This study focused on structural and optical properties of ZnO films grown epitaxially on Gd3Ga5O12 substrates. ZnO films (a = 3.2439 Å and c = 5.2036 Å) were deposited on the (001) and (111) planes of Gd3Ga5O12 (GGG: a = 12.383 Å) garnet substrates by a pulsed laser deposition method. From out-of-plane and in-plane X-ray diffraction measurements, the obtained ZnO films showed a single phase with the (0001) orientation on the GGG (001) and (111) substrates. The epitaxial relations between the ZnO film and GGG (001) substrate were [10-10] ZnO ‖ [100] GGG and [10-10] ZnO ‖ [010] GGG, while the epitaxial relations between the ZnO film and GGG (111) substrate were [10-10] ZnO ‖ [11-2] GGG ±21°. Furthermore, transmittance electron microscopy revealed sharp interfaces between ZnO films and GGG substrates. From photoluminescent spectra, the ZnO films showed donor bound emissions superimposed with free excitons at a low temperature of 10 K.

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).

BiFeO3 thin film has been prepared on Pt/TiO2/SiO2/Si substrate at a temperature as low as 450°C by pulsed-laser deposition. The BiFeO3 thin film is perovskite single-phase, while any nonperovskite phase, such as orthorhombic Bi2Fe4O9, is not included. Dielectric constant of the film is 87, dielectric loss is 0.03, and leakage current density is low. The coexistence of ferroelectricity and ferromagnetism has been confirmed by means of the P-E and M-H hysteresis characteristics. The BiFeO3 thin film shows a well-saturated hysteresis loop with twice the remanent polarization 2Pr = 54 μC/cm2 and coercive field 2Ec = 100 kV/cm for a maximum applied electric field of 100 kV/cm, and also shows a saturated weak ferromagnetic hysteresis loop, as well as a small remanent magnetization with 2Mr = 0.6 emu/cm3 and 2 Hc = 200 Oe for a maximum magnetic field of 10 kOe at room temperature.

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.

(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.

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 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.

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.