scispace - formally typeset
Search or ask a question
Author

Akihiko Kobayashi

Bio: Akihiko Kobayashi is an academic researcher from University of Tokyo. The author has contributed to research in topics: Thin film & Sputtering. The author has an hindex of 6, co-authored 7 publications receiving 202 citations.

Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, the structural properties of the films were analyzed by x-ray diffractometry and the influence of total pressure, oxygen mole fraction in the mixture of Ar-O2, discharge current, and substrate temperature on structural properties were studied.
Abstract: We have been investigating the growth of crystalline titanium dioxide films at deposition temperature between room temperature and about 400 °C. The films were prepared by a dc magnetron reactive sputtering on glass and Si(100) substrates. The structural properties of the films were analyzed by x‐ray diffractometry. The influence of total pressure, oxygen mole fraction in the mixture of Ar–O2, discharge current, and substrate temperature on the structural properties were studied. In addition to higher substrate temperature, low total pressure, high discharge current, and small oxygen mole fraction were shown to be preferable for growing anatase–rutile mixture films. Annealing of the films in air at 850 °C showed that anatase–rutile transformation strongly depends on the deposition temperature; the films deposited at temperature below 400 °C were converted to the anatase–rutile mixture films, and the films deposited at 400 °C to complete rutile films.

124 citations

Journal ArticleDOI
TL;DR: The work functions of the LaB6 thin films fabricated at 300, 750 and 1000 K had values of 2.7 eV and 2.8 eV, respectively as discussed by the authors.

41 citations

Journal ArticleDOI
TL;DR: In this article, the effect of sputtering conditions on the film properties of internal stress and crystalline orientation was investigated, and it was shown that an application of a negative bias (−20 V) to substrates results in a greater stress, so that the (110 and (111) orientation becomes more preferential.
Abstract: Thin films of LaB6 are prepared by a radio frequency (rf) magnetron sputtering technique. The effect of sputtering conditions on the film properties of internal stress and crystalline orientation are investigated. The film deposited at low pressures (<1 Pa) has a strong compressive stress as high as 109 Pa. As the pressure of Ar discharge gas decreases, the internal stress becomes greater and the preferred orientation is transformed in the sequence: (100)→(110)→(111). This behavior can be explained as an energetically favorable structure of LaB6 film by taking both the surface energy and the strain energy into account. An application of a negative bias (−20 V) to substrates results in a greater stress, so that the (110) and (111) orientation becomes more preferential.

27 citations

Journal ArticleDOI
TL;DR: In this article, a magnetron sputtering target and a LaB6 target and Ar discharge gas were used to produce thin LaBx thin films, and the composition of the films was investigated by the ICP method.

11 citations

Journal ArticleDOI
D. Wicaksana1, T. Tsujikawa1, Akihiko Kobayashi1, K. Ono1, Akira Kinbara1 
TL;DR: In this article, the role of energetic ion on the growth of crystalline phases of TiO2 thin films, applied substrate biases during deposition, were characterized using X-ray diffractometry and related to the optical properties of the films.
Abstract: Titania thin films grown by reactive bias sputtering were characterized. In order to investigate the role of energetic ion on the growth of crystalline phases of TiO2 thin films, we applied substrate biases during deposition. The structural properties were analyzed using X-ray diffractometry (XRD), and related to the optical properties of the films. The atomic composition was determined using Rutherford backscattering spectrometry (RBS). Negative substrate bias, Vb, showed a significant influence on the phase formed composition and microstructure: Vb in the range of 15 and 60 V enhanced the growth of crystalline phases and the rutile dominated the phase composition. However, the quantity of rutile decreased when Vb was raised to 100 V. The excess of oxygen was shown in the films by RBS.

7 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: In this article, the metastable phase anatase has been shown to have a wider optical absorption gap than rutile thin films, which is consistent with the high mobility, bandlike conduction observed in anatase crystals.
Abstract: Electrical and optical spectroscopic studies of TiO2 anatase thin filmsdeposited by sputtering show that the metastable phase anatase differs in electronic properties from the well‐known, stable phase rutile. Resistivity and Hall‐effect measurements reveal an insulator–metal transition in a donor band in anatase thin films with high donor concentrations. Such a transition is not observed in rutile thin films with similar donor concentrations. This indicates a larger effective Bohr radius of donor electrons in anatase than in rutile, which in turn suggests a smaller electron effective mass in anatase. The smaller effective mass in anatase is consistent with the high mobility, bandlike conduction observed in anatase crystals. It is also responsible for the very shallow donor energies in anatase. Luminescence of self‐trapped excitons is observed in anatase thin films, which implies a strong lattice relaxation and a small exciton bandwidth in anatase. Optical absorption and photoconductivity spectra show that anatase thin films have a wider optical absorption gap than rutile thin films.

1,560 citations

Journal ArticleDOI
C.A. Davis1
TL;DR: In this paper, a simple model was proposed to explain the formation of compressive stress in thin films deposited with simultaneous bombardment by energetic ions or atoms, and it was shown that the stress σ is proportional to [ Y (1-v) ]E 1 2 (R j+kE 5 3 ), where E is the ion energy, R the net depositing flux, j the bombarding flux, k a material dependent parameter, Y the film material Young's modulus and v the Poisson ratio.

728 citations

Journal ArticleDOI
TL;DR: In this article, the anatase modification of TiO2 shows properties quite different from those of the extensively studied and used rutile phase, such as high electron mobility and the low density of trapping or compensating centers are considered to have contributed to this good response.
Abstract: The anatase modification of TiO2 shows properties quite different from those of the extensively studied and used rutile phase. We have investigated the chemi-resistive behavior of anatase TiO2 thin films exposed to oxidizing and reducing gases (O2, H2 and ethanol) in the temperature range between 300 and 400 °C. The undoped anatase films demonstrate significant and rapid response to ethanol as well as an appreciable response to hydrogen. The high electron mobility and the low density of trapping or compensating centers are considered to have contributed to this good response. Doping the anatase thin films with Sr, Ce, Y and Tb makes then insensitive to hydrogen, but still sensitive to ethanol. The modification of the sensitivity and its dynamics by dopants have been measured and analyzed.

392 citations

Journal ArticleDOI
P. Löbl1, M. Huppertz1, D. Mergel1
TL;DR: In this article, the influence of the process parameters on the optical properties of TiO2 films, such as index of refraction, scattering of light, and absorption, is discussed.

388 citations