Ryozo Fujimoto

A new pulsed laser deposition method using an aperture plate

A new off-axis pulsed laser deposition method using an aperture plate is proposed for the purpose of depositing high surface-quality Ta2O5 thin films without large fragments and/or droplets. The angular distribution of droplets and growth species emitted from the target is examined. Then, the oxygen pressure and laser energy dependencies of the number of droplets and the film thickness are also examined. The results indicate that the aperture plate plays an important role of limiting the path of the traveling droplets and of capturing the droplets traveling toward the off-axis substrate. On the other hand, the film deposition rate is not slow even when using the plate because the species pass through the aperture hole and reach the substrate by scattering. Using a 5 mm aperture plate, a good surface quality Ta2O5 film is obtained under the optimum condition of 200–300 mTorr oxygen pressure.

Off-axis excimer laser deposition of Ta2O5 thin films

Abstract Ta 2 O 5 thin-film with a very low density of droplets was obtained on Si(110) substrate by off-axis excimer laser deposition method. The quality of the films was investigated as a function of the deposition pressure and the substrate position. The film with the thickness of 3000A˚showed a dielectric constantɛ = 26.

Thickness of Ta2O5 thin-films deposited by a new pulsed laser deposition technique

The thickness of the film deposited by a new off-axis pulsed laser deposition method using an aperture plate is studied by observing the laser plume using a streak camera. Interestingly, it appears that the oxygen pressure dependence of the film thickness corresponds to the total emission of the plume integrated over the time and space. It can therefore be concluded that the total emission is proportional to the number of target species that pass through the aperture hole, and that these species are deposited on the off-axis substrates.

Time-Resolved Plasma Expansion Measurements in a Formed Ferrite Plasma Cathode X-Ray Diode

Time-resolved measurements of plasma expansion in a plasma cathode X-ray and electron-beam generator using a formed ferrite plasma source have been made by means of streak-camera photography. The obtained streak images were analyzed in detail by a high-resolution image processing system (spatial resolution: 67 µ m/ pixel, time resolution: 6.5 ns/pixel) to derive the time-dependent expansion velocities. Time-averaged expansion velocities over periods (0.4-1.2 µ s) for plasma growth were 1-1.5 cm/µ s and ~0.5 cm/µ s for the cathode plasma and for the secondary plasma from the anode, respectively. Measurements also show the influence of the cathode driving voltage and the acceleration field intensity upon the plasma expansion.