On the Problem of Depth Distributions in Oxides Following High‐Dose Labelings. (Sputtering and Depth‐Distribution Phenomena, Part III)

It has been shown previously that meaningful depth‐distribution parameters can be obtained with Al, KCl, and Pt, following high‐dose labelings at ≦ 10 keV, by sputtering the targets with 2 or 3 keV ions. We present here similar data for the oxides Al2O3, MgO, NiO, SiO2, TiO2, and UO2 labeled to a high dose at 4 keV. It is found that, when the sputtering energy is 2 keV, the implied ion ranges are roughly a factor of 2 less than might be expected (shown with all oxides), while, when the sputtering energy is 8 keV, the implied ranges are smaller still (Al2O3, TiO2). Moreover, shortened ranges are also found by sputtering oxide skins (Al, Mg, Ti), by sputtering bulk materials at about −150°C (Al2O3, MgO, UO2), by applying an anodizing‐stripping technique (Al2O3), and by comparing high‐dose sticking factors (all oxides). It is concluded that the available evidence is compatible with two extreme views. Possibly the shortened ranges found with high‐dose labeled oxides are in error, for example due to bombardment‐enhanced gas motion when the sputtering technique is used, or due to excess oxide growth when anodizing‐stripping is used; alternatively they may be real, as would be true if an effect such as bombardment‐enhanced gas motion occurred during the labeling.