We developed a tunnel-current based identification method by using nano-gap integrated devices. We performed electrical measurements for mono-nucleotide and oligo-nucleotide during its translocation of molecules between the nano-gap. Based on this determined electrical conductivity for single-nucleotides, we electrically identify the base-type in oligonucleotides, and found that this time-profiles represents the molecular translocation behaviors inside nano-gap. This method could be a promising for an electrical nucleotide sequencing methodology with label-free, high-speed, and low-cost.

Spinel ferrite oxides doping non-magnetic ions show the photo-induced magnetization (PIM) effect at high temperature [1-3]. Such a magnetization enhancement by light irradiation is a unique property in this material. In order effectively to use the PIM effect and precisely to control the magnetism, direct light-emission from light-emitting element substrates would be a useful technique. In this study, spinel ferrite Al0.2Ru0.8Fe2O4 (ARFO) thin films, with the high temperature PIM effect, were prepared on GaAs(001) substrates by a pulsed laser deposition technique to aim integration with light-emitting devices based on GaAs lattice-matched materials in the future. Results showed that (001)-oriented ARFO thin films were successfully grown by using MgO buffer layers. The magnetic properties were approximately the same as ARFO films using other substrates such as Al2O3(0001) or MgO(001).

We have constructed artificial superlattices with a combination of magnetic/magnetic and ferroelectric/ferromagnetic materials using a laser ablation technique. An ideal hetero-epitaxy can be obtained due to the similar crystal structure of the perovskite type di/ferroelectric BaTiO3, Pb(Zr,Ti)O3 (so-called PZT), SrTiO3 and ferro/antiferromagnetic LaFeO3, LaCrO3, (La,Sr)MnO3. First of all, we have controlled ferromagnetic order on LaFeO3/LaCrO3 superlattices formed on SrTiO3(l11) substrate. Such a spin structure(ferromagnetic order) can't be got in bulk condition. In the heterostructured ferromagnetic /ferroelectric devices, (La,Sr)MnO3/PZT there are remarkable and interesting phenomena. The electric properties of the ferromagnetic material can be controlled by the piezoelectric effect via distortion of the crystal structure.

Thin LiNbO3 films are deposited on (001) sapphire substrates by Ar F pulsed laser ablation. The films are evaluated by X-ray diffraction analysis at various temperatures, as well as high-resolution transmission electron microscopy (TEM). The deposited films are highly epitaxial but that are strained, that is, the a-axis is longer and the c-axis is shorter than those of LiNbO3 single crystals. X-ray diffraction analysis at deposition temperature, as well as TEM show that the strain is caused by the difference in thermal expansion coefficients between LiNbO3 and sapphire substrates.

(Zr, Sn)TiO4 is considered as a promising dielectric material for microwave devices owing to the temperature stability of capacitance and excellent microwave properties. Preferential (111)-oriented (ZrSn)TiO4 thin film was obtained by an ArF laser ablation. Properties of the crystallized film were as follows; the temperature coefficient of capacitance TCC was 17.6ppm/°C at 3MHz and the dielectric constant εr, 38 in the microwave range of 1GHz˜10GHz. It has turned out that the crystallization of this material is quite effective for improving dielectrical properties. Surface morphologies were observed by atomic force microscope(AFM). Grains grew on the crystallized film at 1 μm × 1 μm size.

Bismuth based artificial superlattices have been formed by a layer-by-layer laser deposition with in-situ monitoring of RHEED. The Bi2O2/WO6, Bi2O2/SrTa2O9, Bi2O2/SrTa2O9 /SrTiO3 and Bi2O2/SrTa2O9/BaTiO3 are constructed epitaxially by a single, double and triple perovskite layers sandwiched by Bi2O2 layers, respectively. The dielectric constant increases with increasing the number of perovskite layers. And the D-E hysteresis loop (ferroelectric properties) appears along the c-axis direction in odd perovskite layers (n=l and 3). We have also formed the SrTiO3/BiWO6/SrTiO3 multi layers. With this combination, the STO layers are isolated by the BWO layers. The dimensionality of STO layer can be controlled by changing the thickness of BWO layers. Below the BWO thickness of 500 Å, the εr increases monotonously with decreasing the BWO thickness. Therefore, the the coulomb force, which is in proportion to inverse of the distance, plays an essential role for the dielectric constant. The formation of “artificially constructed ferroelectric films” by a layer-by-layer deposition method will be discussed ad an essential approach to elucidate the mechanism of ferroelectricity.

Thin LINbO3 films are deposited on (001) sapphire and (001) LiTaO3 substrates by using pulsed excimer-laser ablation. These films are evaluated by high-resolution X-ray diffraction (HRXRD) analysis. Strained LiNbO3 films in which the a-axis is longer and the c-axis is shorter than those of LiNbO3 single crystals are deposited on the sapphire substrates. On the other hand, extremely high-quality LiNbO3 films in which the a-axis of the films is the same as that of substrates are grown on the LiTaO substrates. X-ray rocking curves for the (006) reflection showed very narrow full width at half maximum (FWHM) of 208 arcsec for the films on the sapphire substrates, and 9 arcsec for the films on LiTaO3 substrates.

Artificial dielectric superlattices of SrTiO3/BaTiO3(STO/BTO) and CaTiO3/BaTiO3 (CTO/BTO) have been formed by a pulsed laser ablation technique with an in situ monitoring of RHEED (reflection high energy electron diffraction) oscillation. The crystal structures can be controlled with atomic order accuracy and a large stress of 400–500 MPa is introduced at the interface between the BTO and STO layers. Xhe superlattices show higher dielectric constant than that of (Sr0.5Ba0.5)TiO3 films against the change of temperature or applied frequency. A large dielectric constant of 900 was observed for the superlattices with a stacking periodicity of 2 unit cells / 2 unit cells. Xhe superlattices show drastically different electrical behavior from that of the solid solution (Sr,Ba)XiO3 films, both with changing temperature and applied frequency. Broad maxima of the dielectric constants occur around 40–50 °C and the values remain large even for the temperature above 200 °C. On the contrary, in the case of CTO/BTO superlattices, lattice constants and dielectric constant do not change so much compared with STO/BTO cases. Lattice mismatch in the STO/BTO and the CTO/BTO superlattices are 2.5% and 5.5%, respectively. In the case of CTO/BTO, misfit dislocations such as stacking faults may occur at the interface between CTO and BTO layers owing to large lattice mismatch. Therefore, lattice strain is introduced effectively below the lattice mismatch of about 3%.

We have formed thin films of ferroelectric and dielectric materials (BaTiO3, SrTiO3 and CaTiO3) by pulsed laser deposition on various kinds of substrates such as SrTiO3, LaAlO3 and MgO(100) single crystals. All the films can be formed epitaxially on the SrTiO3 substrate with c-axis orientation by choosing suitable conditions. The electrical behavior of these films such as dielectric constant and spontaneous polarization is quite similar to that of single crystals in bulk samples. The remanent polarization of BaTiO3 and PbTiO3 films are about 15 μC/cm2 and 80 μC/cm2, respectively. The value of 80 μC/cm2 is almost the same as that theoretically predicted and have not been obtain in the bulk samples. The unique advantage of the pulsed laser deposition technique is its ability to produce highly oriented stoichiometric films that show good electrical properties.

We have obtained STM images and STS data with atomic-scale resolution for SrTIO3 (100) surface annealed in UHV at 1200 °C. A √5×√5-R26.6° surface superstructure indicating oxygen vacancy ordering has been observed. The STS data provide evidence for a localized surface state arising from oxygen vacancies at 1.35 eV below the Fermi level. STM images of the √5×√5 structure correspond to the surface orbital of the ordered Ti-oxygen vacancy.

We have formed PbTIO thin films on SrTiO3 substrate (100) at low temperature of 350°C using an ArF excimer laser ablation technique. Until now, the PbTiO3 films have not been formed at the temperature lower than 500°C using other thin film techniques. The Important points In the present study are the laser excitation of the substrate during the film growth and the lattice matching between the film and the substrate. The film deposited on the SrTiO3 substrate, shows preferential orientation of the c-axis perpendicular to the substrate surface.

Epitaxial growth of Bi2Sr2CuO6 thin films on a SrTiO3, a misoriented SrTiO3 and a Bi2Sr2CaCu2O8 single crystal have been performed using computer-controlled laser molecular beam epitaxy. On the SrTiO3 substrate, the 2201 films consist of two types of domains whose b-axes are perpendicular to each other. In contrast, the 2201 film on the 2212 single crystal has a complete single type of domains. Layer-by-layer growth with a half unit cell thickness of 2201 films is observed.

Thin films of (Ca,Sr)CuO2 and Bi2Sr2Can-1CunO2n+4 are formed by laser molecular beam epitaxy with in-situ reflection high energy electron diffraction observation. The diffraction pattern shows that these materials are formed with layer-by-layer growth. The change of the diffraction intensity as well as the analysis of the total diffraction pattern makes It possible to control the grown of the atomic layer or the unit-cell layer.

By using 1ayer-by-1ayer successive deposition method with excimer laser ablation, the distance between CuO2 planes in the Bi2Sr2Ca1Cu2Oy superconductor has been controlled and super lattices with concentration modulation of Y and Ca have been formed. From the properties of these ‘Tailored films’, it is suggested that there is an interaction between CuO2 layers across Ca layer to affect the Tc value, but there is a very weak interaction across Bi2O2 blocking layers.

An oriented film of YBa2Cu3O7−x superconductor was formed by a spray pyrolysis method. The temperature dependence of resistance showed the Tc-onset at 95K and Tc-zero at 83K with the film on a cubic zirconia single crystal surface. The X-ray diffraction pattern showed that the structure of the film was pure orthorhombic phase. Effect of the substrates and the modification of the substrates surface to form superconductive films are presented.

High Tc YBa2 Cu3 Oy and GdBa2 Cu3 Oy thin films can be made by a laser sputtering method using LnBa2 Cu3 Oy (Ln=Y and Gd) ceramics as targets and cubic zirconia as a substrate in a high vacuum system. The superconcucting onset temperature and the zero resistance temperature of the film are 95 and 80K, respectively. The surfaces of these films were subjected to an irradiation with a focused pulsed excimer laser. Scanning of the beam led to the etching of the surface to form a groove. Photochemical processes on these superconductor films were studied using dynamic mass-spectroscopic method.

A uniform thin TiO2 film with the rutile structure which is usually made at higher than 700°C, can be formed at room temperature by the laser irradiation of adsorbed TiCl4 followed by oxidation and repeated cycles of this procedure on a silicon(100) single crystal surface. The laser irradiation to gaseous mixture of TiCl4 and oxygen from the direction parallel or perpendicular to the substrate, on the other hand, leads to the formation of a TiO2 film consisting of amorphous fine particles. The mechanism of the film formation is briefly discussed.