6. INTENSITY OF IONIZATION LINES

• 6.1. IL intensity
• 6.2. Primary electron energy selection

6.1. IL intensity

The intensity of certain IL is formed by the electrons belonging to it and emitted into vacuum within a solid angle . In practice the intensity of IL at the analyzer's entrance point is determined by the entrance aperture angle , less than . The IL intensity is added to the background Is, formed by secondary electrons entering the aperture. Therefore, the intensity of IL at the analyzer's entrance is:

(6.1.1)

Here (see note) - spectrum of the secondary electrons forming the given IL, w0 - its half-width. This formula is written while assuming the symmetric IL shape, which is usually not true. In a general case the integration limits are chosen accordingly to IL shape.

The double stage model for the IL intensity at the analyzer's entrance gives the following simple expression in the case of homogeneous semi-infinite sample and the normal incidence of primary electrons

(6.1.2)

where ip - primary electron beam current,
- cross section of core level excitation with low angle electron scattering,
nj - volume concentration of the j-th element atoms,
- effective analysis depth,
- EBE factor.

The values of and depend on primary electron energy Ep:

	(6.1.3)

where r - is the EBE coefficient, () - elastic scattering angle, - electrons free pass.

It is possible to modify (6.1.2) for more complicated cases [Ref 3]:

• non-homogeneous samples;
• two layer samples;
• various film growth modes;
• spectra with other angles of primary electrons incidence and secondary electrons emission, etc.

Look further: 6.2. Primary electron energy selection