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22 December 1998 Nucleation and growth control in pulsed laser epitaxy of oxide thin films
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Due to the non-steady state nature of film growth by laser MBE, as well as by the conventional pulsed laser deposition (PLD), we could find an advantage of the method for controlling the film growth. The independent optimization of nucleation and growth processes is possible by pulse sequence and laser energy density. Another critical factor for controlling the growth mode was revealed to exist in the surface state of the substrate as the stating point of film growth. We have developed a wet etching method for automatically finishing SrTiO3 substrate surface to facilitate the layer by layer growth of high Tc and other oxide thin films. The sequential deposition of SrO and BaO monolayers on the treated SrTiO3 substrate greatly reduced the nucleation of precipitates in the YBa2Cu3O7 (YBCO) thin films. Thus, PLD growth of YBCO thin film could be controlled on an atomic scale. Temperature gradient deposition achieved the orientational control of YBCO thin films on (100) and (110) SrTiO3 substrates. Laser MBE successfully produced high quality epitaxial oxide films by 2-dimensional layer by layer manner as well as by step-flow mode, as verified by the sharp RHEED intensity oscillation. This dimension control epitaxy enabled us to fabricate oxide superlattices and quantum wires. With the substrate treatment and buffer layer techniques, together with suitable choice of insulating layer material, we have verified the fabrication of superconducting-insulating-superconducting trilayer which is the prototype for tunneling junctions. A possibility of using (110) oriented YBCO thin films for Josephson THz laser is also discussed.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Hideomi Koinuma, Masashi Kawasaki, Satoru Ohashi, Mikk Lippmaa, Naoyuki Nakagawa, Masashi Iwasaki, and X. G. Qiu "Nucleation and growth control in pulsed laser epitaxy of oxide thin films", Proc. SPIE 3481, Superconducting and Related Oxides: Physics and Nanoengineering III, (22 December 1998);

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