Masato Tazawa

Low temperature deposition of α-Al2O3 thin films by sputtering using a Cr2O3 template

A description about low temperature deposition of a-Al2O3 thin films by sputtering was presented. Cr2O3 thin layer was used as a template. Nanoindentation was used to study the mechanical propertie ...

Apatite Formation on TiO2 Photocatalyst Film in a Pseudo Body Solution

TiO2 photocatalysts film supported on glass plate was soaked in a pseudo body solution (PBS) containing excess phosphate ions. The surfaces were characterized by scanning electron microscopy, energy-dispersive spectroscopy, thin-film X-ray diffraction, and Fourier-transformed infrared methods. After soaking in the pseudo body solution for 1 day, a bone-like apatite layer was formed on the surface of the TiO2. The apatite layer was approximately 0.7 mm thick and made up of thin plate-like crystals. The haze values of dry and wet specimens were 28.47 and 9.51%, respectively. The apatite-coated TiO2 thin film could be used for antibacterial and environmental purification purposes.

Optical constants of V 1-x W x O 2 films

The spectral complex optical constants in the visible and the near-infrared region of VO(2) and V(1-x)W(x)O(2) films deposited on glass substrates were determined from observed reflectance and transmittance spectra for which the least-squares method was used. In the metallic phase, the optical properties were characterized by the Drude model in wavelength regions longer than 750 nm.

Epitaxial growth of W-doped VO2/V2O3 multilayer on α-Al2O3(110) by reactive magnetron sputtering

Multilayer epitaxy with a W-VO2 top layer over a bottom layer of which the crystal phase depends on the starting oxygen flow, was done on a-Al2O3(110) by reactively sputtering a V-W (1.6 at.% wt.) ...

New material design with V1−xWxO2 film for sky radiator to obtain temperature stability

Spectral selective radiating material (SSRM ) such as a SiO film deposited on metallic substrate can be cooled lower than the ambient temperature due to its high IR emission in the spectral region of the atmospheric window under clear sky conditions. In this paper we propose a new stacked SSRM consisting of SiO film and V 1-x W x O 2 thermochromic film to stabilize the surface temperature of the sky radiator. The transition temperature from metallic to semiconductor phase of V 1-x W x O 2 thermochromic film can be adjusted to a temperature near ambient by the control of the doping level of x. The radiative cooling of the new SSRM was simulated using the optical constants of SiO and V 1-x W x O 2 obtained by optical measurements. The results reveal that the newly designed SSRM can attain a stable surface temperature determined by the transition temperature of the V 1-x W x O 2 film.

HIGH-ENERGY CU AND O ION CO-IMPLANTATION INTO SILICA GLASSES

Abstract Optical and structural changes of silica glass substrates implanted with Cu and O ions and subjected to thermal annealing, are examined as a function of the implantation sequence by optical absorption, Rutherford Backscattering Spectrometry (RBS) and thin film X-ray diffraction (XRD) measurements. Before annealing, the distribution of Cu is affected by the implantation sequence and O- followed by Cu-implantation leads to fewer Cu nanoparticles than the Cu- followed by O ion implantation. After annealing, however, the redistribution behavior of Cu and optical absorption features are similar for both co-implanted samples. Nanocrystals of Cu2O are mainly formed by annealing and the absorption peaks at about 340, 450 and 480 nm are observed for the co-implanted samples. The peaks are possibly evidence for the presence of the copper oxide nanocrystals.

Optical property changes of silica glass and sapphire induced by Cu and O implantation

Abstract Single- and multi-energy O and Cu ions were implanted into silica glass (or sapphire) changing the ratios of O and Cu doses as like Cu only (0:1), 1/2O+Cu (0.5:1) and O+Cu (1:1). Optical property changes induced by the ion implantations and successive heat treatments have been studied. Specific optical absorption was clearly observed at about 570 nm, which attributed to Cu nano-particles for the samples of Cu, 1/2O+Cu and Cu+1/2O implantations. Multi-energy implantation at 300 K enhanced the absorption. With the increase of annealing temperature, the size and concentration of Cu particles are increased. The sequence of ion implantation between Cu and O affects the optical absorption and nano-particle formation. Third-order non-linear optical susceptibility, χ(3), has been measured for sapphire samples. The values of χ(3) were 6.5×10−9 esu and 4.0×10−9 esu for Cu and 1/2O+Cu implantation, respectively.

Thin film used to obtain a constant temperature lower than the ambient

Abstract Spectral selective radiating materials (SSRMs) are attractive because of their applicability to passive cooling with no external energy consumption. SSRMs can be cooled by IR emission in the spectral region at 8 and 13 μm of the atmospheric window. We have designed a new SSRM which consists of an SiO film as outer layer, V 1- x W x O 2 thermochromic (TC) film as intermediate layer and blackbody as the substrate respectively. In this study, the radiative cooling powers of the SSRM were simulated using the refractive indexes of SiO and V 1- x W x O 2 obtained separately by optical measurements. The results revealed that the newly designed SSRM can attain a stable surface temperature that can be controlled by varying the value of x in V 1- x W x O 2 . In this manner the transition temperature from metal to semiconductor states can be controlled by altering the value of x .

Growth of samarium monosulfide thin films by co-sputtering deposition

Abstract Thin films of SmS, either the semiconductor phase (S-SmS) or the metal one (M-SmS) stable at atmospheric pressure, were grown for the first time by co-sputtering of a Sm 2 S 3 compound target and a Sm metal target in Ar discharge. The reactive species (sulfur) was self-provided in a controllable way from the dissociation of Sm 2 S 3 during sputtering, thus minimizing the conventional use of toxic H 2 S or contaminative solid sources. X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS) and spectrophotometry were employed in film characterization. Stoichiometric S-SmS films were formed by optimizing the power ratio applied to the two targets, and M-SmS films were directly obtained by slightly enriching the film with Sm. The films were dense with little impurity. The S-SmS and M-SmS films differ substantially in optical properties from the visible region to the IR.

IR properties of SiO deposited on V1−xWxO2 thermochromic films by vacuum evaporation

Abstract In our previous report [Thin Solid Films 281–282 (1996) 232], we designed a new spectral selective radiating material (SSRM) which consists of an SiO film as outer layer, a V 1− x W x O 2 thermochromic (TC) film as intermediate layer and blackbody as the substrate, respectively. This SSRM can attain a stable surface temperature that can be controlled by varying the value of x of V 1− x W x O 2 , namely the transition temperature, T c from the metal to semiconductor phase. In this paper, we report deposition of a SiO film on a V 1− x W x O 2 film on glass substrate and its IR spectral reflectance at lower and higher temperature than T c . We also report an estimated radiative cooling power of the SSRM based on the measured IR spectral reflectance and a discussion concerning the temperature stability of the SSRM.