PARTICLE IN A VARIABLE-SIZE BOX - THE INFLUENCE OF THE TIP IN THIN-FILM ELECTRON INTERFEROMETRY

The influence of the scanning-tunneling-microscopy tip on the conducta nce spectra measured in thin-film electron interferometry is considere d, and is discussed in terms of coupled quantum well. One of the wells is formed by the linear potential drop between the tip and sample, wh ich gives rise to vacuum-field-emission resonances. The spectra of fie ld-emission resonances are shown to be very sensitive to the propertie s of the tip, and can be understood in terms of confining the electron to triangular potential wells of different sizes. The other potential well is formed within the thin-film adlayer, and its spectrum should be largely independent of the properties of the tip. We consider the s pectrum of the coupled system, and discuss it in terms of perturbation theory where we observe the tendency of the levels to repel each othe r when they are closely spaced in energy, and to cause level splitting when the levels are degenerate.