Band structure and Fermi surface of atomically uniform lead films

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Atomically uniform lead films are prepared on Si(111)-(7 x 7) substrates by the molecular beam epitaxy method, and their electronic structures are investigated by high-resolution angle-resolved photoemission spectroscopy and first-principles density functional theory calculations. We have observed the six-fold symmetric Fermi surfaces of Pb/Si(111)-(7 x 7) films. Their topology and size are almost the same regardless of the difference of film thicknesses (17, 21, 24 and 25 monolayers). The comparison between the measured and calculated thin-film Fermi surfaces suggests that the as-prepared Pb/Si(111)-(7 x 7) films are dominated by the hexagonal-close-packed stacking films instead of the face-centered-cubic ones. The theoretical calculations also indicate that spin-orbit coupling plays an important role in the band structures and Fermi surface topologies of Pb films.