SAM and scanning ELS analysis

Several Auger point spectra were recorded for each material, showing that all were laterally homogenous except for the occasional contaminant particle. In addition, time-dependent spectra confirmed that the chemistry of the. surfaces was not altered by electron irradiation. In general the spectral components were poorly resolved in the expanded spectra, even when the analyzer was operated at a nominal resolution of less than I eV. Curve fitting would in principle have assisted in resolving the spectra, but the complex shapes involved in the multi-component spectra would have made interpretation problematic. 

F igure 12. P KLL spectra measured with SAM from InP analyzed in the following conditions (a) as-received (b) atomically clean (c) after 2000-L NO exposure. 

Further information has come from Auger and electron energy loss features spread over an extended KE range which have allowed the depth distribution of oxidized species in the materials to be studied. According to the sputter profile shown in Fig. 9, most of the oxidic species reside within the first 1-2 nm of the surface. This is also the X value associated with the O ,— CB feature seen at Ep = 3(X) eV in Fig. 16 after exposure to 2000 L of NO . Because of the poor chemical sensitivity of ELS it is difficult to decide how far the latter feature may be considered a quantitative indicator of NO -induced surface chemical change. However, its intensity decrea.scd somewhat at Ep = l(X)0 eV (X = 2.5 nm) and became virtually zero at Ep - 2(XX) eV (X = 3.8 nm). SAM has greater chemical. sen- 

Two samples were studied (1) a thin film (ca. 150 nm in thickness) of SiOi grown on a Si(l(K)) wafer, obtained from a commercial source, and (2) a thin film (about 70 nm thick) of silica on silicon grown thermally at 1(XX) K for several hours in oxygen in the laboratory. The latter will be referred to as aged 

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