• Korean Journal of Materials Research
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• v.16 no.5
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• pp.302-307
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• 2006

The formation and processing of organic insulators on the device performance have been studied in the fabrication of organic thin film transistors (OTFTs). The series of polyvinyls, poly-4-vinyl phenol(PVP) and polyvinyltoluene (PVT), were used as solutes and propylene glycol monomethyl ether acetate(PGMEA) as a solvent in the formation of organic insulators. The cross-linking of organic insulators was also attempted by adding the thermosetting material, poly (melamine-co-formaldehyde) as a hardener in the compound. The electrical characteristics measured in the metal-insulator-metal (MIM) structures showed that insulating properties of PVP layers were generally superior to those of PVT layers. Among the layers of PVP series: PVP(10 wt%) copolymer, 5 wt% cross-linked PVP(10 wt%), PVP(20 wt%) copolymer, 5 wt% cross-linked PVP(20 wt%) and 10 wt% cross-linked PVP(20 wt%), the 10 wt% cross-linked PVP(20 wt%) layer showed the lowest leakage current characteristics. Finally, inverted staggered OTFTs using the PVP(20 wt%) copolymer, 5 wt% cross-linked PVP(20 wt%) and 10 wt% cross-linked PVP(20 wt%) as gate insulators were fabricated on the polyether sulphone (PES) substrates. In our experiments, we could obtain the maximum field effect mobility of 0.31 $cm^2/Vs$ in the device from 5 wt% cross-linked PVP(20 wt%) and the highest on/off current ratio of $1.92{\times}10^5$ in the device from 10 wt% cross-linked PVP(20 wt%).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.185-190
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• 2003

In this paper, it was demonstrated that the organic thin film transistors were fabricated by the organic gate insulators with vapor deposition polymerization (VDP) processing. In order to form polyimide as a gate insulator, vapor deposition polymerization process was also introduced instead of spin-coating process, where polyimide film was co-deposited by high-vacuum thermal evaporation from 4,4'-oxydiphthalic anhydride (ODPA) and 4,4'-oxydianiline (ODA) and 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and ODA, and cured at $150^{\circ}C$ for 1hr. Electrical output characteristics in our organic thin film transistors using the staggered-inverted top-contact structure obtained to the saturated slop in the saturation region and the subthreshold non-linearity in the triode region. Field effect mobility, threshold voltage, and on-off current ratio in $0.45\;{\mu}m$ thick gate dielectric layer were about $0.17\;cm^2/Vs$, -7 V, and $10^6\;A/A$, respectively. Details on the explanation of compared to organic thin-film transistors (OTFTS) electrical characteristics of ODPA-ODA and 6FDA-ODA as gate insulators by fabricated thermal co-deposition method.

• Journal of the Korean Ceramic Society
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• v.53 no.4
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• pp.411-416
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• 2016

Benzothienobenzothiophene ($C_8-BTBT$) is a soluble organic small molecule material with high crystallinity resulting from its strong self-organizing properties. In addition, the high mobility and easy fabrication of $C_8-BTBT$ make it very attractive in terms of organic thin-film transistors. In this work, we made $C_8-BTBT$ thin films by using the zone-casting method; we also used an organic solvent to treat the devices with solvent vapor annealing to improve the electrical properties. As a result, we confirmed improved mobility, threshold voltage, and subthreshold swing after solvent vapor annealing. To prove the effect of solvent vapor annealing, we used the simultaneous extraction model to extract the contact resistance from the current-voltage curve. We confirmed that the electrical properties improved with decreasing contact resistance.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.267-270
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• 2007

Organic thin-film transistors (OTFTs) using organic semiconductors as an active layer are of interest for their use in low-cost, lightweight and flexible electronic products. Although the field-effect mobility of OTFTs is still lower than those of inorganic thin-film transistor, the advantages of easy manufacturing and processing make them suitable for selected applications. In this paper, we report the syntheses and characterization of new p-type OTFT materials.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.563-565
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• 2009

We introduce the new modification approaches of photocrosslinkable poly (4-vinylphenol) (PVP) for low hysteresis organic thin film transistors (OTFTs). The dielectric layers were composed of different PVP resin, low molecular melamine, and halogen free photo-initiator. The low hysteresis OTFT from one of the organic gate dielectrics has been realized. The electrical performance of low hysteresis OTFT with photocrosslinkable PVP exhibited a field-effect mobility of 0.2 cm2/Vs, a threshold voltage of - 0.04V, hysteresis of 0.4V.

• Journal of the Korean Vacuum Society
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• v.17 no.3
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• pp.195-198
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• 2008

In this paper, it was demonstrated that organic thin-film transistors (OTFTs) were fabricated with the organic passivation layer by vapor deposition polymerization (VDP) processing. In order to form polymeric film as a passivation 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. In order to investigate by compared with different passivation layer, the other OTFTs is fabricated to passivation by Polyvinylalcohol using spincoating. We can see that two different ways of passivation layer affect electric characteristic of OTFTs. The initial electric characteristic of OTFTs before passivation such as field effect mobility, threshold voltage, and on-off current ratio are $0.24cm^2/Vs$, -3V, and $10^6$, respectively. Then after polyimide passivation layer, field effect mobility change from $0.24cm^2/Vs$ to $0.26cm^2/Vs$, threshold voltage from -3V to 1V and on-off current ratio from $10^6$ to $10^6$, respectively. In the case of polyvinylalcohol passivation, the initial electric characteristic of OTFTs before passivation such as field effect mobility, threshold voltage, and on-off current ratio are $0.13cm^2/Vs$, 0V, and $10^6$, respectively. Then after polyvinylalcohol passivation layer, field effect mobility changes from $0.13cm^2/Vs$ to $0.13cm^2/Vs$, threshold voltage from 0V to 2V, and on-off current ratio from $10^6$ to $10^5$, respectively.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1274-1274
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• 2008

In this report, the effect of substrate temperature on the electrical properties of ink-jet printed triisopropylsilyl (TIPS) pentacene organic thin-film transistors (OTFTs) has been investigated. The electrical properties such as mobility and on/off ratio were decreased as the substrate was heated above room temperature. The field-effect mobility of decreased from $10^{-2}cm^2/Vs$ to $10^{-5}cm^2/Vs$ and the on/off ratio decreased from $10^6$ to $10^4$ when the substrate temperature was heated from room temperature to 60$^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.84-84
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• 2010

In this study, we report on the novel lithographic patterning method to fabricate organic-semiconductor devices based on photo and e-beam lithography with well-known silicon technology. The method is applied to fabricate pentacene-based organic field effect transistors. Owing to their solubility, sub-micron sized patterning of P3HT and PEDOT has been well established via micromolding in capillaries (MIMIC) and inkjet printing techniques. Since the thermally deposited pentacene cannot be dissolved in solvents, other approach was done to fabricate pentacene FETs with a very short channel length (~30nm), or in-plane orientation of pentacene molecules by using nanometer-scale periodic groove patterns as an alignment layer for high-performance pentacene devices. Here, we introduce the atomic layer deposition of $Al_2O_3$ film on pentacene as a passivation layer. $Al_2O_3$ passivation layer on OTFTs has some advantages in preventing the penetration of water and oxygen and obtaining the long-term stability of electrical properties. AZ5214 and ma N-2402 were used as a photo and e-beam resist, respectively. A few micrometer sized lithography patterns were transferred by wet and dry etching processes. Finally, we fabricated sub-micron sized pentacene FETs and measured their electrical characteristics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.384-385
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• 2006

We studied about conductive pastes of the source-drain contacts for OTFTs(organic thin-film transistors) fabricated by direct printing(screen printing) method. We used Ag and conductive carbon black powder as the conductive fillers of pastes. The conductive pastes were manufactured by various dispersing agents and dispersing conditions and source-drain contacts with $100{\mu}m$ of channel length were fabricated. We could obtain the OTFTs which exhibited different field-effect behaviors over a range of source-dram and gate voltages depending on a kind of conductive fillers used conductive pastes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.506-508
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• 2005

In general, organic TFTs are comprised of four components: gate electrode, gate dielectric, organic active semiconductor layer, and source and drain contacts. The TFT current, in turn, is typically determined by channel length and width, carrier field effect mobility, gate dielectric thickness and permittivity, contact resistance, and biasing conditions. More recently, a number of techniques and processes have been introduced to the fabrication of OTFT circuits and displays that aim specifically at reduced fabrication cost. These include microcontact printing for the patterning of metals and dielectrics, the use of photochemically patterned insulating and conducting films, and inkjet printing for the selective deposition of contacts and interconnect pattern. In the fabrication of organic TFTs, microcontact printing has been used to pattern gate electrodes, gate dielectrics, and source and drain contacts with sufficient yield to allow the fabrication of transistors. We were fabricated a pentacene OTFTs on flexible PEN film. Au/Cr was used for the gate electrode, parylene-c was deposited as the gate dielectric, and Au/Cr was chosen for the source and drain contacts; were all deposited by ion-beam sputtering and patterned by microcontact printing and lift-off process. Prior to the deposition of the organic active layer, the gate dielectric surface was treated with octadecyltrichlorosilane(OTS) from the vapor phase. To complete the device, pentacene was deposited by thermal evaporation and patterned using a parylene-c layer. The device was shown that the carrier field effect mobility, the threshold voltage, the subthreshold slope, and the on/off current ratio were improved.