Hidehiko Shimizu

Composition and Structure Control of Cu–Al–O Films Prepared by Reactive Sputtering and Annealing

Cu–Al–O films were prepared on quartz glass substrates at 500–700 °C by sputtering the Cu and Al targets alternately on atomic-layer scale under an Ar-diluted O2 (5–20%) gas atmosphere, and then annealed at 1050 °C under a nitrogen atmosphere. The [Cu]/[Al] ratio was controlled by changing the Cu and Al deposition periods. The composition of as-deposited films corresponded to the slightly oxygen-rich region of the CuO–CuAl2O4–Al2O3 system. Films as-deposited at 500 °C had an amorphous structure, while films as-deposited at 700 °C had CuAl2O4 and CuO phases. After thermal annealing in a nitrogen atmosphere, the composition of the films approached that of the Cu2O–CuAlO2–Al2O3 system line, causing a noticeable appearance of the CuAlO2 phase along with the disappearance of the CuAl2O4 and CuO phases. Cu- and Al-rich annealed films had in addition a Cu2O phase and an amorphous Al2O3 phase, respectively. All annealed films exhibited p-type conductivity. The annealed films with [Cu]/[Al]≈1 had an absorption edge corresponding to the energy gap of CuAlO2. These results indicate that the change in the Cu ion from divalent to monovalent through nitrogen annealing results in the preparation of transparent conductive films dominated by CuAlO2.

Characterization of CuAlO2 Thin Films Prepared on Sapphire Substrates by Reactive Sputtering and Annealing

As-deposited films were prepared on sapphire substrates at 500–680 °C by alternately sputtering Cu and Al targets in Ar-diluted O2 gas atmosphere. The composition of the as-deposited films corresponded to that of the slightly oxygen-rich region of the CuO–CuAl2O4–Al2O3 system. The films as-deposited at 500 °C had an amorphous structure, while the films as-deposited at 680 °C had CuAl2O4 phase but no CuAlO2 phase. Annealing at 1050 °C in nitrogen flow caused a reduction in the molar fraction of oxygen, i.e., the composition of the annealed films with [Cu]/[Al] ≈1 corresponded to CuAlO2. The annealed films were predominated by the CuAlO2 phase. The preferential orientation of the films toward the c-axis normal to the substrate surface is due to the small lattice mismatch between the rhombohedral [010] of delafossite-type CuAlO2 and the hexagonal [1100] of the sapphire substrate. The annealed films had an absorption edge corresponding to the energy gap of CuAlO2 and exhibited p-type conductivity.

Observation of electric-field induced aggregation in crystallizing protein solutions by forward light scattering

Protein aggregation has been observed in-situ in lysozyme solutions under an internal electric field using a forward light scattering technique. Light scattering at small forward angles revealed that the application of a low voltage to the protein solutions significantly promotes aggregate formation. The solutions required a specific amount of time exposed to an electric field before the solution had undergone sufficient protein aggregation. The in-situ results from forward light scattering allow the characterization of the process.

Alternate layer deposition method for the deposition of c-axis oriented hexagonal barium ferrite thin films

Abstract Sputter-deposition of c -axis perpendicularly oriented hexagonal barium ferrite (BaM: BaFe 12 O 19 , and BaW: BaFe 18 O 27 ) thin films was attempted by means of an alternate periodic deposition of Fe 3 O 4 layer (S-layer) and BaFe 6 O 11 layer (R-layer). BaM film with c -axis orientation was obtained at temperatures above 540 C, in which control of the thickness of both S-layer and R-layer was very important to obtain a BaM thin film with c -axis orientation. BaW film, however, was not obtained at the periodic layer deposition condition corresponding to the BaW crystal ( S -layer= 9.3 A,R -layer= 6.9 A ).

Fabrication and Surface Plasmon Excitation Properties of Polystyrene Submicron and Micron Sphere Thin Films

Polystyrene submicron and micron sphere films were fabricated and the optical properties were investigated using surface plasmon spectroscopy (SPS) and reverse irradiation utilizing the SPS Kretschmann configuration. The diameters of the spheres were 0.1 and 1.0 µm. For the 0.1-µm-sphere films, the dip angles of the SPS curves shifted to higher angles with the amount of spheres in the films. However, for the 1.0-µm-sphere films, the SPS curves did not shift with the amount of spheres which is considered to be due to the change of the effective dielectric constant in the decay length of the evanescent field intensity of surface plasmon. Furthermore, emitted light due to reverse irradiation was also observed as a function of the emitted angle in the Kretschmann configuration. The peak angles of the emitted light almost corresponded to the dip angles of the SPS curves and the emitted light was considered to be due to surface plasmon excitation.

SURFACE PLASMON RESONANCE AND EMITTED LIGHT PROPERTIES OF POLYSTYRENE SPHERE FILMS

Polystyrene sphere films were fabricated and the optical properties were investigated using surface plasmon spectroscopy (SPS) and emitted light due to reverse irradiation utilizing SPS Kretschmann configuration. The films were fabricated using sphere dispersed solution with various diameters from about 100 to 300 nm. The morphologies of the fabricated films were observed using atomic force microscopy and the sphere films had almost three layer structure. In SPS curve, large dip and shallow broad dip were observed at around 75° and 50°, respectively. The dips were considered to be due to the three layer structure and some defects in the film. Furthermore, emitted lights due to reverse irradiation were also observed as a function of the emitted angle in the Kretschmann configuration of the SPS measurement. Emitted lights due to surface plasmon excitation were also observed and the peak angle of the emitted light almost corresponded to the dip angle of the SPS curves.