36. VACUUM INSTRUMENTATION
FOR SURFACE STUDIES (DAPS). After establishing comparable conditions for AES and AEAPS, the signal-to-noise ratios are compared. AEAPS is found to be slightly more sensitive for Ti (factor of 2). much more for La (factor of 30) and much less for oxygen (factor of 0.02) than AES. Due to the small number of lines in the threshold spectroscopies and little line overlap, it is possible to detect minor. constituents in multicomponent samples which cannot be found by AES. This is demonstrated for a stainless-steel alloy. DAPS has pronounced surface sensitivity, but a lower signal-to-noise ratio compared to AEAPS (a factor of 6 was determined for Ti). The differences in the depth of information of DAPS and AEAPS allow us. to detect surface enrichment in alloys or preferential sputtering by ion bombardment without any further treatment of the sample. This is demonstrated for a Cr-I 6 Fe-84 alloy. (Brasil) 36 J Kirschner and W Losch, J Vuc Sci Technol, 14 (5), 1977, 1173-l 179. 3585. Auger and energy-loss spectra of boron, boron carbide and boron nitride. (France) Auger and energy-loss spectra of boron and carbon in different chemical environments have been obtained in a Leed-Auger-Sims apparatus. The analysis system enables us to obtain information on Auger spectra, positive and negative secondary ion spectra from the sample sputtered with neutral or ion species and thermal desorption spectra. It is shown that Auger spectra or boron and carbon in different chemical environments, are characteristic of the chemical bound. The KVV transition of boron, as like or in the form of B& and BN is 10 ev shifted to the lower energies from the same KVV Auger transition observed in a silicon crystal highly doped with boron. Furthermore a high energy satellite peak is observed in the three boron structures and can be interpreted by the excitation of an interatomic transition or by shift of EF. The multiplicity of peaks observed in electron energy-loss spectra are due to plasmon effects and interband transitions. These spectra are strongly affected by surface treatments or chemisorbed species as oxygen and nitrogen and are related to the coverage of the adsorbed species. G Dagoury and D Vigner, Vide, 32 (l87), 1977, 51-59 (in French).