• Title/Summary/Keyword: channel layers

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A strategy to enhance the efficiency of land seismic reflection method via controlling seismic energy radiation pattern. (지면 탄성파 반사법의 효율성 향상을 위한 탄성파 발생원 에너지 방사형 변조기법)

  • Kim, Jung-Yul;Kim, Yoo-Sung
    • Proceedings of the Korean Geotechical Society Conference
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    • 2004.03b
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    • pp.807-814
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    • 2004
  • Land seismic reflection survey has been increasingly demanded in various civil engineering works because of its own ability to delineate layers, water table, to detect cavities or fracture zones, to estimate seismic velocities of each layer. However, our shallow subsurface structures are very complex. The relatively thin layer(mostly soil) to the wavelength directly followed by a basic rock with high impedance used to generate complicated surface waves, kind of channel waves with high amplitude that is dominate in entire seismograms and hence the useful reflection events will be almost hopelessly immersed in the undesired surface waves. Thus, it would seem that the use of traditional seismic survey could not be likely to provide in itself a satisfactory information about our exploration targets. This paper hence introduces an efficient measuring strategy illustrating a properly controlled arrangement of the vertical single force sources commonly used, yielding a very sharply elongated form of P-energy with a minimum of S radiation energy, what we call, P-beam source. Abundant experiments of physical modeling showed that in that way the surface waves could be enormously reduced and the reflection events would be additive and thus reinforced. Examples of field data are also illustrated. The contribution of P-beam source will be great in civil engineering area as well as in general geological exploration area.

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Effects of Stress Mismatch on the Electrical Characteristics of Amorphous Silicon TFTs for Active-Matrix LCDs

  • Lee, Yeong-Shyang;Chang, Jun-Kai;Lin, Chiung-Wei;Shih, Ching-Chieh;Tsai, Chien-Chien;Fang, Kuo-Lung;Lin, Hun-Tu;Gan, Feng-Yuan
    • 한국정보디스플레이학회:학술대회논문집
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    • 2006.08a
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    • pp.729-732
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    • 2006
  • The effect of stress match between silicon nitride ($SiN_2$) and hydrogenated amorphous silicon (a-Si:H) layers on the electrical characteristics of thin-film transistors (TFTs) has been investigated. The result shows that modifying the deposition conditions of a Si:H and $SiN_2$ thin films can reduce the stress mismatch at a-Si:H/SiNx interface. Moreover, for best a-Si:H TFT characteristics, the internal stress of gate $SiN_2$ layer with slightly nitrogen-rich should be matched with that of a-Si:H channel layer. The ON current, field-effect mobility, and stability of TFTs can be enhanced by controlling the stress match between a-Si:H and gate insulator. The improvement of these characteristics appears to be due to both the decrease of the interface state density between the a-Si:H and SiNx layer, and the good dielectric quality of the bottom nitride layer.

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2.2 inch qqVGA AMOLED drived by ultra low temperature poly silicon (ULTPS) TFT direct fabricated below $200^{\circ}C$

  • Kwon, Jang-Yeon;Jung, Ji-Sim;Park, Kyung-Bae;Kim, Jong-Man;Lim, Hyuck;Lee, Sang-Yoon;Kim, Jong-Min;Noguchi, Takashi;Hur, Ji-Ho;Jang, Jin
    • 한국정보디스플레이학회:학술대회논문집
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    • 2006.08a
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    • pp.309-313
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    • 2006
  • We demonstrated 2.2inch qqVGA AMOLED display drived by ultra low temperature poly-Si (ULTPS) TFT not transferred but direct fabricated below $200^{\circ}C$. Si channel was crystallized by decreasing impurity concentration even at room temperature. Gate insulator with a breakdown field exceeding 8 MV/cm was realized by Inductively coupled plasma - CVD. In order to reduce stress of plastic, organic film was coated as inter-dielectric and passivation layers. Finally, ULTPS TFT of which mobility is over $20cm^2/Vsec$ was fabricated on transparent plastic substrate and drived OLED display successfully.

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Low-frequency Noise Characteristics of Si0.8Ge0.2 pMOSFET Depending upon Channel Structures and Bias Conditions (채널구조와 바이어스 조건에 따른 Si0.8Ge0.2 pMOSFET의 저주파잡음 특성)

  • Choi Sang-Sik;Yang Hun-Duk;Kim Sang-Hoon;Song Young-Joo;Lee Nae-Eung;Song Jong-In;Shim Kyu-Hwan
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.1
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    • pp.1-6
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    • 2006
  • High performance $Si_{0.8}Ge_{0.2}$ heterostructure metal-oxide-semiconductor field effect transistors (MOSFETs) were fabricated using well-controlled delta-doping of boron and $Si_{0.8}Ge_{0.2}$/Si heterostructure epitaxal layers grown by reduced pressure chemical vapor deposition. In this paper, we report 1/f noise characteristics of the SiGe pMOSFETs measured under various bias conditions of the gate and drain voltages changing in linear operation regions. From the noise spectral density, we found that the gate and drain voltage dependence of the noise represented same features, as usually scaled with $f^{-1}$ However, 1/f noise was found to be much lower in the device with boron delta-doped layer, by a factor of $10^{-1}_10^{-2}$ in comparison with the device fabricated without delta-doped layer. 1/f noise property of delta-doped device looks important because the device may replace bipolar transistors most commonly embedded in high-frequency oscillator circuits.

Fabrication of MFISFET Compatible with CMOS Process Using $SrBi_2Ta_2O_9$(SBT) Materials

  • You, In-Kyu;Lee, Won-Jae;Yang, Il-Suk;Yu, Byoung-Gon;Cho, Kyoung-Ik
    • Transactions on Electrical and Electronic Materials
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    • v.1 no.1
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    • pp.40-44
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    • 2000
  • Metal-ferroelectric-insulator-semoiconductor field effect transistor (MFISFETs) were fabricated using CMOS processes. The Pt/SBT/NO combined layers were etched for forming a conformal gate by using Ti/Cr metal masks and a two step etching method, By the method, we were able to fabricate a small-sized gate with the dimension of $16/4{\mu}textrm{m}$ in the width/length of gate. It has been chosen the non-self aligned source and drain implantation process, We have deposited inter-layer dielectrics(ILD) by low pressure chemical vapor deposition(LPCVD) at $380^{circ}C$ after etching the gate structure and the threshold voltage of p-channel MFISFETs were about 1.0 and -2.1V, respectively. It was also observed that the current difference between the $I_{ON}$(on current) and $I_{OFF}$(off current) that is very important in sensing margin, is more that 100 times in $I_{D}-V_{G}$ hysteresis curve.

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Indium-Zinc Oxide Thin Film Transistors Based N-MOS Inverter (Indium-Zinc 산화물 박막 트랜지스터 기반의 N-MOS 인버터)

  • Kim, Han-Sang;Kim, Sung-Jin
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.30 no.7
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    • pp.437-440
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    • 2017
  • We report on amorphous thin-film transistors (TFTs) with indium zinc oxide (IZO) channel layers that were fabricated via a solution process. We prepared the IZO semiconductor solution with 0.1 M indium nitrate hydrate and 0.1 M zinc acetate dehydrate as precursor solutions. The solution- processed IZO TFTs showed good performance: a field-effect mobility of $7.29cm^2/Vs$, a threshold voltage of 4.66 V, a subthreshold slope of 0.48 V/dec, and a current on-to-off ratio of $1.62{\times}10^5$. To investigate the static response of our solution-processed IZO TFTs, simple resistor load-type inverters were fabricated by connecting a $2-M{\Omega}$ resistor. Our IZOTFTbased N-MOS inverter performed well at operating voltage, and therefore, isa good candidate for advanced logic circuits and display backplane.

A Survey on Qualitative Analysis of Directional VANET MAC Protocols

  • Kim, Bongjae;Cho, Kwangsu;Nam, Choonsung
    • International Journal of Contents
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    • v.10 no.2
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    • pp.9-17
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    • 2014
  • Since vehicles' trajectories are so complex and dense traffic changes in nature frequently, the VANET (Vehicles Ad-hoc Network), using Omni-directional Antenna, has many channel collisions (or overlapping) on Data Link phrases (MAC layers). It is not easy to keep a good seamless communication status for VANET because of its unpredictable network environment. Among VANET research, Directional Antenna have been proposed as one of the most common systematical solutions to reduce (or to mitigate) this miss-communication problems by narrowing communicational ranges and making use of its customized error-detection process. However, even though Directional Antennas help VANET keep good seamless communication, many VANET researchers have reported that Directional VANET still has miss-communicational problems - this has lead to problems like 'Directional Hidden Terminal Problem', 'Deafness', 'Un-accuracy Lobe Scopes' and 'High Deployment Cost' being reported in various papers. To establish well-organized design assessments for a good Directional VANET MAC protocol to overcome these problems, we rearranged and grouped current Directional VANET' qualitative criteria from several current survey papers using these categories- 'Directional Discovery', 'Directional Forwarding' and 'Directional Handover'. In addition, based on the results of the following analysis, we show the essential design concerns that need to be looked at in order to develop a well-designed Directional-VANET MAC protocol.

PIV analysis of free surface effects on flow around a rotating propeller with varying water depth (자유표면과 수심깊이가 회전하는 프로펠러 주위 유동에 미치는 영향에 대한 PIV 해석)

  • Paik Bu Geun;Lee Jung Yeop;Lee Sang Joon
    • 한국가시화정보학회:학술대회논문집
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    • 2004.11a
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    • pp.40-43
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    • 2004
  • The effects of free surface on wake behind a rotating propeller were investigated experimentally in a circulating water channel with the variation of water depth. Instantaneous velocity fields were measured using two-frame PIV technique at tow different blade phases and ensemble-averaged to investigate the phase-averaged flow structure in the wake region. For an isolated propeller, the flow behind the propeller is influenced by the propeller rotation and the free surface. The phase-averaged mean velocity fields show that the potential wake and the viscous wake are formed by the boundary layers developed on the blade surfaces. The interaction between the tip vortices and the slipstream causes the oscillating trajectory of tip vortices. Tip vortices are generated periodically and the slipstream contracts in the near-wake region. The presence of free surface affects the wake structure largely, when the water depth is less than 0.6D. The free surface modifies the vortex structure, especially the tip and trailing vortices and flow structure in slipstreams of the propeller wake behind X/D = 0.3.

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Reflection Seismology in the Southern Ayu Trough, a Slow-spreading Divergent Boundary

  • Hong, Jong-Kuk;Lee, Sang-Mook
    • Ocean and Polar Research
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    • v.24 no.3
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    • pp.189-196
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    • 2002
  • A multichannel seismic survey was conducted in the southern Ayu Trough which is the only spreading boundary between the Philippine Sea and Caroline plates. The seismic system used in this study comprises of 2.46-l sleeve gun and a 12-channel streamer with a group interval of 6.25m. Migration technique was used to analyze seismic velocity, and poststack depth migration was applied to the stacked data. The sediment thickness obtained from the depth section tends to increase with distance from the spreading axis. Sedimentation rates are poorly constrainted in the study area. The apparent half-spreading rates estimated from the sediment thickness and sedimentation rate from DSDP hole on the caroline plate are 4.7mm/yr and 7.9mm/yr at $1^{\circ}24'N\;and\;0^{\circ}42'N$, respectively, which are fester than Previously suggested. On the basis of new oblique spreading geometry, the recalculated spreading rates are 5.4mm/yr and 9.1mm/yr at $1^{\circ}24'N\;and\;0^{\circ}42'N$, respectively. Seismic sections show that the topography is asymmetric across the Ayu Trough and the acoustic basement is rough. These features are consistent with the earlier suggestion that the Ayu Trough is a slow-spreading divergent boundary. A detailed examination of seismic profiles away from the axis shows that sediments can be divided into two layers which implies a possible change in the spreading rate anuor sedimentation condition during the formation of the trough.

Fabrication of Organic Thin Film Transistor(OTFT) for Flexible Display by using Microcontact Printing Process (미세접촉프린팅공정을 이용한 플렉시블 디스플레이 유기박막구동소자 제작)

  • Kim K.Y.;Jo Jeong-Dai;Kim D.S.;Lee J.H.;Lee E.S.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2006.05a
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    • pp.595-596
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    • 2006
  • The flexible organic thin film transistor (OTFT) array to use as a switching device for an organic light emitting diode (OLED) was designed and fabricated in the microcontact printing and low-temperature processes. The gate, source, and drain electrode patterns of OTFT were fabricated by microcontact printing which is high-resolution lithography technology using polydimethylsiloxane(PDMS) stamp. The OTFT array with dielectric layer and organic active semiconductor layers formed at room temperature or at a temperature tower than $40^{\circ}C$. The microcontact printing process using SAM(self-assembled monolayer) and PDMS stamp made it possible to fabricate OTFT arrays with channel lengths down to even nano size, and reduced the procedure by 10 steps compared with photolithography. Since the process was done in low temperature, there was no pattern transformation and bending problem appeared. It was possible to increase close packing of molecules by SAM, to improve electric field mobility, to decrease contact resistance, and to reduce threshold voltage by using a big dielecric.

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