Realization of high-frequency low-cost organic electronics requires high-mobility organic field-effect transistors (OFETs) with short channels, where influence of contact resistance becomes more serious than either lower mobility or longer channel devices. To reduce the contact resistance, we systematically and quantitatively investigate the influence of the lowest unoccupied molecular orbital (LUMO) level of an electron acceptor layer, the active layer thickness, and the side chain of active layer itself on contact resistance of top-contact high-mobility OFETs through a series of comparative analysis. We find that the acceptor of 1,3,4,5,7,8-hexafluoro tetracyano naphtha quinodimethane (F 6 TNAP) with a deeper LUMO level is efficient for carrier injection and that the bulk resistance plays an important role in such devices. By optimizing the parameters, we get the lowest contact resistance of only 110 •cm, and thus recorded effective mobility of 8.0 cm 2 /Vs is attained for polycrystalline thin film transistors and still kept as high as 6 cm 2 /Vs at shorter channel lengths.

Split-gate organic field-effect transistors have been developed for high-speed operation. Owing to the combination of reduced contact resistance and minimized parasitic capacitance, the devices have fast switching characteristics. The cutoff frequencies for the vacuum-evaporated devices and the solution-processed devices are 20 and 10 MHz, respectively. A speed of 10 MHz is the fastest device reported so far among solution-processed organic transistors.

High carrier-mobility organic field-effect transistors are developed employing high-k gate dielectrics so that unprecedentedly high transconductance is realized. 2,9-didecyl-dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (C10-DNTT) solution-crystallized films are coated on hybrid gate insulators of silane self-assembled monolayers and high-k Al2O3 formed by atomic-layer-deposition. Intrinsically high carrier mobility exceeding 10 cm2/Vs in the crystalline C10-DNTT is preserved even on the high-k gate insulators because of suppressed coupling of the field-induced carriers to the polarization of the dielectrics.

Newly developed bonded materials and fabrication processes are expected to firmly bond copper leads to SiC chips for application in next generation power modules. Solid-liquid interdiffusion bonding of copper was performed using Ag-Sn layered films. Microstructural development and mechanical properties of bond layers were investigated. The bond layer grew at the thin film interfaces because of the solidliquid interdiffusion. Cu 6 Sn 5 and Ag 4 Sn or Ag 3 Sn phases were formed at the initial bonding stage, and subsequently, Cu 3 Sn formed between the Cu 6 Sn 5 and Cu as both bond time and temperature increased. Finally, the bond layer was primarily composed of Ag 4 Sn and Cu 3 Sn. The hardness and Young's modulus of Ag 4 Sn were much lower than those of Cu 3 Sn. The growth of the Cu 3 Sn layer that formed between Ag 4 Sn and Cu could be limited by optimizing the design of the faying surface.

This report describes the histochemical and ultrastructural studies of the tail muscles in the anuran tadpole. Histochemical Studies of Nervous System and Muscle in Ca-Mg Deficient Rats.

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