Seita Tanemura

Tungsten doping into vanadium dioxide thermochromic films by high-energy ion implantation and thermal annealing

Abstract Doping of W into VO 2 was done by high-energy (1.0 MeV) ion beam implantation and thermal annealing for the first time. The implantation was performed with different ion doses of 0.86, 2.18 and 6.12×10 15 ions/cm 2 on a VO 2 polycrystalline film sputter-deposited on Si. The film was characterized by Rutherford backscattering spectroscopy, atomic force microscopy and spectrophotometry. Deterioration of thermochromism and change in surface morphology after implantation, resulting from the irradiation damage such as amorphization, were observed and the extent increased with ion dose. Recrystallization of the implanted film and recovery of thermochromism were obtained by annealing at 400°C in air for 60 min. The W doping resulted in a substantial reduction in the critical temperature τ c for the phase transition of VO 2 .

V1−xMoxO2 thermochromic films deposited by reactive magnetron sputtering

Abstract Thin films of V 1− x Mo x O 2 ( x =0–0.041) for thermochromic windows were formed by dual-target reactive magnetron sputtering. The composition, crystal structure, morphology and optical properties of the films were evaluated by Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), atomic force microscopy (AFM) and spectrophotometry respectively. The relationship between the transition temperature τ c and x in V 1− x Mo x O 2 was clarified through precise determinations of the dopant concentration and the value of τ c . A linear reduction in τ c by approximately −12°C (at.% Mo) −1 was confirmed for the films with least doping, while the reduction efficiency decreased with higher dopant concentrations. V 1− x Mo x O 2 films with desired x values were also fabricated using a V−Mo (Mo, 4.0 at.%) alloy target. Investigations of the thermochromism of the V 1− x Mo x O 2 films suggest their potential for advanced windows.

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.) ...

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.

Formation of β‐Si3N4 by nitrogen implantation into SiC

Polycrystalline β‐SiC samples were implanted with 50 keV 15N ions with fluences ranging from 3×1017 to 1.5×1018 ions/cm2 at elevated temperature up to 1100 °C. Nitrogen depth profiles were measured as a function of implantation temperature and annealing temperature using nuclear reaction analysis, Rutherford backscattering spectroscopy, and Auger electron spectroscopy. It was found that the maximum concentration and the width of nitrogen depth profiles implanted at 1100 °C were reduced distinctly in comparison with the profiles implanted below 930 °C or annealed at 1100 °C. The redistribution of nitrogen implanted in SiC at 1100 °C was ascribed to the formation of β‐Si3N4 crystallites in SiC, which was confirmed by x‐ray diffraction at glancing incidence.

Thermal behaviour of nitrogen implanted into zirconium

Abstract Zirconium films were implanted with 15 N ions of energy 50 keV to a total fluence of 1 × 10 18 ions cm -2 in an attempt to study the formation process and thermal stability of ZrN layers produced by high fluence implantation of nitrogen. Subsequent to the implantation at room temperature, samples were annealed at temperatures of 300 °C–900 °C. The depth profiles of the implanted nitrogen were measured by nuclear reaction analysis using the 15 N(p,αγ) 12 C at E R = 429 keV, and the surfaces were examined by thin film X-ray diffraction (XRD) and scanning electron microscopy. There were many blisters 0.2–0.4 μm in diameter on the surface of the as-implanted samples and double peaks were observed in the nitrogen depth profiles; they were in both sides of the mean projected range. It was found that most of the blisters became extinct after annealing above 400 °C, and the XRD peak (111) intensity was increased with the increase in the annealing temperature. Moreover, 14 N and 15 N implantations were superimposed on Zr samples in order to study the atomic migration of nitrogen at each stage of high fluence implantation. It was found that the decrease in the peak at the deeper layers was related to blister extinction and nitrogen diffusion into underling zirconium which could be correlated with radiation damage induced by post-implanted ions.

Retention of nitrogen implanted into metals

Abstract Retention of nitrogen implanted into various kinds of metals (Al, V, Ti, Fe, Co, Ni, Zr, Nb, Mo, Ta, and W) was calculated by the dynamic-SASAMAL code assuming planer surface binding energy and diffusion toward the surface for nitrogen over the concentration of saturated nitride phase. As the value of surface binding energy ( E s ), the sum of the heat of sublimation of the metal ( H s ) and the heat of formation of the nitride ( H f ) times the nitrogen concentration ( C ) at the surface layer was used ( E s = H s + CH f ). The effects of values of H s , H f , and the displacement threshold energy on the retention were studied. The agreements between the calculated results and the experimental results obtained by NRA using 15 N(p, αγ) 12 C reaction were satisfactory for depth profiles and retention of nitrogen implanted into metals of Al, Ti, Ni, and Zr at a wide range of fluence from 6 × 10 16 to 6 × 10 17 ions cm −2 .

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.

Annealing of silica glasses implanted with high-energy copper ions

Silica glasses were implanted with 1.8 MeV Cu ions at a dose of 0.32–1.3×1017 ions/cm2 at a temperature of less than 300° C. The thermal annealing of the samples was carried out in air in the range of 300–1100° C, and the effects on the formation and growth of Cu nanoparticles were examined as a function of ion dose and annealing temperature using Rutherford backscattering spectrometry and optical absorption measurements. It was found that the broad absorption band between 250–400 nm was increased and the average radius of Cu particles was slightly decreased where the total concentration of Cu was not changed up to 700° C. This suggests that small Cu precipitates were generated. The surface plasmon resonance absorption at approximately 570 nm was clearly developed at 800° C. In addition, the average radius of Cu particles increased as the annealing temperature increased from 800–1000° C. However, the concentration of Cu began to decrease at temperatures above 800° C. The plasmon absorption also decreased in intensity with increasing temperature, which indicated that the amount of Cu particles had decreased. The decrease of the amount of Cu particles was affected by ion dose.

Evaluation of porosity and composition in reactively r.f.-sputtered Ti1 − xZrxN films

Abstract Thin films of Ti1 − xZrxN were deposited on silicon substrates by reactive r.f. sputtering of a segmented Ti-Zr target in an Ar + N2 discharge. The crystal structure and microstructure of the films deposited under various negative substrate bias voltages were studied by X-ray diffraction (XRD) and field emission scanning electron microscopy. The determination of composition was carried out by the measurement of Rutherford backscattering spectrometry (RBS), and the porosity of the films was evaluated quite quantitatively based on the data of both the apparent thickness measured by surface profilometer and the mass thickness obtained from RBS and XRD. An interstitial crystal structure model was introduced for the porosity calculation, and the possibility of oxide formation for Tiand orZr in the films containing high oxygen concentration was taken into account in the porosity evaluation. The bias effect on the porosity, oxygen impurities, internal stress and resistivity of the deposited films was studied in detail.