• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.659-660
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• 2007

• Applied Chemistry for Engineering
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• v.24 no.3
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• pp.219-226
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• 2013

Organic semiconductor-based soft electronics has potential advantages for next-generation electronics and displays, which request mobile convenience, flexibility, light-weight, large area, etc. Organic field-effect transistors (OFET) are core elements for soft electronic applications, such as e-paper, e-book, smart card, RFID tag, photovoltaics, portable computer, sensor, memory, etc. An optimal multi-layered structure of organic semiconductor, insulator, and electrodes is required to achieve high-performance OFET. Since most organic semiconductors are self-assembled structures with weak van der Waals forces during film formation, their crystalline structures and orientation are significantly affected by environmental conditions, specifically, substrate properties of surface energy and roughness, changing the corresponding OFET. Organo-compatible insulators and surface treatments can induce the crystal structure and orientation of solution- or vacuum-processable organic semiconductors preferential to the charge-carrier transport in OFET.

• 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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.1
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• pp.47-52
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• 2007

Organic field-effect transistors (OFETS) are of interest for use in widely area electronic applications. We fabricated a copper phthalocyanine (CuPc) based field-effect transistor with varying channel length. The CuPc FET device was made a top-contact type and the channel length was a $100\;{\mu}m,\;50\;{\mu}m,\;40\;{\mu}m,\;and\;30\;{\mu}m$ and the channel width was a fixed at 3 mm. We observed a typical current-voltage (I-V) characteristics in CuPc FET with varying channel length (L) and we calculated the effective mobility. Also, we measured a capacitance-voltage (C-V) by applied bias voltage with varying frequency at 43, 100, 1000 Hz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.389-390
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• 2008

We fabricated organic field-effect transistors (OFETs) based a fluorinated copper phthalocyanine ($F_{16}CuPc$) as an active layer. And we observed the surface morphology of the $F_{16}CuPc$ thin film. The $F_{16}CuPc$ thin film thickness was 40nm, and the channel length was $50{\mu}m$, channel width was 3mm. We observed the typical current-voltage (I-V) characteristics and capacitance-voltage (C-V) in $F_{16}CuPc$ FET and we calculated the effective mobility.

• Transactions on Electrical and Electronic Materials
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• v.12 no.1
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• pp.40-42
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• 2011

An organic field-effect transistor (OFET) was fabricated using a copper phthalocyanine (CuPc) as the active layer on the silicon substrate. The CuPc FET device was configured as a top-contact type. The substrate temperature was room temperature. The CuPc thickness was 40 nm, and the channel length and channel width were 100 ${\mu}m$ 3 mm, respectively. Typical current-voltage (I-V) characteristics of the CuPc FET were observed and subsequently compared to the UV/ozone treatment on substrate surface.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.399-405
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• 2018

We report the fabrication of organic field-effect transistors (OFETs) via spray coating of electrochemically exfoliated graphene (EEG) and conducting polymer hybrid as electrodes. To reduce the roughness and sheet resistance of the EEG electrodes, subsequent coating of conducting polymer (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)) and acid treatment was performed. After that, active channel layer was developed by spin coating of semiconducting poly(3-hexylthiophene) on the hybrid electrodes to define the bottom gate bottom contact configuration. The OFET devices with the EEG/PEDOT:PSS hybrid electrodes showed a reasonable electrical performances (field effect mobility = $0.15cm^2V^{-1}\;s^{-1}$, on/off current ratio = $10^2$, and threshold voltage = -1.57V). Furthermore, the flexible OFET devices based on the Polydimethlsiloxane (PDMS) substrate and ion gel dielectric layer exhibited higher electrical performances (field effect mobility = $6.32cm^2V^{-1}\;s^{-1}$, on/off current ratio = $10^3$, and threshold voltage = -1.06V) and excellent electrical stability until 1000 cycles of bending test, which means that the hybrid electrode is applicable to various organic electronic devices, such as flexible OFETs, supercapacitors, organic sensors, and actuators.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.31-32
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• 2010

In our previous reports [1-3], electron transport for the switching and memory devices using alkyl thiol-tethered Ru-terpyridine complex compounds with metal-insulator-metal crossbar structure has been presented. On the other hand, among organic memory devices, a memory based on the OFET is attractive because of its nondestructive readout and single transistor applications. Several attempts at nonvolatile organic memories involve electrets, which are chargeable dielectrics. However, these devices still do not sufficiently satisfy the criteria demanded in order to compete with other types of memory devices, and the electrets are generally limited to polymer materials. Until now, there is no report on nonvolatile organic electrets using nano-interfaced organic monomer layer as a dielectric material even though the use of organic monomer materials become important for the development of molecularly interfaced memory and logic elements. Furthermore, to increase a retention time for the nonvolatile organic memory device as well as to understand an intrinsic memory property, a molecular design of the organic materials is also getting important issue. In this presentation, we report on the OFET memory device built on a silicon wafer and based on films of pentacene and a SiO2 gate insulator that are separated by organic molecules which act as a gate dielectric. We proposed push-pull organic molecules (PPOM) containing triarylamine asan electron donating group (EDG), thiophene as a spacer, and malononitrile as an electron withdrawing group (EWG). The PPOM were designed to control charge transport by differences of the dihedral angles induced by a steric hindrance effect of side chainswithin the molecules. Therefore, we expect that these PPOM with potential energy barrier can save the charges which are transported to the nano-interface between the semiconductor and organic molecules used as the dielectrics. Finally, we also expect that the charges can be contributed to the memory capacity of the memory OFET device.[4]

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.303-304
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• 2009

We fabricated organic field-effect transistors (OFETs) based a fluorinated copper phthalocyanine. ($F_{16}CuPc$) as an active layer. And we observed the surface morphology of the $F_{16}CuPc$ thin film. The $F_{16}CuPc$ thin film thickness was 40nm, and the channel length was $50{\mu}m$, channel width was 3mm. We observed the typical current-voltage (I-V) characteristics and capacitance-voltage (C-V) in $F_{16}CuPc$ FET and we calculated the effective mobility.

• Transactions on Electrical and Electronic Materials
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• v.8 no.4
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• pp.170-173
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• 2007

Organic field-effect transistors (OFETs) are of interest for use in widely area electronic applications. We fabricated the organic field-effect transistor based a copper phthalocyanine (CuPc) as an active layer on the silicon substrate. The CuPc FET device was made a topcontact type and the substrate temperature was room temperature and $150^{\circ}C$. The CuPc thickness was 40 nm, and the channel length was $50{\mu}m$, channel width was 3 mm. We observed the typical current-voltage (I-V) characteristics and capacitance-voltage (C-V) in CuPc FET and we calculated the effective mobility with each device. Also, we observed the AFM images with different substrate temperature.