Reis Simas, E. ; Kang, E. S. H. ; Gassmann, A. ; Katholing, E. ; Janietz, S. ; Seggern, H. von (2015)
Cross-linkable random copolymers as dielectrics for low-voltage organic field-effect transistors.
In: J. Mater. Chem. C, 3 (35)
doi: 10.1039/c5tc00352k
Article, Bibliographie
Abstract
A large number of cross-linkable dielectrics with good dielectric properties have been reported; however, all of them suffer from disadvantages like uncontrolled pre-crosslinking, necessity of high process temperatures and the need for an additional cross-linking compound. In this contribution, two new poly(methyl methacrylate) polymers are introduced which can be cross-linked due to the attached benzyl azide (N-3) monomer units making the addition of hardeners or initiators obsolete. The synthesis of the copolymers as well as their successful characterization and usage as gate dielectrics for organic field-effect transistors is demonstrated. The investigated polymers have been labeled PAZ 12 and PAZ 14 according to their azide content in mol%. The additional building blocks of the polymers are methyl methacrylate for PAZ 12 and methyl methacrylate and styrene monomer units in about an equal ratio for PAZ 14. Spin-coated thin films were cross-linked by a thermal treatment at 110 degrees C followed by an UV exposure at a wavelength of 254 nm yielding insoluble, smooth and electrically dense polymeric networks. Optimal cross-linking parameters were obtained using infrared spectroscopy to follow the N-3 vibrational mode. Its disappearance confirms a complete cross-linking reaction, and thus fully reacted azide groups facilitate the analytics. The dielectric properties of the cross-linked thin films have been studied by impedance spectroscopy. The application of double layer dielectrics results in lower dielectric losses and lower leakage currents in the subsequently produced pentacene-based field-effect transistors. These devices operate at voltages below -6 V and show hysteresis-free current-voltage characteristics with hole mobilities up to 0.16 cm(2) V-1 s(-1). PAZ 12 appears to be superior to PAZ 14 due to a lower total layer thickness of down to 92 nm still providing good insulation in the transistor presumably related to a lower free volume that arises in the cross-linked network of the two-component containing copolymer PAZ 12.
| Item Type: | Article |
|---|---|
| Erschienen: | 2015 |
| Creators: | Reis Simas, E. ; Kang, E. S. H. ; Gassmann, A. ; Katholing, E. ; Janietz, S. ; Seggern, H. von |
| Type of entry: | Bibliographie |
| Title: | Cross-linkable random copolymers as dielectrics for low-voltage organic field-effect transistors |
| Language: | English |
| Date: | 2015 |
| Publisher: | The Royal Society of Chemistry |
| Journal or Publication Title: | J. Mater. Chem. C |
| Volume of the journal: | 3 |
| Issue Number: | 35 |
| DOI: | 10.1039/c5tc00352k |
| Abstract: | A large number of cross-linkable dielectrics with good dielectric properties have been reported; however, all of them suffer from disadvantages like uncontrolled pre-crosslinking, necessity of high process temperatures and the need for an additional cross-linking compound. In this contribution, two new poly(methyl methacrylate) polymers are introduced which can be cross-linked due to the attached benzyl azide (N-3) monomer units making the addition of hardeners or initiators obsolete. The synthesis of the copolymers as well as their successful characterization and usage as gate dielectrics for organic field-effect transistors is demonstrated. The investigated polymers have been labeled PAZ 12 and PAZ 14 according to their azide content in mol%. The additional building blocks of the polymers are methyl methacrylate for PAZ 12 and methyl methacrylate and styrene monomer units in about an equal ratio for PAZ 14. Spin-coated thin films were cross-linked by a thermal treatment at 110 degrees C followed by an UV exposure at a wavelength of 254 nm yielding insoluble, smooth and electrically dense polymeric networks. Optimal cross-linking parameters were obtained using infrared spectroscopy to follow the N-3 vibrational mode. Its disappearance confirms a complete cross-linking reaction, and thus fully reacted azide groups facilitate the analytics. The dielectric properties of the cross-linked thin films have been studied by impedance spectroscopy. The application of double layer dielectrics results in lower dielectric losses and lower leakage currents in the subsequently produced pentacene-based field-effect transistors. These devices operate at voltages below -6 V and show hysteresis-free current-voltage characteristics with hole mobilities up to 0.16 cm(2) V-1 s(-1). PAZ 12 appears to be superior to PAZ 14 due to a lower total layer thickness of down to 92 nm still providing good insulation in the transistor presumably related to a lower free volume that arises in the cross-linked network of the two-component containing copolymer PAZ 12. |
| Divisions: | 11 Department of Materials and Earth Sciences 11 Department of Materials and Earth Sciences > Material Science 11 Department of Materials and Earth Sciences > Material Science > Electronic Materials |
| Date Deposited: | 22 Feb 2016 12:35 |
| Last Modified: | 13 Aug 2021 14:08 |
| PPN: | |
| Funders: | The authors thank the German Science Foundation (DFG) for financial support of this work (project no. SE 941/16-1) and the Helmholtz Association for funding the Virtual Institute VH-VI-530. |
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