• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.3
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• pp.83-90
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• 2019

In this paper, Mg-doped AlN epilayers for power semiconductor devices are grown by mixed-source hydride vapor phase epitaxy. Magnesium is used as p-type dopant material in the grown AlN epilayer. The AlN epilayers on the GaN-templated sapphire substrate and GaN-templated-patterned sapphire substrate (PSS), respectively, as the base substrates for device application, were selectively grown. The surface and the crystal structures of the AlN epilayers were investigated by field emission scanning electron microscopy (FE-SEM) and high-resolution-X-ray diffraction (HR-XRD). From the X-ray photoelectron spectroscopy (XPS) and Raman spectra results, the p-type AlN epilayers grown by using the mixed-source HVPE method could be applied to power devices.

• The Korean Journal of Ceramics
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• v.7 no.1
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• pp.36-40
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• 2001

In order to fabricate uncooled IR sensors for pyroelectric applications, multilayered thin films of Pt/PbTiO$_3$/Pt/Ti/Si$_3$N$_4$/SiO$_2$/Si and thermally isolating membrane structures of square-shaped/cantilevers-shaped microstructures were prepared. Cavity was also fabricated via direct silicon wafer bonding and etching technique. Metallic Pt layer was deposited by ion beam sputtering while PbTiO$_3$ thin films were prepared by sol-gel technique. Micromachining technology was used to fabricate microstructured-membrane detectors. In order to avoid a difficulty of etching active layers, silicon-nitride membrane structure was fabricated through the direct bonding and etching of the silicon wafer. Although multilayered thin film deposition and device fabrications were processed independently, these could b integrated to make IR micro-sensor devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.300-300
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• 2008

In this study, the advanced DuoPIGatron-type ion beam (IB) system was applied to inorganic thin film for aligning liquid crystal (LC). LC alignment on $Ta_2O_5$ via IB irradiation was embodied. As a result of IB irradiation, the homogeneously aligned liquid crystal display (LCD) on $Ta_2O_5$ was observed with low pretilt angles. The $Ta_2O_5$ were deposited on indium-tin-oxide coated Coming 1737 glass substrates by rf magnetron sputtering at $200^{\circ}C$. The deposition process resulted in forming very uniform thin film on glass substrates without any defects. To confirm the application of the inorganic alignment on modem display optical devices, we fabricated twisted nematic LCD and measured optical property and response time. As a result of the experiment, the electro optical characteristics of the LCD fabricated by using IB irradiation on $Ta_2O_5$ alignment layer were similar with the other LCD fabricated by using rubbing process.

• Journal of IKEEE
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• v.23 no.1
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• pp.134-142
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• 2019

As the development of internet of energy (IoE) technologies and spread of various electronic devices have diversified patterns of energy consumption, the reliability of demand prediction has decreased, causing problems in optimization of power generation and stabilization of power supply. In this study, we propose a deep learning method, 1-Dimention-Convolution and Bidirectional Long Short-Term Memory (1D-ConvBLSTM), that combines a convolution neural network (CNN) and a Bidirectional Long Short-Term Memory(BLSTM) for highly reliable demand forecasting by effectively extracting the energy consumption pattern. In experimental results, the demand is predicted with the proposed deep learning method for various number of learning iterations and feature maps, and it is verified that the test data is predicted with a small number of iterations.

• The Journal of the Convergence on Culture Technology
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• v.8 no.5
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• pp.749-754
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• 2022

High adhesion and water resistance of the skin surface are required for wearable and skin-attachable electronic patches in various medical applications. In this study, we report a stretchable electronic patch that mimics the drainable structure pattern of the hexagonal channels of frog's pads and the sucker of an octopus based on carbon-based conductive polymer composite materials. The hexagonal channel structure that mimics the pads of frogs drains water and improves adhesion through crack arresting effect, and the suction structure that mimics an octopus sucker shows high adhesion on wet surfaces. In addition, the high-adhesive electronic patch has excellent adhesion to various surfaces such as silicone wafer (max. 4.06 N/cm²) and skin replica surface (max. 1.84 N/cm²) in dry and wet conditions. The high skin-adhesive electronic patch made of a polymer composite material based on a polymer matrix and carbon particles can reliably detect electrocardiogram (ECG) in dry and humid environments. The proposed electronic patch presents potential applications for wearable and skin-attachable electronic devices for detecting various biosignals.

• The Journal of the Korea Contents Association
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• v.7 no.8
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• pp.21-30
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• 2007

Due to the growth of embedded systems and the development of semi-conductor and storage devices, digital convergence devises is ever growing. Digital convergence devices are equipments into which various functions such as communication, playing movies and wave files and electronic dictionarys are integrated. Example are portable multimedia players(PMPs), personal digital assistants(PDAs), and smart phones. Therefore, these devices need an efficient file system which manages and controls various types of files. In designing such file systems, the size constraint for small embedded systems as well as performance and compatibility should be taken into account. In this paper, we suggest the partial buffer cache technique. Contrary to the traditional buffer cache, the partial buffer cache is used for only the FAT meta data and write-only data. Simulation results show that we could enhance the write performance more than 30% when the file size is larger than about 100 KBytes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.3
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• pp.991-1013
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• 2020

E-health services have provided interoperability between personal health devices in personal area network, based the ISO/IEEE 11073 standard. In the healthcare system, the manager handles most agents concurrently through wireless communication. However, due to the distance limitation and the increased number of agents, it may be difficult to provide continuous connectivity. Recently, body area devices have been equipped with various applicable agents, which can even handle agents on behalf of the manager. A BAD may act as an intermediary device to increase system efficiency and performance. In this study, a device called "proxy", which can be installed as software on BAD devices, is proposed. The data measured by an agent can be sent to the proxy first, and subsequently be sent to the manager again. Agents and the manager are not aware of the proxy existence and work normally without the proxy. Furthermore, a new smart proxy and modified manager are proposed. The smart proxy acts as one agent handling measurement data from several agents, which can transmit a significant amount of data at once. The proxy and smart proxy maintain compatibility with existing devices that conform to the 20601 standard. The proposed schemes are verified and the complexities of devices are analyzed. The analysis shows no significant difference among the proxy, smart proxy, and manager. Simulations exhibit that the proposed schemes can improve the system performance.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.3 s.40
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• pp.13-17
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• 2006

Dense and periodic arrays of holes and tungsten none dots were fabricated on silicon oxide and silicon. The holes were approximately 25 nm wide, 40 nm deep, and 60 nm apart. To obtain nano-size patterns, self-assembling resists were used to produce layer of hexagonally ordered parallel cylinders of polymethylmethacrylate(PMMA) in polystyrene(PS) matrix. The PMMA cylinders were degraded and removed with acetic acid rinse to produce a PS mask for pattern transfer. The silicon oxide was removed by fluorine-based reactive ion etching(RIE). Selectively deposited tungsten nano dots were formed inside nano-sized trench by using a low pressure chemical vapor deposition(LPCVD) method. Tungsten nano dot and trenched silicon sizes were 26 nm and 30 nm, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.491-491
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• 2011

Transparent and flexible electronic devices that are light-weight, unbreakable, low power consumption, optically transparent, and mechanical flexible possibly have great potential in new applications of digital gadgets. Potential applications include transparent displays, heads-up display, sensor, and artificial skin. Recent reports on transparent and flexible field-effect transistors (tf-FETs) have focused on improving mechanical properties, optical transmittance, and performances. Most of tf-FET devices were fabricated with transparent oxide semiconductors which mechanical flexibility is limited. And, there have been no reports of transparent and flexible all-organic tf-FETs fabricated with organic semiconductor channel, gate dielectric, gate electrode, source/drain electrode, and encapsulation for sensor applications. We present the first demonstration of transparent, flexible all-organic sensor based on multifunctional organic FETs with organic semiconductor channel, gate dielectric, and electrodes having a capability of sensing infrared (IR) radiation and mechanical strain. The key component of our device design is to integrate the poly(vinylidene fluoride-triflouroethylene) (P(VDF-TrFE) co-polymer directly into transparent and flexible OFETs as a multi-functional dielectric layer, which has both piezoelectric and pyroelectric properties. The P(VDF-TrFE) co-polumer gate dielectric has a high sensitivity to the wavelength regime over 800 nm. In particular, wavelength variations of P(VDF-TrFE) molecules coincide with wavelength range of IR radiation from human body (7000 nm ~14000 nm) so that the devices are highly sensitive with IR radiation of human body. Devices were examined by measuring IR light response at different powers. After that, we continued to measure IR response under various bending radius. AC (alternating current) gate biasing method was used to separate the response of direct pyroelectric gate dielectric and other electrical parameters such as mobility, capacitance, and contact resistance. Experiment results demonstrate that the tf-OTFT with high sensitivity to IR radiation can be applied for IR sensors.

• Korean Journal of Optics and Photonics
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• v.18 no.1
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• pp.50-55
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• 2007

Using the Selective Area Growth (SAG) technology of Metal Organic Chemical Vapor Deposition (MOCVD), we successfully integrated an active device and passive devices on the same substrate. In other words, we integrated a Semiconductor Optical Amplifier (SOA) as an active device and an S-bend waveguide and a Multi Mode Interference (MMI) waveguide as passive devices. The SOA is successfully integrated with passive devices on the same substrate. The Cross-Gain Modulation (XGM) characteristic of the integrated SOA and the loss of an MMI and an S-bend waveguide were measured. Measured XGM characteristics of the SOA showed an extinction ratio of 8.82 dB. The total loss of the MMI and S-bend waveguide was 18 dB.