acoustic resonator (FBAR) filter is widely used in communication and military fields because of its advantages of high upper frequency, ample power capacity, [...] Read more.
On the background that the operating frequency of electronic devices tends to the radio frequency (RF) segment, a film bulk acoustic resonator (FBAR) filter is widely used in communication and military fields because of its advantages of high upper frequency, ample power capacity, small size, and low cost. However, the complex and harsh working environment puts higher requirements for packaging FBAR filters. Based on the Anand constitutive equation, the stress–strain response of the bonded ceramic package was studied by the finite element method for the FBAR filter-bonded ceramic package, and the thermal fatigue life of the device was predicted. We developed solder models with various spillage morphologies based on the random generation technique to examine the impact of spillage on device temperature reliability. The following are the primary conclusions: (1) Solder undergoes periodic deformation, stress, and strain changes throughout the cycle. (2) The corner of the contact surface between the chip and the solder layer has the largest stress at the end of the cycle, measuring 19.377 MPa. (3) The Engelmaier model predicts that the gadget will have a thermal fatigue life of 1928.67 h. (4) Expanding the layered solder area caused by any solder overflow mode may shorten the device’s thermal fatigue life. The thermal fatigue life of a completely spilled solder is higher than that of a partially spilled solder. Full article
(This article belongs to the Special Issue Advances in Microelectronics Reliability)
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4 pages, 204 KiB  
Editorial
Editorial for the Special Issue on Magnetic and Spin Devices, Volume II
by Viktor Sverdlov and Seung-Bok Choi
Micromachines 2023, 14(11), 2131; https://doi.org/10.3390/mi14112131 - 20 Nov 2023
Viewed by 683
Abstract
Although the miniaturization of metal–oxide–semiconductor field effect transistors (MOSFETs)—the main driver behind an outstanding increase in the speed, performance, density, and complexity of modern integrated circuits—is continuing, numerous outstanding technological challenges in complimentary metal–oxide–semiconductor (CMOS) device miniaturization are slowly bringing the downscaling to [...] Read more.
Although the miniaturization of metal–oxide–semiconductor field effect transistors (MOSFETs)—the main driver behind an outstanding increase in the speed, performance, density, and complexity of modern integrated circuits—is continuing, numerous outstanding technological challenges in complimentary metal–oxide–semiconductor (CMOS) device miniaturization are slowly bringing the downscaling to saturation [...] Full article
(This article belongs to the Special Issue Magnetic and Spin Devices, Volume II)
14 pages, 2576 KiB  
Article
Phononic-Crystal-Based SAW Magnetic-Field Sensors
by Mohsen Samadi, Julius Schmalz, Jana Marie Meyer, Fabian Lofink and Martina Gerken
Micromachines 2023, 14(11), 2130; https://doi.org/10.3390/mi14112130 - 20 Nov 2023
Viewed by 959
Abstract
In this theoretical study, we explore the enhancement of sensing capabilities in surface acoustic wave (SAW)-based magnetic field sensors through the integration of engineered phononic crystals (PnCs). We particularly focus on amplifying the interaction between the SAW and magnetostrictive materials within the PnC [...] Read more.
In this theoretical study, we explore the enhancement of sensing capabilities in surface acoustic wave (SAW)-based magnetic field sensors through the integration of engineered phononic crystals (PnCs). We particularly focus on amplifying the interaction between the SAW and magnetostrictive materials within the PnC structure. Through comprehensive simulations, we demonstrate the synchronization between the SAWs generated by IDTs and the resonant modes of PnCs, thereby leading to an enhancement in sensitivity. Furthermore, we investigate the ΔE effect, highlighting the sensor’s responsiveness to changes in external magnetic fields, and quantify its magnetic sensitivity through observable changes in the SAW phase velocity leading to phase shifts at the end of the delay line. Notably, our approach yields a magnetic field sensitivity of approximately S~138 °mT for a delay line length of only 77 µm in homogeneous magnetic fields. Our findings underline the potential of PnCs to advance magnetic field sensing. This research offers insights into the integration of engineered materials for improved sensor performance, paving the way for more effective and accurate magnetic field detection solutions. Full article
(This article belongs to the Special Issue Novel Surface and Bulk Acoustic Wave Devices)
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21 pages, 6380 KiB  
Review
A Review of Silver Wire Bonding Techniques
by Bin An, Hongliang Zhou, Jun Cao, Pingmei Ming, John Persic, Jingguang Yao and Andong Chang
Micromachines 2023, 14(11), 2129; https://doi.org/10.3390/mi14112129 - 20 Nov 2023
Viewed by 1158
Abstract
The replacement of gold bonding wire with silver bonding wire can significantly reduce the cost of wire bonding. This paper provides a comprehensive overview of silver wire bonding technology. Firstly, it introduces various types of silver-based bonding wire currently being studied by researchers, [...] Read more.
The replacement of gold bonding wire with silver bonding wire can significantly reduce the cost of wire bonding. This paper provides a comprehensive overview of silver wire bonding technology. Firstly, it introduces various types of silver-based bonding wire currently being studied by researchers, including pure silver wire, alloy silver wire, and coated silver wire, and describes their respective characteristics and development statuses. Secondly, the development of silver-based bonding wire in manufacturing and bonding processes is analyzed, including common silver wire manufacturing processes and their impact on silver wire performance, as well as the impact of bonding parameters on silver wire bonding quality and reliability. Subsequently, the reliability of silver wire bonding is discussed, with a focus on analyzing the effects of corrosion, electromigration, and intermetallic compounds on bonding reliability, including the causes and forms of chlorination and sulfurization, the mechanism and path of electromigration, the formation and evolution of intermetallic compounds, and evaluating their impact on bonding strength and reliability. Finally, the development status of silver wire bonding technology is summarized and future research directions for silver wire are proposed. Full article
(This article belongs to the Special Issue MEMS Packaging Technologies and 3D Integration, 2nd Edition)
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17 pages, 5264 KiB  
Article
Numerical Study on a Liquid Cooling Plate with a Double-Layer Minichannel for a Lithium Battery Module
by Yu Xu and Ruijin Wang
Micromachines 2023, 14(11), 2128; https://doi.org/10.3390/mi14112128 - 20 Nov 2023
Viewed by 953
Abstract
The liquid cooling system of lithium battery modules (LBM) directly affects the safety, efficiency, and operational cost of lithium-ion batteries. To meet the requirements raised by a factory for the lithium battery module (LBM), a liquid cooling plate with a two-layer minichannel heat [...] Read more.
The liquid cooling system of lithium battery modules (LBM) directly affects the safety, efficiency, and operational cost of lithium-ion batteries. To meet the requirements raised by a factory for the lithium battery module (LBM), a liquid cooling plate with a two-layer minichannel heat sink has been proposed to maintain temperature uniformity in the module and ensure it stays within the temperature limit. This innovative design features a single inlet and a single outlet. To evaluate the performance of the liquid cooling system, we considered various discharge rates while taking into account the structure, flow rate, and temperature of the coolant. Our findings indicate that at a mass outflow rate of 20 g/s, a better cooling effect and lower power consumption can be achieved. An inlet temperature of 20 °C, close to the initial temperature of the battery string, may be the most appropriate because a higher temperature of the coolant will cause a higher temperature of LBM, so far as to exceed the safe threshold value. In the case of larger rate discharge, the design of a double-layer MCHS at the bottom and an auxiliary one at the side can effectively reduce the maximum temperature LBM (within 28 °C) and maintain the temperature difference in the single cell at approximately 4 °C. In the case of non-constant discharges, the temperature difference between cells increases with the maximum temperature. When the discharge rate is reduced, the large temperature difference helps the temperature to drop rapidly. This can provide guidance for the design of cooling systems for the LBM. Full article
(This article belongs to the Special Issue Heat and Mass Transfer in Micro/Nanochannels)
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13 pages, 16250 KiB  
Article
Broadband Continuous Transverse Stub (CTS) Array Antenna for High-Power Applications
by Yunfei Sun, Kelin Zhou, Juntao He, Zihan Yang, Chengwei Yuan and Qiang Zhang
Micromachines 2023, 14(11), 2127; https://doi.org/10.3390/mi14112127 - 20 Nov 2023
Viewed by 851
Abstract
A continuous transverse stub (CTS) array antenna with broad bandwidth and high-power handling capacity is proposed in this paper. The technologies of multi-step impedance matching and T-shaped electromagnetic band-gap (EBG) loading are utilized, which improved the antenna operating frequency bandwidth. An H-plane lens [...] Read more.
A continuous transverse stub (CTS) array antenna with broad bandwidth and high-power handling capacity is proposed in this paper. The technologies of multi-step impedance matching and T-shaped electromagnetic band-gap (EBG) loading are utilized, which improved the antenna operating frequency bandwidth. An H-plane lens horn is used to feed the CTS array. As a result, a good bandwidth capability of more than 32% is achieved, with a gain variation less than 3.0 dB. The measured sidelobe level (SLL) is below −18 dB in the entire frequency range. Moreover, the power handling capacity of the antenna is more than 80 MW and can reach the GW level after arraying, which indicates that this antenna has application potential in the high-power microwave (HPM) field. Full article
(This article belongs to the Special Issue Microwave Passive Components, 2nd Edition)
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12 pages, 3960 KiB  
Article
Influence of Temperature and Incidence Angle on the Irradiation Cascade Effect of 6H-SiC: Molecular Dynamics Simulations
by Yaolin Chen, Hongxia Liu, Cong Yan and Hao Wei
Micromachines 2023, 14(11), 2126; https://doi.org/10.3390/mi14112126 - 19 Nov 2023
Viewed by 800
Abstract
SiC devices have been typically subjected to extreme environments and complex stresses during operation, such as intense radiation and large diurnal amplitude differences on the lunar surface. Radiation displacement damage may lead to degradation or failure of the performance of semiconductor devices. In [...] Read more.
SiC devices have been typically subjected to extreme environments and complex stresses during operation, such as intense radiation and large diurnal amplitude differences on the lunar surface. Radiation displacement damage may lead to degradation or failure of the performance of semiconductor devices. In this paper, the effects of temperature and incidence angle on the irradiation cascade effect of 6H-SiC were investigated separately using the principles of molecular dynamics. Temperatures were set to 100 K, 150 K, 200 K, 250 K, 300 K, 350 K, 400 K and 450 K. The incidence direction was parallel to the specified crystal plane, with angles of 8°, 15°, 30°, 45°, 60° and 75° to the negative direction of the Z-axis. In this paper, the six types of defects were counted, and the microscopic distribution images and trajectories of each type of defect were extracted. The results show a linear relationship between the peak of the Frenkel pair and temperature. The recombination rate of Frenkel pairs depends on the local temperature and degree of aggregation at the center of the cascade collision. Increasing the angle of incidence first inhibits and then promotes the production of total defects and Frenkel pairs. The lowest number of total defects, Frenkel pairs and antisite defects are produced at a 45° incident angle. At an incidence angle of 75°, larger size hollow clusters and anti-clusters are more likely to appear in the 6H-SiC. Full article
(This article belongs to the Section D1: Semiconductor Devices)
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10 pages, 3656 KiB  
Article
Controllable Carrier Doping in Two-Dimensional Materials Using Electron-Beam Irradiation and Scalable Oxide Dielectrics
by Lu Wang, Zejing Guo, Qing Lan, Wenqing Song, Zhipeng Zhong, Kunlin Yang, Tuoyu Zhao, Hai Huang, Cheng Zhang and Wu Shi
Micromachines 2023, 14(11), 2125; https://doi.org/10.3390/mi14112125 - 19 Nov 2023
Cited by 1 | Viewed by 1281
Abstract
Two-dimensional (2D) materials, characterized by their atomically thin nature and exceptional properties, hold significant promise for future nano-electronic applications. The precise control of carrier density in these 2D materials is essential for enhancing performance and enabling complex device functionalities. In this study, we [...] Read more.
Two-dimensional (2D) materials, characterized by their atomically thin nature and exceptional properties, hold significant promise for future nano-electronic applications. The precise control of carrier density in these 2D materials is essential for enhancing performance and enabling complex device functionalities. In this study, we present an electron-beam (e-beam) doping approach to achieve controllable carrier doping effects in graphene and MoS2 field-effect transistors (FETs) by leveraging charge-trapping oxide dielectrics. By adding an atomic layer deposition (ALD)-grown Al2O3 dielectric layer on top of the SiO2/Si substrate, we demonstrate that controllable and reversible carrier doping effects can be effectively induced in graphene and MoS2 FETs through e-beam doping. This new device configuration establishes an oxide interface that enhances charge-trapping capabilities, enabling the effective induction of electron and hole doping beyond the SiO2 breakdown limit using high-energy e-beam irradiation. Importantly, these high doping effects exhibit non-volatility and robust stability in both vacuum and air environments for graphene FET devices. This methodology enhances carrier modulation capabilities in 2D materials and holds great potential for advancing the development of scalable 2D nano-devices. Full article
(This article belongs to the Special Issue 2D Materials: Devices and Functionalities)
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11 pages, 3419 KiB  
Article
Metal Oxide Nanowire-Based Sensor Array for Hydrogen Detection
by Dario Zappa, Navpreet Kaur, Abderrahim Moumen and Elisabetta Comini
Micromachines 2023, 14(11), 2124; https://doi.org/10.3390/mi14112124 - 19 Nov 2023
Viewed by 963
Abstract
Accurate hydrogen leakage detection is a major requirement for the safe and widespread integration of this fuel in modern energy production devices, such as fuel cells. Quasi-1D nanowires of seven different metal oxides (CuO, WO3, Nb-added WO3, SnO2 [...] Read more.
Accurate hydrogen leakage detection is a major requirement for the safe and widespread integration of this fuel in modern energy production devices, such as fuel cells. Quasi-1D nanowires of seven different metal oxides (CuO, WO3, Nb-added WO3, SnO2, ZnO, α-Bi2O3, NiO) were integrated into a conductometric sensor array to evaluate the hydrogen-sensing performances in the presence of interfering gaseous compounds, namely carbon monoxide, nitrogen dioxide, methane, acetone, and ethanol, at different operating temperatures (200–400 °C). Principal component analysis (PCA) was applied to data extracted from the array, demonstrating the ability to discriminate hydrogen over other interferent compounds. Moreover, a reduced array formed by only five sensors is proposed. This compact array may be easily implementable into artificial olfaction systems used in real hydrogen detection applications. Full article
(This article belongs to the Special Issue Micro and Nano Technology in Gas Sensing)
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13 pages, 2324 KiB  
Article
Phase-Controlled Tunable Unconventional Photon Blockade in a Single-Atom-Cavity System
by Hong Li, Ming Liu, Feng Yang, Siqi Zhang and Shengping Ruan
Micromachines 2023, 14(11), 2123; https://doi.org/10.3390/mi14112123 - 19 Nov 2023
Viewed by 813
Abstract
In the past few years, cavity optomechanical systems have received extensive attention and research and have achieved rapid development both theoretically and experimentally. The systems play an important role in many fields, such as quantum information processing, optomechanical storage, high-precision measurement, macroscopic entanglement, [...] Read more.
In the past few years, cavity optomechanical systems have received extensive attention and research and have achieved rapid development both theoretically and experimentally. The systems play an important role in many fields, such as quantum information processing, optomechanical storage, high-precision measurement, macroscopic entanglement, ultrasensitive sensors and so on. Photon manipulation has always been one of the key tasks in quantum information science and technology. Photon blockade is an important way to realize single photon sources and plays an important role in the field of quantum information. Due to the nonlinear coupling of the optical force system, the energy level is not harmonic, resulting in a photon blockade effect. In this paper, we study the phase-controlled tunable unconventional photon blockade in a single-atom-cavity system, and the second-order nonlinear crystals are attached to the cavity. The cavity interacts with squeezed light, which results in a nonlinear process. The system is driven by a complex pulsed laser, and the strength of the coherent driving contains the phase. We want to study the effect of squeezed light and phase. We use the second-order correlation function to numerically and theoretically analyze the photon blockade effect. We show that quantum interference of two-photon excitation between three different transition pathways can cause a photon blockade effect. When there is no squeezed light, the interference pathways becomes two, but there are still photon blockade effects. We explore the influence of the tunable phase and second-order nonlinear strength on the photon blockade effect. We calculate the correlation function and compare the numerical results with the analytical results under certain parameters and find that the agreement is better. Full article
(This article belongs to the Special Issue Chip Scale Quantum Technologies)
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13 pages, 8718 KiB  
Article
Electrophoretic Deposition of Multi-Walled Carbon Nanotube Coatings on CoCrMo Alloy for Biomedical Applications
by Bożena Łosiewicz, Patrycja Osak and Karolina Górka-Kulikowska
Micromachines 2023, 14(11), 2122; https://doi.org/10.3390/mi14112122 - 18 Nov 2023
Cited by 2 | Viewed by 1172
Abstract
Carbon nanotubes are a promising material for use in innovative biomedical solutions due to their unique chemical, mechanical, electrical, and magnetic properties. This work provides a method for the development of ultrasonically assisted electrophoretic deposition of multi-walled carbon nanotubes on a CoCrMo dental [...] Read more.
Carbon nanotubes are a promising material for use in innovative biomedical solutions due to their unique chemical, mechanical, electrical, and magnetic properties. This work provides a method for the development of ultrasonically assisted electrophoretic deposition of multi-walled carbon nanotubes on a CoCrMo dental alloy. Functionalization of multi-walled carbon nanotubes was carried out by chemical oxidation in a mixture of nitric and sulfuric acids. The modified and unmodified multi-walled carbon nanotubes were anaphoretically deposited on the CoCrMo alloy in an aqueous solution. Chemical composition was studied by Fourier transform infrared spectroscopy. Surface morphology was examined by scanning electron microscopy. The mechanism and kinetics of the electrochemical corrosion of the obtained coatings in artificial saliva at 37 °C were determined using the open-circuit potential method, electrochemical impedance spectroscopy, and anodic polarization curves. The capacitive behavior and high corrosion resistance of the tested electrodes were revealed. It was found that the kinetics of electrochemical corrosion of the CoCrMo electrode significantly decreased in the presence of the functionalized multi-walled carbon nanotube coating. Electrophoretic deposition was shown to be an effective, low-cost, and fast method of producing nanotubes with controlled thickness, homogeneity, and packing density. Full article
(This article belongs to the Special Issue Advances in Manufacturing, Characterization and Applications of Functional Micro/Nano Structured Surfaces)
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8 pages, 2602 KiB  
Communication
Effect of Channel Shape on Performance of Printed Indium Gallium Zinc Oxide Thin-Film Transistors
by Xingzhen Yan, Bo Li, Yiqiang Zhang, Yanjie Wang, Chao Wang, Yaodan Chi and Xiaotian Yang
Micromachines 2023, 14(11), 2121; https://doi.org/10.3390/mi14112121 - 18 Nov 2023
Viewed by 886
Abstract
Printing technology will improve the complexity and material waste of traditional deposition and lithography processes in device fabrication. In particular, the printing process can effectively control the functional layer stacking and channel shape in thin-film transistor (TFT) devices. We prepared the patterning indium [...] Read more.
Printing technology will improve the complexity and material waste of traditional deposition and lithography processes in device fabrication. In particular, the printing process can effectively control the functional layer stacking and channel shape in thin-film transistor (TFT) devices. We prepared the patterning indium gallium zinc oxide (IGZO) semiconductor layer with Ga, In, and Zn molar ratios of 1:2:7 on Si/SiO2 substrates. And the patterning source and drain electrodes were printed on the surface of semiconductor layers to construct a TFT device with the top contact and bottom gate structures. To overcome the problem of uniform distribution of applied voltages between electrode centers and edges, we investigated whether the circular arc channel could improve the carrier regulation ability under the field effect in printed TFTs compared with a traditional structure of rectangular symmetry and a rectangular groove channel. The drain current value of the IGZO TFT with a circular arc channel pattern was significantly enhanced compared to that of a TFT with rectangular symmetric source/drain electrodes under the corresponding drain–source voltage and gate voltage. The field effect properties of the device were obviously improved by introducing the arc-shaped channel structure. Full article
(This article belongs to the Special Issue Future Prospects of Thin-Film Transistors and Their Applications)
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14 pages, 57718 KiB  
Article
Advanced Design and Fabrication of Dual-Material Honeycombs for Improved Stiffness and Resilience
by Jiajing Dong, Songtao Ying, Zhuohao Qiu, Xixi Bao, Chengyi Chu, Hao Chen, Jianjun Guo and Aihua Sun
Micromachines 2023, 14(11), 2120; https://doi.org/10.3390/mi14112120 - 18 Nov 2023
Viewed by 991
Abstract
Auxetic re-entrant honeycomb (AREH) structures, consisting of a single soft or tough material, have long faced the challenge of balancing stiffness and rebound resilience. To achieve this balance, dual-material printing technology is employed to enhance shock absorption by combining layers of soft and [...] Read more.
Auxetic re-entrant honeycomb (AREH) structures, consisting of a single soft or tough material, have long faced the challenge of balancing stiffness and rebound resilience. To achieve this balance, dual-material printing technology is employed to enhance shock absorption by combining layers of soft and tough materials. Additionally, a novel structure called the curved re-entrant honeycomb (CREH) structure has been introduced to improve stiffness. The selected materials for processing the composite structures of AREH and CREH are the rigid thermoplastic polymer polylactic acid (PLA) and the soft rubber material thermoplastic polyurethane (TPU), created utilizing fused deposition modeling (FDM) 3D printing technology. The influence of the material system and structure type on stress distribution and mechanical response was subsequently investigated. The results revealed that the dual-material printed structures demonstrated later entry into the densification phase compared to the single-material printed structures. Moreover, the soft material in the interlayer offered exceptional protection, thereby ensuring the overall integrity of the structure. These findings effectively serve as a reference for the design of dual-material re-entrant honeycombs. Full article
(This article belongs to the Special Issue 3D Printing Technology and Its Applications)
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13 pages, 9652 KiB  
Article
Modeling of a Broadband Microwave Composite Thin Film Absorber
by Ying Zhang, Yanze Gao, Suhui Yang, Zhuo Li, Xin Wang and Jinying Zhang
Micromachines 2023, 14(11), 2119; https://doi.org/10.3390/mi14112119 - 18 Nov 2023
Viewed by 834
Abstract
Composite thin film absorbers show superior performance and have a wide range of applications. Obtaining a broadband composite thin film absorber is a challenge. In this work, we proposed a modeling of a broadband microwave composite thin film absorber based on the impedance [...] Read more.
Composite thin film absorbers show superior performance and have a wide range of applications. Obtaining a broadband composite thin film absorber is a challenge. In this work, we proposed a modeling of a broadband microwave composite thin film absorber based on the impedance matching theory and equivalent circuit model of the square loop. The unit cell of the absorber was composed of metal square loops with high magnetic conductivity deposited on the polyethylene substrate, and an FR-4 (epoxy glass cloth) substrate was the spacer substrate layer. The simulation results show that the absorptivity of the absorber reached more than 90% in the frequency range of 8.7–18 GHz for TE and TM waves under normal incidence. The thickness of the designed absorber was 2.05 mm (0.059 λmax, λmax corresponds to the maximum absorption wavelength). The simulation results show that the energy distribution in the proposed absorber was mainly localized in the top metal FSS layer due to the ohmic loss of metal, and the dielectric loss played a small role in the absorption of the absorber. Our work provides a design approach to improve the efficiency of optoelectronic devices and thermal detectors and has application prospects in radar and aircraft stealth applications. Full article
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14 pages, 2875 KiB  
Article
Design and Analysis of a Low-Voltage VCO: Reliability and Variability Performance
by Tayebeh Azadmousavi and Ebrahim Ghafar-Zadeh
Micromachines 2023, 14(11), 2118; https://doi.org/10.3390/mi14112118 - 18 Nov 2023
Viewed by 919
Abstract
This paper investigates an adaptive body biasing (ABB) circuit to improve the reliability and variability of a low-voltage inductor–capacitor (LC) voltage-controlled oscillator (VCO). The ABB circuit provides VCO resilience to process variability and reliability variation through the threshold voltage adjustment of VCO’s transistors. [...] Read more.
This paper investigates an adaptive body biasing (ABB) circuit to improve the reliability and variability of a low-voltage inductor–capacitor (LC) voltage-controlled oscillator (VCO). The ABB circuit provides VCO resilience to process variability and reliability variation through the threshold voltage adjustment of VCO’s transistors. Analytical equations considering the body bias effect are derived for the most important relations of the VCO and then the performance is verified using the post-layout simulation results. Under a 0.16% threshold voltage shift, the sensitivity of the normalized phase noise and transconductance of the VCO with the ABB circuit compared to the constant body bias (CBB) decreases by around 8.4 times and 3.1 times, respectively. Also, the sensitivity of the normalized phase noise and transconductance of the proposed VCO under 0.16% mobility variations decreases by around 1.5 times and 1.7 times compared to the CBB, respectively. The robustness of the VCO is also examined using process variation analysis through Monte Carlo and corner case simulations. The post-layout results in the 180 nm CMOS process indicate that the proposed VCO draws a power consumption of only 398 µW from a 0.6 V supply when the VCO frequency is 2.4 GHz. It achieves a phase noise of −123.19 dBc/Hz at a 1 MHz offset and provides a figure of merit (FoM) of −194.82 dBc/Hz. Full article
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36 pages, 9094 KiB  
Review
Microfluidic Blood Separation: Key Technologies and Critical Figures of Merit
by Karina Torres-Castro, Katherine Acuña-Umaña, Leonardo Lesser-Rojas and Darwin R. Reyes
Micromachines 2023, 14(11), 2117; https://doi.org/10.3390/mi14112117 - 18 Nov 2023
Viewed by 1468
Abstract
Blood is a complex sample comprised mostly of plasma, red blood cells (RBCs), and other cells whose concentrations correlate to physiological or pathological health conditions. There are also many blood-circulating biomarkers, such as circulating tumor cells (CTCs) and various pathogens, that can be [...] Read more.
Blood is a complex sample comprised mostly of plasma, red blood cells (RBCs), and other cells whose concentrations correlate to physiological or pathological health conditions. There are also many blood-circulating biomarkers, such as circulating tumor cells (CTCs) and various pathogens, that can be used as measurands to diagnose certain diseases. Microfluidic devices are attractive analytical tools for separating blood components in point-of-care (POC) applications. These platforms have the potential advantage of, among other features, being compact and portable. These features can eventually be exploited in clinics and rapid tests performed in households and low-income scenarios. Microfluidic systems have the added benefit of only needing small volumes of blood drawn from patients (from nanoliters to milliliters) while integrating (within the devices) the steps required before detecting analytes. Hence, these systems will reduce the associated costs of purifying blood components of interest (e.g., specific groups of cells or blood biomarkers) for studying and quantifying collected blood fractions. The microfluidic blood separation field has grown since the 2000s, and important advances have been reported in the last few years. Nonetheless, real POC microfluidic blood separation platforms are still elusive. A widespread consensus on what key figures of merit should be reported to assess the quality and yield of these platforms has not been achieved. Knowing what parameters should be reported for microfluidic blood separations will help achieve that consensus and establish a clear road map to promote further commercialization of these devices and attain real POC applications. This review provides an overview of the separation techniques currently used to separate blood components for higher throughput separations (number of cells or particles per minute). We present a summary of the critical parameters that should be considered when designing such devices and the figures of merit that should be explicitly reported when presenting a device’s separation capabilities. Ultimately, reporting the relevant figures of merit will benefit this growing community and help pave the road toward commercialization of these microfluidic systems. Full article
(This article belongs to the Special Issue Blood Flow in Microfluidic Medical Devices)
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20 pages, 6021 KiB  
Review
Recent Advances in Flexible Multifunctional Sensors
by Ya Chang, Xiangyu Qi, Linglu Wang, Chuanbo Li and Yang Wang
Micromachines 2023, 14(11), 2116; https://doi.org/10.3390/mi14112116 - 18 Nov 2023
Cited by 1 | Viewed by 1094
Abstract
Wearable electronics have received extensive attention in human–machine interactions, robotics, and health monitoring. The use of multifunctional sensors that are capable of measuring a variety of mechanical or environmental stimuli can provide new functionalities for wearable electronics. Advancements in material science and system [...] Read more.
Wearable electronics have received extensive attention in human–machine interactions, robotics, and health monitoring. The use of multifunctional sensors that are capable of measuring a variety of mechanical or environmental stimuli can provide new functionalities for wearable electronics. Advancements in material science and system integration technologies have contributed to the development of high-performance flexible multifunctional sensors. This review presents the main approaches, based on functional materials and device structures, to improve sensing parameters, including linearity, detection range, and sensitivity to various stimuli. The details of electrical, biocompatible, and mechanical properties of self-powered sensors and wearable wireless systems are systematically elaborated. Finally, the current challenges and future developmental directions are discussed to offer a guide to fabricate advanced multifunctional sensors. Full article
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21 pages, 7654 KiB  
Article
A 3D-Printed Micro-Optofluidic Chamber for Fluid Characterization and Microparticle Velocity Detection
by Emanuela Cutuli, Dario Sanalitro, Giovanna Stella, Lorena Saitta and Maide Bucolo
Micromachines 2023, 14(11), 2115; https://doi.org/10.3390/mi14112115 - 18 Nov 2023
Viewed by 1228
Abstract
This work proposes a multi-objective polydimethylsiloxane (PDMS) micro-optofluidic (MoF) device suitably designed and manufactured through a 3D-printed-based master–slave approach. It exploits optical detection techniques to characterize immiscible fluids or microparticles in suspension inside a compartment specifically designed at the core of the device [...] Read more.
This work proposes a multi-objective polydimethylsiloxane (PDMS) micro-optofluidic (MoF) device suitably designed and manufactured through a 3D-printed-based master–slave approach. It exploits optical detection techniques to characterize immiscible fluids or microparticles in suspension inside a compartment specifically designed at the core of the device referred to as the MoF chamber. In addition, we show our novel, fast, and cost-effective methodology, dual-slit particle signal velocimetry (DPSV), for fluids and microparticle velocity detection. Different from the standard state-of-the-art approaches, the methodology focuses on signal processing rather than image processing. This alternative has several advantages, including the ability to circumvent the requirement of complex and extensive setups and cost reduction. Additionally, its rapid processing speed allows for real-time sample manipulations in ongoing image-based analyses. For our specific design, optical signals have been detected from the micro-optics components placed in two slots designed ad hoc in the device. To show the devices’ multipurpose capabilities, the device has been tested with fluids of various colors and densities and the inclusion of synthetic microparticles. Additionally, several experiments have been conducted to prove the effectiveness of the DPSV approach in estimating microparticle velocities. A digital particle image velocimetry (DPIV)-based approach has been used as a baseline against which the outcomes of our methods have been evaluated. The combination of the suitability of the micro-optical components for integration, along with the MoF chamber device and the DPSV approach, demonstrates a proof of concept towards the challenge of real-time total-on-chip analysis. Full article
(This article belongs to the Special Issue Micro/Nanostructures in Sensors and Actuators)
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15 pages, 7591 KiB  
Article
Design and Fabrication of a Novel Corona-Shaped Metamaterial Biosensor for Cancer Cell Detection
by Nourelhouda Dadouche, Zinelabiddine Mezache, Junwu Tao, Enas Ali, Mohammad Alsharef, Abdullah Alwabli, Amar Jaffar, Abdullah Alzahrani and Achouak Berazguia
Micromachines 2023, 14(11), 2114; https://doi.org/10.3390/mi14112114 - 18 Nov 2023
Viewed by 1128
Abstract
The early detection and diagnosis of cancer presents significant challenges in today’s healthcare. So, this research, suggests an original experimental biosensor for cell cancer detection using a corona-shaped metamaterial resonator. This resonator is designed to detect cancer markers with high sensitivity, selectivity, and [...] Read more.
The early detection and diagnosis of cancer presents significant challenges in today’s healthcare. So, this research, suggests an original experimental biosensor for cell cancer detection using a corona-shaped metamaterial resonator. This resonator is designed to detect cancer markers with high sensitivity, selectivity, and linearity properties. By exploiting the unique properties of the corona metamaterial structure in the GHz regime, the resonator provides enhanced interaction of electromagnetic waves and improved detection skills. Through careful experimental, simulation, and optimization studies, we accurately demonstrate the resonator’s ability to detect cancer. The proposed detection system is capable of real-time non-invasive cancer detection, allowing for rapid intervention and better patient outcomes. The sensitivity value was confirmed through simulation, estimated at 0.1825 GHz/RIU. The results of two different simulation methods are used: the simulation software CST Studio Suite (version 2017) based on the finite element method (FEM), and the simulation software ADS (version 2019) based on the equivalent circuit method, thereby increasing confidence in the convergence of simulation and measurement results. This work opens new avenues for developing advanced detection technologies in the field of oncology, and paves the way for more effective cancer diagnosis. The experimental study verified that this realized sensor has very small frequency shifts, significantly small electrical dimension and miniaturization, high sensitivity, and good linearity. The suggested configurations showed a capacity for sensing cancer cells in the GHz regime. Full article
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14 pages, 7610 KiB  
Article
Infrared UAV Target Detection Based on Continuous-Coupled Neural Network
by Zhuoran Yang, Jing Lian and Jizhao Liu
Micromachines 2023, 14(11), 2113; https://doi.org/10.3390/mi14112113 - 18 Nov 2023
Viewed by 1197
Abstract
The task of the detection of unmanned aerial vehicles (UAVs) is of great significance to social communication security. Infrared detection technology has the advantage of not being interfered with by environmental and other factors and can detect UAVs in complex environments. Since infrared [...] Read more.
The task of the detection of unmanned aerial vehicles (UAVs) is of great significance to social communication security. Infrared detection technology has the advantage of not being interfered with by environmental and other factors and can detect UAVs in complex environments. Since infrared detection equipment is expensive and data collection is difficult, there are few existing UAV-based infrared images, making it difficult to train deep neural networks; in addition, there are background clutter and noise in infrared images, such as heavy clouds, buildings, etc. The signal-to-clutter ratio is low, and the signal-to-noise ratio is low. Therefore, it is difficult to achieve the UAV detection task using traditional methods. The above challenges make infrared UAV detection a difficult task. In order to solve the above problems, this work drew upon the visual processing mechanism of the human brain to propose an effective framework for UAV detection in infrared images. The framework first determines the relevant parameters of the continuous-coupled neural network (CCNN) through the image’s standard deviation, mean, etc. Then, it inputs the image into the CCNN, groups the pixels through iteration, then obtains the segmentation result through expansion and erosion, and finally, obtains the final result through the minimum circumscribed rectangle. The experimental results showed that, compared with the existing most-advanced brain-inspired image-understanding methods, this framework has the best intersection over union (IoU) (the intersection over union is the overlapping area between the predicted segmentation and the label divided by the joint area between the predicted segmentation and the label) in UAV infrared images, with an average of 74.79% (up to 97.01%), and can effectively realize the task of UAV detection. Full article
(This article belongs to the Special Issue Novel Computing Architectures and Digital Circuit Designs Using Memristors and Memristive Systems, 2nd Edition)
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14 pages, 13202 KiB  
Article
Effects of Block Copolymer Terminal Groups on Toughening Epoxy-Based Composites: Microstructures and Toughening Mechanisms
by Gang Li, Wenjie Wu, Xuecheng Yu, Ruoyu Zhang, Rong Sun, Liqiang Cao and Pengli Zhu
Micromachines 2023, 14(11), 2112; https://doi.org/10.3390/mi14112112 - 17 Nov 2023
Cited by 1 | Viewed by 992
Abstract
Despite the considerable research attention paid to block copolymer (BCP)-toughened epoxy resins, the effects of their terminal groups on their phase structure are not thoroughly understood. This study fills this gap by closely examining the effects of amino and carboxyl groups on the [...] Read more.
Despite the considerable research attention paid to block copolymer (BCP)-toughened epoxy resins, the effects of their terminal groups on their phase structure are not thoroughly understood. This study fills this gap by closely examining the effects of amino and carboxyl groups on the fracture toughness of epoxy resins at different temperatures. Through the combination of scanning electron microscopy and digital image correlation (DIC), it was found that the amino-terminated BCP was capable of forming a stress-distributing network in pure epoxy resin, resulting in better toughening effects at room temperature. In a 60 wt.% silica-filled epoxy composite system, the addition of a carboxyl-terminated BCP showed little toughening effect due to the weaker filler/matrix interface caused by the random dispersion of the microphase of BCPs and distributed silica. The fracture toughness of the epoxy system at high temperatures was not affected by the terminal groups, regardless of the addition of silica. Their dynamic mechanical properties and thermal expansion coefficients are also reported in this article. Full article
(This article belongs to the Special Issue Microelectronics Assembly and Packaging: Materials and Technologies)
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11 pages, 4292 KiB  
Article
Deformability-Based Isolation of Circulating Tumor Cells in Spiral Microchannels
by Roya Mohammadali and Morteza Bayareh
Micromachines 2023, 14(11), 2111; https://doi.org/10.3390/mi14112111 - 17 Nov 2023
Cited by 1 | Viewed by 842
Abstract
The isolation of circulating tumor cells (CTCs) and their analysis are crucial for the preliminary identification of invasive cancer. One of the effective properties that can be utilized to isolate CTCs is their deformability. In this paper, inertial-based spiral microchannels with various numbers [...] Read more.
The isolation of circulating tumor cells (CTCs) and their analysis are crucial for the preliminary identification of invasive cancer. One of the effective properties that can be utilized to isolate CTCs is their deformability. In this paper, inertial-based spiral microchannels with various numbers of loops are employed to sort deformable CTCs using the finite element method (FEM) and an arbitrary Lagrangian–Eulerian (ALE) approach. The influences of cell deformability, cell size, number of loops, and channel depth on the hydrodynamic behavior of CTCs are discussed. The results demonstrate that the trajectory of cells is affected by the above factors when passing through the spiral channel. This approach can be utilized for sorting and isolating label-free deformable biological cells at large scales in clinical systems. Full article
(This article belongs to the Special Issue Microfluidic Chips and Microdevices for Biomedical Engineering)
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14 pages, 5928 KiB  
Article
Design of a Femtosecond Laser Percussion Drilling Process for Ni-Based Superalloys Based on Machine Learning and the Genetic Algorithm
by Zhixi Zhao, Yunhe Yu, Ruijia Sun, Wanrong Zhao, Hao Guo, Zhen Zhang and Chenchong Wang
Micromachines 2023, 14(11), 2110; https://doi.org/10.3390/mi14112110 - 17 Nov 2023
Cited by 1 | Viewed by 807
Abstract
Femtosecond laser drilling is extensively used to create film-cooling holes in aero-engine turbine blade processing. Investigating and exploring the impact of laser processing parameters on achieving high-quality holes is crucial. The traditional trial-and-error approach, which relies on experiments, is time-consuming and has limited [...] Read more.
Femtosecond laser drilling is extensively used to create film-cooling holes in aero-engine turbine blade processing. Investigating and exploring the impact of laser processing parameters on achieving high-quality holes is crucial. The traditional trial-and-error approach, which relies on experiments, is time-consuming and has limited optimization capabilities for drilling holes. To address this issue, this paper proposes a process design method using machine learning and a genetic algorithm. A dataset of percussion drilling using a femtosecond laser was primarily established to train the models. An optimal method for building a prediction model was determined by comparing and analyzing different machine learning algorithms. Subsequently, the Gaussian support vector regression model and genetic algorithm were combined to optimize the taper and material removal rate within and outside the original data ranges. Ultimately, comprehensive optimization of drilling quality and efficiency was achieved relative to the original data. The proposed framework in this study offers a highly efficient and cost-effective solution for optimizing the femtosecond laser percussion drilling process. Full article
(This article belongs to the Special Issue Future Prospects of Additive Manufacturing)
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22 pages, 6495 KiB  
Article
The Nonlinear Dynamics of a MEMS Resonator with a Triangular Tuning Comb
by Lijuan Zhang, Huabiao Zhang, Xinye Li, Ningguo Qiao, Xianping Gao and Yunxiao Ji
Micromachines 2023, 14(11), 2109; https://doi.org/10.3390/mi14112109 - 17 Nov 2023
Viewed by 591
Abstract
The nonlinear dynamic response of a MEMS resonator with a triangular tuning comb is studied. The motion equation with dis-smooth tuning electrostatic force is derived according to Newton’s second law. The analytical solution of the periodic response is obtained using the harmonic balance [...] Read more.
The nonlinear dynamic response of a MEMS resonator with a triangular tuning comb is studied. The motion equation with dis-smooth tuning electrostatic force is derived according to Newton’s second law. The analytical solution of the periodic response is obtained using the harmonic balance method and section integral method. The singularity theory is then applied to investigate the bifurcation of the periodic response of the untuned system. The transition sets on the DC-AC voltage plane dividing the planes into several persistent regions are obtained. The bifurcation diagrams’ topological structures and jump phenomena corresponding to different parameter regions are analyzed. We explore the effects of tuning voltage on the response. This demonstrates that the amplitude–frequency curves present more hardening characteristics with increased tuning voltage. Many twists, bifurcation points, and unstable solutions appear, leading to complicated jump phenomena. Two bifurcation points exist on the response curves: the smooth and dis-smooth bifurcation points, with the latter occurring on the switching plane of non-uniform fingers. Full article
(This article belongs to the Section E：Engineering and Technology)
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15 pages, 4966 KiB  
Article
Design and Experimental Evaluation of a Dual-Cantilever Piezoelectric Film Sensor with a Broadband Response and High Sensitivity
by Wei Xin, Zhaoyang He and Chaocheng Zhao
Micromachines 2023, 14(11), 2108; https://doi.org/10.3390/mi14112108 - 17 Nov 2023
Viewed by 808
Abstract
Cantilever-beam-type PVDF (Polyvinylidene Fluoride) piezoelectric film sensors are commonly utilized for vibration signal detection due to their simple structures and ease of processing. Traditional cantilevered PVDF piezoelectric film sensors are susceptible to the influence of the second-order vibration mode and have a low [...] Read more.
Cantilever-beam-type PVDF (Polyvinylidene Fluoride) piezoelectric film sensors are commonly utilized for vibration signal detection due to their simple structures and ease of processing. Traditional cantilevered PVDF piezoelectric film sensors are susceptible to the influence of the second-order vibration mode and have a low lateral stress distribution at the free end, which limit their measurement bandwidth and sensitivity. This study is on the design of a dual-cantilever PVDF piezoelectric film sensor based on the principle of cantilevered piezoelectric film sensors. The results of the experiments indicate that, compared to a typical single-arm piezoelectric cantilever beam vibration sensor, the developed sensor has a longer second-order natural frequency that ranges from 112 Hz to 453 Hz, while the first-order natural frequency is maintained at around 12 Hz. This leads to a better ratio of the second-order natural frequency to the first-order natural frequency and a wider frequency response range. At the same time, the sensitivity is increased by a factor of 3.48. Full article
(This article belongs to the Special Issue Piezoelectric Actuators and Sensors: Materials, Devices and Applications)
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17 pages, 8709 KiB  
Article
Kinetic and Parametric Analysis of the Separation of Ultra-Small, Aqueous Superparamagnetic Iron Oxide Nanoparticle Suspensions under Quadrupole Magnetic Fields
by Stefano Ciannella, Xian Wu, Cristina González-Fernández, Bahareh Rezaei, Jacob Strayer, Hyeon Choe, Kai Wu, Jeffrey Chalmers and Jenifer Gomez-Pastora
Micromachines 2023, 14(11), 2107; https://doi.org/10.3390/mi14112107 - 17 Nov 2023
Cited by 1 | Viewed by 1195
Abstract
Superparamagnetic iron oxide nanoparticles (SPIONs) have gathered tremendous scientific interest, especially in the biomedical field, for multiple applications, including bioseparation, drug delivery, etc. Nevertheless, their manipulation and separation with magnetic fields are challenging due to their small size. We recently reported the coupling [...] Read more.
Superparamagnetic iron oxide nanoparticles (SPIONs) have gathered tremendous scientific interest, especially in the biomedical field, for multiple applications, including bioseparation, drug delivery, etc. Nevertheless, their manipulation and separation with magnetic fields are challenging due to their small size. We recently reported the coupling of cooperative magnetophoresis and sedimentation using quadrupole magnets as a promising strategy to successfully promote SPION recovery from media. However, previous studies involved SPIONs dispersed in organic solvents (non-biocompatible) at high concentrations, which is detrimental to the process economy. In this work, we investigate, for the first time, the magnetic separation of 20 nm and 30 nm SPIONs dispersed in an aqueous medium at relatively low concentrations (as low as 0.5 g·L−1) using our custom, permanent magnet-based quadrupole magnetic sorter (QMS). By monitoring the SPION concentrations along the vessel within the QMS, we estimated the influence of several variables in the separation and analyzed the kinetics of the process. The results obtained can be used to shed light on the dynamics and interplay of variables that govern the fast separation of SPIONs using inexpensive permanent magnets. Full article
(This article belongs to the Special Issue Fluid Manipulation: From Fundamentals to Applications)
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18 pages, 13997 KiB  
Article
Experiment and Simulation Study of the Laser-Induced Cavitation Bubble Technique for Forming a Microgroove in Aluminum Foil
by Liangliang Wang, Chun Su, Xiaofeng Jia, Zhongning Guo and Zhixiang Zou
Micromachines 2023, 14(11), 2106; https://doi.org/10.3390/mi14112106 - 17 Nov 2023
Viewed by 942
Abstract
The present work introduces a laser-induced cavitation bubble technique for forming an axisymmetric structure (i.e., microgroove) and the dynamics of a cavitation bubble from initial expansion to the collapse stages that were also simulated. Furthermore, the shock wave signals and dynamic properties of [...] Read more.
The present work introduces a laser-induced cavitation bubble technique for forming an axisymmetric structure (i.e., microgroove) and the dynamics of a cavitation bubble from initial expansion to the collapse stages that were also simulated. Furthermore, the shock wave signals and dynamic properties of the cavitation bubble were recorded using a hydrophone and a high-speed camera. The experiments on microgrooves formed by laser-induced cavitation bubble stamping were carried out, and the effects of laser energy, the initial position of the bubble, and the number of impacts on the microformability of aluminum sheets are discussed. The depth of the microgroove was investigated using experiments, and it was found that the process can serve as a rapid technique for impressing microfeatures on thin-sheet metals. The experimental results showed that as the initial position of the bubble increased, the deformation depth decreased. As the laser energy and number of impacts increased, the deformation depth increased. The results of the response surface experiments showed that a laser energy of 27 mJ, 3 impacts, and a bubble position of 3 mm were optimal for the process. By using the optimal parameters, flat and smooth microgrooves with a forming depth of 102.54 µm were successfully fabricated. Furthermore, the maximum thickness thinning of the microgroove section occurred at the entrance areas, and this area had the greatest hardness. This also indicated that the greatest amount of plastic deformation of the material and grain refinement occurred in this area. On the other hand, the aluminum foil did not undergo oxidation during the plastic deformation process. These results demonstrated that laser-induced bubble stamping is an advanced micromachining method with promising applications. Full article
(This article belongs to the Section E：Engineering and Technology)
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13 pages, 6695 KiB  
Article
A 40–50 GHz RF Front-End with Integrated Local Oscillator Leakage Calibration
by Peigen Zhou, Pinpin Yan, Jixin Chen, Zhe Chen and Wei Hong
Micromachines 2023, 14(11), 2105; https://doi.org/10.3390/mi14112105 - 16 Nov 2023
Viewed by 959
Abstract
This article presents a transmitter (TX) front-end operating at frequencies covering 40–50 GHz, including a differential quadrature mixer with integrated amplitude and phase imbalance tuning, a power amplifier, and a detection mixer (DM) that supports local oscillator (LO) leakage signal or image signal [...] Read more.
This article presents a transmitter (TX) front-end operating at frequencies covering 40–50 GHz, including a differential quadrature mixer with integrated amplitude and phase imbalance tuning, a power amplifier, and a detection mixer (DM) that supports local oscillator (LO) leakage signal or image signal calibration. Benefiting from the amplitude and phase imbalance tuning network of the in-phase quadrature (IQ) signal generator at the LO input, the TX exhibits more than 30 dBc image signal rejection over the full frequency band without any post-calibration. Based on the LO leakage signal fed back by the DM integrated at the RF output, the LO leakage of the TX has been improved by more than 10 dB through the LO leakage calibration module integrated in the quadrature mixer. When the intermediate frequency (IF) signal is fixed at 1 GHz, the TX’s 1 dB compressed output power (OP1 dB) is higher than 13.5 dBm over the operating band. Thanks to the LO leakage signal calibration unit and the IQ signal generator, the TX is compliant with the error vector magnitude (EVM) requirement of the IEEE 802.11aj standard up to the 64-quadrature amplitude modulation (QAM) operating mode. Full article
(This article belongs to the Special Issue Recent Advances in Microwave Components and Devices)
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11 pages, 7511 KiB  
Article
Comprehensive Comparison of MOCVD- and LPCVD-SiNx Surface Passivation for AlGaN/GaN HEMTs for 5G RF Applications
by Longge Deng, Likun Zhou, Hao Lu, Ling Yang, Qian Yu, Meng Zhang, Mei Wu, Bin Hou, Xiaohua Ma and Yue Hao
Micromachines 2023, 14(11), 2104; https://doi.org/10.3390/mi14112104 - 16 Nov 2023
Viewed by 1057
Abstract
Passivation is commonly used to suppress current collapse in AlGaN/GaN HEMTs. However, the conventional PECV-fabricated SiNx passivation layer is incompatible with the latest process, like the “passivation-prior-to-ohmic” method. Research attention has therefore turned to high-temperature passivation schemes. In this paper, we systematically [...] Read more.
Passivation is commonly used to suppress current collapse in AlGaN/GaN HEMTs. However, the conventional PECV-fabricated SiNx passivation layer is incompatible with the latest process, like the “passivation-prior-to-ohmic” method. Research attention has therefore turned to high-temperature passivation schemes. In this paper, we systematically investigated the differences between the SiNx/GaN interface of two high-temperature passivation schemes, MOCVD-SiNx and LPCVD-SiNx, and investigated their effects on the ohmic contact mechanism. By characterizing the device interface using TEM, we reveal that during the process of MOCVD-SiNx, etching damage and Si diffuses into the semiconductor to form a leakage path and reduce the breakdown voltage of the AlGaN/GaN HEMTs. Moreover, N enrichment at the edge of the ohmic region of the LPCVD-SiNx device indicates that the device is more favorable for TiN formation, thus reducing the ohmic contact resistance, which is beneficial to improving the PAE of the device. Through the CW load-pull test with drain voltage VDS = 20V, LPCVD-SiNx devices obtain a high PAE of 66.35%, which is about 6% higher than MOCVD-SiNx devices. This excellent result indicates that the prospect of LPCVD-SiNx passivation devices used in 5G small terminals will be attractive. Full article
(This article belongs to the Special Issue Latest Advancements in Semiconductor Materials, Devices, and Systems)
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12 pages, 5505 KiB  
Article
Coupled Nanomechanical Graphene Resonators: A Promising Platform for Scalable NEMS Networks
by Brittany Carter, Uriel F. Hernandez, David J. Miller, Andrew Blaikie, Viva R. Horowitz and Benjamín J. Alemán
Micromachines 2023, 14(11), 2103; https://doi.org/10.3390/mi14112103 - 16 Nov 2023
Viewed by 1200
Abstract
Arrays of coupled nanoelectromechanical resonators are a promising foundation for implementing large-scale network applications, such as mechanical-based information processing and computing, but their practical realization remains an outstanding challenge. In this work, we demonstrate a scalable platform of suspended graphene resonators, such that [...] Read more.
Arrays of coupled nanoelectromechanical resonators are a promising foundation for implementing large-scale network applications, such as mechanical-based information processing and computing, but their practical realization remains an outstanding challenge. In this work, we demonstrate a scalable platform of suspended graphene resonators, such that neighboring resonators are persistently coupled mechanically. We provide evidence of strong coupling between neighboring resonators using two different tuning methods. Additionally, we provide evidence of inter-resonator coupling of higher-order modes, demonstrating the rich dynamics that can be accessed with this platform. Our results establish this platform as a viable option for realizing large-scale programmable networks, enabling applications such as phononic circuits, tunable waveguides, and reconfigurable metamaterials. Full article
(This article belongs to the Special Issue Feature Papers of Micromachines in Physics 2023)
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