Spectra of electrons
reflected from the
Nb/Si two-layer
targets
Nb/Al/Nb/Si multilayer
targets
Nb/AlOx-Al/Nb
structure
Theoretical interpretation
Consistent
solution of elastic and inelastic problems
Accuracy
of layer thickness measurements
Comparison
of electron spectroscopy and Transmission electron microscopy results
Consistent
solution of elastic and inelastic problems
The calculation of electron energy spectra reflected from heterogeneous in depths targets is based on formulas (7), (9), (10), (14).
Fig. 1. Reflected electrons spectra
Solid line shows experimental data, dashed blue line – calculation for two-layer model. Varying the top Nb-layer thickness for target the Nb-layer thickness has been obtained that fits experimental data best (fitting-procedure). Nb-layer thickness: x=30 nm.
Fig. 2. Reflected electrons spectra
Solid line shows experimental data, dashed red line – calculation for multilayer model. Target has been represented as consisted of 4 layers. Niobium concentration profile recovered (fitting-procedure) from experimental spectrum is depicted on Fig.2.
Fig.3 Fitting-procedure
The model as such together with all its parameters has been kept constant. Solid line – experiment data, dashed blue line – calculation.
Fig.4 Fitting-procedure
The model as such together with all its parameters has been kept constant. Solid line – experiment data, dashed red line – calculation.
Accuracy of layer thickness measurements
Fig. 5. Reflected electrons spectra
Solid blue line – experiment data, dashed blue line – calculation, thin dashed line - experimental error range. Nb layer thickness x=30 nm is defined with error 1 nm.
Fig.6 Fitting-procedure
Comparison of electron spectroscopy and Transmission electron microscopy results
Fig.7
Cross-section of Nb/Al-AlOx/Nb SIS junction
(T.
Imamura, S. Hasuo. IEEE Trans. Magnetics, 1991, v.27(2), p.3172-3175)
Fig.7 shows typical image of cross-section of Nb/AlOx-Al/Nb tunnel structure got by TEM. Electron spectroscopy conclusion about sharp Al-AlOx/Nb interface and diffused Nb/Al one is consistent with TEM results.