Carbon Film Synthesis on the Water by Excimer Laser Irradiation
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Figure 1 shows the irradiation chamber. It had cylindrical shape of 120mm in diameter and 220mm in height. The amount of the gas dissolved in the water is in proportion to the gas pressure by Henry's law. To dissolve more gas, this chamber was planed to be able to resist a pressure of 350kPa. Approximately 60 percent volume of this chamber was filled with water and upper part was filled with gas. Laser light was irradiated through the silica glass window and focused just below the water surface. Chemical species were observed by emission spectrum. An optical fiber was attached to this chamber to detect the emission light by exciting, and emission light was guided to a polychromator.
Spectrum analyses First, spectra of emission light were observed to get basic data of produced chemical species by laser irradiation. Table I shows irradiation conditions. An ArF excimer laser was used, because absorption edge of water is nearly the emission wavelength of the laser. The chamber was filled with deaerated water, Methane, Hydrogen and Oxygen respectively, then the laser was irradiated. All of them were excited and produced chemical species were observed. Next the water dissolving these gases filled chamber and laser was irradiated. There was a little difference in color by changing gases with the naked eye. However no influence was observed from spectrum analyses by dissolving these gases.
261 Mat. Res. Soc. Symp. Proc. Vol. 555 ©1999 Materials Research Society
Synthesis of material C, radical was produced by excimer laser irradiation to methane. So there was a possibility of making carbide on the water by excited methane in the gas part. Further there was another possibility of making particles in the water by excited methane dissolved in the water, although it made no difference in spectra whether the methane dissolved in the water or not. Table II shows synthesis conditions. Conditions of laser irradiation were the same as the spectrum analyses. Pressure of the gas dissolved in the water was 35OkPa. The pressure of the gas part was 1OlkPa. In this case, the pressure of the gas part was lower than that of the gas dissolved in the water, during the laser irradiation. So the dissolved gas bubbled up like sparkling water, and the pressure in this chamber became higher during the laser irradiation. But the pressure of the gas could be considered to be constant during the laser irradiation, because the time of the laser irradiation was much shorter than that of the gas bubbled out. From this experiment, a film was obtained on the water. It was a circle of about 50mm in diameter. RESULTS Observations by Microscopes The film was easy to break. Figure 2 shows a SEM image of the film. Meshwork was observed. The thickness of this film was 2 jv m by SEM. Figure 3 shows a TEM image of the film. These small particles were about 30 nm in diameter. These small particles were gathered and made meshwork, we thought. We are now surveying the production mechanism of this meshwork.
Laser beam Lens
Table I Irradiation conditions Laser
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