Kazuki Yoshimura

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 ...

Characterization of niobium oxide electrochromic thin films prepared by reactive d.c. magnetron sputtering

Abstract Niobium oxide electrochromic thin films were prepared by reactive d.c. magnetron sputtering, and their physical properties, such as surface structure, composition, optical transmittance, reflectance and absorption, were studied. The surface morphology of the heated sample is very different from that of the unheated sample. Auger electron spectroscopy (AES) measurements show that the composition of the amorphous film is close to Nb2O5 as well as the crystallized sample. The crystallized and amorphous samples show very different absorption behavior. The band gap is estimated to be 3.41 eV for the crystallized sample and 3.45 eV for the amorphous sample.

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.

Energy-dependent deposition processes of size-selected Ag nanoclusters on highly-oriented pyrolytic graphite

Singly charged cations of silver atoms and clusters (Agn+, n=1,3,5,7,9) were deposited on highly oriented pyrolytic graphite substrates at well-controlled, various collision energies. The total amount of Ag atoms remaining on the substrates after collision was quantified by measuring the Ag 3d5/2 photoelectron intensities. The collision energy dependence of the amount of deposited Ag atoms revealed that, for all the species, there are three distinct energy regions, for which soft landing, rebounding, or implantation is a dominant process, and that the energy ranges for the processes strongly depend on the cluster size. The deposition efficiency vs collision energy curve for each cluster is well fitted to that for Ag1, by considering the difference between the contact area of Ag1 with the surface and that of the cluster, reflecting the compactness of the clusters. Boundaries between the different deposition regimes for the clusters were less distinct than those for Ag1. Considering anisotropy in shape of a...

Fragmentation and ion-scattering in the low-energy collisions of small silver cluster ions (Agn+: n=1−4) with a highly oriented pyrolytic graphite surface

Fragmentation and ion-scattering processes in the low-energy (0–200 eV) collisions of Agn+ (n=1–4) with a highly oriented pyrolytic graphite (HOPG) surface have been investigated by employing a tandem time-of-flight mass spectrometer. It was found that the fragmentation of scattered cluster ions is due to unimolecular dissociation in the energy range studied. A marked difference between the fragmentation pattern of incident Ag3+ and that of Ag4+ has been found: The intact scattered cluster ion was observed for Ag3+ while only fragment ions for Ag4+. From the incident energy dependence of fragment ion intensities, it was deduced that internal energies of the scattered parent ions have upper and lower limits. These limitations are probably due to the adsorption and the implantation of the projectile clusters on the surface. Ion-scattering yield was found to increase with cluster size. Both the incident energy and cluster size dependencies of ion-scattering yields were reproduced by a model calculation in wh...

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.

CROSS-SECTIONAL OBSERVATIONS BY HRTEM OF THE STRUCTURE OF NICKEL OXIDE ELECTROCHROMIC THIN FILMS IN THE AS-DEPOSITED STATE AND THE BLEACHED STATE

Abstract To investigate the microstructure of nickel oxide electrochromic thin films prepared by reactive DC magnetron sputtering, cross-sectional observations of sputtered nickel oxide films have been performed using a high resolution electron microscope. High resolution images were observed for as-deposited and bleached samples. These images show that the surface morphology of these samples is quite different. The bleached sample consists of needle-like microcrystallites, while the as-deposited sample consists of columnar crystals and has a smooth surface. Diffraction patterns indicate that crystallized NiO is the dominant structure in both samples. The fact that no trace of Ni(OH) 2 was observed implies that the boundary and the surface of NiO microcrystallites play important roles in the electrochromic reaction.

Non-destructive deposition and diffusion–aggregation of size-selected silver nanoclusters on glassy carbon substrates as probed by real-time X-ray photoelectron spectroscopy

Abstract Silver nanoclusters, generated and size-selected in the gas phase and soft landed on low-temperature glassy carbon substrates, were characterized by real-time X-ray photoelectron spectroscopy (XPS). It has been found that the 3d core–electron binding energies of the deposited clusters gradually decrease with time in size-specific manners. The observation clearly showed that the clusters are deposited intact on the surface and diffuse and aggregate, leading to larger clusters. This demonstrates that the real-time XPS can provide key information on states and behaviors of size-selected nanoclusters deposited on surfaces.

Optical properties of alumina ceramics as a substrate of thin film solar cells

Abstract For full understanding of the optical properties of alumina ceramics which are used as a substrate of thin film c-Si solar cells, we carried out computer simulations of diffuse reflectance and measurements of angle-resolved reflectance. As the result of the computer simulations, we obtained a theoretical expression for the reflectance properties of alumina ceramics with flat surface. The expression can be applied for the measured reflectance of alumina ceramics with rough surface when an effect of surface condition was taken into account.