Physical properties of metal-doped zinc oxide films for surface acoustic wave application

Metal-doped ZnO [MZO] thin films show changes of the following properties by a dopant. First, group III element (Al, In, Ga)-doped ZnO thin films have a high conductivity having an n-type semiconductor characteristic. Second, group I element (Li, Na, K)-doped ZnO thin films have high resistivity due to a dopant that accepts a carrier. The metal-doped ZnO (M = Li, Ag) films were prepared by radio frequency magnetron sputtering on glass substrates with the MZO targets. We investigated on the optical and electrical properties of the as-sputtered MZO films as dependences on the doping contents in the targets. All the MZO films had shown a preferred orientation in the [002] direction. As the quantity and the variety of metal dopants were changed, the crystallinity and the transmittance, as well as optical band gap were changed. The electrical resistivity was also changed with changing metal doping amounts and kinds of dopants. An epitaxial Li-doped ZnO film has a high resistivity and very smooth surface; it will have the most optimum conditions which can be used for the piezoelectric devices

Transport properties of nitrogen doped p‐gallium selenide single crystals

Nitrogen doped gallium selenide single crystals are studied through Hall effect and photoluminescence measurements in the temperature ranges from 150 to 700 K and from 30 to 45 K, respectively. The doping effect of nitrogen is established and room temperature resistivities as low as 20 Ω cm are measured. The temperature dependence of the hole concentration can be explained through a single acceptor‐single donor model, the acceptor ionization energy being 210 meV, with a very low compensation rate. The high quality of nitrogen doped GaSe single crystals is confirmed by photoluminescence spectra exhibiting only exciton related peaks. Two phonon scattering mechanisms must be considered in order to give quantitative account of the temperature dependence of the hole mobility: scattering by 16.7 meV A′1 homopolar optical phonons with a hole‐phonon coupling constant g2=0.115 and scattering by 31.5 meV LO polar phonon with a hole Fröhlich constant αh⊥[email protected]

Epitaxial growth of Bi₁₂GeO₂₀ thin film optical waveguides using excimer laser ablation

Thin-film optical waveguides of the photorefractive optical material bismuth germanium oxide (Bi12GeO20) have been epitaxially grown onto heated zirconia substrates by excimer laser ablative sputtering. The epitaxial nature and stoichiometry of the films were verified using x-ray diffraction analysis. Waveguide modes were observed for effective refractive indices in close agreement with theoretical predictions

Memorized polarization-dependent light scattering in rare-earth-ion-doped glass

We report the observation of memorized polarization-dependent light scattering in a Eu2 + -doped fluoroaluminate glass sample. Anisotropic light scattering along the plane of the light polarization was observed in the glass sample after the excitation of a focused 800 nm, 150 fs laser beam at a repetition rate of 200 kHz. When we changed the direction of the light polarization and irradiated the same location, we observed an anisotropic light-scattering pattern identical to the original one at the beginning, but then observed a new pattern along the new direction of the light polarization while the original light-scattering pattern disappeared gradually with the passage of time. This observed phenomenon was considered to be due to the light scattering of the polarization-dependent permanent microstructure induced by the polarized ultrashort pulsed laser itself

Wavelength dependence of photoreduction of Ag+ ions in glasses through the multiphoton process

We have investigated the wavelength dependence of the photoreduction of Ag+ ions in glass irradiated by visible femtosecond pulses. These pulses, issued at wavelengths ranging from 400 to 800 nm, were nonresonant with the glass absorption. In this article, a relationship between threshold powers, wavelengths, and linear and nonlinear refractive indices is described. The nonlinear refractive index of Ag+-doped glass was measured by an optical Kerr shutter method. The wavelength dependence of threshold powers of the photoreduction is explained by considering linear and nonlinear refractive indices. The mechanism of the photoreduction is also discussed