Transition from terrace to step modulation in the surface state wave function at vicinal Cu(1 1 1)

Surface states on vicinal Cu(775): STM and photoemission study

“…One appealing explanation for the transition from step-to terrace-modulation that has been advanced is that a reduction of the projected band-gap with increasing vicinal angle causes the terrace-modulated surface state wavefunction to switch to step-modulated [9]. As a result it is important to confirm the presence of any band gap on our surface and to track its change with vicinal-cut angle.…”

“…This overlap will cause the terracemodulated state to become a broad resonance and loose spectral weight [9] and cause it to be un- observable in an EDC of the surface. Further as shown in the figure and discussed earlier in [9] due to the fixed (111) orientation of the terrace, the step-modulated state remains in the projected bandgap for all the vicinal angles show in Fig. 6, thus giving a strong PE signal.…”

One-dimensional versus two-dimensional electronic states in vicinal surfaces

“…In reality, the 1D or 2D nature appears unambiguously defined in surfaces with very large or very small d values, respectively. A less clear behaviour is found for intermediate d values [4,5], [11]- [14]. A number of different explanations have been given to explain this 1D-2D transition, and all of them lead to similar critical values around d c ∼ 20 Å for both Au(1 1 1) and Cu(1 1 1) vicinal surfaces.…”

“…Probably the most interesting observation concerns the change in the dimensionality of the surface state as one varies the superlattice constant d of the step array, as schematically depicted in figure 1. For relatively small d, surface states display electron propagation across the steps, and hence 2D behaviour [4,5,7,8]. In contrast, step arrays with large d lead to weakly dispersing bands, i.e.…”

“…A number of different explanations have been given to explain this 1D-2D transition, and all of them lead to similar critical values around d c ∼ 20 Å for both Au(1 1 1) and Cu(1 1 1) vicinal surfaces. They include the finite coherence length of the surface state [4], the Fermi wavelength of surface electrons [13] and the onset of overlap with bulk states [4,5,7]. The latter is a consequence of the progressive formation of a surface resonance as the projected bulk band gap around the Fermi energy closes [11].…”