fig6

Figure 6. I-V characteristics are reported in this figure; the blue curve, A, is collected in the surface reconstruction Si(111)√3 × √3-Bi β-phase, and the brown curve, B, in Si island-√3 × √3. For better visibility, curve B is multiplied tenfold. The dashed lines illustrate the methodology for determining the energy gap. Note that the tunneling current signal span spans almost five decades. The energy gaps are determined at a measured current level of 10 fA, which is the average noise of the current-voltage converter.