contamination limits

[Michael Deal]

Jim and I just discussed the metal contamination level issue.  We suggest 
the following limits from TXRF or TOF-SIMS measurements:

For "semiclean":   metal contamination should be less than 1x10^12 cm-2
    This is based on the agreed upon purity of some of the targets used in 
the SCT sputtering system (99.95% pure)

For "clean": metal contamination should be less than 1x10^11 cm-2
     This is based on past results of our cleans, etc.

							-mike