Bio Organic-Based Gate Dielectric Materials for Thin Film Transistors
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Bio Organic-Based Gate Dielectric Materials for Thin Film Transistors James G. Grote1, Fahima Ouchen1,2, Donna M. Joyce1, Kristi M. Singh1,3,Narayanan Venkat1,2, Steven R. Smith1,2, Perry P. Yaney1,4, Emily M. Heckman1,Carrie M. Bartsch1 and Rajesh R. Naik1 1
US Air Force Research Laboratories, Wright-Patterson Air force Base, OH 45433 University of Dayton Research Institute, Dayton, OH 45469 3 UES Inc., Dayton, OH 45432 4 Department of Physics and Electro-Optics Program, University of Dayton, OH 45469 2
ABSTRACT The potential of bio-dielectrics for thin film transistor applications was explored via the incorporation of titanium dioxide (TiO2) nanoparticles, rutile form, a high dielectric constant (ε) ceramic, in the deoxyribonucleic acid (DNA) bio-polymer. The DNA-ceramic hybrid films were fabricated from stable suspensions of the TiO2 nanoparticles in viscous, aqueous DNA solutions. Dielectric characterization revealed that the incorporation of TiO2 in DNA resulted in enhanced dielectric constant (14.3 at 1 kHz for 40 wt % TiO2) relative to that of DNA in the entire frequency range of 1 kHz-1 MHz. Variable temperature dielectric measurements, in the 20-80⁰C range, of the DNA-TiO2 films revealed that the ceramic additive stabilizes DNA against large temperature dependent variations in both ε and the dielectric loss factor tan δ. The bulk resistivity of the DNA-TiO2 hybrid films was measured to be two to three orders of magnitude higher than that of the control DNA films, indicating their potential for utilization as insulating dielectrics in transistor and capacitor applications.
INTRODUCTION The performance of polymer based dielectric materials for thin film transistors is generally limited by low relative permittivity (ε) and this limitation has been overcome by the generation of polymer-ceramic nanocomposites incorporating high ε ceramic fillers [1] such as barium titante (BaTiO3) and titanium dioxide (TiO2) in the polymer matrix. By virtue of the higher dielectric constant, the hybrid dielectric can also serve as a more efficient gate dielectric to help reduce drive voltage for the performance enhancement of thin film transistors (TFTs) and field effect transistors (FETs) [2-4] in electronic applications. The utilization of biopolymer-based materials, such as DNA, as a dielectric has some natural advantages. Biomaterials are inherently capable of reducing environmental footprint since they stem from ‘green’ materials. We have fond that DNA-based biopolymers are relatively low cost (~$25/gram), lightweight and are amenable to a variety of low temperature film fabrication processes including drop casting, spin-coating, vapor deposition [5] and inkjet printing. Besides their processability, DNA-based biopolymers have also been extensively used as host materials in a variety of electrical and opto-electronic devices [3] and are reported to have a dielectric constant of 7.8 [3,4], which is higher than that of most of the known synthetic polymers. Further increase in ε by the incorporation of ceramic nanoparticles
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