| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1990: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1989: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
It has been revealed that the laser irradiation of the surface of inorganic substances, such as copper containing oxide superconductor, leads to the emission of ions, atoms and clusters. This process is dependent on the laser influence. By utilizing this laser ablation process, inorganic thin films are formed on substrates in the oxygen atmosphere. In 1989, we have demonstrated that clusters are emitted from the Bi_2Sr_2CaCu_2O_8 and Bi_2Sr_2CuO_6 surface, and these phases are formed using this cluster formation process. We have developed this process to decompose the targets into smaller pieces, that is ions and atoms. These ions and atoms are accumulated on the substrates. In the case of Bi_2Sr_2CuO_6 ablation, atomic species of Bi, Sr and Cu are observed. The thin film formation of Bi_2Sr_2CuO_6 is carried out in the various oxidation gases. As a result, it has been revealed that NO_2>N_2O>O_2 are effective in this order for the oxidation process. In the NO_2 atmosphere, even the low pressure of 10^<-4> torr is effective to crystallize the thin films. In the N_2O atmosphere, the Bi_2Sr_2CuO_6 phase is crystallized at 50 to 100C lower temperature than in the O_2 gas. This is explained by the strong oxidation power of O radical formed by the laser irradiation. In the mixed N_2O and O_2 gas, the oxygen is incorporated enough in the films. In the O_2 atmosphere alone, the impurity CuO is segregated an the surface to make a rough surface. The irradiation of laser light during the thin film formation is effective for the low temperature thin film formation. Even the low intensity light of the order of 10mJ/cm^2 is effective enough. Thus, the laser ablation method is effective for the formation of inorganic thin films and also it is important to choose the atmosphere, such as NO_2 and N_2O, to form thin films at lower temperature.
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