Nanoscale Self-Assembled Organic Dielectrics for Ultra-Low Voltage High-Speed Electronic Devices (24062)
Self-assembling siloxane fabrication of extremely thin nanostructurally ordered, pinhole-free, ultra-high-capacitance/low leakage organic dielectrics has been achieved by Northwestern University scientists. These organic nanoinsulators can be efficiently integrated into large thin film transistor (TFT) structures using a variety of substrates.
ADVANTAGE: The organic nanoinsulators overcome the dielectric limitations of conventional "high k" dielectric materials and in turn enable the construction of low-bias, low-leakage current organic thin film transistors (OTFTs); suitable for numerous electronic and flexible display applications.
SUMMARY: Organic thin-film transistors (OTFTs) based on π-electron materials have been extensively investigated for applications where current inorganic semiconductors cannot be employed, including low-cost electronic devices and flexible displays. A variety of OTFTs employing p-type and n-type organic semiconductors have been produced, however typical biases required to achieve acceptable performance with conventional dielectric materials (silicon oxide, polymers, etc.) are too high for practical use (50-100V). Lower operating OTFT biases can be achieved by increasing the dielectric capacitance (Ci) and/or reducing dielectric layer thickness.
This invention creates, via a solution phase self-assembly process, nanoscopic high-Ci organic dielectrics, critical to producing low-bias, low-leakage current OTFTs. Combining the elements of (a) self-assembled a,ω-difunctional hydrocarbon chains (Cl3Si(CH2)8SiCl3) (b) polarizable "push-pull" stilbazolium layers and (c) octachlorotrisiloxane capping layers afford an oriented, robust, multilayer, conformal polysiloxane dielectric coating with minimal defects. Devices with 2.3-5.5 nm dielectric layer thickness were generated on silicon and ITO substrates employing various combinations of the process elements. Maximum capacitances of 385-710 nF/cm2 at 102 Hz were determined versus 5-10 nF/cm2 for conventional 300 nm SiO2. OTFTs constructed with the nanoinsulators employing p-type and n-type organic semiconductors exhibit typical output characteristics (Figs 1A, 1B) at threshold voltages 1-9% of similar devices prepared with 300 nm SiO2 dielectric These nanostructured organic dielectrics can be incorporated into large TFT structures having a variety of substrates and organic semiconductors. TFT response achieved at low operational biases offers potential for a range of low-power and high-frequency electronic applications.
Tobin Marks, Antonio Facchetti and Myung-Han Yoon
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