• Advances in nano research
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• 제15권5호
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• pp.385-399
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• 2023

Hexagonal boron nitride (h-BN), commonly referred to as Boron Nitride Nanoribbons (BNNRs), is an electrical insulator characterized by high thermal stability and a wide bandgap semiconductor property. This study delves into the electronic properties of two BNNR configurations: Armchair BNNRs (ABNNRs) and Zigzag BNNRs (ZBNNRs). Utilizing the nearest-neighbour tight-binding approach and numerical methods, the electronic properties of BNNRs were simulated. A simplifying assumption, the Hamiltonian matrix is used to compute the electronic properties by considering the self-interaction energy of a unit cell and the interaction energy between the unit cells. The edge perturbation is applied to the selected atoms of ABNNRs and ZBNNRs to simulate the electronic properties changes. This simulation work is done by generating a custom script using numerical computational methods in MATLAB software. When benchmarked against a reference study, our results aligned closely in terms of band structure and bandgap energy for ABNNRs. However, variations were observed in the peak values of the continuous curves for the local density of states. This discrepancy can be attributed to the use of numerical methods in our study, in contrast to the semi-analytical approach adopted in the reference work.

• Transactions on Electrical and Electronic Materials
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• 제14권5호
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• pp.250-253
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• 2013

In this paper, we fabricated 3D pillar type silicon-oxide-nitride-oxide-silicon (SONOS) devices for high density flash applications. To solve the limitation between erase speed and data retention of the conventional SONOS devices, bandgap-engineered (BE) tunneling oxide of oxide-nitride-oxide configuration is integrated with the 3D structure. In addition, the tunneling oxide is modulated by another method of $N_2$ ion implantation ($N_2$ I/I). The measured data shows that the BE-SONOS device has better electrical characteristics, such as a lower threshold voltage ($V_{\tau}$) of 0.13 V, and a higher $g_{m.max}$ of 18.6 ${\mu}A/V$ and mobility of 27.02 $cm^2/Vs$ than the conventional and $N_2$ I/I SONOS devices. Memory characteristics show that the modulated tunneling oxide devices have fast erase speed. Among the devices, the BE-SONOS device has faster program/erase (P/E) speed, and more stable endurance characteristics, than conventional and $N_2$ I/I devices. From the flicker noise analysis, however, the BE-SONOS device seems to have more interface traps between the tunneling oxide and silicon substrate, which should be considered in designing the process conditions. Finally, 3D structures, such as the pillar type BE-SONOS device, are more suitable for next generation memory devices than other modulated tunneling oxide devices.

• 한국전기전자재료학회논문지
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• 제26권3호
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• pp.198-203
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• 2013

Dye-sensitized solar cells (DSSCs) based on titanium dioxide ($TiO_2$) have been extensively studied because of their promising low-cost alternatives to conventional semiconductor based solar cells. DSSCs consist of molecular dye at the interface between a liquid electrolyte and a mesoporous wide-bandgap semiconductor oxide. Most efforts for high conversion efficiencies have focused on dye and liquid electrolytes. However, interface engineering between dye and electrode is also important to reduce recombination and improve efficiency. In this work, for interface engineering, we deposited semiconducting ferroelectric $BiFeO_3$ with bandgap of 2.8 eV on $TiO_2$ nanoparticles and nanotubes. Photovoltaic properties of DSSCs were characterized as a function of thickness of $BiFeO_3$. We showed that ferroelectric $BiFeO_3$-coated $TiO_2$ electrodes enable to increase overall efficiency of DSSCs, which was associated with efficient electron transport due to internal electric field originating from electric polarization. It was suggested that engineering the dye-$TiO_2$ interface using ferroelectric materials as inorganic modifiers can be key parameter for enhanced photovoltaic performance of the cell.

• 한국전기전자재료학회논문지
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• 제36권1호
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• pp.74-80
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• 2023

Gallium oxide (Ga₂O₃) thin films were grown on c-, a-, m-, r-plane sapphire substrates using a mist chemical vapor deposition system. Various growth temperature range of 400~600℃ was applied for Ga₂O₃ thin film deposition. Then, several structural properties were characterized such as film thickness, crystal phase, lattice orientation, surface roughness, and optical bandgap. Under the certain growth temperature of 500℃, all grown Ga₂O₃ featured rhombohedral crystal structures and well-aligned preferred orientation to sapphire substrate. The films grown on c-and r-plane sapphire substrates, showed low surface roughness and large optical bandgap compared to those on a-and m-plane substrates. Therefore, various sapphire orientation can be potentially applicable for future Ga₂O₃-based electronics applications.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2002년도 종합학술발표회 논문집 Vol.12 No.1
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• pp.34-38
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• 2002

기존에 제안된 도파관 스위치의 경우, 도파관의 E-plane에 PBG 기판을 내장하게 되는데, 이 경우 PBG 기판의 저항값을 조절해주는 MEMS 스위치의 바이어스 라인에 대한 문제점이 발생한다 본 논문에서는 PBG 기판을 도파관의 H-plane에 놓음으로써 바이어스 라인을 RF로부터 쉽게 분리하고, 또한 단일 공진 주파수를 갖는 PBG의 경우에 제한된 기판의 길이로 인하여 bandwidth가 좁아지는 문제점을 서로 다른 공진 주파수를 갖는 PBG 기판의 연결을 통해서 bandwidth를 약 80%이상 증가시킬 수 있음을 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기물성,응용부문
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• pp.60-61
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• 2005

Electrodes were fabricated on a single ZnO nanowire by photolithography process, metal evaporation, and lift-off. The slow photoresponses of the ZnO nanowire under the continuous illumination of 325nm-wavelength light (corresponding to above-bandgap excitation) indicate that the traps related to oxygen vacancy disturb the flow of electron in ZnO nanowire. The photoresponse and PL spectra were measured, and observed that the excitonic band in the PL spectrum was absent in the photoresponse.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 춘계학술대회 논문요약집
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• pp.10-10
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• 2004

유전율이 서로 다른 물질을 나노 크기로 주기적으로 배열하여 황자 띠간격(Photonic bandgap)을 이루게 하는 광결정(Photonic crystal)에 인위적인 결함을 부가하여 광파워 분배 및 Mux/Demux 등 광회로 기능 수행을 할 수 있도록 집적화한 광도파로 소자가 미래형 정보통신사회를 위한 초고집적화, 초고속화, 저전력 및 신기능 등의 특성을 위하여 요구된다. 이러한 나노 광결정 소자는 다양한 방법으로 제작이 시도되고 있는데, 나노 임프린트 기술은 실장밀도가 높으며, 수십 나노급의 패턴이 주기적으로 배열된 구조물의 성형에 큰 장점이 있어서 본 연구에서 다루어졌다.(중략)

• JSTS:Journal of Semiconductor Technology and Science
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• 제11권3호
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• pp.182-189
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• 2011

In this work, a tunneling field-effect transistor (TFET) based on heterojunctions of compound and Group IV semiconductors is introduced and simulated. TFETs based on either silicon or compound semiconductors have been intensively researched due to their merits of robustness against short channel effects (SCEs) and excellent subthreshold swing (SS) characteristics. However, silicon TFETs have the drawback of low on-current and compound ones are difficult to integrate with silicon CMOS circuits. In order to combine the high tunneling efficiency of narrow bandgap material TFETs and the high mobility of III-V TFETs, a Type-I heterojunction tunneling field-effect transistor (I-HTFET) adopting $Ge-Al_xGa_{1-x}As-Ge$ system has been optimized by simulation in terms of aluminum (Al) composition. To maximize device performance, we considered a nanowire structure, and it was shown that high performance (HP) logic technology can be achieved by the proposed device. The optimum Al composition turned out to be around 20% (x=0.2).

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2012년도 추계학술대회
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• pp.221-224
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• 2012

본 논문에서는 MEMS 가속도센서를 위한 CMOS 인터페이스 회로를 설계하였다. 설계된 CMOS 인터페이스 회로는 CVC(Capacitance to Voltage Converter), 그리고 SC-Integrator와 Comparator를 포함하는 ${\Sigma}{\Delta}$ Modulator로 구성되어 있다. 회로에 일정한 Bias를 공급할 수 있도록 Bandgap Reference를 이용하였으며, 저주파 잡음과 offset을 감소시키기 위하여 ${\Sigma}{\Delta}$ Modulator에 CHS(Chopper-Stabilization) 기법을 사용하였다. 그 결과 설계된 ${\Sigma}{\Delta}$ Modulator의 출력은 입력 전압 진폭이 100mV가 증가할 때 duty cycle은 10%의 비율로 증가하고, 전체 회로의 Sensitivity는 x, y축은 0.45V/g, z축은 0.28V/g의 결과를 얻을 수 있었다. 제안된 CMOS 인터페이스 회로는 CMOS 0.35um공정을 이용하여 설계되었다. 입력 전압은 3.3V이며, 샘플링 주파수는 2MHz이다. 설계된 칩의 크기는 PAD를 포함하여 $0.96mm{\times}0.85mm$이다.

• 한국광학회지
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• 제19권1호
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• pp.9-14
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• 2008

본 논문에서는 테라헤르츠 대역에서 동작하는 새로운 구조의 Yagi-Uda 안테나를 설계하였다. 제안한 Yagi-Uda 안테나는 안테나의 driver를 반 파장 다이폴이 아닌 전 파장 다이폴을 사용함으로써 공진주파수에서 $2000{\Omega}$ 정도의 높은 입력 저항을 얻을 수 있었다. 바이어스 선에 Photonic Bandgap 구조를 적용하여 바이어스 선로로의 전류누설을 최소화 하였고, 안테나를 얇은 기판에 설계함으로써 기판의 비유전율로 인한 안테나의 임피던스 저하를 막고 Yagi-Uda 안테나 고유의 단방향 지향적인 복사특성을 나타나게 하였다. 따라서 제안한 Yagi-Uda 안테나는 포토믹서와의 임피던스 부정합 문제를 개선하여 테라헤르츠파의 출력을 증가 시킬 수 있을 것이라 예상한다.