High-performance pentacene field-effect transistors using Al2O3 gate dielectrics prepared by atomic layer deposition (ALD)

High-performance pentacene field-effect transistors have been fabricated using Al2O3 as a gate dielectric material grown by atomic layer deposition (ALD). Hole mobility values of 1.5 ± 0.2 cm/V s and 0.9 ± 0.1 cm/V s were obtained when using heavily n-doped silicon (n-Si) and ITO-coated glass as gate electrodes, respectively. These transistors were operated in enhancement mode with a zero turn-on voltage and exhibited a low threshold voltage (< 10 V) as well as a low sub-threshold slope (<1 V/decade) and an on/off current ratio larger than 10. Atomic force microscopy (AFM) images of pentacene films on Al2O3 treated with octadecyltrichlorosilane (OTS) revealed well-ordered island formation, and X-ray diffraction patterns showed characteristics of a ‘‘thin film’’ phase. Low surface trap density and high capacitance density of Al2O3 gate insulators also contributed to the high performance of pentacene field-effect transistors. 2007 Elsevier B.V. All rights reserved. PACS: 85.30.Tv; 72.80.Le; 77.55.+f; 81.15. z