Formation and characterization of thin superconducting Y-Ba-Cu-O films

Author

Gyusuk Kim, New Jersey Institute of Technology

Document Type

Thesis

Date of Award

1-31-1990

Degree Name

Master of Science in Electrical Engineering - (M.S.)

Department

Electrical and Computer Engineering

First Advisor

Kenneth Sohn

Second Advisor

Roy H. Cornely

Third Advisor

Marek Sosnowski

Abstract

Thin Y-Ba-Cu-O superconducting films were fabricated reproducibly on MgO (100) substrates by two different processes ; (1) deposition at a low substrate temperature fiom a single sintered YBa₂Cu_3.3O_x target using RF diode reactive sputtering followed by a post-annealing at around 830 ° C ; (2) deposition at the crystallization temperature under oxidizing atmosphere. The superconducting properties of films deposited by process (1) and (2) were studied. The variation of film composition and thickness as a function of distance from the target gas pressure and distance between target and substrate was studied. The Dependence of the film composition and deposition rate on the substrate temperature was studied.

Film crystal structures were characterized by X-ray diffraction using a Cu Kα source and compositions were determined by Rutherford backscattering spectroscopy ( RBS ). Transition temperature ( T_c ) was determined by four-probe resistance measurement. Parameters for sputter deposition of the highest Tc Y-Ba-Cu-O films were ; substrate temperature, 130 ° C; sputtering gas mixture, 10 m Torr (10% oxygen 90% Argon); distance between cathode and anode, 2.5 inch; target power density, 4.87 watts/cm². The deposition rate was in the range of 2.4 - 2.6 nm/min. The post-deposition annealing was carried out under these condition; oxygen pressure > 100. Torr; temperature, 830 ° C for 10 min; warmming rate, 2.3 ° C/min; cooling rate, 5 ° C/min. Ba and Cu deficiencies were observed in the films deposited at the crystallization temperature. Post-deposition high temperature treatment results in poor surface morphoology, cracking, or undesirable interdiffusion, and limits the choice of substrate material.

It was concluded that the prefered deposition condition for a high quality thin superconducting YBa-CU-0 films with our RF diode sputtering system is the process (2) using target with Cu and Ba contents increased.

Recommended Citation

Kim, Gyusuk, "Formation and characterization of thin superconducting Y-Ba-Cu-O films" (1990). Theses. 2784.
https://digitalcommons.njit.edu/theses/2784