• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.12
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• pp.1009-1013
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• 2009

In this study, we have been synthesized the dielectric layer using pure organic and organic-inorganic hybrid precursor on flexible substrate for improving of the organic thin film transistors (OTFTs) and, design and fabrication of organic thin-film transistors (OTFTs) using small-molecule organic semiconductors with pentacene as the active layer with record device performance. In this work OTFT test structures fabricated on polymerized substrates were utilized to provide a convenient substrate, gate contact, and gate insulator for the processing and characterization of organic materials and their transistors. By an adhesion development between gate metal and PI substrate, a PI film was treated using $O_2$ and $N_2$ gas. The best peel strength of PI film is 109.07 gf/mm. Also, we have studied the electric characteristics of pentacene field-effect transistors with the polymer gate-dielectrics such as cyclohexane and hybrid (cyclohexane+TEOS). The transistors with cyclohexane gate-dielectric has higher field-effect mobility, $\mu_{FET}=0.84\;cm^2/v_s$, and smaller threshold voltage, $V_T=-6.8\;V$, compared with the transistor with hybrid gate-dielectric.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.61-62
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• 2006

In this paper, it was demonstrated that organic thin- film transistors (OTFTs) were fabricated with the organic adhesion layer between an organic semiconductor and a gate insulator by vapor deposition polymerization (VDP) processing. In order to form polymeric film as an adhesion layer, VDP process was also introduced instead of spin-coating process, where polymeric film was co-deposited by high-vacuum thermal evaporation from 6FDA and ODA followed by curing. The saturated slop in the saturation region and the subthreshold nonlinearity in the triode region were c1early observed in the electrical output characteristics in our organic thin film transistors using the staggered-inverted top-contact structure. Field effect mobility, threshold voltage, and on-off current ratio in 15-nm-thick organic adhesion layer were about $0.5\;cm^2/Vs$, -1 V, and $10^6$, respectively. We also demonstrated that threshold voltage depends strongly on the delay time when a gate voltage has been applied to bias stress.

• Journal of Electrical Engineering and Technology
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• v.4 no.1
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• pp.118-122
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• 2009

Organic thin film transistors with a pentacene active layer and various polymer gate insulators were fabricated and their performances were investigated. Characteristics of pentacene thin film transistors on different polymer substrates were investigated using an atomic force microscope (AFM) and x-ray diffraction (XRD). The pentacene thin films were deposited by thermal evaporation on the gate insulators of various polymers. Hexamethyldisilazane (HMDS), polyvinyl acetate (PVA) and polymethyl methacrylate (PMMA) were fabricated as the gate insulator where a pentacene layer was deposited at 40, 55, 70, 85, 100 oC. Pentacene thin films on PMMA showed the largest grain size and least trap concentration. In addition, pentacene TFTs of top-contact geometry are compared with PMMA and $SiO_2$ as gate insulators, respectively. We also fabricated pentacene TFT with Poly (3, 4-ethylenedioxythiophene)-Polysturene Sulfonate (PEDOT:PSS) electrode by inkjet printing method. The physical and electrical characteristics of each gate insulator were tested and analyzed by AFM and I-V measurement. It was found that the performance of TFT was mainly determined by morphology of pentacene rather than the physical or chemical structure of the polymer gate insulator

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.598-601
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• 1999

There is currently considerable interest in the applications of conjugated polymers, oligomers and small molecules for thin-film electronic devices. Organic materials have potential advantages to be utilized as semiconductors in field effect transistor and light emitting didoes. In this study, Pentacene thin film transistors(TFTs) were fabricated on glass substrate. Aluminum and Gold wei\ulcorner used fur the gate and source/drain electrodes. Silicon dioxde was deposited as a gate insulator by PECVD and patterned by R.I.E. The semiconductor layer of pentacene was thermally evaporated in vaccum at a pressure of about 10$^{-8}$ Torr and a deposition rate 0.3$\AA$/sec. The fabricated devices exhibited the field-effect mobility as large as 0.07cm$^2$/Vs and on/off current ratio larger than 10$^{7}$

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.9
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• pp.527-531
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• 2016

In this study, p-type thin film transistors consisting of CuO channels were fabricated by sol-gel process, with copper (II) acetate monohydrate precursors. At $500^{\circ}C$, the deposited films were fully converted into monoclinic phase CuO. The fabricated CuO thin film transistors deliver field effect mobility in saturation regime of $0.015cm^2/Vs$, and $I_{on}/I_{off}$ of ${\sim}10^3$. The degradation of the performance of the fabricated CuO thin film transistor caused by the exposure to air has been studied.

• Journal of Sensor Science and Technology
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• v.27 no.3
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• pp.182-185
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• 2018

Zinc oxide (ZnO) thin films have the advantages of growing at a low temperature and obtaining high charge mobility (carrier mobility) [1]. Furthermore, the zinc oxide thin film can be used to control application resistance depending on its oxygen content. ZnO has the desired physical properties, a transparent nature, with a flexible display that makes it ideal for use as a thin-film transistor. Though these transparent flexible thin-film transistors can be manufactured in various manners, manufacturing large-area transistors using a solution process is easier owing to the low cost and flexible substrate. The advantage of being able to process at low temperatures has been attracting attention as a preferred method. However, in the case of a thin-film transistor fabricated through a solution process, it is reported that charge mobility is lower. To improve upon this, a method of improving the crystallinity through heat treatment and increasing electron mobility has been reported. However, as the heat treatment temperature is relatively high at $500^{\circ}C$, an application where a flexible substrate is absent would be more suitable.

• Journal of the Semiconductor & Display Technology
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• v.19 no.2
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• pp.72-76
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• 2020

The author demonstrated organic ferroelectric thin-film transistors with ferroelectric materials of P(VDF-TrFE) and an amorphous oxide semiconducting In-Ga-Zn-O channel on the silicon substrates. The organic ferroelectric layers were deposited on an oxide semiconductor layer by Langmuir-Blodgett method and then annealed at 128℃ for 30min. The carrier mobility and current on/off ratio of the memory transistors showed 9 ㎠V^-1s^-1 and 6 orders of magnitude, respectively. We can conclude from the obtained results that proposed memory transistors were quite suitable to realize flexible and werable electronic applications.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.117-124
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• 2018

Junctionless amorphous InGaZnO thin film transistors with different film thickness have been fabricated. Their device performance parameters were extracted and gate oxide breakdown voltages were analyzed with different film thickness. The device performances were enhanced with increase of film thickness but the gate oxide breakdown voltages were decreased. The device performances were enhanced with increase of temperatures but the gate oxide breakdown voltages were decreased due to the increased drain current. The drain current under illumination was increased due to photo-excited electron-hole pair generation but the gate oxide breakdown voltages were decreased. The reason for decreased breakdown voltage with increase of film thickness, operation temperature and light intensity was due to the increased number of channel electrons and more injection into the gate oxide layer. One should decide the gate oxide thickness with considering the film thickness and operating temperature when one decides to replace the junctionless amorphous InGaZnO thin film transistors as BEOL transistors.

• ETRI Journal
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• v.34 no.6
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• pp.966-969
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• 2012

From a practical viewpoint, the topic of electrical stability in oxide thin-film transistors (TFTs) has attracted strong interest from researchers. Positive bias stress and constant current stress tests on indium-gallium-zinc-oxide (IGZO)-TFTs have revealed that an IGZO-TFT with a larger Ga portion has stronger stability, which is closely related with the strong binding of O atoms, as determined from an X-ray photoelectron spectroscopy analysis.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1455-1458
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• 2008

Amorphous silicon (a-Si:H) thin-film transistors (TFTs) are fabricated on flexible organic polymer foil substrates. As-fabricated performance, electrical bias-stability at elevated temperatures, electrical response under mechanical flexing, and prolonged mechanical stability of the TFTs are studied. TFTs made on plastic at ultra low process temperatures of $150^{\circ}C$ show initial electrical performance like TFTs made on glass but large gate-bias stress instability. An abnormal saturation of the instability against operation temperature is observed.