Yoshio Manabe

Optical nonlinearities of Au/SiO2 composite thin films prepared by a sputtering method

Third‐order nonlinear optical properties of Au/SiO2 composite thin films have been investigated by means of a degenerate four‐wave mixing at room temperature. In the optical‐absorption spectra the absorption peak due to the surface plasmon resonance of Au particles is observed at the wavelength around 530 nm. With increasing the mean diameter of Au particles, the absorption at the peak is increased and the full width at half‐maximum of the absorption band is decreased from 130 to 80 nm. The third‐order nonlinear susceptibility χ(3) exhibits a peak at the wavelength of the absorption peak and the maximum value of χ(3) is obtained to be 2.0×10−7 esu. The size‐dependent enhancement of the χ(3) in Au particles with the mean diameter of 3.0–33.7 nm has been also investigated. The value of χ(3)/α (α: absorption coefficient) for the films is increased upon an increase of mean diameter of Au particles. This is explained by the size dependences of the local‐field factor and the imaginary part of dielectric constan...

Silicon nitride thin films prepared by the electron cyclotron resonance plasma chemical vapor deposition method

Silicon nitride thin films prepared by the electron cyclotron resonance plasma chemical vapor deposition method at low substrate temperature ( 1017 Ω⋅cm and >10 MV/cm, respectively. These properties of silicon nitride thin films are close to those of stoichiometric silicon nitride (Si3N4) prepared by the thermal chemical vapor deposition method at high temperature (>600 °C). The interface trap state density between the silicon nitride film and silicon substrate was 4×1011 cm2/eV in the silicon band gap. An optical emission spectroscopy during the deposition indicated that the intensities of nitrogen molecular ions were much stronger than those of nitrogen molecules, and the silane was sufficiently decomposed into silicon and hydrogen atoms. It is consider...

Effects of heat treatment on Ag particle growth and optical properties in Ag/SiO 2 glass composite thin films

Small Ag particles were embedded in SiO 2 glass thin films by a multi-target sputtering method. The mean diameter of Ag particles in the as-deposited film with 28.0 at. % of Ag was estimated to be 4.4 nm and it was increased to 24.0 nm when the film was heat-treated at 700 °C for 3 h. The diameter was proportional to the cube root of the heat-treatment time, suggesting that the Ag particles grew in the supersaturated solid solution. In the optical absorption spectra of the heat-treated films, the absorption peak due to the surface plasmon resonance of Ag particles was observed about 410 nm. The peak intensity became large and the full width at half maximum of the absorption band was decreased with increasing the diameter of Ag particles.

Thomson scattering measurements of electron temperature and density in an electron cyclotron resonance plasma

Electron temperature Te and density ne in the source region of an electron cyclotron resonance discharge have been measured by incoherent Thomson scattering of the beam from a 0.5 J yttrium aluminum garnet laser. This is the first experiment in which this technique, routinely used on fusion plasmas, has been applied to a processing plasma. Measurements were made in an argon discharge at pressures from 0.3 to 2 mTorr and microwave powers from 250 to 1000 W. Velocity distributions were measured both parallel and perpendicular to the magnetic field and a slight anisotropy of electron temperature was observed for low‐pressure discharges. Temperatures in the range of 1–5 eV and densities in the range of 2–10×1017 m−3 were measured. Te and ne were found to strongly depend on pressure but only weakly on the input power and discharge magnetic field. No deviations from a Maxwellian velocity distribution were observed.

Preparation and Nonlinear Optical Properties of Ag/SiO2 Glass Composite Thin Films

A multitarget sputtering method was applied to prepare Ag particles embedded in SiO2 glass thin films. In the optical absorption spectra of the films, the absorption peak due to the surface plasmon resonance of Ag particles was clearly observed at the wavelength of 390–406 nm. The full width at half-maximum of the absorption band is decreased with increasing diameter of Ag particles. The third-order nonlinear susceptibility at 400 nm was estimated to be 1.6×10-8 esu for the film with 9.0 at% of Ag by means of a degenerated four-wave mixing.

Properties of Hydrogenated Amorphous Silicon Prepared by ECR Plasma CVD Method

Hydrogenated amorphous silicon (a-Si:H) films were prepared by the microwave electron-cyclotron-resonance (ECR) plasma CVD method using SiH4 gas without intentional substrate heating. The influence of the deposition conditions in the ECR plasma CVD method on the properties of a-Si:H films was studied and the properties were correlated with plasma optical emission spectra of similar deposition conditions. Photoconductivity of ~10-6 (Ω cm)-1 under simulated AM1 (100 mW/cm2) illumination was obtained for the as-grown film with an optical gap of ~2.1 eV at the SiH4 gaspressure of 2×10-4 Torr. The photoconductivities, the optical gaps and the B values estimated from optical absorption measurements were widely changed when SiH4 gas pressure condition was changed. Infrared absorption spectra also showed that the Si-H2 stetching mode at ~2100 cm-1 and (Si-H2)n wagging mode at ~845 cm-1 increased as SiH4 gas pressure increased. Measurements of optical emission spectra in the SiH4 ECR plasma showed that the emission intensity ratio of Si (288 nm) to SiH (414 nm) was larger than that in conventional RF plasma CVD, and that the photoconductivities and optical gaps increased as this ratio increased.

Zinc oxide thin films prepared by the electron-cyclotron-resonance plasma sputtering method

Zinc oxide (ZnO) thin films have been prepared by a sputtering deposition utilizing electron-cyclotron-resonance (ECR) plasma. An X-ray diffraction analysis indicated that the ZnO films were highly c-axis oriented. The electrical resistivity of ZnO films is as high as 2.5 MΩcm. It is confirmed that the ZnO films exhibit strong piezoelectricity. For a film-thickness-to-wavelength ratio h/λ of about 0.16, the effective electromechanical coupling coefficient k2 for a surface acoustic wave was 0.7%, which is above 90% of the calculated value. The measured values of k2 are comparable to those of the films fabricated by other conventional sputtering methods. In addition, optical emission spectroscopy was carried out during the deposition.

Low Temperature Preparation of Hydrogenated Amorphous Silicon by Microwave Electron-Cyclotron-Resonance Plasma CVD

Hydrogenated amorphous silicon films were deposited by microwave electron-cyclotron-resonance plasma CVD technique using pure mono silane gas without intentional substrate heating. A high photoconductivity value of 10-6~10-5(Ωcm)-1 under simulated AM1 (100mW/cm2) illumination was obtained for the as-grown films with optical gaps of ~2.1 eV. Localized tail states estimated from optical absorption measurements are discussed with the characteristics of the films.

Role of Ions and Radical Species in Silicon Nitride Deposition by ECR Plasma CVD Method

The growth kinetics of silicon nitride (SiN) films prepared by the electron cyclotron resonance (ECR) CVD method have been investigated. Studying both the compositional properties of films deposited by a shielding mask to a plasma stream just above the silicon wafer and optical emission spectrometry resulting from the discharge of SiH4/N2 mixture gas and N2 gas, it is deduced that N2 ions can directly contribute to the formation of SiN films. Although N2 radicals also can play a role in SiN formation, ion- assisted effects seem to be necessary for dense SiN formation.

Thomson Scattering Diagnostics of an ECR Processing Plasma

Information of electron behaviour in processing plasmas was obtained for the first time by the Thomson scattering measurements of electron cyclotron resonance (ECR) plasmas after overcoming various difficulties of the experiment. At relatively high microwave power of 500 W and high argon gas pressure of 2 mTorr, the measurements yielded electron temperature and density to be 9±3 eV and (9±2)×1017 m-3, respectively. Ways of improving detection limit and/or accuracy are discussed.