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We utilized scanning probe microscopy (SPM) based on a metal-oxide-silicon field-effect transistor (MOSFET) to image interdigitated electrodes covered with oxide films that were several hundred nanometers in thickness. The signal varied depending on the thickness of the silicon dioxide film covering the electrodes. We deposited a 400- or 500-nm-thick silicon dioxide film on each sample electrode. Thick oxide films are difficult to analyze using conventional probes because of their low capacitance. In addition, we evaluated linearity and performed frequency response measurements; the measured frequency response reflected the electrical characteristics of the system, including the MOSFET, conductive tip, and local sample area. Our technique facilitated analysis of the passivation layers of integrated circuits, especially those of the back-end-of-line (BEOL) process, and can be used for subsurface imaging of various dielectric layers.
Hoontaek Lee; Kumjae Shin; Wonkyu Moon. Capacitive Measurements of SiO2 Films of Different Thicknesses Using a MOSFET-Based SPM Probe. Sensors 2021, 21, 4073 .
AMA StyleHoontaek Lee, Kumjae Shin, Wonkyu Moon. Capacitive Measurements of SiO2 Films of Different Thicknesses Using a MOSFET-Based SPM Probe. Sensors. 2021; 21 (12):4073.
Chicago/Turabian StyleHoontaek Lee; Kumjae Shin; Wonkyu Moon. 2021. "Capacitive Measurements of SiO2 Films of Different Thicknesses Using a MOSFET-Based SPM Probe." Sensors 21, no. 12: 4073.
We report on the importance of considering manufacturing inaccuracies in underwater acoustic projectors by elucidating how small variations affect the response characteristics of a projector array in the presence of mutualloading effects. A wave-based distributed mechanical model accurately calculates changes arising from small variations, so rapid changes occurring in the vicinity of transducer resonance can be simulated. The results showed the effects of mutual loading between projector units, and confirmed that changes can be drastically intensified in the presence of manufacturing inaccuracies. A voltage adjustment method to compensate for these changes is also demonstrated as a solution. This framework could guide the design of projector arrays in SONAR systems for a variety of applications and, in particular, may contribute significantly to determining manufacturing tolerances.
Hoontaek Lee; Wonkyu Moon. The Effects of Manufacturing Inaccuracies in an Underwater Acoustic Projector Array on the Acoustic Interactions. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 2020, PP, 1 -1.
AMA StyleHoontaek Lee, Wonkyu Moon. The Effects of Manufacturing Inaccuracies in an Underwater Acoustic Projector Array on the Acoustic Interactions. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control. 2020; PP (99):1-1.
Chicago/Turabian StyleHoontaek Lee; Wonkyu Moon. 2020. "The Effects of Manufacturing Inaccuracies in an Underwater Acoustic Projector Array on the Acoustic Interactions." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control PP, no. 99: 1-1.
Miniaturized capacitive microphones often show sensitivity degradation in the low-frequency region due to electrical and acoustical time constants. For low-frequency sound detection, conventional systems use a microphone with a large diaphragm and a large back chamber to increase the time constant. In order to overcome this limitation, an electret gate on a field-effect transistor (ElGoFET) structure was proposed, which is the field-effect transistor (FET) mounted diaphragm faced on electret. The use of the sensing mechanism consisting of the integrated FET and electret enables the direct detection of diaphragm displacement, which leads its acoustic senor application (ElGoFET microphone) and has a strong ability to detect low-frequency sound. We studied a theoretical model and design for low-frequency operation of the ElGoFET microphone prototype. Experimental investigations pertaining to the design, fabrication, and acoustic measurement of the microphone were performed and the results were compared to our analytical predictions. The feasibility of the microphone as a low-frequency micro-electromechanical system (MEMS) microphone, without the need for a direct current bias voltage (which is of particular interest for applications requiring miniaturized components), was demonstrated by the flat-band frequency response in the low-frequency region.
Kumjae Shin; Chayeong Kim; Min Sung; Junsoo Kim; Wonkyu Moon. A Modeling and Feasibility Study of a Micro-Machined Microphone Based on a Field-Effect Transistor and an Electret for a Low-Frequency Microphone. Sensors 2020, 20, 5554 .
AMA StyleKumjae Shin, Chayeong Kim, Min Sung, Junsoo Kim, Wonkyu Moon. A Modeling and Feasibility Study of a Micro-Machined Microphone Based on a Field-Effect Transistor and an Electret for a Low-Frequency Microphone. Sensors. 2020; 20 (19):5554.
Chicago/Turabian StyleKumjae Shin; Chayeong Kim; Min Sung; Junsoo Kim; Wonkyu Moon. 2020. "A Modeling and Feasibility Study of a Micro-Machined Microphone Based on a Field-Effect Transistor and an Electret for a Low-Frequency Microphone." Sensors 20, no. 19: 5554.
This study presents a new type of composite consisting of piezoelectric poly(γ‐benzyl‐α, l‐glutamate) (PBLG) polymer fibers, which contain a large dipole moment, and the elastomer polydimethylsiloxane (PDMS) as the matrix material. PBLG microfibers were fabricated and polarized using the electrospinning method and cast in PDMS to form a unidirectional continuous‐fiber composite. The PBLG/PDMS composite was characterized based on various aspects such as crystalline structure, mechanical properties, piezoelectricity, and electromechanical response. The piezoelectric charge constants in the transverse and longitudinal modes were measured to be 10.2 and 54 pC/N, respectively, which are the largest piezoelectric coefficients of biocompatible polymers up to date. The thin PBLG/PDMS composite film can produce up to 200 mV peak‐to‐peak under sinusoidal actuation and exhibit ultra‐sensitivity up to 615 mV N−1. These results show the great potential of the highly flexible piezoelectric polymer fiber‐based composite for use in a variety of applications such as energy harvesting devices, biomechanical self‐powered structures, and force sensors. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48884.
Duc-Nam Nguyen; Wonkyu Moon. Piezoelectric polymer microfiber‐based composite for the flexible ultra‐sensitive pressure sensor. Journal of Polymer Science 2019, 137, 1 .
AMA StyleDuc-Nam Nguyen, Wonkyu Moon. Piezoelectric polymer microfiber‐based composite for the flexible ultra‐sensitive pressure sensor. Journal of Polymer Science. 2019; 137 (29):1.
Chicago/Turabian StyleDuc-Nam Nguyen; Wonkyu Moon. 2019. "Piezoelectric polymer microfiber‐based composite for the flexible ultra‐sensitive pressure sensor." Journal of Polymer Science 137, no. 29: 1.
A parametric array (PA) loudspeaker is a highly directional audio source that might grant one's convenience if it is used with mobile devices. However, conventional PA loudspeakers is almost impossible to apply in mobile devices using a battery because of the large power consumption and large device size. In this study, a PA loudspeaker system (PALS) was fabricated and evaluated to show that those difficulties could be overcome to apply it to mobile devices. In order to construct a PALS for demonstration, a power amplifier and signal-processing unit should also be properly designed and built. The PA source transducer should also be designed and built for a mobile device application. These components were integrated into a single PALS. The PALS generated a 125-dB primary wave and 62 dB of a different frequency wave (DFW) through the PA at 0.45 m in a 3 m × 3 m × 2 m semi-anechoic chamber. We confirmed that the half-power bandwidth (HPBW) formed a 6° beam at 83 kHz of DFW and 90 kHz of the primary wave (PW), and the HPBW formed a 7.3° beam at 5 kHz of DFW and a 7.1° beam at 10 kHz of DFW, respectively. Lastly, the power required was 6.65 W without a matching circuit, and 3.25 W with such a circuit.
Hongmin Ahn; Kyounghun Been; In-Dong Kim; Chong Hyun Lee; Wonkyu Moon. A Critical Step to Using a Parametric Array Loudspeaker in Mobile Devices. Sensors 2019, 19, 4449 .
AMA StyleHongmin Ahn, Kyounghun Been, In-Dong Kim, Chong Hyun Lee, Wonkyu Moon. A Critical Step to Using a Parametric Array Loudspeaker in Mobile Devices. Sensors. 2019; 19 (20):4449.
Chicago/Turabian StyleHongmin Ahn; Kyounghun Been; In-Dong Kim; Chong Hyun Lee; Wonkyu Moon. 2019. "A Critical Step to Using a Parametric Array Loudspeaker in Mobile Devices." Sensors 19, no. 20: 4449.
Parametric array (PA) sources generate a directional sound beam, via the PA phenomenon. Practical PA sources, such as PA loudspeakers, have high power consumption, low sound quality, and high cost. The stepped-plate transducer, which consists of a Langevin transducer, a horn, and a radiating plate with steps, can provide high-intensity sound and a highly directional sound beam in the acoustic axis. This study investigated the use of a stepped-plate transducer to make a PA source with high directivity and a wide bandwidth. A stepped-plate transducer that had two different resonance frequencies (f1 = 77.5 kHz, f2 = 87.4 kHz) was designed for wide bandwidth, and the three different heights of the steps on the plate (ts1 = 2.28 mm, ts2 = 2.14 mm, ts3 = 2.02 mm) were intended to provide high directivity sound beams. The fabricated stepped-plate transducer demonstrated a 50 ± 3 dB sound pressure level for the difference frequency wave in the 4–19 kHz frequency range (with equalization), and 4.2–5.1° of HPBW was shown for the highly directional sound beam.
Yonghwan Hwang; Wonkyu Moon. A wide-band in-air parametric array source composed of a circular plate with steps and a Langevin transducer with a horn. Applied Acoustics 2018, 141, 223 -233.
AMA StyleYonghwan Hwang, Wonkyu Moon. A wide-band in-air parametric array source composed of a circular plate with steps and a Langevin transducer with a horn. Applied Acoustics. 2018; 141 ():223-233.
Chicago/Turabian StyleYonghwan Hwang; Wonkyu Moon. 2018. "A wide-band in-air parametric array source composed of a circular plate with steps and a Langevin transducer with a horn." Applied Acoustics 141, no. : 223-233.
We propose a method for measuring the capacitance of a thin layer using a Tip-on-Gate of Field-Effect Transistor (ToGoFET) probe. A ToGoFET probe with a metal-oxide-semiconductor field-effect transistor (MOSFET) with an ion-implant channel was embedded at the end of a cantilever and a Pt tip was fabricated using micro-machining. The ToGoFET probe was used to detect an alternating electric field at the dielectric surface. A dielectric buried metal sample was prepared; a sinusoidal input signal was applied to the buried metal lines; and the ToGoFET probe detected the electric field at the tip via the dielectric. The AC signal detected by the ToGoFET probe was demodulated by a simple AC-to-DC converter. Experimentally, it was shown that an electric field could be measured at the surface of the dielectric layer above a buried metal line. This promising result shows that it is possible to measure the surface local capacitance.
Kumjae Shin; Dae Sil Kang; Sang Hoon Lee; Wonkyu Moon. A scanning microscopy technique based on capacitive coupling with a field-effect transistor integrated with the tip. Ultramicroscopy 2015, 159, 1 -10.
AMA StyleKumjae Shin, Dae Sil Kang, Sang Hoon Lee, Wonkyu Moon. A scanning microscopy technique based on capacitive coupling with a field-effect transistor integrated with the tip. Ultramicroscopy. 2015; 159 ():1-10.
Chicago/Turabian StyleKumjae Shin; Dae Sil Kang; Sang Hoon Lee; Wonkyu Moon. 2015. "A scanning microscopy technique based on capacitive coupling with a field-effect transistor integrated with the tip." Ultramicroscopy 159, no. : 1-10.
Capacitive-type transduction is now widely used in MEMS microphones. However, its sensitivity decreases with reducing size, due to decreasing air gap capacitance. In the present study, we proposed and developed the Electret Gate of Field Effect Transistor (ElGoFET) transduction based on an electret and FET (field-effect-transistor) as a novel mechanism of MEMS microphone transduction. The ElGoFET transduction has the advantage that the sensitivity is dependent on the ratio of capacitance components in the transduction structure. Hence, ElGoFET transduction has high sensitivity even with a smaller air gap capacitance, due to a miniaturization of the transducer. A FET with a floating-gate electrode embedded on a membrane was designed and fabricated and an electret was fabricated by ion implantation with Ga+ ions. During the assembly process between the FET and the electret, the operating point of the FET was characterized using the static response of the FET induced by the electric field due to the trapped positive charge at the electret. Additionally, we evaluated the microphone performance of the ElGoFET by measuring the acoustic response in air using a semi-anechoic room. The results confirmed that the proposed transduction mechanism has potential for microphone applications.
Kumjae Shin; Junsik Jeon; James Edward West; Wonkyu Moon. A Micro-Machined Microphone Based on a Combination of Electret and Field-Effect Transistor. Sensors 2015, 15, 20232 -20249.
AMA StyleKumjae Shin, Junsik Jeon, James Edward West, Wonkyu Moon. A Micro-Machined Microphone Based on a Combination of Electret and Field-Effect Transistor. Sensors. 2015; 15 (8):20232-20249.
Chicago/Turabian StyleKumjae Shin; Junsik Jeon; James Edward West; Wonkyu Moon. 2015. "A Micro-Machined Microphone Based on a Combination of Electret and Field-Effect Transistor." Sensors 15, no. 8: 20232-20249.
An experimental analysis was performed to understand the effects of environmental and operational conditions on the frequency stability of a piezoelectric microcantilever sensor (PEMS). Variation of the resonant frequency was analyzed with changes in the relative humidity (RH), vacuum state, DC bias voltage, oscillating voltage, and time.
Sangkyu Lee; Yeolho Lee; JeongSuong Yang; Joonwon Kim; Wonkyu Moon. Experimental Analysis on Frequency Stability of Piezoelectric Microcantilever Sensor Under Varying Environmental and Operational Conditions. Procedia Engineering 2011, 25, 1517 -1520.
AMA StyleSangkyu Lee, Yeolho Lee, JeongSuong Yang, Joonwon Kim, Wonkyu Moon. Experimental Analysis on Frequency Stability of Piezoelectric Microcantilever Sensor Under Varying Environmental and Operational Conditions. Procedia Engineering. 2011; 25 ():1517-1520.
Chicago/Turabian StyleSangkyu Lee; Yeolho Lee; JeongSuong Yang; Joonwon Kim; Wonkyu Moon. 2011. "Experimental Analysis on Frequency Stability of Piezoelectric Microcantilever Sensor Under Varying Environmental and Operational Conditions." Procedia Engineering 25, no. : 1517-1520.
Carbon nanotube (CNT) is an attractive material for needle-like conducting electrodes because it has high electrical conductivity and mechanical strength. However, CNTs cannot provide the desired properties in certain applications. To obtain micro- and nanoneedles having the desired properties, it is necessary to fabricate functional needles using various other materials. In this study, functional micro- and nanoneedle electrodes were fabricated using a tungsten tip and an atomic force microscope probe with a CNT needle template and electrodeposition. To prepare the conductive needle templates, a single-wall nanotube nanoneedle was attached onto the conductive tip using dielectrophoresis and surface tension. Through electrodeposition, Au, Ni, and polypyrrole were each coated successfully onto CNT nanoneedle electrodes to obtain the desired properties.
Taechang An; Wooseok Choi; Eunjoo Lee; In-Tae Kim; Wonkyu Moon; Geunbae Lim. Fabrication of functional micro- and nanoneedle electrodes using a carbon nanotube template and electrodeposition. Nanoscale Research Letters 2011, 6, 306 -306.
AMA StyleTaechang An, Wooseok Choi, Eunjoo Lee, In-Tae Kim, Wonkyu Moon, Geunbae Lim. Fabrication of functional micro- and nanoneedle electrodes using a carbon nanotube template and electrodeposition. Nanoscale Research Letters. 2011; 6 (1):306-306.
Chicago/Turabian StyleTaechang An; Wooseok Choi; Eunjoo Lee; In-Tae Kim; Wonkyu Moon; Geunbae Lim. 2011. "Fabrication of functional micro- and nanoneedle electrodes using a carbon nanotube template and electrodeposition." Nanoscale Research Letters 6, no. 1: 306-306.
We design and fabricate a V-shaped metal–oxide–semiconductor (MOS) transistor probe with the focused-ion-beam (FIB) nano tip to measure surface electric properties. The V-shaped structure is selected for its better lateral stiffness, and the specific dimensions are determined using the parallel beam approximation (PBA). The deposition conditions for the nano tip are also investigated for better tip sharpness. The high working frequency of the MOS transistor improves the scanning speed and the high sensitivity reduces the additional equipment required. The detection properties of the device are investigated with PZT poling patterns. The measured results show well-defined patterns, promising that the device can detect surface electric properties with high sensitivity and high working frequency.
Sang H. Lee; Geunbae Lim; Wonkyu Moon; Hyunjung Shin; Cheong-Wol Kim. V-shaped metal–oxide–semiconductor transistor probe with nano tip for surface electric properties. Ultramicroscopy 2008, 108, 1094 -1100.
AMA StyleSang H. Lee, Geunbae Lim, Wonkyu Moon, Hyunjung Shin, Cheong-Wol Kim. V-shaped metal–oxide–semiconductor transistor probe with nano tip for surface electric properties. Ultramicroscopy. 2008; 108 (10):1094-1100.
Chicago/Turabian StyleSang H. Lee; Geunbae Lim; Wonkyu Moon; Hyunjung Shin; Cheong-Wol Kim. 2008. "V-shaped metal–oxide–semiconductor transistor probe with nano tip for surface electric properties." Ultramicroscopy 108, no. 10: 1094-1100.
A new method is proposed and developed to measure adhesive forces by use of the force-distance curve of a micro cantilever with an extremely small amount of testing material such as adhesive proteins. The contact area should be well-controlled at a reasonable value. Even though the area is desired to be as small as possible, a contact region of several micrometers by several micrometers is adopted in order to avoid obtaining meaningless measured values and uncertainty in the contact areas. An AFM cantilever is used after having been modified with a micro glass bead to enlarge the contact area for adhesion. A glass plate with micro-scale circular patterns is fabricated from a glass wafer by micro-machining processes in order to control precisely the contact area in adhesion tests. In the proposed method the adhesive materials are directly applied to the bead attached at the AFM cantilever before it is applied on the top area of the truncated cone on the fabricated glass plate. The developed method is applied to measure the adhesive forces of Cell-Tak® (which is a commercial extracted mussel adhesive) and recombinant Mgfp-5 (which is a recombinant mussel adhesive protein) and the statistical credibility of the measured adhesive force data is enormously improved as a result.
Sungjoo Kim; Wonkyu Moon; JongHyup Jeon. A Reliable Method to Measure the Adhesive Force with a Tiny Amount of Adhesive Material. The Journal of Adhesion 2008, 84, 60 -77.
AMA StyleSungjoo Kim, Wonkyu Moon, JongHyup Jeon. A Reliable Method to Measure the Adhesive Force with a Tiny Amount of Adhesive Material. The Journal of Adhesion. 2008; 84 (1):60-77.
Chicago/Turabian StyleSungjoo Kim; Wonkyu Moon; JongHyup Jeon. 2008. "A Reliable Method to Measure the Adhesive Force with a Tiny Amount of Adhesive Material." The Journal of Adhesion 84, no. 1: 60-77.
In this article, the constitutive relations of three types of piezoelectric bender—the unimorph bender, bimorph bender and triple-layer bender—are derived based on beam theory under the quasi-static equilibrium condition. The relation coefficients are expressed in terms of the geometrical and material properties of the benders. Constitutive relations are derived for a range boundary conditions (fixed-free, fixed-roll and fixed-simply supported) under conditions allowing different lengths of the piezoelectric and elastic layers. The complicated constitutive relations can be easily formulated and verified by using the function for handling symbolic calculations. The derived constitutive relations may assist in the determination of the optimal values of geometrical parameters in the design of actuators and sensors for particular applications.
Jong-Kyu Park; Won-Kyu Moon. Constitutive relations for piezoelectric benders under various boundary conditions. Sensors and Actuators A: Physical 2004, 1 .
AMA StyleJong-Kyu Park, Won-Kyu Moon. Constitutive relations for piezoelectric benders under various boundary conditions. Sensors and Actuators A: Physical. 2004; ():1.
Chicago/Turabian StyleJong-Kyu Park; Won-Kyu Moon. 2004. "Constitutive relations for piezoelectric benders under various boundary conditions." Sensors and Actuators A: Physical , no. : 1.