Katsuhiro Yokota

Resistivities of titanium nitride films prepared onto silicon by an ion beam assisted deposition method

Cubic titanium nitride (TiN) films preferentially oriented to the (200) lattice plane were deposited onto (111) silicon wafers using an ion beam assisted deposition technique with an electron cyclotron resonance ion source for ionizing nitrogen gas and an electron beam evaporator for evaporating Ti metals. The resistivities of the TiN films were inversely proportional to the average size of the crystallites making up the TiN films and decreased with increasing substrate temperature and film thickness. TiN films thicker than 50 nm had resistivities around 30 µ Ω cm, slightly higher than the resistivities of TiN crystals.

Compositional structure of dual TiNO layers deposited on SUS 304 by an IBAD technique

Abstract Surfaces of stainless steel SUS 304 were coated with dual titanium oxynitride (TiNO) layers using a nitrogen ion beam-assisted deposition technique. The N ions were accelerated at energy of 0.5–2.0 keV with an intensity of 0.1 mA/cm 2 on the substrate surface. First, a TiNO film was deposited on substrates at 700 °C, and subsequently, another TiN film was deposited on the previous TiNO film surface at 400 °C. Hydrogen carbon nitride, CrFe, and metal carbide M 23 C 6 were produced in the near-surface region of stainless steel during the TiNO deposition at 700 °C, and three characteristic layers consisting of iron nitride, chromium nitride and nickel nitride were formed between the TiNO films deposited and the stainless steel. These characteristic layers disappeared during deposition of the TiNO layer at a temperature of 400 °C.

Preparation of titanium-oxide films by solid-state reactions of titanium/silicon-oxide/silicon structures

Abstract Titanium films were deposited in a vacuum on thermally oxidized silicon. When the titanium/silicon-oxide/silicon structures were heated in oxygen to temperatures of 800–1000°C, titanium oxide films grew on the silicon substrates by a solid-state reaction that involved titanium atoms substituting silicon atoms in silicon oxide. The thickness of the titanium oxide films increased proportionally to that of deposited titanium films. The dielectric constant, resistivity, and breakdown field strength were significantly influenced by treating temperature. The 1000°C-prepared TiO2 films had the dielectric constant of (15–25) eo, the resistivity of 1010 Ω cm, and the breakdown field strength around 106 V/cm.

Relationship between etch pit densities and oxygen concentrations on CdTe

The density of etch pits and the concentration of O in melt‐grown CdTe increased as the residual gas pressure in ampoules during preparation increased. The etch pit density increased proportionally to the integral strength of an infrared TeO2 absorption band, which presents the oxygen concentration.

Segregation coefficients and activation of indium in cadmium telluride grown from tellurium-rich melt by the Bridgman technique

Abstract In-doped CdTe was grown from Te excess CdTe melts by the Bridgman technique. The segregation coefficient of the In atoms in the CdTe crystals was almost independent of the concentration of the In atoms and the Te atom excess with respect to the stoichiometric CdTe ratio for high In atom concentrations. The segregation coefficient was obviously dependent on the concentration of In atoms and excess Te atom concentration for low In atom concentrations. The electrical activity of the In atoms in the CdTe crystals decreased with increasing excess Te atom concentration. Degradation of the activity was caused by the solid solubility limit of the In atoms, the formation of acceptor-like complexes such as V 2− Cd −In + Cd , and the formation of undesirable compounds such as InTe, In 2 Te 3 and CdIn 2 Te 4 .

Interactions between arsenic and boron implanted in silicon during annealing

Arsenic ions (As+) and Boron ions (B+) were implanted into silicon (Si) at energies such that their respective projected ranges differ. In the implanted Si, the overlapping population of implanted As and B atoms occurred in the region in Si almost midway between their projected ranges near the surfaces after annealing. The only region in Si with As atoms concentration more than three times as large as the B atom concentration became n type.

Behavior of Excess Te Atoms in Undoped p-type CdTe Annealed under Te Vapor Pressures

The number of Te atoms and hole concentrations in undoped p-type CdTe quenched into water after annealing were investigated as functions of annealing temperature and Te2 vapor pressure. The number of Te atoms diffused from the annealing atmosphere into CdTe increased with increasing annealing temperature and Te2 vapor pressure, but decreased with additional increasing Cd vapor pressure. Te precipitates were observed by a scanning electron microscope in CdTe with diffused Te atoms more than approximately 1×1019 cm-3. The number of Te precipitates was increased with increasing Te vapor pressure, but was decreased by adding Cd vapor pressure. It was found that the precipitates resulted in a decrease in the concentration of the holes in p-type CdTe.

Degradation of High-Temperature Superconductor YBa2Cu3O7-x in Water

The degradation of YBa1Cu3O7-x(YBCO) sintered disks was examined by soaking the disks in water at 25°C. By magnetic susceptibility measurements, the degree of the degradation was found to depend on the pressure aplied when forming the disk from YBCO powders. From the analysis of our results, we derived an optimum pressure of 16.5 kbar to minimize degradation.

EL2, EL3, and EL6 defects in GaAs highly implanted with sulfur

Sulfur ions were implanted into a semi-insulating GaAs wafer at 50 keV at a dose of 1×1015 cm−2. The implanted GaAs wafer was annealed at temperatures of 650–1000 °C for 15 min. Deep levels were measured in regions with carrier concentrations lower than 3×1017 cm−3, after layers of various thicknesses were removed from the surface of the wafer. The dominant defects in samples annealed at temperatures lower than 850 °C were EL2 and EL6, while 1000 °C annealed samples exhibited isolated EL2 and EL3 defects. Isolated EL2 defects were observed in regions of carrier concentrations lower than 1×1017 cm−3, and EL3 defects were observed in regions of carrier concentrations higher than 2×1017 cm−3.

Plasma-assisted low temperature boridation of pure iron and steels

Abstract An investigation was conducted on the boridation of pure iron and alloy steels, such as S45C, SCM415, SK3 and SKH55. These materials were boridized in a glow discharge of Ar and BCl3 at temperatures as low as 500 °C. Results show that the thickness of boridation increases with increasing substrate temperature and boridation time. The addition agent Mn reduces the boridation rates of pure iron and alloy steels, but C enhances the boridation rates.