Atushi Yokotani

X-ray emission spectroscopic studies of silicon precipitation in surface layer of SiO2 induced by argon excimer laser irradiation

Abstract The ultra-soft X-ray emission spectra were taken from surfaces of bulk silica glass and silica glass films exposed to an argon excimer laser ( λ =126 nm) and compared with the spectra taken from the virgin surfaces. The precipitation of crystalline silicon is found to take place in thin surface layers of the irradiated bulk silica glass and 15 nm film. An estimation of concentration of crystalline silicon precipitation with the depth is given on the basis of the measurements of Si L 2,3 X-ray emission spectra obtained at different accelerating voltages of the electron beam on the X-ray tube. Based upon the precipitation conditions for these samples, we discuss the crystalline silicon precipitation mechanism: the electronic excitation induces the bond-breaking between Si and O atoms, although there is a critical density of photons for the bond-breaking and temperature rise enhances the crystalline silicon precipitation.

Crystallized hydroxyapatite coatings deposited by PLD with targets of different densities

We successfully achieved the poly-crystallized coatings of bio-active hydroxyapatite on titanium plates. We used several ceramic HAp targets sintered at a temperature of 500°C, 700°C, 900°C and 1100°C, and irradiation by KrF excimer laser at a fluence of about 4J/cm2. The depositions were performed under 1Torr H2O atmosphere at room temperature. In this condition, a poly-crystallized HAp layer was formed only using a target sintered at 900°C. We estimated the charged fragments from these targets by a simple ion-probe collection and found that the energy distribution of charged fragments depended on the densities of the targets.

Surface analysis system by VUV photons-stimulated desorption

We developed a novel surface analysis system using a vacuum ultraviolet (VUV) photons. When the VUV photons were irradiated on the material surface, surface desorption was stimulated. The desorbed species were analyzed by the mass analyzer. First, we studied the decomposition process excited by VUV excimer lamps. We found that the different photon energy resulted in the different time dependence of the fragment detection even if the contamination had similar chemical construction. It suggested that the tracing the decomposition process We developed an analyzing system, called “photo-stimulated desorption mass spectrometer (PSD)”. A broadband VUV radiation for surface desorption was obtained from the Ar plasma excited by a Q-SW Nd:YAG laser. We selected and scanned wavelength by a monochromator. The desorbed species were analyzed by the quadrupole mass analyzer. We scanned the VUV wavelength and obtained the mass data. This PSD system enables us to analyze without damage on the sample.We developed a novel surface analysis system using a vacuum ultraviolet (VUV) photons. When the VUV photons were irradiated on the material surface, surface desorption was stimulated. The desorbed species were analyzed by the mass analyzer. First, we studied the decomposition process excited by VUV excimer lamps. We found that the different photon energy resulted in the different time dependence of the fragment detection even if the contamination had similar chemical construction. It suggested that the tracing the decomposition process We developed an analyzing system, called “photo-stimulated desorption mass spectrometer (PSD)”. A broadband VUV radiation for surface desorption was obtained from the Ar plasma excited by a Q-SW Nd:YAG laser. We selected and scanned wavelength by a monochromator. The desorbed species were analyzed by the quadrupole mass analyzer. We scanned the VUV wavelength and obtained the mass data. This PSD system enables us to analyze without damage on the sample.

Generation and amplification of ultra-short-pulsed vacuum ultraviolet radiation

We have been developing an ultra-short-pulsed vacuum ultraviolet (VUV) laser system for advanced applications such as micro and precise processing and photochemical reactions. We propose and construct a new VUV laser system to generate output energy of sub-mJ with a pulse width of sub-picosecond at the wavelength of 126 nm. A VUV seed pulse was generated in Xe gas at the pressure of 1.2 Torr with high conversion efficiency as the 7th harmonics of a 882 nm Ti:Sapphire laser. The Ar2* amplification medium was generated in an optical-field-induced ionized Ar plasma pumped by another 800 nm Ti:Sapphire laser with an amplification factor of 400. VUV output at 1 µJ in the sub-picosecond pulse will be obtained at a repetition rate of 1 kHz, leading to an average power of 1 mW at 126 nm. It will be useful VUV coherent source for applications of precise and micro laser processing.We have been developing an ultra-short-pulsed vacuum ultraviolet (VUV) laser system for advanced applications such as micro and precise processing and photochemical reactions. We propose and construct a new VUV laser system to generate output energy of sub-mJ with a pulse width of sub-picosecond at the wavelength of 126 nm. A VUV seed pulse was generated in Xe gas at the pressure of 1.2 Torr with high conversion efficiency as the 7th harmonics of a 882 nm Ti:Sapphire laser. The Ar2* amplification medium was generated in an optical-field-induced ionized Ar plasma pumped by another 800 nm Ti:Sapphire laser with an amplification factor of 400. VUV output at 1 µJ in the sub-picosecond pulse will be obtained at a repetition rate of 1 kHz, leading to an average power of 1 mW at 126 nm. It will be useful VUV coherent source for applications of precise and micro laser processing.