Naoto Kikuchi

Elastic and plastic energies in sputtered multilayered Ti-TiN films estimated by nanoindentation

Abstract Energetic parameters for describing mechanical properties, which makes it possible to discuss deformation behavior of a film elastically and plastically, are presented. Elastic energy and dissipated energy estimated from the area surrounded by a load–displacement curve obtained by nanoindentation measurement indicate the energy to deform a film elastically and plastically. The energy dissipated ratio defined as the ratio of dissipated energy to total applied energy to a film indicates the tendency for plastic deformation of a film. By considering the two energies and the energy dissipated ratio, deformation behavior of compositionally modulated Ti–TiN films with a multilayered structure was examined. At a modulation period of 10 nm, the reduction of the dissipated energy and the energy dissipated ratio were observed. Since the dissipated energy is consistent with energy for the propagation of the dislocations related to plastic deformation, it was assumed that the reduction was caused by a pinning effect for the propagation of the dislocations at interfaces of Ti and TiN.

Preparation of amorphous Si1−xCx (0≤x≤1) films by alternate deposition of Si and C thin layers using a dual magnetron sputtering source

Abstract Amorphous Si 1− x C x (0≤ x ≤1) films have been prepared by alternately depositing thin Si and C layers on aluminosilicate glass substrates by magnetron sputtering. The apparatus used in the experiment was a dual-cathode sputtering machine with a carrousel type substrate holder. When a substrate passes in front of the cathode by rotating the substrate holder at a rotation rate of 60 rev./min, a thin Si layer of 0.057 nm (d.c. current: 0.2 A) and a thin C layer of 0.028 nm (d.c. current: 0.4 A) were alternately deposited on the substrate, resulting in the preparation of SiC film. The C/Si compositional ratio of films deposited was controlled by changing the discharge power (the flux) of Si and C. The structural, optical and mechanical properties of the deposited films were examined as a function of C concentration ( x ). Results of X-ray photoelectron spectroscopy showed that the film composition changed from x =0 to x =1 with increasing C flux ratio. The peak positions of Si 2p and C 1s shifted also, showing the formation of SiC bond in the films. The X-ray diffraction measurements showed that films deposited were amorphous for all the composition. The maximum hardness of approximately 30 GPa was obtained for a film deposited at x ≈0.5 by a nanoindentation. This value was almost equal to that of a SiC film deposited by conventional r.f. sputtering of SiC. Internal stresses of films ranged from −0.5 to −1.0 GPa (compressive) and were 1/2–1/4 compared to that of the SiC film deposited from a by a conventional sputtering of SiC without rotating substrate.

Effects of excess oxygen introduced during sputter deposition on carrier mobility in as-deposited and postannealed indium–tin–oxide films

Electrical and structural properties of indium–tin–oxide (ITO) films with various Sn concentrations deposited under a high oxygen partial pressure were examined to find out how the excess oxygen behaves as a scattering and trapping center of electron carriers and to show evidence that excess oxygen is weakly bound with Sn4+ ions on In3+ sites with single-charge SnIn•. ITO films with Sn concentrations of 1–25 wt % were deposited on glass substrates by rf sputtering under various oxygen concentrations in the discharge gas (0.3%–100%); the substrate temperature was kept at 773 K during deposition. With increasing O2 flow ratio in the discharge gas from 0.3% to 100%, the Hall mobility and the carrier density were found to decrease from ∼40 to ∼20 cm2 V−1 s−1 and from ∼5.0×1020 to ∼2.0×1018 cm−3, respectively. The dependence of the slope of mobility–temperature curve on the O2 flow ratio and Sn concentration has been examined. For high Sn concentration, the slope changes from negative to positive as the O2 flo...

Imidized organic thin films deposited on glass substrates

Imidized organic thin films were deposited onto glass substrates by rf magnetron sputtering of polyimide (Kapton) target. The mass spectra of sputtered species indicated that target materials were cracked into smaller molecules and the generated films on glass substrates were not identified to be polyimide but wear properties of the films were found to be rather superior to Kapton.

EFFECTS OF COIL DC POTENTIAL ON ION ENERGY DISTRIBUTION MEASURED BY AN ENERGY-RESOLVED MASS SPECTROMETER IN IONIZED PHYSICAL VAPOR DEPOSITION

Energy distribution of Ar+ and Ti+ ions and plasma conditions have been investigated for various dc potentials of the rf inductive coil in ionized physical vapor deposition. The sputtering cathode used in the experiment is a conventional magnetron sputtering source with a Ti target (55 mmφ) which is coupled with a rf coil (60 mm φ, made of Cu). The mass spectrometer used to measure ion energy distributions is an energy-resolved type plasma monitor. The coil dc potential is controlled by changing the resistance of the resistor in the termination inductance-capacitance-resistance (LCR) circuit connecting the coil to the ground. By increasing the resistance of the LCR circuit, the peak of the Ar+ energy spectra shifts to a lower energy. In addition, it is found by the probe measurements that the plasma potential decreases with increasing the termination resistance. The changes in the peak energy in the ion energy spectra show a good agreement with the change in the plasma potential; as a result of the change...

Fabrication of (Cu, C)Ba2CuOy superconducting thin film by RF magnetron sputtering

We report the superconducting properties of (Cu, C)Ba2CuOy thin films deposited by RF magnetron sputtering from targets with a nominal composition of Ba2Cu1.5Oy. The thin films were grown in mixed Ar (5~40 mTorr), O2 (0~1.2 mTorr) and CO2 (0~1.8 mTorr) atmosphere. The epitaxial c-axis oriented thin films with c-axis length in the range between 7.96 A and 8.82 A were obtained on SrTiO3(100) substrates, but superconductivity was observed only for the films which have the c-axis length with 8.01 A and 8.32 A. By optimizing deposition conditions, the excellent (Cu, C)Ba2CuOy thin film with Tc = 62K and superconducting transition width ΔTc = 1.5 K was successfully obtained.

Deposition of superconducting (Cu, C)–Ba–O films by pulsed laser deposition at moderate temperature

Superconducting (Cu, C)?Ba?O thin films have been epitaxially grown on (100) SrTiO3 at a low growth temperature of 500?600??C by pulsed laser deposition. The dependences of their crystallinity and transport properties on preparation conditions have been investigated in order to clarify the dominant parameters for carbon incorporation and the emergence of superconductivity. It has been revealed that the CO3 content in the films increases with increasing both the parameters of partial pressure of CO2 during film growth and those of growth rate and enhancement of superconducting properties. The present study has also revealed that the structural and superconducting properties of the (Cu, C)?Ba?O films are seriously deteriorated by the irradiation of energetic particles during deposition. Suppression of the radiation damage is another key for a high and uniform superconducting transition. By these optimizations, a superconducting onset temperature above 50?K and a zero-resistance temperature above 40?K have been realized.

Polyimide-based organic thin films prepared by rf magnetron sputtering

Abstract Organic thin films were sputter-deposited onto glass substrates in an N2/CF4 mixture discharge gas using a polyimide (Kapton) target. FTIR observation showed that the thin films contained imide bases. The compositions of the films determined by XPS depended on CF4 concentration in the gas and F included films were obtained. The surface energy of the thin films measured by the contact angle method ranged between 17 and 64 mJ/m2. The dielectric constant of the thin films at 1 MHz was measured and the lowest dielectric constant e was approximately 2.0.

Characterization of electronic structure of superconducting (Cu, C)-Ba-O films by in situ photoemission spectroscopy

Change of electronic structure of superconducting (Cu, C)-1201 thin films grown by pulsed laser deposition with superconducting critical temperature Tc has been characterized by means of in situ photoemission spectroscopy. The finite spectral weight at the Fermi level in the valence band of (Cu, C)-1201 superconducting thin films and a rigid-band-like approach of the main peak of the valence band toward the Fermi level with a rise of Tc has been observed, which reveals hole-doping-induced superconductivity of this system. The obtained Ba 4d and Cu 2p signals with an increase of Tc suggest excess oxygen should be introduced around Ba ions in the early stage of the emergence of superconductivity. Then, they should be preferentially introduced around Cu ions. The changes of core signals with Tc and comparisons of the obtained data with infinite-layer and other cuprate superconductor compounds suggest that the (Cu, C)–O charge reservoir in this system is in the heavily hole-doped state, similar to that of the Cu–O chain in YBa2Cu3O7−δ.

In-situ characterization of transport properties of superconducting (Cu, C)-1201 films

Transport properties of (Cu, C)-1201 thin films have been characterized by in-situ four probe method without breaking vacuum, subsequent to their growth by pulsed laser deposition, in order to clarify intrinsic transport properties. Owing to the in-situ measurements, degradation of contact resistance and normal state conductivity were successfully suppressed. Obtained results reveal the positive correlation between Tc and normal state conductivity δ at 290 K, and that between Tc and temperature coefficient of resistivity (TCR) at 290 K. The films exhibit Tc(ρ=0) > 20 K on the cases of δ[290 K] > 4 x 102 S/cm and TCR > 1.5 x 10-3 K-1. The high Tc with low conductivity of (Cu, C)-1201 films indicates the presence of extrinsic defects such as grain boundaries. The absence of saturation of Tc with an increase of TCR indicates doping level of the (Cu, C)-1201 films in this study should be in between under-doped to optimally-doped states. They suggest there would be some room for further increases of Tc.