| AVS 62nd International Symposium & Exhibition | |
| Applied Surface Science | Tuesday Sessions |
| Session AS+NS-TuM |
| Session: | Chemical/Molecular Information from Sub-micron Features and Materials |
| Presenter: | Li Zeng, Northwestern University |
| Authors: | L. Zeng, Northwestern University A. Walker, Northwestern University R. Turrisi, University of Milano-Bicocca, Italy M.C. Hersam, Northwestern University T.J. Marks, Northwestern University M.J. Bedzyk, Northwestern University |
| Correspondent: | Click to Email |
Organic thin-film transistors (OTFTs) are viewed as the new generation thin-film transistors (TFT) for future low-cost, printable, structural flexible electronics, and related processable solution-based organic and inorganic semiconductors. However, one major limitation of OTFTs is that the organics semiconductors exhibit relatively low carrier mobility, which requires high operating voltage in order to achieve an operational drain current. One route to reduce the operation voltage is to increase the capacitance of the dielectric layer as the drain current increases linearly with respect to the dielectric capacitance for constant operating voltages and channel dimensions. A class of materials called self-assembled nano-dielectrics (SAND) with phosphoric acid-functionalized organic precursors sandwiched between ultrathin layers of high-k inorganic oxide materials has been synthesized and applied in the TFT field. These materials show exceptionally large capacitance, excellent insulating properties, and are also suitable for ambient atmosphere fabrication. The hybrid nature of these materials utilizing the distinct properties of both the organic and inorganic components can be incorporated into the low-operating voltage semiconductor-based OTFTs to enhance the performance.
Despite the impressive performance and flexibility of SANDs, some fundamental aspects of dielectric behavior remain unexplored. Particularly, the behavior of the Br¯ counteranions that are paired with the phosphonic acid-based -electron (PAE) cationic building blocks are poorly understood. It is believed that the location, distribution of the Br¯ counteranions, as well as their response to applied AC and DC electric fields, are critical to the behavior of the dielectric in device-like environments. Therefore, long-period X-ray Standing Wave (LP-XSW), which is a powerful technique sensitive to heavy atom distributions, was used to characterize a three-layer SAND structure deposited on synthetic Si/Mo multilayer substrates. The elemental distributions of Br and reference elements were extracted from the analysis of XSW data. These accurate measurements are important for better understanding counteranion distributions, charge transport, dipole-semiconductor interactions, and future device modeling and engineering.