A Surface Tailoring Method of Ultrathin Polymer Gate Dielectrics for Organic Transistors: Improved Device Performance and the Thermal Stability Thereof

Tailoring the surface of the dielectric layer is of critical importance to form a good interface with the following channel layer for organic thin film transistors (OTFTs). Here, a simple surface treatment method is applied onto an ultrathin (<15 nm) organosilicon-based dielectric layer via the initiated chemical vapor deposition (iCVD) to make it compatible with organic semiconductors without degrading its insulating property. A molecular-thin oxide capping layer is formed on a 15 nm thick poly(1,3,5-trimetyl-1,3,5-trivinyl cyclotrisiloxane) (pV3D3) by a brief oxygen plasma treatment. The capping layer greatly enhances the thermal stability of the dielectrics, without degrading the original mechanical flexibility and insulating performance of the dielectrics. Moreover, the surface silanol functionalities formed by the plasma treatment can also be utilized for the surface modification with silane compounds. The surface-modified dielectrics are applied to fabricate low-voltage operating (<5 V) pentacene-based OTFTs. The highest field-effect mobility of the device with the surface-treated 15 nm thick pV3D3 is 0.59 cm² V^-1 s^-1, which is improved up to two times compared to the TFT with the pristine pV3D3. It is believed that the simple surface treatment method can widely extend the applicability of the highly robust, ultrathin, and flexible pV3D3 gate dielectrics to design the surface of the dielectrics to match well various kinds of organic semiconductors. A molecular-thin oxide capping layer is formed on ultrathin (≈15 nm) polymer dielectrics by a brief oxygen plasma treatment to enhance the thermal stability up to 280 °C. The formed silanol functionalities at the surface can also be utilized to modify the surface of ultrathin dielectrics by use of various silane compounds, which enable tailoring the interface between semiconductor and ultrathin dielectrics.