• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.100-100
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• 2016

Among various two-dimensional (2D) materials, 2D semiconductors and insulators have attracted a great deal of interest from nanoscience community beyond graphene, due to their attractive and unique properties. Such excellent characteristics have triggered highly active researches on 2D materials, such as hexagonal boron nitride (hBN), molybdenum disulfide (MoS2), and tungsten diselenide (WSe2). New physics observed in 2D semiconductors allow for development of new-concept devices. Especially, these emerging 2D materials are promising candidates for flexible and transparent electronics. Recently, van der Waals heterostructures (vdWH) have been achieved by putting these 2D materials onto another, in the similar way to build Lego blocks. This enables us to investigate intrinsic physical properties of atomically-sharp heterostructure interfaces and fabricate high performance optoelectronic devices for advanced applications. In this talk, fundamental properties of various 2D materials will be introduced, including growth technique and influence of defects on properties of 2D materials. We also fabricate high performance electronic/optoelectronic devices of vdWH, such as transistors, memories, and solar cells. The device platform based on van der Waals heterostructures show huge improvement of devices performance, high stability and transparency/flexibility due to unique properties of 2D materials and ultra-sharp heterointerfaces. Our work paves a new way toward future advanced electronics based on 2D materials.

• Transactions on Electrical and Electronic Materials
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• 제10권4호
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• pp.111-115
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• 2009

We present a study on the reflection of optically controlled microwave pulses from non uniform plasma layers in semiconductors. The transient response of the microwave pulses in different plasma layers has been evaluated by means of the reflection function of dielectric microstrip lines. The lines were used with an open-ended termination containing an optically induced plasma region, which was illuminated by a light source. The reflection characteristics impedance resulting from the presence of plasma is evaluated by means of the equivalent transmission line model. We have analyzed the variation of the transient response in a 0.01 cm layer with a surface frequency in the region of 128 GHz. In the reflection the variation of the diffusion length $L_D$ is large compared with the absorption depth $1/{\alpha}_l$. The variation of the characteristic response of the plasma layer with differentially localized pulses has been evaluated analytically. The change of the reflection amplitude has been observed at depths of 0.1 cm, 0.01 cm and $0.1{\times}10^{-5}$ cm respectively.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.336-336
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• 2013

Zinc oxide (ZnO) based transparent oxide semiconductors have been studied due to their high transmittance and electrical conductivity. Pure ZnO have unstable optical and electrical properties at high temperatures but doped ZnO thin films can have stable optical and electrical properties. In this paper, transparent oxide semiconductors of Y-doped ZnO thin films prepared by sol-gel method. The ionic radius of $Y^{3+}$ (0.90 A) is close to that of $Zn^{2+}$ (0.74 A), which makes Y suitable dopant for ZnO thin films. The Sn-doped ZnO thin films were deposited onto quartz substrates with different atomic percentages of dopant which were Y/Zn = 0, 1, 2, 3, 4, and 5 at.%. These thin films were pre-heated at $150^{\circ}C$ for 10 min and then annealed at $500^{\circ}C$ or 1 h. The structural and optical properties of the Y-doped ZnO thin films were investigated using field-emission scanning electronmicroscopy (FE-SEM), X-ray diffraction (XRD), UV-visible spectroscopy, and photoluminescence (PL).

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.497-497
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• 2013

Semiconducting amorphous InGaZnO (a-IGZO) has attracted significant research attention as improved deposition techniques have made it possible to make high-quality a-IGZO thin films. IGZO thin films have several advantages over thin film transistors (TFTs) based on other semiconducting channel layers.The electron mobility in IGZO devices is relatively high, exceeding amorphous Si (a-Si) by a factor of 10 and most organic devices by a factor of $10^2$. Moreover, in contrast to other amorphous semiconductors, highly conducting degenerate states can be obtained with IGZO through doping, yet such a state cannot be produced with a-Si. IGZO thin films are capable of mobilities greaterthan 10 $cm^2$/Vs (higher than a-Si:H), and are transparent at visible wavelengths. For oxide semiconductors, carrier concentrations can be controlled through oxygen vacancy concentration. Hence, adjusting the oxygen partial pressure during deposition and post-deposition processing provides an effective method of controlling oxygen concentration. In this study, we deposited IGZO thinfilms at optimized conditions and then analyzed the film's electrical properties, surface morphology, and crystal structure. Then, we explored how to generate IGZO thin films using DC magnetron sputtering. We also describe the construction and characteristics of a bottom-gate-type TFT, including the output and transfer curves and bias stress instability mechanism.

• Nuclear Engineering and Technology
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• 제52권8호
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• pp.1817-1825
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• 2020

Background: Cosmic ray-induced particles can lead to failure of semiconductors packaged for export during air transport. This work performed MCNP 6.2 simulations to optimize shielding against neutrons and protons induced by cosmic radiation Methods and materials: The energy spectra of protons and neutrons by incident angle at the flight altitude were determined using atmospheric cuboid model. Various candidates for the shielding materials and the geometry of the Unit Load Device Container were evaluated to determine the conditions that allow optimal shielding at all sides of the container. Results: It was found that neutrons and protons, at the flight altitude, generally travel with a downward trajectory especially for the particles with high energy. This indicated that the largest number of particles struck the top of the container. Furthermore, the simulation results showed that, among the materials tested, borated polyethylene and stainless steel were the most optimal shielding materials. The optimal shielding structure was also determined with the weight limit of the container in consideration. Conclusions: Under the determined optimal shielding conditions, a significantly reduced number of neutrons and protons reach the contents inside the container, which ultimately reduces the possibility of semiconductor failure during air transport.

• 한국전기전자재료학회논문지
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• 제30권10호
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• pp.665-671
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• 2017

Herein, we report the fabrication of low-voltage N-type organic field-effect transistors by using high capacitance fluorinated polymer gate dielectrics such as P(VDF-TrFE), P(VDF-TrFE-CTFE), and P(VDF-TrFE-CFE). Electron-withdrawing functional groups in PVDF-based polymers typically cause the depletion of negative charge carriers and a high contact resistance in N-channel organic semiconductors. Therefore, we incorporated intermediate layers of a low-k polymerto prevent the formation of a direct interface between PVDF-based gate insulators and the semiconducting active layer. Consequently, electron depletion is inhibited, and the high charge resistance between the semiconductor and source/drain electrodes is remarkably improved by the in corporation of solution-processed charge injection layers.

• 전기전자학회논문지
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• 제22권2호
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• pp.339-343
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• 2018

본 연구는 IGBT 구조에서 JFET 영역의 드라이브 인 확산거리 및 JFET영역의 윈도우의 크기에 따라서 항복전압과 온상태 전압강하 특성을 분석하였다. 시간은 동일하게 하면서 온도를 상승시켜 확산거리를 조정하였으며, 그 결과 항복전압은 감소되나, 온 상태 전압 강하 특성은 현저하게 좋아지는 것을 알 수 있었다. 따라서 드리프트 층의 비저항을 변화시켜 항복전압을 1440V로 고정하여 1.15V의 낮은 온 상태 전압 강하 값을 얻을 수 있었다. 따라서 본 연구결과를 토대로 Planar Gate IGBT에서는 JFET 영역의 공정 및 설계 파라미터를 효율적으로 조절한다면 같은 항복전압을 기준으로 상당히 낮은 온 상태 전압 강하 값을 확보할 수 있어, 소비전력의 측면에서 충분히 활용할 수 있을 것으로 판단된다.

• 전기학회논문지P
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• 제65권2호
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• pp.114-121
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• 2016

This paper is Instant space vector PWM(Pulse Width Modulation)power conversion devices in switching power semiconductors from my generation to losses and switching when the voltage surge and current surge of electronic noise(EMI: Electro Magnetic Interference / RFI: Radio Frequency Interference)to effectively minimize the power soft-switching power conversion circuit topologies of auxiliary resonant DC tank for the purpose of high performance realization of the electric power conversion system by the high-speed switching of a semiconductor device(AQRDCT simultaneously : an active auxiliary resonance using auxiliary Quasi-resonant DC tank)DC link snubber switch has adopted a three-phase voltage inverter. AQRDCL proposed in this paper can reduce the effective and current peak stress of the power semiconductors of the auxiliary resonant snubber circuit compared to the conventional active-resonant DC link snubber, it is not necessary to install the clamp switch of the auxiliary resonant DC link, DC the peak current and power loss of the bus line can be reduced.

• 산업공학
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• 제21권2호
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• pp.229-236
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• 2008

Recently, ubiquitous computing paradigm considers as a tool for making innovation and competitive strength in manufacturing industry like other industries. Particularly, the location-based service that enables us to trace real-time logistics make effective management of schedules for inventory control, facilities and equipments, jobs planning, and facilitate the processes of information management and intelligence, which relate with ERP and SCM in organizations. Our study tries to build the location-based system for products of semiconductors in manufacturing place and suggests the good conditions and effective tracking procedures for positions of products. Our study show that the system is good for the saving of time in tracking products, however, it has to be improved in terms of accuracy. The study verifies the application of RFID technology in manufacturing industry and suggests the improvement of photograph process through RFID. In addition, our research introduces the future operation of FAB in semiconductors' processes that relate with real-time automation and RFID in manufacturing company.

• 한국응용과학기술학회지
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• 제30권2호
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• pp.290-296
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• 2013

We analysed interfacial traps in organic thin-film transistors (TFTs) in which pentacene and 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) organic semiconductors were deposited by means of vacuum-thermal evaporation and drop-coating methods, respectively. The thermally-deposited pentacene film consists of dentritic grains with the average grain size of around 1 m, while plate-like crystals over a few hundred microns are observed in the solution-processed TIPS-pentacene film. From the transfer characteristics of both TFTs, lower subthreshold slope of 1.02 V/decade was obtained in the TIPS-pentacene TFT, compared to that (2.63 V/decade) of the pentacene transistor. The interfacial trap density values calculated from the subthreshold slope are about $3.4{\times}10^{12}/cm^2$ and $9.4{\times}10^{12}/cm^2$ for the TIPS-pentacene and pentacene TFTs, respectively. Herein, lower subthreshold slope and less interfacial traps in TIPS-pentacene TFTs are attributed to less domain boundaries in the solution-processed TIPS-pentacene film.