In this study, ZnO f ilms heavily doped with Al or Ga were grown on a polarity-controlled buffer layer using pulsed laser deposition. The films prepared using a 1 mol% Al-doped target with the buffer layer grown at 700 °C had the c(+)-face, whereas the films with the buffer layer grown at 400 °C had the c(-)-face, which means that the polarity control can be successfully carried out using the buffer layer. However, the films prepared using targets doped with more than 1 mol% Al or Ga had the c(+)-face regardless of the polarity of the buffer layer. The 1 mol% Al-doped ZnO film with the c(+)-face had lower electron concentration and higher growth rate than the film with the c(-)-face. This result indicates that the Al content in the film with the c(-)-face was larger than that in the film with the c(+)-face.

We have investigated the polarity of zinc oxide (ZnO) and Al-doped ZnO films grown on (11¯20) and (0001) sapphire substrates, using coaxial impact collision ion scattering spectroscopy. The films grown by pulsed laser deposition with a nominally undoped ZnO ceramic target had a (000¯1) surface, whereas the films prepared with a 1 mol% Al-doped ZnO ceramic target had a (0001) surface. The usage of Al-doped and undoped targets caused no difference in the in-plane lattice orientation. Electron microscope observations revealed that polarity change due to doping occurred without the formation of any interfacial phase between ZnO and sapphire.

We report on the effect of sample non-uniformity on the results of Hall-effect measurements. False positive Hall coefficients were obtained from an evidently n-type ZnO single crystal, although four electrodes with low contact resistance were made and the Van der Pauw parameter for this electrode configuration was close to 1.00. Further position-sensitive characterization revealed that the false positive Hall coefficient was due to non-uniform electrical properties of the sample. To demonstrate a false positive sign of the Hall coefficient due to sample non-uniformity, we devised a model structure made from evident n-type ZnO thin film and successfully reproduced a false positive Hall coefficient from n-type ZnO.

Zinc oxide (ZnO) films doped with aluminum (Al) were deposited with a pulsed laser deposition technique to characterize the charge compensation phenomena in ZnO. In particular, oxygen radical (O*) irradiation during film deposition was used to modify the oxygen stoichiometry. Irradiation with O* decreased electron concentration in Al-doped ZnO. The lattice parameter of the resultant films also varied with the growth conditions. However, no obvious correlation between electron concentration and lattice parameter was found. The self-diffusion coefficients indicated the presence of non-equilibrium defects. The properties of the films are discussed from the viewpoint of non-equilibrium compensated defects detected in the diffusion measurements.

A nanometer-scale ZnO light emission array device was fabricated using the multi-level metallization technique of the CMOS process. Square arrays of pits with an inverted pyramid shape made from {111}Si planes were formed on a (100)Si substrate using selective etching. ZnO was deposited on the substrate by chemical vapor deposition (CVD), and the surface of the deposited ZnO film was carefully polished by chemical mechanical planarization (CMP). As a result, ZnO-filled nanometer-scale arrays were obtained after removing the ZnO layer except for the ZnO in the pits by CMP. Cathodoluminescence (CL) from the ZnO arrays was observed.

Ho ion solubility and diffusivity were evaluated in barium titanate ceramics in which Ho ions were implanted with an accelerating voltage of 500 keV. The depth profile of the ions was composed of three regions in the post-annealed sample: the first was the precipitation region, the second was a region created by lattice diffusion of Ho ions, and the third was a region created by grain-boundary diffusion. The Ho lattice diffusion characteristics were similar to those of Ni ion diffusion in barium titanate ceramics, and we concluded that the diffusion mechanism was the same as that responsible for Ni ions. The Ho ions diffused through the B-site (Ti-site) and were then exchanged with A-site ions. This mechanism suggests that a small number of Ho ions dissolved in the B-site. Preferential grain-boundary diffusion was also observed. The grain-boundary diffusion coefficients were four to five orders of magnitude larger than the volume diffusion coefficients. The solubility of Ho ions was estimated to be a few thousand parts per million in barium titanate ceramics.

Defect structures in ZnO thin films were studied to clarify the mechanism of charge compensation and crystallinity degradation induced by alloying. Regarding the undoped ZnO films, it was indicated that the degree of non-equilibrium behavior in the films deposited by PLD was much less than in the films prepared by the other two methods, i.e., MBE and sputtering, and, moreover, the solid-state diffusion behavior in the PLD-grown undoped ZnO was close to that of bulk ZnO. The heavily Al-doped films and alloy films with high concentrations of MgO exhibited significant non-equilibrium behavior, even for those prepared by PLD. It was indicated that the high concentration of extrinsic elements, e.g., Al and Mg, introduces non-equilibrium defects into ZnO films and those defects are the cause of the crystallinity degradation and thermal instability of the films.

Zinc oxide (ZnO) single crystals were grown by the hydrothermal method using lithium and potassium hydroxide as mineralizer and properties of the grown crystals were characterized from the viewpoints of epitaxial wafer applications. The growth sector dependence of impurity and defect concentrations were characterized by secondary ion mass spectroscopy and photoluminescence. As a result, it was clearly shown that defect and impurity distribution in the obtained crystal was anisotropic, and this anisotropy is affected by the choice of the seed crystal shape and growth direction. Annealing effect on flatness of the wafer surface was also examined, and it was found that high temperature annealing with flat single crystalline cover is appropriate for removal of scratch and formation of atomically flat surface. Moreover, we show the possible miss-evaluation of Hall coefficient of ZnO due to anisotropy in defects and impurities distributions.

Dielectric properties and microstructure were investigated in BaTiO3 ceramics with various additives, Ho2O3, MgO, Ho2O3/MgO, and La2O3. The dielectric constants were increased up to ∼4000 and ∼3000 at 25°C in the 1 mol% Ho-doped and 0.5 mol% Mg-doped BaTiO3 materials, respectively. The BaTiO3 material codoped with 3 mol% Ho + 1.5 mol% Mg led to increase dielectric constant up to ∼6000 at 25°C and the dielectric constant peak around Curie temperature was suppressed at temperature range of from 25°C to 125°C. The size of BaTiO3 grains depended on the content and kind of an additive. Core-shell grains and secondary phase were also dependent on an additive. Core-shell grains were formed completely in Ho-doped BaTiO3 except for 0.5 mol%, but the structure was little observed in Mg- and La-doped BaTiO3 material. Codoped BaTiO3 also formed the core-shell grains.

Hydrogen doping effects on luminescence properties of bulk ZnO samples were examined by using a pulse-modulated plasma irradiation technique. Three kinds of ZnO samples, including both single- and poly-crystals, were employed as specimens. Secondary-ion-mass-spectroscopy analysis revealed that the surface layer to 100 nm was doped with hydrogen after the irradiation and its concentration was in the order of 1017 cm-3. The efficiency of band edge emission was increased by the hydrogenation. However, the degree of the improvements depended on impurity and defect concentration in the original samples.

Tracer oxygen diffusion coefficients, D*, in polycrystalline yttria doped with Ca have been determined by a gas–solid exchange technique and secondary ion mass spectrometry. Samples containing few pores were used to avoid their influences on diffusion profiles. The resulting profiles were assigned only to volume diffusion; no grain boundary diffusion was observed. According to the effects of Ca doping on D*, the Ca contents are divided into three regions. In a Ca content region of 0–0.17 mol%, D* changed a little with Ca doping and took a minimum experimentally at 0.02 mol%. D* increased significantly within a range of 0.17–0.54 mol% and saturated at 0.54 mol% or above because of a solubility limit. The activation energies of oxygen diffusion were estimated at 249–282 kJ/mol.

[Ba2CuO2(CO3)]m[ACuO2]n(A=Sr) superlattices containing oxycarbonate blocks as charge reservoir have been prepared on SrTiO3 using the molecular beam epitaxy technique. First, thin films of the oxycarbonate cuprate Ba2CuO2(CO3) have been prepared on SrTiO3(001) using NO2 gas as an oxidant and CO2 gas. The films have been grown at 500°C. At higher substrate temperature or at lower CO2 pressure Ba2CuO3 was formed instead of Ba2CuO2(CO3), and the films becomes amorphous at lower temperature. X-ray diffraction and reflection high-energy electron diffraction observations indicated that (BaxSr1−x)2CuO2(CO3) grew along the [001] crystal orientation on SrTiO3(001) with the following epitaxial relationship: Ba2CuO2(CO3)[100]//SrTiO3[110] and Ba2CuO2(CO3)[110]//SrTiO3 [100]. Depth profile of secondary ion mass spectrometry signals indicated the incorporation of carbon into the films. Secondly, the oxycarbonate cuprates and infinite layers have been alternately stacked. It was confirmed that Ba2CuO2(CO3)was inserted between several unit cells of SrCuO2. Electrical measurements show the as grown films to have a semiconducting behavior.

Oxygen diffusion in bicrystal SrTiO3 was investigated with the aid of resistive anode encoder of secondary-ion mass spectrometry. The diffusion profiles of 18O on volume, grain boundary (joining interface), and dislocation were separately determined from the three-dimensional distribution of 18O in the bicrystal SrTiO3. The volume diffusion of oxygen is found to be dependent on (i) Nb doping concentration, (ii) crystallographic orientation, and (iii) nonequilibrium oxygen defects that are annihilated by thermal annealing. The feature of 18O diffusion image along the dislocation in (100) and (110) bicrystals can be explained by the dislocation array introduced by the mechanical polishing.

We investigated the growth of high-quality homoepitaxial diamond on the (111) face in a microwave-assisted plasma chemical-vapor-deposition system incorporating an individual substrate heating/cooling device. The grown diamond films were characterized by scanning electron microscopy, reflection high-energy electron diffraction, atomic force microscopy, confocal micro-Raman spectroscopy, and secondary ion mass spectrometry. The (111) diamond films show a tendency to incorporate a significant amount of hydrogen during chemical-vapor-deposition growth. Hydrogen incorporation degrades the crystal quality and surface smoothness. The amount of incorporated hydrogen decreases with the decrease in deposition temperature. We have shown that the crystal quality and surface smoothness of homoepitaxial diamond strongly depend on the substrate temperature. Independent control of the substrate temperature and incident microwave power is essential for high-quality diamond homoepitaxy.

We have characterized heteroepitaxial diamond films on Pt(111) using the nondestructive technique of confocal Raman spectroscopy to investigate the variation in structure and strain with depth. The spectral depth profiles of heteroepitaxial diamond showed the diamond peak at 1332–1335 cm-1 and four bands centered at 1230 cm-1, 1470–1490 cm-1, 1530–1580 cm-1, and 1640 cm-1 near the surface. The diamond peak shifted to the single crystal peak position at 1332 cm-1 as the linewidth was broadened with free surface proximity. The compressive strain in the heteroepitaxial diamond crystal decreased and turned into the random strain. At the same time, the Raman band at 1470–1490 cm-1 grew in intensity. The constituents of non-diamond phase in the heteroepitaxial growth regions are different from those formed in the randomly oriented regions.