摘要 : A pulsed laser deposition technique is investigated for fabricating high-quality epitaxial films of YBa_2Cu_3O_y superconductor using fourth harmonic of the YAG laser. The harmonic has a photon energy comparable to the KrF excimer... 展开 A pulsed laser deposition technique is investigated for fabricating high-quality epitaxial films of YBa_2Cu_3O_y superconductor using fourth harmonic of the YAG laser. The harmonic has a photon energy comparable to the KrF excimer laser and has potential for industrial use because of its effectiveness, safety and low running cost. High-quality films have been reproducibly prepared on SrTiO_3 (100) and MgO(100) single crystal substrates by optimizing the experimental conditions. Films on the respective substrates have critical temperatures T_c = 90 K and 85 (+-1) K and critical currents 0.6 * 10~6 and 0.5 * 10~6 A cm~(-1). X-ray diffraction revealed a spectrum composed entirely of (00l) diffraction peaks (l = 1-13) which are sharply resolved by K_(#alpha# 1) and K_(#alpha# 2) X-rays of copper isotopes, indicating formation of epitaxial films having good crystallinity with c-axis orientation. Scanning electron microscopy and atomic force microscopy showed good surface morphology : only a small number (0.5 #mu#m~(-2)) and small sizes (<0.2 #mu#m diameter) of particles, and a good surface flatness (approx +-20 nm). Optimum conditions in the present method differ from previous reports using excimer lasers and require a lower pulse frequency, lower deposition energy, higher substrate temperature and higher oxygen pressure. This may be due to high densities of particles in the ablation plume, which are produced by irradiation with YAG pulsed laser having a shorter pulse width than the excimer laser. 收起