THE EFFECT OF OXIDANT ON RESPUTTERING OF BI FROM BI-SR-CA-CU-O FILMS

The type and partial pressure of oxidant mixed with argon can affect the selective sputtering of Bi in composite-target, magnetron-sputtered Bi-Sr-Ca-Cu-O films. Comparative studies using oxygen and ozone show that ozone is a more potent oxidant, as well as a more potent source of resputterers than is oxygen. Severe resputtering from ozone is significantly reduced by a - 40 V potential on the sample block. We suggest that oxygen causes resputtering by forming O2+, which interacts with the target to produce energetic O-. In contrast, ozone may form lower-energy O-by electron impact in the dark space. Negative oxygen ions from the target itself may be responsible for a background resputtering effect. Our results and those found for Y-Ba-Cu-O by others are comparable. Bi in Bi-Sr-Ca-Cu-O behaves as Ba in Y-Ba-Cu-O, with regard to selective resputtering; furthermore, the response of Sr, Ca, and Cu to oxygen in sputtered Bi-Sr-Ca-Cu-O is similar to what is observed for Cu in Y-Ba-Cu-O.