• Title, Summary, Keyword: Thin film transistors

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Influence of Oxygen Partial Pressure on ZnO Thin Films for Thin Film Transistors

  • Kim, Jae-Won;Kim, Ji-Hong;Roh, Ji-Hyoung;Lee, Kyung-Joo;Moon, Sung-Joon;Do, Kang-Min;Park, Jae-Ho;Jo, Seul-Ki;Shin, Ju-Hong;Yer, In-Hyung;Koo, Sang-Mo;Moon, Byung-Moo
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.106-106
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    • 2011
  • Recently, zinc oxide (ZnO) thin films have attracted great attention as a promising candidate for various electronic applications such as transparent electrodes, thin film transistors, and optoelectronic devices. ZnO thin films have a wide band gap energy of 3.37 eV and transparency in visible region. Moreover, ZnO thin films can be deposited in a poly-crystalline form even at room temperature, extending the choice of substrates including even plastics. Therefore, it is possible to realize thin film transistors by using ZnO thin films as the active channel layer. In this work, we investigated influence of oxygen partial pressure on ZnO thin films and fabricated ZnO-based thin film transistors. ZnO thin films were deposited on glass substrates by using a pulsed laser deposition technique in various oxygen partial pressures from 20 to 100 mTorr at room temperature. X-ray diffraction (XRD), transmission line method (TLM), and UV-Vis spectroscopy were employed to study the structural, electrical, and optical properties of the ZnO thin films. As a result, 80 mTorr was optimal condition for active layer of thin film transistors, since the active layer of thin film transistors needs high resistivity to achieve low off-current and high on-off ratio. The fabricated ZnO-based thin film transistors operated in the enhancement mode with high field effect mobility and low threshold voltage.

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Fabrication and Characterization of Zinc-Tin-Oxide Thin Film Transistors Prepared through RF-Sputtering

  • Do, Woori;Choi, Jeong-Wan;Ko, Myeong-Hee;Kim, Eui-Hyeon;Hwang, Jin-Ha
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.207.2-207.2
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    • 2013
  • Oxide-based thin film transistors have been attempted as powerful candidates for driving circuits for active-matrix organic light-emitting diodes and transparent electronics. The oxide TFTs are based on the amorphous multi-component oxides involving zinc, indium, and/or tin elements as main cation sources. The current work employed RF sputtering in order to deposit zinc-tin oxide thin films applicable to transparent oxide thin film transistors. The deposited thin film was characterized and probed in terms of materials and devices. The physical/chemical characterizations were performed using X-ray diffraction, Atomic Force Microscopy, Spectroscopic Ellipsometry, and X-ray Photoelectron Spectroscopy. The thin film transistors were fabricated using a bottom-gated structure where thermally-grown silicon oxide layers were applied as gate-dielectric materials. The inherent properties of oxide thin films are combined with the corresponding device performances with the aim to fabricating the multi-component oxide thin films being optimized towards transparent electronics.

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New Dynamic Logic Gate Design Method for Improved TFT Circuit Performance

  • Jeong, Ju-Young;Kim, Jae-Geun
    • Journal of Information Display
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    • v.6 no.1
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    • pp.17-21
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    • 2005
  • We explored a new way of designing dynamic logic gates with low temperature polysilicon thin film transistors to increase the speed. The proposed architecture of logic gates utilizes the structural advantage of smaller junction capacitance of thin film transistors. This method effectively blocks leakage of current through the thin film transistors. Furthermore, the number of transistors used in logic gates is reduced thereby reducing power consumption and chip area. Through HSPICE .simulation, it is confirmed that the circuit speed is also improved in all logic gates designed.

Electrical Characterization of Amorphous Zn-Sn-O Transistors Deposited through RF-Sputtering

  • Choi, Jeong-Wan;Kim, Eui-Hyun;Kwon, Kyeong-Woo;Hwang, Jin-Ha
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.304.1-304.1
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    • 2014
  • Flat-panel displays have been growing as an essential everyday product in the current information/communication ages in the unprecedented speed. The forward-coming applications require light-weightness, higher speed, higher resolution, and lower power consumption, along with the relevant cost. Such specifications demand for a new concept-based materials and applications, unlike Si-based technologies, such as amorphous Si and polycrystalline Si thin film transistors. Since the introduction of the first concept on the oxide-based thin film transistors by Hosono et al., amorphous oxide thin film transistors have been gaining academic/industrial interest, owing to the facile synthesis and reproducible processing despite of a couple of shortcomings. The current work places its main emphasis on the binary oxides composed of ZnO and SnO2. RF sputtering was applied to the fabrication of amorphous oxide thin film devices, in the form of bottom-gated structures involving highly-doped Si wafers as gate materials and thermal oxide (SiO2) as gate dielectrics. The physical/chemical features were characterized using atomic force microscopy for surface morphology, spectroscopic ellipsometry for optical parameters, X-ray diffraction for crystallinity, and X-ray photoelectron spectroscopy for identification of chemical states. The combined characterizations on Zn-Sn-O thin films are discussed in comparison with the device performance based on thin film transistors involving Zn-Sn-O thin films as channel materials, with the aim to optimizing high-performance thin film transistors.

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Downscaling of self-aligned inkjet printed polymer thin film transistors

  • Noh, Yong-Young;Sirringhaus, Henning
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.1564-1567
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    • 2008
  • We demonstrate here a self-aligned printing approach that allows downscaling of printed organic thin-film transistors to channel lengths of 100 - 400 nm. A perfected down-scaled polymer transistors (L= 200 nm) showing high transition frequency over 1.5 Mhz were realized with thin polymer dielectrics, controlling contact resistance, and minimizing overlap capacitance via self-aligned gate configuration.

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Wet-processed Thin-film Transistors of Pantacene

  • Minakata, Takashi
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.94-97
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    • 2008
  • We have fabricated wet-processed thin-film transistors of unsubstituted pentacene by two kinds of fabrications both solution and dispersion processes. Transistor performances with thin film structures including grain structures in the films by two pro cesses are studied.

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Effects of an Aluminum Contact on the Carrier Mobility and Threshold Voltage of Zinc Tin Oxide Transparent Thin Film Transistors

  • Ma, Tae-Young
    • Journal of Electrical Engineering and Technology
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    • v.9 no.2
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    • pp.609-614
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    • 2014
  • We fabricated amorphous zinc tin oxide (ZTO) transparent thin-film transistors (TTFTs). The effects of Al electrode on the mobility and threshold voltage of the ZTO TTFTs were investigated. It was found that the aluminum (Al)-ZTO contact decreased the mobility and increased the threshold voltage. Traps, originating from $AlO_x$, were assumed to be the cause of degradation. An indium tin oxide film was inserted between Al and ZTO as a buffer layer, forming an ohmic contact, which was revealed to improve the performance of ZTO TTFTs.

Effect of Sputtering Working Pressure on the Optical and Electrical Properties of InZnO Thin-Film Transistors (스퍼터링 공정 압력이 InZnO 박막트랜지스터의 광학 및 전기적 특성에 미치는 영향)

  • Park, Ji-Min;Kim, Hyoung-Do;Jang, Seong Cheol;Kim, Hyun-Suk
    • Korean Journal of Materials Research
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    • v.30 no.4
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    • pp.211-216
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    • 2020
  • Amorphous In-Ga-Zn-O (a-IGZO) thin film transistors, because of their relatively low mobility, have limits in attempts to fulfill high-end specifications for display backplanes. In-Zn-O (IZO) is a promising semiconductor material for high mobility device applications with excellent transparency to visible light region and low temperature process capability. In this paper, the effects of working pressure on the physical and electrical properties of IZO films and thin film transistors are investigated. The working pressure is modulated from 2 mTorr to 5 mTorr, whereas the other process conditions are fixed. As the working pressure increases, the extracted optical band gap of IZO films gradually decreases. Absorption coefficient spectra indicate that subgap states increase at high working pressure. Furthermore, IZO film fabricated at low working pressure shows smoother surface morphology. As a result, IZO thin film transistors with optimum conditions exhibit excellent switching characteristics with high mobility (≥ 30㎠/Vs) and large on/off ratio.

Investigation of contact resistance between metal electrodes and amorphous gallium indium zinc oxide (a-GIZO) thin-film transistors

  • Kim, Woong-Sun;Moon, Yeon-Keon;Lee, Sih;Kang, Byung-Woo;Kwon, Tae-Seok;Kim, Kyung-Taek;Park, Jong-Wan
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.546-549
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    • 2009
  • In this paper, we investigated the effects of different source/drain (S/D) electrode materials in thin film transistors (TFTs) based on indium-gallium-zinc oxide (IGZO) semiconductor. A transfer length and effective resistances between S/D electrodes and amorphous IGZO thin-film transistors were examined. Intrinsic TFT parameters were extracted by the transmission line method (TLM) using a series of TFTs with different channel lengths measured at a low drain voltage. The TFTs fabricated with Cu S/D electrodes showed the lowest contact resistance and transfer length indicating good ohmic characteristics, and good transfer characteristics with a field-effect mobility (${\mu}_{FE}$) of 10.0 $cm^2$/Vs.

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Amorphous Indium-Tin-Zinc-Oxide (ITZO) Thin Film Transistors

  • Jo, Gwang-Min;Lee, Gi-Chang;Seong, Sang-Yun;Kim, Se-Yun;Kim, Jeong-Ju;Lee, Jun-Hyeong;Heo, Yeong-U
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.170-170
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    • 2010
  • Thin-film transistors (TFT) have become the key components of electronic and optoelectronic devices. Most conventional thin-film field-effect transistors in display applications use an amorphous or polycrystal Si:H layer as the channel. This silicon layers are opaque in the visible range and severely restrict the amount of light detected by the observer due to its bandgap energy smaller than the visible light. Therefore, Si:H TFT devices reduce the efficiency of light transmittance and brightness. One method to increase the efficiency is to use the transparent oxides for the channel, electrode, and gate insulator. The development of transparent oxides for the components of thin-film field-effect transistors and the room-temperature fabrication with low voltage operations of the devices can offer the flexibility in designing the devices and contribute to the progress of next generation display technologies based on transparent displays and flexible displays. In this thesis, I report on the dc performance of transparent thin-film transistors using amorphous indium tin zinc oxides for an active layer. $SiO_2$ was employed as the gate dielectric oxide. The amorphous indium tin zinc oxides were deposited by RF magnetron sputtering. The carrier concentration of amorphous indium tin zinc oxides was controlled by oxygen pressure in the sputtering ambient. Devices are realized that display a threshold voltage of 4.17V and an on/off ration of ${\sim}10^9$ operated as an n-type enhancement mode with saturation mobility with $15.8\;cm^2/Vs$. In conclusion, the fabrication and characterization of thin-film transistors using amorphous indium tin zinc oxides for an active layer were reported. The devices were fabricated at room temperature by RF magnetron sputtering. The operation of the devices was an n-type enhancement mode with good saturation characteristics.

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