Organic Field-Effect-Transistors for the Study of Correlation Phenomena

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Organic semiconductors such as pentacene are endowed with a small dielectric constant and very large effective masses for both electrons and holes. It turns them into ideal candidates to search for novel electron correlation phenomena, as indicated by the recent demonstrations of the fractional quantum Hall effect and superconductivity in field effect transistors based on tetracene and penctacene. 1-3 Here we wish to perform low-temperature magneto-transport investigations (if necessary also magneto-optical and cyclotron resonance studies to determine the effective masses) on single crystal field effect transistors that meet the following challenges: low-temperature p- and n-ohmic contacts, leakage-free gate isolation, good surface quality and maximum suppresion of extrinsic scattering processes. Field effect transistors with these prerequisites open up an entire spectrum of experiments on correlation phenomena related to the fractional quantum Hall effect, the metal-insulator transition in 2D, Wigner crystallization, spin an charge density waves, and the competition between superconductivity and magnetic ordering. The above specifications on contacts, gate isolation and surface morphology are of equal relevance for applications, despite our emphasis on basic, fundamental electronic transport mechanimus.