We describe the preparation of an α-phenyl-4'-(diphenylamino)stilbene (TPA) single crystal and the evaluation of its hole transport property. Based on the characterization using optical microscopy, polarizing microscopy, and X-ray diffraction, a large-scale TPA single crystal of dimensions 7.0×0.9×0.8mm is successfully synthesized using a solution method based on the solubility and supersolubility curves of the TPA. Notably, the current in the long-axis direction is larger than those in the short-axis and thickness directions (i(long) > i(short) > i(thickness)), which reveals the anisotropic charge transfer of the TPA single crystal. The observed anisotropic conductivity is well explained by the orientation of the triphenylamine unit in the TPA single crystal. Furthermore, the activation energy of the long-axis direction in the TPA single crystal is lower than that of the short-axis in TPA and all the axes in the α-phenyl-4'-[bis(4-methylphenyl)amino]stilbene single crystal reported in our previous study.

We examined single crystal growth of benzothienobenzothiophene-based organic semiconductors by solution coating method using liquid crystal and investigated its electrical characteristics. As the results, we revealed that the averaged mobility in the saturation region reached 2.08 cm2/Vs along crystalline b-axis, and 1.08 cm2/Vs along crystalline a-axis.

Carrier transport characteristics of TIPS-pentacene single crystalline film were controlled by changing the deposition condition of the blade-coating method. Anisotropic carrier transport in the single crystalline grain was visualized by means of the time-resolved microscopic optical second harmonic generation (TRM-SHG) measurement. Slow deposition yields the film with high mobility and large transport anisotropy. For molecular crystals, intermolecular interaction can be modified easily by changing the process condition.

We investigated a control of the crystalline orientation of soluble organic semiconductor single crystals using liquid crystal solvents aligned by the electric field to improve the performance of organic thin-film transistors. We clarified that the semiconductor single crystal grows to the direction parallel to the liquid crystal alignment oriented by the lateral electric field.

Fe thin films were deposited directly and via Ag underlayer on glass and MgO(100) substrates by MBE. Polycrystal Fe films grew on the glass substrate while single crystal films grew on the MgO(100) substrate. Fe film growth followed the Volmer-Weber mode for both cases. The Fe film structure was influenced by the surface roughness of Ag underlayer at the early stage of film growth. The relationships between the Fe thin film morphology and the magnetic properties are discussed.

The size dependent properties of the intrinsic Josephson junctions in Bi2Sr2CaCu2Oy single crystal mesas in the external magnetic field are studied. The mesas of (1-140) µm long with 7-29 junctions were fabricated and their current-voltage characteristics were measured in external magnetic field applied parallel to the CuO2 layers up to 0.16 T. In zero magnetic field, multiple resistive branches with large hysteresis were observed in the current-voltage characteristics for the fabricated mesas. Almost identical critical currents were also observed for all the junctions in each mesa. With applied magnetic field, Ic of the longer mesas showed a complex magnetic field dependence as compared to that of the short mesas (of about 1 µm in length). It was observed that the lower critical magnetic field of the junctions decreased and approached a constant value with increasing number of junctions and also with increasing length of the junctions. Similar magnetic behavior was obtained by numerical simulations based on coupled sine-Gordon equations for such stacked junctions.

Using LiTaO3 and LiNbO3 single crystals, we wish to miniaturize a powerful ultrasonic vibrator. We studied the method of measuring mechanical fractures of resonators with good reproducibility and collected data on mechanical fractures of crystals due to high input electric power. Chip resonators with a 4 MHz and 8 MHz shear mode were selected for the test samples. The driving frequency was swept near the resonance frequency, the duration time was short enough to raise the resonant vibrations and the driving voltage increased in one-volt increments. The method is free from unstable temperature increases. Values of the fracture limit for the driving current were measured and transformed to mechanical vibration velocities. These showed a nearly normal distribution. It was a surprise that concavity in the crater was observed at the center of the 16 MHz LiNbO3 resonator due to high input power. It was confirmed that the elastic fracture limit was latently very high for LiNbO3 and LiTaO3 single crystals.

Vanadyl-phthalocyanine (VOPc) single crystals were prepared on KBr substrate by molecular beam epitaxy (MBE). Their maximum size is 1380.16 µm3. The morphology of the VOPc single crystal was investigated from the results of UV/VIS spectra and RHEED. They suggest that the VOPc single crystal may be grown with pseudomorphic layers. The growing process was expained by Volmer-Weber model. The third order nonlinear optical property of VOPc single crystal was measured with Maker fringe method. The value of the third order optical susceptibility (χ(3)) of VOPc single crystal was estimated to be about 10-9 esu from the result of Maker fringe.

We have systematically grown and characterized (Bi, Pb)2Sr2CaCu2Oy (BPSCCO) single crystals, and investigated the tunneling properties and the intrinsic Josephson effects of the single crystals as a function of the nominal composition of Pb, x. It was observed that Pb atoms (ions) were monotonically substituted for Bi atoms (ions) in the (Bi, Pb)-O layers of the crystals with increasing x in a region of 0x0.5, while the modulation structure was maintained in a range of 0x0.3, but disappeared in x0.3, accompanying the decrease of c-lattice parameter and Tc. Moreover, it was found that the energy gaps Δ of BPSCCO depend hardly on x for x0.5, which are about 24 meV, so that the Pb-induced electronic change in the (Bi, Pb)-O layer do not perturb the electronic states in this superconducting system. And it was confirmed that the currentvoltage characteristics of the BPSCCO single crystals had multiple resistive branches corresponding to a series array of several hundreds Josephson junctions, and showed Shapiro steps and zero-crossing steps with the voltage separation of the order of mV resulting from the phase locking of about a hundred Josephson junctions among them under microwave irradiation. The estimated number of junctions gave the concept that the intrinsic Josephson junctions consist of the superconducting block layers and the insulating layers in the BPSCCO single crystals.

In order to investigate the characteristics of the superconducting gap structures of BSCCO oxide superconductor, tunneling spectrum measurements were carried out with several junctions on the bulk single crystal surfaces. Point contact tunneling studies by means of the M/I/S and S/(I)/S junctions have shown the reproducible gap values, 2Δ (//c-axis) of 402 meV, at the cleaved crystal surfaces, and the ratio of 2Δ(//)/kBTc5.50.3 indicates the strong coupling superconductor of this material. Somewhat larger gap values, 2Δmax(c-axis)701 meV, have been also observed at the lateral surface, and these various gap values observed on each surface of the same crystal indicate the characteristic of the large gap anisotropy, Δ()/Δ(//)1.8, of this material.