“…The results obtained by Alves et al are more in agreement with similar threshold, of the order of 40 eV, for Al and O along <10-10> and lower values for Al along <0001> [3], see also Zinkle [2]. Ref a [4], b [5], c [6], d [7], e [8], f [9,10] As can be seen in this table the values given for a single oxide display a very large spread, frequently by a factor up to two. The spectroscopic methods give the most specific values, but are limited frequently to oxygen defects.…”