Lou Temperature Growth of Superconducting Yba a cu,0 7-X Thin Films by Metalorganic Chemical Vapor Deposition
- PDF / 203,691 Bytes
- 4 Pages / 420.48 x 639 pts Page_size
- 43 Downloads / 229 Views
LOWTEMPERATURE GROWTH OF SUPERCONDUCTING YBa2 Cu1O,-_ THIN FILMS BY METALORGANIC CHEMICAL VAPOR DEPOSITION Keiichi Kanehori, Nobuyuki Sugii and Katsuki Miyauchi Central Research Laboratory, Hitachi. Ltd., Tokyo, Japan.
ABSTRACT Thin YBa 2 Cu3O,_fiIms were grown by thermal and plasma enhanced MOCVD, and the effects of growth temperature on the film properties were studied. The crystallinity of the films deteriorated with growth temperature, so superconductity decreased with growth temperature. Thin films grown by thermal MOCVD at 600°C, 650"C, 700°C and 750°C had zero-resistivity at 10K. 71K, 83K and 84K, respectively. The growth temperature for superconducting films is decreased by plasma enhancement. Thin films grown by plasma enhanced MOCVD at 5150C and 580°C had zero-resistivity at 60K and 85K. The critical current density of films grown by plasma enhanced MOCVD at 580°C was 10A/cm' at 77K.
INTRODUCTION Netalorganic chemical vapor deposition (NOCVD)is thought to be one of the most desirable methods of growing oxide superconducting thin films, because it has high composition controllability, high reliability and high productivity. However, to grow superconducting YBa2 CuaO,,_ thin films by this method, high growth temperarures of over 750'C [1,2,3], at which the reaction between superconductor and substrate proceeds[4], have been required. Thus, to enable NOCVD to be applied to microelectronics processes, a concerted effort has been made to decrease the growth temperature. This paper reports crystallographic and electrical properties of Y-Ba-Cu-O thin films grown by thermal MOCVDand plasma enhanced MOCVD at temperatures lower than 750°C.
EXPERIMENTAL The tetramethylheptadioene (THD) complexes of Y. Ba and Cu were employed as metal sources. They were sublimated and transferred to the growth chamber by Ar carrier gas. Oxygen gas was used as an oxidant. SrTiO, (100) single crystals polished with phosphoric acid at 90'C were used as substrates. The substrate size was 10mm X 5mm. Thermal MOCVDwas conducted using a conventional low pressure MOCVD apparatus [5]. The growth chamber was a quartz tube heated by an electric furnace. Plasma enhanced MOCVDwas conducted using the magneto -microwave plasma type apparatus :,wn in Fig. 1. The frequency of the microwave, generated by a magnetron, was 2.45GHz. The magenetic field was controlled at nearly 875G in order to satisfy the elecron-cyclotron resonance condition. In both methods, the films were slowly cooled in an 02 atomosphere as shown in a
Mat. Res. Soc. Symp. Proc. Vol. 169. ©1990 Materials Research Society
590
previous paper[5]. The crystallographic properties of the films were determined by the X-ray diffraction method. The electrical properties were studied by the conventional four probe method.
RESULTS ANDDISCUSSION Thin films were grown by thermal NOCVD in the temperature range from 650°C to 750'C under the following conditions: sublimation temperature and Ar flow 2 rate for Y, Ba and Cu complexes were 110°C-50cm'/min, 240°C-50cm /min and 115*C50cm2 /min; 0
Data Loading...
