• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.50 no.4
• /
• pp.161-168
• /
• 2001

Organic thin film transitors(TFTs) are of interest for use in broad area electronic applications. For example, in active matrix liquid crystal displays(AMLCDs), organic TFTs would allow the use of inexpensive, light-weight, flexible, and mechanically rugged plastic substrates as an alternative to the glass substrates needed for commonly used hydrogenated amorphous silicon(a-Si:H). Recently pentacene TFTs with carrier field effect, mobility as large as 2 $cm^2V^{-1}s^{-1}$ have been reported for TFTs fabricated on silicon substrates, and it is higher than that of a-Si:H. But these TFTs are fabricated on silicon wafer and $SiO_2$ was used as a gate insulator. $SiO_2$ deposition process requires a high insulator which is polyimide and photo acryl. We investigated trasfer and output characteristics of the thin film transistors having active layer of pentacene. We calculated field effect mobility and on/off ratio from transfer characteristics of pentacene thin film transistor, and measured IR absorption spectrum of polymide used as the gate dielectric layer. It was found that using the photo acryl as a gate insulator, threshold voltage decreased from -12.5 V to -7 V, field effect mobility increased from 0.012 $cm^2V^{-1}s^{-1}$ to 0.039 $cm^2V^{-1}s^{-1}$ , and on/off current ratio increased from $10^5\;to\;10^6$. It seems that TFTs using photo acryl gate insulator is apt to form channel than TFTs using polyimide gate insulator.

• Macromolecular Research
• /
• v.10 no.2
• /
• pp.75-79
• /
• 2002

Organic materials have considerable attention as active semiconductors for device applications such as thin-film transistors (TFTs) and diodes. Pentacene is a p-type organic semiconducting material investigated for TFTs. In this paper, we reported the morphological and electrical characteristics of pentacene TFT films. The pentacene transistors showed the mobility of 0.8 $\textrm{cm}^2$/Vs and the grains larger than 1 ${\mu}{\textrm}{m}$. Deep-level transient spectroscopy (DLTS) measurements were carried out on metal/insulator/organic semiconductor structure devices that had a depletion region at the insulator/organic-semiconductor interface. The duration of the capacitance transient in DLTS signals was several ten of seconds in the pentacene, which was longer than that of inorganic semiconductors such as Si. Based on the DLTS characteristics, the energy levels of hole and electron traps for the pentacene films were approximately 0.24, 1.08, and 0.31 eV above Ev, and 0.69 eV below Ec.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07b
• /
• pp.1313-1316
• /
• 2005

In the present paper, it was investigated that adhesion layer on gate insulator could affect the electrical characteristics for the organic thin film transistors (OTFTs). The polyimide (PI) as organic adhesion layer was fabricated by using the vapor deposition polymerization (VDP) processing . It was found that electrical characteristics improved comparing OTFTs using adhesion layer to another. We researched adhesion layer as a function of thickness. For inverted-staggered top contact structure, field effect mobility, threshold voltage, and on-off current ratio of OTFTs using adhesion layer of PI 15 nm thickness on the gate insulator with a thickness of 0.2 ${\mu}m$ were about 0.5 $cm^2/Vs$, -0.8 V, and $10^6$, respectively.

• Journal of Information Display
• /
• v.4 no.2
• /
• pp.1-6
• /
• 2003

In this paper, we demonstrate that the organic electrophosphorescent device is driven by the organic thin film transistor with spin-coated photoacryl gate insulator. It was found that electrical output characteristics in our organic thin film transistors using the staggered-inverted top-contact structure showed the non-saturated slope in the saturation region and the sub-threshold nonlinearity in the triode region, where we obtained the maximum power luminance that was about 90 $cd/m^2$. Field effect mobility, threshold voltage, and on-off current ratio in 0.45 ${\mu}m$ thick gate dielectric layer were 0.17 $cm^2/Vs$, -7 V, and $10^6$ , respectively. 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 cured at 150${\sqsubset}$for 1hr. It was also found that field effect mobility, threshold voltage, on-off current ratio, and sub-threshold slope with 0.45 ${\mu}m$ thick gate dielectric films were 0.134 $cm^2/Vs$, -7 V, and $10^6$ A/A, and 1 V/decade, respectively.

• Journal of the Microelectronics and Packaging Society
• /
• v.12 no.4 s.37
• /
• pp.359-363
• /
• 2005

The organic insulation devices with MIM (metal-insulator-metal) structures as PVP gate insulation films were prepared for the application of organic thin film transistors (OTFT). The co-polymer organic insulation films were synthesized by using PVP(poly-4-vinylphenol) as solute and PGMEA (propylene glycol monomethyl ether acetate) as solvent. The cross-linked PVP insulation films were also prepared by addition of poly (melamine-co-formaldehyde) as thermal hardener. The leakage current of the cross-linked PVP films was found to be about 300 pA with low current noise. and showed better property in electrical properties as compared with the co-polymer PVP insulation films. In addition, cross-linked PVP insulation films showed better surface morphology (roughness), showing about 0.11${\~}$0.18 nF in capacitance for all PVP film samples.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08b
• /
• pp.1315-1318
• /
• 2007

Hafnium dioxide nano film as gate insulator for organic thin film transistors is prepared by atomic layer deposition. Mostly crystalline of $HfO_2$ films can be obtained with oxygen plasma and with water at relatively low temperature of $150^{\circ}C$. $HfO_2$ was deposited as a uniform rate $1.2A^{\circ}/cycle$. The morphology and performances of OTFT will be discussed.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.661-664
• /
• 2004

In this paper, it was demonstrated that the organic thin film transistors with the organic gate insulators were fabricated by vapor deposition polymerization (VDP) processing. The configuration of OTFTs was a staggered-inverted top-contact structure and gate dielectric layer was deposited with 0.45 ${\mu}m$ thickness. In order to form polyimide as a gate insulator, VDP process was also introduced instead of spin-coating process. Polyimide film was respectively co-deposited with different materials. One was from a 4,4'-oxydiphthalic anhydride (ODPA) and 4, 4'-oxydianiline (ODA) and the other was from 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and ODA. And it was also cured at 150 $^{\circ}C$ for 1 hour followed by 200 $^{\circ}C$ for 1 hour. Electrical characteristics of the organic thin-film transistors were detailed comparisons between the ODPA-ODA and the 6FDA-ODA which were used as gate insulator.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08b
• /
• pp.1220-1224
• /
• 2007

The effects of plasma damages to the organic thin film transistor (OTFT) during the fabrication process are investigated; metal deposition process on the organic gate insulator by plasma sputtering mainly generates the process induced damages of bottom contact structured OTFTs. For this study, various deposition methods (thermal evaporation, plasma sputtering, and neutral beam based sputtering) and metals (gold and Indium-Tin Oxide) have been tested for their damage effects onto the Poly 4-vinylphenol(PVP) layer surface as an organic gate insulator. The surface damages are estimated by measuring surface energies and grain shapes of organic semiconductor on the gate insulator. Unlike thermal evaporation and neutral beam based sputtering, conventional plasma sputtering process induces serious damages onto the organic surface as increasing surface energy, decreasing grain sizes, and degrading TFT performance.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2009.10a
• /
• pp.566-567
• /
• 2009

We have examined the silicon nitride ($SiN_x$) as gate insulator with the ammonia ($NH_3$) plamsa treatment for the soluble derivatives of polythiophene as p-type channel materials of organic thin film transistors (OTFTs). Fabrications of the jetting-processed OTFTs with $SiN_x$ as gate insulator by $NH_3$ plasma treatment can be similar to performance of OTFTs with silicon dioxide ($SiO_2$) insulator.

• Journal of the Korean Vacuum Society
• /
• v.13 no.3
• /
• pp.99-102
• /
• 2004

In this work the electrical characteristics of organic thin film transistors with the surface-treated organic gate insulator have been studied. For the surface treatment of gate dielectric, Ar plasma was used. Pentacene and PVP were used as active and dielectric layers respectively. Pentacene was thermally evaporated in vacuum at a pressure of about $10^{-6}$ Torr and at a deposition rate of 0.5 $\AA$/sec. PVP was spin coated and cured at $100^{\circ}C$. before pentacene deposition. organic thin film transistors with surface-treated gate insulators have provided improved operation characteristics.