Souichi Ogawa

INFRARED RADIATION DETECTOR WITH YBA2CU3OX THIN FILM

We investigated an infrared (IR) radiation detector using a c-axis oriented YBa2Cu3OX thin film with a microbridge structure. The photoresponse was measured under IR radiation and was found to depend on the bias current. A bolometric response was observed under relatively low bias current, which was inversely proportional to the square root of the modulation frequency of IR irradiation. The frequency dependence can be explained by a heat diffusion process that is similar to that of a microbolometer. With increasing bias current, a nonbolometric response was observed just above the superconducting transition temperature (Tc). This was caused by the enhancement of additional flux creep induced by modulated IR light, which was equivalent to an increase in resistance. The maximum responsivity and noise equivalent power (NEP) were 1.7×104 V/W and 2.1×10-14 W/Hz1/2, respectively.

Gold-carbon composite thin films for electrochemical gas sensor prepared by reactive plasma sputtering

Abstract We have investigated the properties of gold-carbon composite thin films prepared by a plasma sputtering deposition using argon and methane mixture gas. These composite films have an uneven surface in submicron scale or consist of nano-scale particles of gold polycrystalline. Such morphological properties can be controlled by the sputtering voltage and the partial pressure of methane gas. The working electrode of electrochemical gas sensor has needed a stable gas sensitivity and a good gas selectivity. Our composite film is one of the excellent candidates for a thin film working electrode of electrochemical gas sensor. It is described that the output current of sensor is related to the preparation conditions of the thin films and increase linearly as the concentration of PH3 gas ranging from 0.1 to 1.0 ppm is increasing.

In situ formation of ohmic contact electrodes of Cu and Ag onto the fractured surface of (Bi, Pb)-Sr-Ca-Cu-O ceramics

Ohmic contacts on (Bi, Pb)-Sr-Ca-Cu-O (BSCCO) superconductor ceramics have been studied. When the electrodes were formed on the as-sintered surface of a BSCCO pellet, nonohmic characteristics were observed. Analysis by X-ray photoelectron spectroscopy suggests that the surface layer of the BSCCO pellet is degraded. When the fractured section of a BSCCO pellet was used, both Cu and Ag electrodes were found to be ohmic without thermal annealing.

PT THIN FILMS PREPARED BY LOW ENERGY PLASMA SPUTTERING

Abstract Platinum thin film has been prepared by low energy plasma sputtering deposition. Surface smoothness, stress in the film, crystal grain size and crystal orientation have been investigated for target voltages between 10 and 500 V. The effect of substrate temperature has also been studied. A minimum roughness of 1.1 nm was obtained with voltage of 20 or 30 V at room temperature. Auger analysis suggests that the deposition mechanism at 30 V is similar to the layer-by-layer (two-dimensional) deposition, while that at 100 V is significantly different. The formation of a very smooth surface is thought to be related to the layer-by-layer deposition process. The (111) oriented thin film was obtained at the target voltage of 30 V at room temperature.

The effect of B and P ion implantation on superconducting magnetic shielding in NbTi sheets

Superconducting magnetic shielding properties of B and P ion implanted NbTi sheet(50wt.%)in thickness of 10μm has been studied for different implantation conditions. Samples were implanted with 300keV and the fluencies were between 0 and 1×1017 ions cm−2. Magnetic shield effects(ΔBm: maximum magnetic shield effect and ΔB1T: magnetic shield effect for 1T)depend on implantation conditions. The value of ΔBm and ΔB1T decreased gradually with increasing dose contents for the samples doses <1×1015 and increased with proportion to dose contents for the sample more than that. In the case of dose to 1×1017 cm−2, the value of ΔBm was 3 times larger than that of non-implanted NbTi sheet and also the value of ΔB1T was 8 times and more. It is concluded that the increase of ΔBm and ΔB1T induce to the precipitation of microcrystal of α-Ti among the NbTi cubic structure by the ion implantation.

Pressure dependence of the electrical properties of TaN thin films

Abstract The pressure dependence of the electrical properties of TaN thin films was studied with a view to using the films for pressure measurement over a wide range. These films have properties that make them suitable for use as sensors in resistive thermoconductive vacuum gauges: a large effective heat-conducting area and a large temperature coefficient of resistance. The TaN thin films were deposited by reactive sputtering onto Corning 7059 glass. The sensor thus formed was found to be sensitive to pressure changes in the range 7 × 10 −5 −760 Torr . The sensitivity of the gauge increased with the resistance of the film and could be varied by changing the film dimensions even when the surface area was kept constant; it also increased with increasing surface area of the film.

Deposition of AlN Thin Films on Polycarbonate Sheets Using Reactive Magnetron Sputtering Technique

AlN hard coatings were deposited on polycarbonate sheets for protective films of plastic lenses. Transparent AlN films were synthesized at room temperature by reactive magnetron sputtering of Al in nitrogen-argon atmosphere. The deposited films were found to exhibit good scratch resistance, chemical resistance and weatherability. These AlN films on polycarbonate sheets showed good mechanical and chemical properties enough for practical application.