||Lucile C. Teague, Oana D. Jurchescu, Curt A Richter, Sankar Subramanian, John E Anthony, Thomas N Jackson, David J. Gundlach, James G. Kushmerick
To date, scanning Kelvin probe microscopy (SKPM) has been utilized to correlate the relationship between film structure and charge transport in a number of organic thin-film transistor (OTFT) devices. This technique provides a direct measurement of the intrinsic charge transport in the active organic as well as providing a detailed view of charge injection at the source and drain contacts. For the work presented here, SKPM was used to simultaneously probe the potential distribution in electrically biased single crystal difluoro bis(triethylsilylethynyl) anthradithiophene (diF-TESADT) organic thin film transistors. DiF-TESADT is one of a number of organic materials being studied for potential use in organic based electronics, and recent studies of diF-TESADT OTFTs have shown that charge mobilities on the order of 0.4 cm2/V•s can be achieved for spun-cast devices, while charge mobilities of 6 cm2/V•s have been achieved for single crystal devices. We will discuss our recent findings which suggest that significant changes in device performance can occur when the organic crystal is stressed over a timescale of a few minutes. More specifically, we will show SKPM data that reveal changes in potential drops at the contacts as a function of time. These results suggest that active organic material can become charged over a timescale of a few minutes, decreasing the current flow in the device from source to drain.  Gundlach, D. J.; Royer, J. E.; Park, S. K.; Subramanian, S.; Jurchescu, O. D.; Hamadani, B. H.; Moad, A. J.; Kline, R. J.; Teague, L. C.; Kirillov, O.; Richter, C. A.; Kushmerick, J. G.; Richter, L. J.; Parkin, S. R.; Jackson, T. N.; Anthony, J. E. Nature Mater. 2008, 7, 216-221.  Jurchescu, O. D.; Hamadani, B. H.; Xiong, H. D.; Park, S. K.; Subramanian, S.; Zimmerman, N. M.; Anthony, J. E.; Jackson, T. N.; Gundlach, D. J. Appl. Phys. Lett. 2008, 92, 132103.  Jurchescu, O. D.; Subramanian, S.; Kline, R. J.; Hudson, S. D.; Anthony, J. E.; Jackson, T. N.; Gundlach, D. J. Chem. Mater. 2008, 20, 6733-6737.