Tateki Sakakibara

Properties of titanium oxide film prepared by reactive cathodic vacuum arc deposition

Abstract TiO 2 thin films were deposited on a soda-glass substrate as a function of gas pressure (0.1–2.0xa0Pa) using conventional unfiltered vacuum arc deposition (UFA), and also deposited using a macroparticle-filtered arc deposition source (FAD). Crystalline structure, microhardness, elastic modulus, and optical properties (transmittance, reflectance, refractive index, extinction coefficient, absorption coefficient, and optical bandgap) were measured or evaluated. All films deposited on unheated substrates were amorphous, and post-annealed films as well as films deposited with in-situ heating were of the crystalline anatase phase. Similar mechanical and optical properties were obtained for the films deposited by UFA over a wide pressure range (0.1–1.0xa0Pa). After the annealing process, the films became harder, and the extinction coefficient of the film increased. The transmittance and the extinction coefficients of films deposited by FAD were found to be slightly superior to those of films deposited by UFA. The optical bandgap was about 3.25xa0eV for as-deposited amorphous material prepared by both UFA and FAD as well as for in-situ heated anatase film prepared by FAD.

ZnO film formation using a steered and shielded reactive vacuum arc deposition

Abstract Zinc oxide (ZnO) thin films were prepared on a borosilicate glass substrate by a steered and shielded reactive vacuum arc deposition method. The cathode spot was driven on a cathode surface using weak and strong permanent magnets, placed behind the cathode. The radial magnetic flux densities at the bottom of cathode shoulder were 1.0 mT and 5.5 mT, respectively. The arc was operated at DC 30 A and the in-process pressure was varied from 0.1 to 5.0 Pa. No bias was applied to the substrate. The substrate temperature was below 75°C after 20-min deposition. The deposition rate increased with the in-process pressure until 1.0 Pa with both weak and strong magnets. X-Ray diffraction analysis revealed that all films had a strong ZnO (200) peak, indicating c-axis orientation. In particular, the films strongly oriented to (200) were obtained at 0.5–3.0 Pa for the strong magnet. Highly transparent films in visual region were obtained at 0.5 and 3.0 Pa with both weak and strong magnets. A refractive index at 600 nm varied from 1.75 to 1.95. With the strong magnet, electric resistivity varied from 10−3 to 15 Ω cm as the pressure increased. However, with the weak magnet, resistivity of the order of 10−3 Ω cm was obtained over a wide pressure range of 0.1–1.0 Pa.

Effect of substrate bias on AlN thin film preparation in shielded reactive vacuum arc deposition

Abstract Aluminum nitride (AlN) thin films were prepared using reactive cathodic vacuum arc deposition in conjunction with a macrodroplet shield plate. Various bias conditions, such as no bias (floating), 0-V bias (same potential as anode), DC bias of −10 to −30 V, and RF power of 25–200 W, were applied to the substrate table. For floating bias, a -axis-oriented film was obtained. For 0-V bias, the films prepared on molybdenum substrate showed no preferential orientation, although the film prepared on silicon and borosilicate glass showed a -axis-orientation. For RF bias, the orientation changed from the a - to the c -axis as the RF power increased. The hardest (27 GPa) film was obtained for 0-V bias, and the hardness of the other films ranged from 19 to 24 GPa. The refractive index of the film prepared on quartz substrate was approximately 2.0 over the visual and infrared regions for all films. The extinction coefficient was less than 0.01 over the visual and infrared regions, with the exception of the film prepared under the 0-V bias condition, which showed a higher value.

Preparation of metal nitride and oxide thin films using shielded reactive vacuum arc deposition

Abstract Various metal nitride and oxide thin films were prepared using a shielded reactive vacuum arc deposition. The cathode materials used as metal ion sources were Al, Ti, Cu, Cr, and Zn. These nitride and oxide films were deposited in pure N 2 and O 2 gas flows, respectively. First, the films were deposited for a short period by both non-shielded and shielded methods, and the macrodroplet appearance on the films was compared. Macrodroplets were reduced remarkably, to less than one-hundredth for Al in N 2 , Zn in N 2 and Al in O 2 . For Ti in N 2 , Cr in N 2 , Cu in N 2 , Ti in O 2 , and Zn in O 2 , the macrodroplets were reduced by one-third, although they were not reduced for Cr in O 2 . X-ray diffraction analysis revealed that crystallized films were AlN, TiN, CrN, Cu 3 N with Cu, CuO, and ZnO, and that amorphous films were Al 2 O 3 , TiO 2 and Cr oxide. Zn 3 N 2 were weakly synthesized in Zn metal film. AlN, Al 2 O 3 and TiO 2 films were very transparent with refractive indices of 2.1, 1.6 and 2.3 at 500xa0nm, respectively. ZnO film also exhibited good transparency.

Cathode spot motion in vacuum arc of zinc cathode under oxygen gas flow

Magnetically steered cathode spot(s) of a vacuum arc with a zinc (Zn) cathode was(were) observed using a high-speed video camera. The camera can take 4500 frames per second of 256/spl times/256 pixels. The transverse magnetic flux density for steering the cathode spot was 1.0 and 5.5 mT at the bottom of the cathode (64 mm in diameter) shoulder. The arc was operated at an arc current of dc 30 A and O/sub 2/ flow rate of 40 ml/min. The pressure was varied from 0.1 Pa to 5.0 Pa. The principal results obtained in the present study were as follows. The cathode spots were driven in the retrograde direction. When a strong magnet was used, the number of the cathode spots was smaller, the cathode spots revolved at the outer region of the cathode surface more of the time, and the velocity of the cathode spots was higher than when a weak magnet was used. The velocity of the cathode spots increased as the pressure increased.

Cathodic arc deposition with activated anode (CADAA) for preparation of in situ doped thin solid films

Abstract Cathodic arc deposition with an activated anode was developed for preparing doped thin solid films. The activated anode was a water-cooled crucible, and the material in it was evaporated and ionized by passing a partial arc current through the crucible. As an example, aluminum-doped zinc oxide (ZnO:Al) was synthesized by a Zn cathodic arc in an oxygen (O 2 ) gas flow at 1.0xa0Pa. Al powder was used as a dopant precursor and placed in the crucible. The anodic plume plasma appears on the crucible anode, which is composed of cathode material of Zn and anode material of Al as well as a reactive gas of O 2 . Energy dispersive X-ray analysis revealed that the prepared-film contained Zn, Al and O. The ZnO:Al film on the glass substrate was transparent with a very strong X-ray diffraction peak of ZnO.

Synthesis of a-axis-oriented AlN film by a shielded reactive vacuum arc deposition method

Abstract Aluminum nitride (AlN) thin films were fabricated by a non-shielded conventional reactive vacuum arc deposition method and by a shielded vacuum arc deposition method in which a droplet-shielding plate was located between the cathode and substrate. The properties of the films, such as surface morphology, number of droplets, deposition rate, crystalline structure, optical properties, hardness, and elastic modulus were investigated. The films deposited by the non-shielded method were metallic silver, very rough due to many macrodroplets, and easily peeled off from the substrate, whereas the films deposited by the shielded method were transparent in the visual and near-infra-red regions, smooth and almost droplet-free, and adhered well. The former exhibited a c -axis orientation, whilst the latter showed a -axis orientation. The refractive indices of the films deposited by the shielded method were 1.9–2.1, and the extinction coefficients were less than 10 −2 . The films were much harder and stiffer than boro-silicated glass.

Influence of gap length and pressure on medium vacuum arc with Ti cathode in various ambient gases

Abstract Voltage, plasma potential and electron temperature of a medium vacuum arc ignited between Ti cathode and disk stainless steel anode were measured in various ambient gases; H 2 , N 2 , He and Ar. Gap length was varied from 75 to 450 mm. The result showed that the voltage increased with gap length and gas pressure, and that the voltages in H 2 and N 2 were higher than those in He and Ar. The influence of the gas species on the voltage was explained on the basis of: the mean free path; ionization and excitation processes of the gas; and ambipolar diffusion.

Anode mode in cathodic arc deposition apparatus with various cathodes and ambient gases

The anode mode of a vacuum arc in a cathodic arc deposition apparatus was observed as a function of ambient gas pressure ranging from 0.01 to 300 Pa. The chamber (400 mm in diameter and 600 mm in length) made of stainless steel (SUS304) acted as the anode. The arc was operated at a relatively low constant current of 50 A. The cathode materials used were Al, Ti, Fe, Ni, and Cu, and ambient gases were He, Ne, Ar, H2, N2, O2, and CH4. The principal results are as follows. (1) As the pressure was increased, the anode mode changed from diffuse-arc to footpoint to plane luminous to anode-spot mode. (2) The anode mode and resultant arc voltage increase were strongly dependent on gas species, and weakly on the cathode material. (3) Comparing diatomic and polyatomic (H2, N2, O2, and CH4) with mono-atomic molecule gases (He, Ne, and Ar), the onset pressure of the anode mode transition in the former was lower, the arc voltage higher, and the footpoints more numerous, smaller, and clearer. Both the dependence of the ambient pressure and the influence of the cathode materials and gas species on the anode mode changes were explained by the ion deficiency theory.