Effect of Glow Discharge Current on Composition of Y-Ba-Cu-0 Films by High Pressure Dc Sputtering Process
- PDF / 228,473 Bytes
- 4 Pages / 420.48 x 639 pts Page_size
- 64 Downloads / 180 Views
EFFECT OF GLOW DISCHARGE CURRENT ON COMPOSITION OF Y-Ba-Cu-O FILMS BY HIGH PRESSURE DC SPUTTERING PROCESS R.J. Lin, Y.C. Chen and P.T. Wu Materials Research Laboratories, Industrial Technology Research Institute, 195 Chung-hsing Rd., Sec. 4, Chutung, Hsinchu 31015, Taiwan, R.O.C. ABSTRACT The Y-Ba-Cu-O (YBCO) films were grown on (100)MgO substrate by the high pressure DC diode sputtering process. The targets were YBCO compounds made by solid-state reaction. The sputtering gas was Ar-50%02 , and total pressure was 1.5 torr. As-deposited superconducting YBCO films can be prepared at low substrate temperature at high discharge current. For Y1 Ba2 Cu3 Ox target, the atomic ratio Ba/Y in the films almost remains constant (Ba/Y = 1.7) and Cu content monotonically increases with increasing discharge current. The Cu content in the film approaches to that of the target at low discharge current. Concentrations of 0 and O in plasma markedly increase during increase of discharge current. High Cu content at large discharge current may be caused by action of electrical field on Ba+ and Y*. INTRODUCTION It is well known that superconducting YBCO films with high quality can be prepared by several kinds of sputtering systems [1-3]. The feature of these process is that the deviation of film composition from the target composition strongly relates to the geometry of electrodes and operation conditions (types of sputtering gas, total gas pressure, discharge power and bias voltage of the substrate, etc.). The reported mechanisms that cause composition change are the bombardment of high energy electrons and negative oxygen ions to the film surface [4-5] and different angular distribution of ejected atoms [6]. For our high pressure DC sputtering system [7-8], these mechanisms can not explain that the Cu content in the films is much higher than that of the target. We conjecture that this may be attributed to difference of plasma environment. In this paper, the effect of glow discharge current on the composition of the films and preliminary study of plasma environment by an optical emission spectroscope will be discussed. EXPERIMENTAL The YBCO films were prepared by the high pressure DC planar diode sputtering process from a compound target. The target (diameter 4.5cm; thickness 0.4cm) was made by a solid-state reaction of Y2 0 3 , BaCO 3 and CuO in the stoichiometric ratio of Y: Ba:Cu = 1:2:0.8, 1:2:1.5 or 1:2:3. The target was sintered at 9300C for 15 hr in air. The base pressure of the vacuum system 3 prior to deposition was 1x10- torr. The sputtering gas was Ar-50%02 , and total pressure was 1.5 torr. The target-to-substrate separation was 2cm. The substrate was (100)MgO single crystal. The substrate was preheated to 380°C by IR quartz heater. The sputtering voltage and current were Mat. Res. Soc. Symp. Proc. Vol. 169. •1990 Materials Research Society
636
The stable tem220-240 volt and 0.4-0.8 amperes, respectively. The substrate temperperature of the substrate was 380-420°C. ature was measured by a K-type thermocouple, whose naked
Data Loading...
