Escape length of Auger electrons

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Abstract
Sputter deposition of Mo atoms on W substrates (and vice versa) was shown to form uniform overlayers. Such overlayers are ideally suited for studies of the escape length of Auger electrons. The results show that the escape length increases with Auger electron energy as expected. In both Mo and W the escape length of 48-eV Auger electrons is about 5 Å. For 1736-eV Auger electrons it increases to 24 Å in Mo and 17 Å in W. For a Mo overlayer on W, the Mo signal can reach an intensity 1.2 times that of the bulk Mo signal due to the higher backscattering coefficient of W. For a W overlayer on Mo, a corresponding reduction in the W signal compared to bulk W, i.e., an increase in the apparent escape depth was observed. With a model in which the backscattering effect is incorporated, one obtains satisfactory agreement with the experimental results. In addition the result indicates that while high-energy Auger peaks are generated by the primary beam alone, a substantial fraction of observed low-energy Auger electrons are generated by backscattered electrons. For the case of the Mo (120-eV) Auger signal with 3-keV primary beam energy, this fraction amounts to approximately 40%.