Yasuyuki Kageyama

Vibrating gyroscope consisting of three layers of polysilicon thin films

Abstract A vibrating gyroscope consisting of three layers of polysilicon thin films has been developed. It has an upper electrode over a resonating mass for detecting accurately the sensing vibration oscillated by the Coriolis force . The resonant frequencies of both the driving and sensing vibrations are controlled by the DC bias to comb electrodes that are used for detecting the driving vibration. The offset on the angular rate output due to the mechanical and electromechanical couplings is decreased by an unbalanced differential oscillation. With this tuning method and the offset reduction, the angular rate was detected. The resolution of 1° s −1 is achieved.

Effect of a declination angle of substrate position on magnetron sputter deposition from a YBa2Cu3O7−x target

Thin‐film deposition by magnetron sputtering of a multielement target was carried out with respect to the geometrical factors between a target and the substrates. The thin films were deposited on substrates which were located semicircularly over a YBa2Cu3O7−x target in several declination angles measured from the normal to the target surface. The deposition rate decreased to about one‐third with the change in the angle from 0° to 90°. In the angles of 45°, 60°, and 75°, films showed significant instability in the atmosphere, which appeared to be caused by an excessive concentration of Ba atoms in the films. Target composition was almost reproduced in the films deposited in the angle of 90°.

Polycrystalline silicon thin films with hydrofluoric acid permeability for underlying oxide etching and vacuum encapsulation

Specialized fabrication techniques created polycrystalline silicon (poly-Si) thin films that were permeable to a concentrated hydrofluoric acid (HF) solution, in order to support in situ vacuum encapsulation of surface microsensor devices on silicon wafers. 0.1-μm-thick poly-Si thin films were made permeable through processes of amorphous silicon film formation by low pressure chemical vapor deposition, successive postannealing for crystallization, and excessive phosphorus diffusion by a phosphorus oxichloride predeposition. Permeability was obtained both on borophosphosilicate glass and nondoped silica glass sacrificial layers. Porous microstructures at the silicon grain boundaries, which were induced by heavy doping of phosphorus and consequent segregation of soluble precipitates, were first observed using a secondary electron microscope and a field emission secondary electron microscope. These observations confirmed that the submicron pores permitted passage of the fluid to dissolve the underlying sacr...

Ion-beam-induced chemical-vapor deposition of FePt and CoPt particles

FePt and CoPt particles have been directly deposited on Si3N4 substrate by ion-beam-induced chemical-vapor deposition (IBICVD) with a focused ion-beam system. The as-deposited FePt particles are amorphous and crystallize into fcc structure after annealing at 600°C. The as-deposited CoPt particles and the CoPt particles annealed at 600°C are both in fcc structure, but annealing improves the crystallization of the CoPt particles. After applying a 20‐kOe magnetic field perpendicular to the Si3N4 substrate, the magnetic force microscopy images of annealed FePt and CoPt particles both show concentric domain patterns, implying the alternately up- and downward perpendicular components of magnetizations. The successful fabrication of FePt and CoPt particles may lead to the potential application of IBICVD for nanoparticles and clusters which have not been synthesized yet.

Pyroelectric property of Pb5Ge3O11 thin films prepared by laser ablation

Pb 5 Ge 3 O 11 films were prepared by laser ablation, and pyroelectricity was obtained in the films after annealing. Stoichiometric films were formed at oxygen pressures around 5 x 10 -1 Torr during deposition. It was found that an unreported precursor phase was grown on Pt/Ti/SiO 2 /Si substrates at a temperature of 520°C. Subsequent annealing at 500°C for 2 h in air made it possible for the film to have (001) oriented texture of ferroelectric Pb 5 Ge 3 O 11 . This sample showed remanent polarization of 1.4 μC/cm 2 with a ferroelectric hysteresis loop of an asymmetric shape and a pyroelectric coefficient of 4.3 nC/cm 2 K, while these values were about one third of those reported for single crystal Pb 5 Ge 3 O 11 in a polarization direction. The inferiority in this ferroelectricity is thought due to the lead-deficient phase involved in the film. Although this localized second phase still remains, the appreciable reduction in the process temperature for texturing a Pb 5 Ge 3 O 11 film in the c-plane as low as around 500°C is attributed to the sufficient supply of oxygen during the deposition.

Temperature dependence of magnetic domain structures of single-crystal Co thin films and particles

Submicron-sized Co particles were fabricated by patterning single-crystal Co thin films, and their magnetic domain structures were observed by magnetic force microscopy (MFM) with temperature up to 200 °C. The Co films (19–220 nm in thickness with their c axis parallel to the surface normal) were epitaxially deposited onto Al2O3 (001) single-crystal substrates by electron-beam evaporation. Prior to dot fabrication, magnetic properties of these films were measured by a vibrating-sample magnetometer and a torque meter with changing temperature from room temperature 4 to 200 °C to confirm the film’s quality, and then, from these films circular dots with diameters of 0.5, 1, and 2.5μm were patterned by electron-beam lithography and Ar-ion-beam etching. For the thick (220 nm) film case, maze patterns in domain structure were clearly observed in all types of dots. MFM images taken at elevated temperatures did not show drastic change in the domain pattern; whereas for the 56-nm-thick film’s case, thin stripe dom...

Formation of porous grain boundaries in polycrystalline silicon thin films

Unique polycrystalline silicon (poly-Si) thin films, which were permeable to a concentrated hydrofluoric acid solution through their porous grain boundaries, were investigated to elucidate the formation mechanism of their microstructure. 0.1-μm-thick permeable poly-Si thin films were made through processes of amorphous silicon film formation by low pressure chemical vapor deposition, successive postannealing for crystallization, and excess phosphorus diffusion by a phosphorus oxichloride predeposition. At the grain boundaries, porous microstructures were formed after the films were cleaned in an SC1 solution (a 1:1:5 mixture of NH4OH:H2O2:H2O at 80 °C for 10 min), whereas segregated soluble precipitates observed by a field emission secondary electron microscope were present before the SC1 cleaning. Auger electron microscope revealed that the surface of the precipitates mainly consist of silicon (∼80 at. %) and oxygen (∼20 at. %). As a result of transmission electron microscope observation, it is concluded...

Temperature dependence of magnetic domain structures of Co particles fabricated by electron beam lithography

Submicron-sized Co particles were fabricated by patterning single crystal Co thin films, and their magnetic domain structures were observed by magnetic force microscopy (MFM) with temperature up to 200 /spl deg/C. The Co films (220 nm in thickness) were epitaxially deposited onto Al/sub 2/O/sub 3/ [001] single-crystal substrates by electron beam evaporation, and from these films (with their c-axis parallel to the surface normal) circular dots with diameters of 0.5, 1, and 2.5 /spl mu/m were patterned by electron beam lithography and Ar ion beam etching. Maze patterns in domain structure were clearly observed in all types of dots. MFM images taken at elevated temperatures did not show prominent change in the domain pattern, which implies stability of Co magnetization up to this temperature. Landau-Lifshitz-Gilbert (LLG) simulation results showed good agreement with these experimental data, and also predicted that a vortex structure will be obtained with thinner (50 nm) dots at 200 /spl deg/C.

Fabrication and characterization of cobalt nanoparticles by IBICVD

The focus of this study is to explore the size limitation and to study the morphology and the structure of cobalt particles by a novel technique.

Observations of Y-Ba-Cu-O Films by Scanning Electron Microscopy and Auger Electron Spectroscopy

Structures of Y-Ba-Cu-O sputter-deposited films were investigated by Scanning Electron Microscopy (SEM) and Auger Electron Spectroscopy (AES). After heat treatment, the films showed different morphology for different substrates, i.e., A12O3 and MgO, and for different thicknesses of 0.1 μm and 1.2 μm. Only for YBaCuO(P.1μm)/MgO, highly oriented crystal growth is seen, and for other systems, inhomogeneous crystal growths are seen. An interface roughning caused by preferential interdiffusion of Ba into an A12O3 substrate was observed. A surface enrichment of Cu is found for the thick films. These differences in morphology are considered to be due to the differences in the diffusion processes.