• ETRI Journal
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• v.30 no.3
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• pp.347-354
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• 2008

In this paper, the design of a low-power 512-bit synchronous EEPROM for a passive UHF RFID tag chip is presented. We apply low-power schemes, such as dual power supply voltage (VDD=1.5 V and VDDP=2.5 V), clocked inverter sensing, voltage-up converter, I/O interface, and Dickson charge pump using Schottky diode. An EEPROM is fabricated with the 0.25 ${\mu}m$ EEPROM process. Power dissipation is 32.78 ${\mu}W$ in the read cycle and 78.05 ${\mu}W$ in the write cycle. The layout size is 449.3 ${\mu}m$ ${\times}$ 480.67 ${\mu}m$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.112-116
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• 2007

We have investigated the hysteresis phenomenon of a hydrogenated amorphous silicon thin film transistor (a-Si:H TFT) and analyzed the effect of hysteresis phenomenon when a-Si:H TFT is a pixel element of active matrix organic light emitting diode (AMOLED). When a-Si:H TFT is addressed to different starting gate voltages, such as 10V and 5V, the measured transfer characteristics with 1uA at $V_{DS}$ = 10V shows that the gate voltage shift of 0.15V is occurred due to the different quantities of trapped charge. When the step gate-voltage in the transfer curve is decreased from 0.5V to 0.05V, the gate-voltage shift is decreased from 0.78V to 0.39V due to the change of charge do-trapping rate. The measured OLED current in the widely used 2-TFT pixel show that a gate-voltage of TFT in the previous frame can influence OLED current in the present frame by 35% due to the change of interface trap density induced by different starting gate voltages.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.83-83
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• 2008

Metal-oxide-silicon-on-insulator (MOSOI) structures were fabricated to study the effect caused by reactive ion etching (RIE) and sacrificial oxidation process on silicon-on-insulator (SOI) layer. The MOSOI capacitors with an etch-damaged SOI layer were characterized by capacitance-voltage (C-V) measurements and compared to the sacrificial oxidation treated samples and the reference samples without etching treatment. The measured C-V curves were compared to the numerical results from 2-dimensional (2-D) simulations. The measurements revealed that the profile of C-V curves significantly changes depending on the SOI surface condition of the MOSOI capacitors. The shift in the measured C-V curves, due to the difference of the fixed oxide charge ($Q_f$), together with the numerical simulation analysis and atomic force microscopy (AFM) analysis, allowed extracting the fixed oxide charges ($Q_f$) in the structures as well as 2-D carrier distribution profiles.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.187-195
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• 2010

IP camera which transmits image signal in network includes web server, network interface unit and CCD(Charge-Coupled Device) module. IP camera is able to transmit image signals by network in real time and to monitor the scene image always by IP or Web address. IP camera is substituted for analog camera now gradually according to the development and progress of camera technology and expect it to extend the boundary in rolling stock gradually cause of the excellent expansibility and noise solution of analog camera. We survey the IP camera system composition in rolling stock and so this can be a help to develop and design IP camera system, because it has unsolved problems for common use of IP camera.

• Journal of Electrochemical Science and Technology
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• v.11 no.1
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• pp.1-13
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• 2020

As research on secondary batteries becomes important, interest in analytical methods to examine the condition of secondary batteries is also increasing. Among these methods, the electrochemical impedance spectroscopy (EIS) method is one of the most attractive diagnostic techniques due to its convenience, quickness, accuracy, and low cost. However, since the obtained spectra are complicated signals representing several impedance elements, it is necessary to understand the whole electrochemical environment for a meaningful analysis. Based on the understanding of the whole system, the circuit elements constituting the cell can be obtained through construction of a physically sound circuit model. Therefore, this mini-review will explain how to construct a physically sound circuit model according to the characteristics of the battery cell system and then introduce the relationship between the obtained resistances of the bulk (R_b), charge transfer reaction (R_ct), interface layer (R_SEI), diffusion process (W) and battery characteristics, such as the state of charge (SOC), temperature, and state of health (SOH).

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.197.2-197.2
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• 2014

그래핀(graphene)의 라만 스펙트럼은 전하밀도(charge density)와 기계적 변형(strain)에 민감하여 연구에 널리 활용되고 있다. 본 연구에서는 기계적 박리법으로 만든 그래핀에 황산 수용액으로 p-형 화학도핑(chemical doping)을 유발시키고 전하밀도의 변이에 따른 라만 스펙트럼의 변화를 조사하였다. 이러한 변화를 통해 황산과 물 분자의 계면 확산을 이해하고, $SiO_2/Si$ 기판의 화학적 특성이 미치는 영향을 파악하고자 하였다. 분자의 효율적인 계면 확산을 위해 고온 산화반응을 이용하여 그래핀의 기저면에 나노공(nanopore)을 만든 후, 액상에서 라만 스펙트럼을 측정하였다. 증류수 속에 담궜을 때 물 분자가 그래핀-기판 계면 사이로 확산되면서 열처리에 의해 유발된 정공이 사라짐을 확인하고, D-봉우리의 가역적인 변화로부터 그래핀의 구조적 변화를 유추하였다. 황산 농도를 증가시켰을 때 G와 2D-봉우리의 진동수가 상호간에 일정한 비율로 증가하여 정공의 밀도가 증가함 알 수 있었다. 동일한 시료에 대해 황산의 농도를 감소시킴으로써 p-형 도핑을 제거하고 동일한 반응을 가역적으로 반복할 수 있었다. 상기한 분자의 2차원 확산 현상은 나노공의 유무와 기판의 전처리 조건에 따라 크게 달라진다는 사실을 확인 할 수 있었다. 또한 여러 파장에서 측정된 전하밀도와 기계적 변형에 의한 G와 2D-봉우리의 진동수 변화로부터 다른 연구자들이 활용할 수 있는 검정곡선을 제시하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.382.1-382.1
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• 2014

Graphene field-effect transistors (GFET) is one of candidates for future high speed electronic devices since graphene has unique electronic properties such as high Fermi velocity (vf=10^6 m/s) and carrier mobility ($15,000cm^2/V{\cdot}s$) [1]. Although the contact property between graphene and metals is a crucial element to design high performance electronic devices, it has not been clearly identified. Therefore, we need to understand characteristics of graphene/metal contact in the GFET. Recently, it is theoretically known that graphene on metal can be doped by presence of interface dipole layer induced by charge transfer [2]. It notes that doping type of graphene under metal is determined by difference of work function between graphene and metal. In this study, we present the GFET fabricated by contact metals having high work function (Pt, Ni) for p-doping and low work function (Ta, Cr) for n-doping. The results show that asymmetric conductance depends on work function of metal because the interfacial dipole is locally formed between metal electrodes and graphene. It induces p-n-p or n-p-n junction in the channel of the GFET when gate bias is applied. In addition, we confirm that charge transfer regions are differently affected by gate electric field along gate length.

• Journal of the Korean institute of surface engineering
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• v.52 no.5
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• pp.258-264
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• 2019

Assembling heterostructures by combining dissimilar oxide semiconductors is a promising approach to enhance charge separation and transfer in photoelectrochemical (PEC) water splitting. In this work, the CuO nanorods array/$Cu_2O$ thin film bilayered heterostructure was successfully fabricated by a facile method that involved a direct electrodeposition of the $Cu_2O$ thin film onto the vertically oriented CuO nanorods array to serve as the photoelectrode for the PEC water oxidation. The resulting copper-oxide-based heterostructure photoelectrode exhibited an enhanced PEC performance compared to common copper-oxide-based photoelectrodes, indicating good charge separation and transfer efficiency due to the band structure realignment at the interface. The photocurrent density and the optimal photocurrent conversion efficiency obtained on the CuO nanorods/$Cu_2O$ thin film heterostructure were $0.59mA/cm^2$ and 1.10% at 1.06 V vs. RHE, respectively. These results provide a promising route to fabricating earth-abundant copper-oxide-based photoelectrode for visible-light-driven hydrogen generation using a facile, low-cost, and scalable approach of combining electrodeposition and hydrothermal synthesis.

• Journal of Korea Society of Digital Industry and Information Management
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• v.14 no.4
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• pp.9-16
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• 2018

This study described partial discharge(PD) distribution analysis between the XLPE(Cross-Linked PolyEthylene)and EPDM(Ethylene Propylene Diene Monomer) interface with unsupervised classification. The ${\phi}-q-n$ patterns were analyzed using phase resolved partial discharge(PRPD). K-means cluster analysis forms a cluster based on similarities and distances among scattered individuals, and analyzes the characteristics of the formed clusters, dividing the multivariate data into several groups according to the similarity of each characteristic, Is a statistical analysis that makes it easier to navigate. It was confirmed that the phase angle of the cluster with the maximum discharge charge was concentrated around $0^{\circ}$ and $180^{\circ}$ at 30 kV after the initial phase distribution localized around $90^{\circ}$ and $300^{\circ}$ expanded to the whole phase angle according to the voltage rise. The Euclidean distance between the center of gravity and the discharge charge in the ${\Phi}-q$ cluster increased with increasing applied voltage.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.285-295
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• 2021

The inverse spinel Cobalt ferrite (CoFe₂O₄, CFO) is considered to be a promising alternative to commercial graphite anodes for lithium ion batteries (LIBs). However, the further development of CFO is limited by its unstable structure during battery cycling and low electrical conductivity. In an effort to address the challenge, we construct three-dimensional hierarchical flower-like CFO nanoclusters (CFO NCs)-decorated carbonized cotton carbon fiber (CFO NCs/CCF) composite. This structure is consisted of microfibers and nanoflower cluster composited of CFO nanoparticle, in which CCF can be used as a long-range conductive matrix, while flower-like CFO NCs can provide abundant active sites, large electrode/electrolyte interface, short lithium ion diffusion path, and alleviated structural stress. As anode materials in LIBs, the flower-like CFO NCs/CCF exhibits excellent electrochemical performance. After 100 cycles at a current density of 0.3 A g^-1, the CFO NCs/CCF delivers a discharge/charge capacity of 1008/990 mAh g^-1. Even at a high current density of 15 A g^-1, it still maintains a charge/discharge capacity of 362/361 mAh g^-1.