Characterization of poly(vinylidene fluoride-trifluoroethylene) 50/50 copolymer films as a gate dielectric |
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Authors: | Soojin Wi N Senthilkumar Shi-Woo Rhee |
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Affiliation: | (1) Department of Chemical Engineering, Laboratory for Advanced Molecular Processing (LAMP), Pohang University of Science and Technology (POSTECH), Pohang, 790-784, Korea |
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Abstract: | Thin films of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) 50/50 copolymer were prepared by spin coating on p-Si
substrate. Thermal behavior of the film was observed by measuring the film thickness with ellipsometry as a function of the
temperature and abrupt volume expansion was observed at 130–150 °C. Capacitance-voltage (C-V) and current-voltage (I-V) behavior
of the aluminum/P(VDF-TrFE)/p-Si MIS (metal-insulator-semiconductor) structures were studied and dielectric constant of the
P(VDF-TrFE) film was measured to be about 15.3 at optimum condition. No hysteresis was observed in the C-V curve for films
as deposited and annealed (70–200 °C). Films annealed at temperatures higher than the volume expansion temperature showed
substantial surface roughness due to the crystallization. Flat band voltage (VFB) of the MIS structure with as deposited films was about −0.3 V and increased up to −2.0 V with annealing. This suggested
that positive charges were generated in the film. Electronic properties of the annealed P(VDF-TrFE) film at above melting
temperature were degraded substantially with larger shift in flat band voltage, low dielectric constant and low breakdown
voltage. Organic thin film transistor with pentacene active layer and P(VDF-TrFE) as a gate dielectric layer showed a mobility
of 0.31 cm2/V·s and threshold voltage of −0.45 V. |
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