| 초록 |
Organic field effect transistors (OTFTs) have received intense interest for applications requiring structural flexibility, large area coverage, low temperature processing and low-cost. Pentacene TFTs have demonstrated the highest performance among TFTs with an organic semiconductor channel. A major limitation, however, has been unusually high operating voltages (20~100 V), a concern for portable, battery-powered device applications. This stems from the use of low permittivity organic gate dielectrics e.g. parylene, εr=3. A combination of higher permittivity gate dielectric and reduced dielectric thickness leads to lower voltage operation. Recently, low-voltage pentacene OTFTs with very thin (2.5 nm) amorphous molecular gate dielectric was reported. Flexible polymer substrates, characterized by rough surfaces, benefit from the use of high-K dielectrics given the ability to accommodate thicker films without need to increase operating voltage. This leads to the suppression of pinhole formation and minimization of problems associated with step coverage. OTFTs with a low operating voltage of 5 V were previously demonstrated with the high K-perovskite dielectrics barium strontium titanate (BST, εr = 16) and barium zirconium titanate (BZT, εr = 17.3) with thickness of 130 nm. Here we report the successful fabrication of low voltage (＜ 5 V) organic transistors with high-K gate oxides (200 nm thick) with the highest reported dielectric constant, by approximately a factor of 3 (εr =50), prepared by an all room temperature process. |
