• Title/Summary/Keyword: Dielectric Materials

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Interfacial Charge Transport Anisotropy of Organic Field-Effect Transistors Based on Pentacene Derivative Single Crystals with Cofacial Molecular Stack (코페이셜 적층 구조를 가진 펜타센 유도체 단결정기반 유기트랜지스터의 계면 전하이동 이방성에 관한 연구)

  • Choi, Hyun Ho
    • Journal of Adhesion and Interface
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    • v.20 no.4
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    • pp.155-161
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    • 2019
  • Understanding charge transport anisotropy at the interface of conjugated nanostructures basically gives insight into structure-property relationship in organic field-effect transistors (OFET). Here, the anisotropy of the field-effect mobility at the interface between 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) single crystal with cofacial molecular stacks in a-b basal plane and SiO gate dielectric was investigated. A solvent exchange method has been used in order for TIPS-pentacene single crystals to be grown on the surface of SiO2 thin film, corresponding to the charge accumulation at the interface in OFET structure. In TIPS-pentacene OFET, the anisotropy ratio between the highest and lowest measured mobility is revealed to be 5.2. By analyzing the interaction of a conjugated unit in TIPS-pentacene with the nearest neighbor units, the mobility anisotropy can be rationalized by differences in HOMO-level coupling and hopping routes of charge carriers. The theoretical estimation of anisotropy based on HOMO-level coupling is also consistent with the experimental result.

Scanning Kelvin Probe Microscopy analysis of silicon carbide device structures (Scanning Kelvin Probe Microscopy를 이용한 SiC 소자의 분석)

  • Jo, Yeong-Deuk;Ha, Jae-Geun;Koh, Jung-Hyuk;Bang, Uk;Kim, Sang-Cheol;Kim, Nam-Gyun;Koo, Sang-Mo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2008.06a
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    • pp.132-132
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    • 2008
  • Silicon carbide (SiC) is an attractive material for high-power, high-temperature, and high-frequency applications. So far, atomic force microscopy (AFM) has been extensively used to study the surface charges, dielectric constants and electrical potential distribution as well as topography in silicon-based device structures, whereas it has rarely been applied to SiC-based structures. In this work, the surface potential and topography distributions SiC with different doping levels were measured at a nanometer-scale resolution using a scanning kelvin probe force microscopy (SKPM) with a non-contact mode AFM. The measured results were calibrated using a Pt-coated tip and a metal defined electrical contacts of Au onto SiC. It is assumed that the atomically resolved surface potential difference does not originate from the intrinsic work function of the materials but reflects the local electron density on the surface. It was found that the work function of the Au deposited on SiC surface was higher than that of original SiC surface. The dependence of the surface potential on the doping levels in SiC, as well as the variation of surface potential with respect to the schottky barrier height has been investigated. The results confirm the concept of the work function and the barrier heights of metal/SiC structures.

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Ferroelectric Properly of Bi3.75La0.25Ti3O12 Ceramic Sintered in the Ambient (분위기 소결공정에 의한 Bi3.75La0.25Ti3O12세라믹의 강유전특성)

  • 김응권;박춘배;박기엽;송준태
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.15 no.9
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    • pp.783-787
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    • 2002
  • In recent year, B $i_{4-}$x L $a_{x}$ $Ti_3$ $O_{12(BLT)}$ is one of promising substitute materials for the ferroelectric random access memory(FRAM) applications. But the systematic composition is still insufficient, so this experiment was carried out in ceramic ambient sintering process which has the very excellent ferroelectric property. Samples were prepared by a bulk and the purpose which was estimated with a suitability of thin films applications. The density of B $i_{3.75}$ L $a_{0.25}$ $Ti_3$ $O_{12}$ was high and the XRD pattern showed that the intensity of main peak (117) was increased at the argon ambient sintering. Controlling the quantity of oxygen, crystallization showed a thin, long plate like type, and we obtained the excellent dielectric and polarization properties at the argon atmosphere sintering. Also this sintering process was effective at the bulk sample. Argon ambient sintered sample produced higher permittivity of 154, the remanent polarization(2Pr) of 6.8 uC/$\textrm{cm}^2$ compared with that sintered in air and oxygen ambient. And this sintering process showed a possibility which could be applied to thin films process..

Study on the Different Characteristic of Chemical and Electronic Properties (SiOC 박막의 화학적 특성과 전기적인 특성에 대한 차이점에 관한 연구)

  • Oh, Teresa
    • Journal of the Korean Vacuum Society
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    • v.18 no.1
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    • pp.49-53
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    • 2009
  • The chemical properties of SiOC film was studied for inter-layer insulator. SiOC film was formed with non polarity due to the appropriate union by the alkyl and hydroxyl group. An amorphous structure of non polarity can induce the low dielectric constant materials. The chemical properties of thin film can define the bonding structure owing to the ionic variation, and the analysis of chemical properties was researched by the carbon content using the FTIR spectra, and induced the film with non polarity. The electrical properties is the electron flow, and is always not the same as the chemical properties. The electrical properties of SiOC film with various flow rate ratios was analyzed and researched the correlation between the chemical properties. SiOC film showed the increasing of the leakage current after annealing process, and abruptly increased the carbon content at some samples. But the sample with increasing the carbon content decreased the leakage current. It means that the chemical properties is not the same as the electrical properties, and the carbon is related with the variation of the bonding structure, and does not contribute the current flow.

Thermal Conductivity Measurement of High-k Oxide Thin Films (High-k 산화물 박막의 열전도도 측정)

  • Kim, In-Goo;Oh, Eun-Ji;Kim, Yong-Soo;Kim, Sok-Won;Park, In-Sung;Lee, Won-Kyu
    • Journal of the Korean Vacuum Society
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    • v.19 no.2
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    • pp.141-147
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    • 2010
  • In this study, high-k oxide films like $Al_2O_3$, $TiO_2$, $HfO_2$ were deposited on Si, $SiO_2$/Si, GaAs wafers, and then the thermal conductivity was measured by using thermo-reflectance method which utilizes the reflectance variation of the film surface produced by the periodic temperature variation. The result shows that high-k oxide films with 50 nm thickness have high thermal conductivity of 0.80~1.29 W/(mK). Therefore, effectively dissipate the heat generated in the electric circuit such as CMOS memory device, and the heat transfer changes according to the micro grain size.

Design of a VHF-UHF Band Blade Antenna for Aircraft Applications (VHF-UHF 대역 항공기용 블레이드 안테나 설계)

  • Go, Jooseoc;Hur, Jun;Kay, Youngchul;Choo, Hosung
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.25 no.6
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    • pp.619-627
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    • 2014
  • In this paper, we designed a blade antenna for VHF-UHF band(500 MHz~3 GHz) to be used as aircraft antennas. Unlike previously reported researches that use high-dielectric materials and insert rectangular extended grounds, the antenna structure was designed by optimizing the curvature of both a radiator and an extended ground whose shape is varied by changing the exponent of an n-th polynomial. Based on the optimized structure, we measured impedance matching and gain performances to evaluate the antenna in the VHF-UHF band(500 MHz~3 GHz). As a result, we confirmed that the antenna shows matching characteristics of less than -6 dB and has average gains of greater than -5 dBi in the entire VHF-UHF band.

Properties Optimization for Perovskite Oxide Thin Films by Formation of Desired Microstructure

  • Liu, Xingzhao;Tao, Bowan;Wu, Chuangui;Zhang, Wanli;Li, Yanrong
    • Journal of the Korean Ceramic Society
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    • v.43 no.11 s.294
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    • pp.715-723
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    • 2006
  • Perovskite oxide materials are very important for the electronics industry, because they exhibit promising properties. With an interest in the obvious applications, significant effort has been invested in the growth of highly crystalline epitaxial perovskite oxide thin films in our laboratory. And the desired structure of films was formed to achieve excellent properties. $Y_1Ba_2Cu_3O_{7-x}$ (YBCO) superconducting thin films were simultaneously deposited on both sides of 3 inch wafer by inverted cylindrical sputtering. Values of microwave surface resistance R$_2$ (75 K, 145 GHz, 0 T) smaller than 100 m$\Omega$ were reached over the whole area of YBCO thin films by pre-seeded a self-template layer. For implementation of voltage tunable high-quality varactor, A tri-layer structured SrTiO$_3$ (STO) thin films with different tetragonal distortion degree was prepared in order to simultaneously achieve a large relative capacitance change and a small dielectric loss. Highly a-axis textured $Ba_{0.65}Sr_{0.35}TiO_3$ (BST65/35) thin films was grown on Pt/Ti/SiO$_2$/Si substrate for monolithic bolometers by introducing $Ba_{0.65}Sr_{0.35}RuO_3$ (BSR65/35) thin films as buffer layer. With the buffer layer, the leakage current density of BST65/35 thin films were greatly reduced, and the pyroelectric coefficient of $7.6\times10_{-7}$ C $cm^{-2}$ $K^{-1}$ was achieved at 6 V/$\mu$m bias and room temperature.

The study on the properties of binary mixture(crystalline silica/AIN) filled EMC(Epoxy Molding Compounds) (결정성 실리카/질화 알루미늄 혼합충진에 따른 EMC의 물성 연구)

  • 김원호;홍용우;배종우;황영훈;김부웅
    • Journal of the Microelectronics and Packaging Society
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    • v.6 no.4
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    • pp.41-48
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    • 1999
  • Silica is the most popular materials as a filler of EMC for microelectronic packaging. However, because of its low thermal conductivity, the use of silica is restricted to parts requiring high thermal dissipation. The superior fluidity of EMC can be achieved with a combination of filler size distribution. In this study, physical properties of EMC filled with the crystalline silica(13$\mu\textrm{m}$) which have high fluidity and low cost and the AlN(2 $\mu\textrm{m}$) which have high thermal conductivity and low coefficient of thermal expansion were evaluated by changing the AlN/silica ratios. As a result of the evaluation of physical properties of EMC, the optimum mixing ratio of AlN/crystalline silica was 0.3/0.7. In this condition, binary mixture(AlN/crystalline silica) filled EMC showed superior properties, i.e., in the thermal conductivity, CTE, dielectric constant, flexural strength, and thermal shock resistance without reduction of fluidity.

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A study on the Frequency Dependence of Dynamic Pyroelectric Properties for $Pb_{1-x}La_{x}Ti_{1-x/4}O_3$(x=0.1)(PLT(10)) Ferroelectric Thin Film ($Pb_{1-x}La_{x}Ti_{1-x/4}O_3$(x=0.1)(PLT(10)) 강유전체 박막에서 동적 초전특성의 주파수 의존성에 관한 연구)

  • 차대은;장동훈;강성준;윤영섭
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11a
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    • pp.104-107
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    • 2001
  • The fabricated La-modified lead titanate (PLT) thin flirt without poling treatment was investigated for modulation frequency dependence of pyroelectric properties by the dynamic method. $Pb_{1-x}La_{x}Ti_{1-x/4}O_3$PLT (x=0.1) thin film having 10 mol% La content was deposited on a Pt/$TiO_{x}$/$SiO_2$/Si substrate by sol-gel method. The PLT(10) thin film exhibits a relatively excellent dielectric property. The pyroelectric coefficient (p) of the PLT(10) thin film is 6.6 x $10^{-9}$C/$\textrm{cm}^2$.K without frequency dependence. The figure of merits for the voltage responsivity and specific detectivity are 1.03${\times}$$10^{-11}$/C.cm/J and 1.46 x $10^{-9}$C.cm/J, respectively. The PLT(10) thin film has voltage responsivity ($R_{V}$) of 5.15 V/W at 8 Hz. Noise equivalent power (NEP) and specific detectivity (D*) of the PLT(10) thin film are 9.93 x $10^{-8}$W/Hz$^{1/2}$ and 1.81 x $10^{6}$ cmHz$^{1/2}$/W at the same frequency of 100 Hz, respectively. The results means that PLT thin film having 10 mol % La content is suitable for the sensing materials of pyroelectric IR sensors.

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Dielectric and piezoelectric properties of the PSS-PT-PZ ceramics doped with $La_2$O_3 ($La_2$O_3가 첨가된 PSS-PT-PZ 세라믹의 유전 및 압전특성)

  • 이성갑;박인길;류기원;이영희
    • Electrical & Electronic Materials
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    • v.5 no.2
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    • pp.198-206
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    • 1992
  • (P $b_{1-x}$L $a_{x}$)[(S $b_{1}$2/S $n_{1}$2/) $Ti_{y}$ Z $r_{1-y}$] $O_{3}$(0.leq.x.leq.0.04, 0.25.leq.y.leq.0.40) 세라믹을 1250[.deg.C]에서 2시간동안 유지시켜 일반 소성법으로 제작하였으며 조성 및 L $a_{2}$ $O_{3}$첨가량에 따른 구조적, 압전적 특성을 관찰하였다. L $a_{2}$ $O_{3}$의 첨가량이 3-4[mol%]인 경우 La-rich의 pyrochlore상이 형성되었다. 시편의 평균결정립 크기는 1-2[.mu.n]의 크기를 나타내었으며 PbTi $O_{3}$조성이 증가함에 따라 다소 감소하는 경향을 나타내었다. 각 조성의 시편에 대해 PbTi $O_{3}$ 및 L $a_{2}$ $O_{3}$의 첨가량이 증가할수록 유전상수는 증가하는 경향을 나타내었으며 상전이 온도인 큐리온도는 PbTi $O_{3}$조성이 감소할수록 L $a_{2}$ $O_{3}$첨가량이 증가할수록 감소하는 경향을 나타내었다. 압전 전하계수 및 전기기계 결합계수는 L $a_{2}$ $O_{3}$첨가량 및 PbTi $O_{3}$조성에 따라 증가하였으며 L $a_{2}$ $O_{3}$가 4[mol%]첨가된 0.10PSS-0.40PT-0.50PZ 시편에서 각각 250x$10^{-12}$[C/N], 29.7[%]의 최대값을 나타내었다. 기계적 품질계수는 L $a_{2}$ $O_{3}$첨가량 및 PbTi $O_{3}$조성이 증가할수록 감소하는 경향을 나타내었으며 0.10PSS-0.25PT-0.65PZ 시편에서 138의 최대값을 나타내었다.다.

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