Tatsuo Hasegawa

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The use of single crystals has been fundamental to the development of semiconductor microelectronics and solid-state science. Whether based on inorganic or organic materials, the devices that show the highest performance rely on single-crystal interfaces, with their nearly perfect translational symmetry and exceptionally high chemical purity. Attention has(More)
We have developed an efficient algorithm for simulating the equilibrium shape of a microdroplet placed on a flat substrate that has a fine, discontinuous, and arbitrarily shaped hydrophilic/hydrophobic patterned surface. The method uses a hybrid energy-minimization technique that combines the direct search method to determine the droplet shape around(More)
Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature(More)
Solution processibility is a unique advantage of organic semiconductors, permitting the low-cost production of flexible electronics under ambient conditions. However, the solution affinity to substrate surfaces remains a serious dilemma; liquid manipulation is more difficult on highly hydrophobic surfaces, but the use of such surfaces is indispensable for(More)
We developed a novel method for obtaining the distribution of trapped carriers over their degree of localization in organic transistors, based on the fine analysis of electron spin resonance spectra at low enough temperatures where all carriers are localized. To apply the method to pentacene thin-film transistors, we proved through continuous wave(More)
The fabrication of single-crystalline thin-film arrays for an organic ferroelectric small molecule is achieved by a simple solution process without additional thermal annealing. Based on a cooperative proton tautomerism through a hydrogen-bonding network, films show the polarity switching with an operating voltage of less than 5 V at room temperature. This(More)
Silver nanocolloid, a dense suspension of ligand-encapsulated silver nanoparticles, is an important material for printing-based device production technologies. However, printed conductive patterns of sufficiently high quality and resolution for industrial products have not yet been achieved, as the use of conventional printing techniques is severely(More)
Nanoscale molecular rotors that can be driven in the solid state have been realized in Cs2([18]crown-6)3[Ni(dmit)2]2 crystals. To provide interactions between the molecular motion of the rotor and the electronic system, [Ni(dmit)2]- ions, which bear one S=1/2 spin on each molecule, were introduced into the crystal. Rotation of the [18]crown-6 molecules(More)
A novel molecular based proton-electron mixed conductor, (H3BBIM(+))(TCNQ)(Cl(-))(0.5)(H(2)O) (1), where H3BBIM(+) is 2-(2-1H-benzimidazolyl)-1H-benzimidazolium and TCNQ is 7,7,8,8-tetracyano-p-quinodimethane, was synthesized. The salt exhibited peculiar phase transitions as a result of proton-electron coupling phenomena within the crystal. Salt 1 is(More)
One-dimensional dielectric (N.H.N)( infinity ) hydrogen-bonding chains of monoprotonated 1,4-diazabicyclo[2.2.2]octane (HDABCO(+)) were introduced into an electrically conducting 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) salt as the countercation structure. Room-temperature electrical conductivity was approximately 10(-)(3) S cm(-)(1), with a(More)