Field-effect transistors made from macroscopic single crystals of tetracene and related semiconductors on polymer dielec
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We report properties of devices made by the adhesion of semiconductor crystals, including several tetracene specimens, to polymer gate dielectrics along with measurements of tetracene crystals on conventional Si/SiO2 dielectric surfaces. For the best tetracene, pentacene, and alpha-6T devices, mobilities exceeding 0.1 cm2/V were measured, correlating well with expectations based on the literature, and in the case of tetracene and alpha-6T, exceeding the thin film mobility value. The devices were prepared in the open laboratory using simpler crystal handling techniques than had been thought necessary.
I. INTRODUCTION
Starting from the very earliest investigations of organic semiconductor thin film field-effect transistors (FETs), there has been a desire to prepare devices using single crystals as the active materials to conduct the most rigorous fundamental experiments and also to understand the limits of thin film performance. It was appreciated that thin film device features, such as grain boundaries and interface stresses and inhomogeneities could affect, and even severely limit, the mobility measured across the entire area of a film. The effects of the grain boundaries, in particular, have been observed directly.1 Data obtained from single-crystal devices would be useful in distinguishing thin film attributes from intrinsic limitations of bulk crystalline semiconductors of the same nominal composition. There is also the added attraction of fabricating circuits using preformed single crystals, thus separating the semiconductor single-crystal growth process from other device fabrication steps that might affect the semiconductor purity or stability. The first single-crystal organic semiconductor FET was reported by the Horowitz/ Garnier group and used alpha-sexithiophene (␣6T).2,3 This represents the introduction of single-crystal measurements on prefabricated FETs. Subsequent work by Schon et al. was discredited. Only recently, renewed effort has been made to characterize organic single-crystal FETs. Podzorov et al. (Los Alamos server preprint #0210555) first applied parylene a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2004.0254 J. Mater. Res., Vol. 19, No. 7, Jul 2004
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dielectric on rubrene single crystals and achieved initial mobilities of approximately 1 cm2/V and higher values more recently after refining the original technique.4 Butko et al. have prepared pentacene and tetracene crystal devices with vapor-deposited parylene as the gate dielectric. (arxiv.org/abs/cond-mat/0305402). As the current work was being completed, a preprint appeared from deBoer, Morpurgo, and Klapwijk at Delft describing microscopic tetracene crystal FETs on conventional Si/SiO2 substrates (arXiv:cond-mat/0307320 v1 14 Jul 2003). Similar techniques have been used by Batlogg et al. (Los Alamos server preprint #0306206). In this work, we report properties of devices made by the adhesion of semiconductor crystals to polymer gate dielectri
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