328
16 VLEED Capability and Sensitivity
16.3 Summary
An examination of the VLEED spectral sensitivity to the bond-geometry and to the
SPB parameters clarified the following:
(1) The VLEED spectra are sensitive to the bond geometry instead of the individual
atomic dislocations. Individually varying atomic position is not practical in simulating the process of surface bond forming. Agreement of the trends between
the measurements and calculations realized by adjusting the bond variables
challenges further efforts towards quantifying the O-Cu(001) bonding kinetics.
(2) The shape of the I-E curve is sensitive to the integral of the elastic potential
ReV(z), which determines the phase change of the diffracted electron beams.
(3) The absolute intensity of the I-E curve is dominated by the integral of the inelastic damping ImV(Z, E). Thus the parameters in the ImV(z, E) can compensate
for the inaccuracy of the calibration of experimental data.
(4) It is uncovered that electrons out of the second layer predominate the inelastic
damping. Therefore, LEED at very low energies is the unique technique that
collects nondestructive information from a single atomic layer of a surface and
covers the valence band energy.
The self-consistency between the outcomes and the constraints, on the sense of SPB
integrations, the SPB is premised evidences sufficiently that the decoding technique
and the modeling approaches are essentially correct, and therefore the capacity and
the reliability of the VLEED in turn are fully uncovered. The present approach
reveals the performence of bonds and electrons in terms of bond geometry, Bragg
diffraction, intensity loss by the valence DOS, ImV(z, E), absorption, and the elastic
SPB diffraction featured by the ReV(z).
References
1. V. Pouthier, C. Ramseyer, C. Girardet, P. Zeppenfeld, V. Diercks, R. Halmer, Characterization
of the Cu (110) − (2×1) O reconstruction by means of molecular adsorption. Phys. Rev. B
58(15), 9998 (1998)
2. C.Q. Sun, C.L. Bai, Modelling of non-uniform electrical potential barriers for metal surfaces
with chemisorbed oxygen. J. Phys. Condensed Matter 9(27), 5823–5836 (1997)
3. C.Q. Sun, Spectral sensitivity of the VLEED to the bonding geometry and the potential barrier
of the O-Cu(001) surface. Vacuum 48(5), 491–498 (1997)
4. T. Lederer, D. Arvanitis, G. Comelli, L. Tröger, K. Baberschke, Adsorption of oxygen on Cu
(100). I. local structure and dynamics for two atomic chemisorption states. Phys. Rev. B 48(20),
15390 (1993)
5. R. Mayer, C.-S. Zhang, K. Lynn, Evidence for the absence of a c (2×2) superstructure for
oxygen on Cu (100). Phys. Rev. B 33(12), 8899 (1986)
6. C.Q. Sun, Oxidation electronics: bond-band-barrier correlation and its applications. Prog. Mater
Sci. 48(6), 521–685 (2003)
7. C.Q. Sun, Angular-resolved VLEED from O-Cu(001): Valence bands, chemical bonds,
potential barrier, and energy states. Int. J. Mod. Phys. B 11(25), 3073–3091 (1997)
16 VLEED Capability and Sensitivity
16.3 Summary
An examination of the VLEED spectral sensitivity to the bond-geometry and to the
SPB parameters clarified the following:
(1) The VLEED spectra are sensitive to the bond geometry instead of the individual
atomic dislocations. Individually varying atomic position is not practical in simulating the process of surface bond forming. Agreement of the trends between
the measurements and calculations realized by adjusting the bond variables
challenges further efforts towards quantifying the O-Cu(001) bonding kinetics.
(2) The shape of the I-E curve is sensitive to the integral of the elastic potential
ReV(z), which determines the phase change of the diffracted electron beams.
(3) The absolute intensity of the I-E curve is dominated by the integral of the inelastic damping ImV(Z, E). Thus the parameters in the ImV(z, E) can compensate
for the inaccuracy of the calibration of experimental data.
(4) It is uncovered that electrons out of the second layer predominate the inelastic
damping. Therefore, LEED at very low energies is the unique technique that
collects nondestructive information from a single atomic layer of a surface and
covers the valence band energy.
The self-consistency between the outcomes and the constraints, on the sense of SPB
integrations, the SPB is premised evidences sufficiently that the decoding technique
and the modeling approaches are essentially correct, and therefore the capacity and
the reliability of the VLEED in turn are fully uncovered. The present approach
reveals the performence of bonds and electrons in terms of bond geometry, Bragg
diffraction, intensity loss by the valence DOS, ImV(z, E), absorption, and the elastic
SPB diffraction featured by the ReV(z).
References
1. V. Pouthier, C. Ramseyer, C. Girardet, P. Zeppenfeld, V. Diercks, R. Halmer, Characterization
of the Cu (110) − (2×1) O reconstruction by means of molecular adsorption. Phys. Rev. B
58(15), 9998 (1998)
2. C.Q. Sun, C.L. Bai, Modelling of non-uniform electrical potential barriers for metal surfaces
with chemisorbed oxygen. J. Phys. Condensed Matter 9(27), 5823–5836 (1997)
3. C.Q. Sun, Spectral sensitivity of the VLEED to the bonding geometry and the potential barrier
of the O-Cu(001) surface. Vacuum 48(5), 491–498 (1997)
4. T. Lederer, D. Arvanitis, G. Comelli, L. Tröger, K. Baberschke, Adsorption of oxygen on Cu
(100). I. local structure and dynamics for two atomic chemisorption states. Phys. Rev. B 48(20),
15390 (1993)
5. R. Mayer, C.-S. Zhang, K. Lynn, Evidence for the absence of a c (2×2) superstructure for
oxygen on Cu (100). Phys. Rev. B 33(12), 8899 (1986)
6. C.Q. Sun, Oxidation electronics: bond-band-barrier correlation and its applications. Prog. Mater
Sci. 48(6), 521–685 (2003)
7. C.Q. Sun, Angular-resolved VLEED from O-Cu(001): Valence bands, chemical bonds,
potential barrier, and energy states. Int. J. Mod. Phys. B 11(25), 3073–3091 (1997)