Geometric and electronic structure of reconstructed semiconductor surfaces

The combination of high-resolution photoemission spectroscopy (PES) using synchrotron radiation, and reflection high-energy electron diffraction (RHEED), along with other techniques, have been used to examine the atomic-scale geometric and electronic properties of clean and adsorbate-covered semiconductor surfaces. The surfaces studied have been probed via core-level, valence band, and angle-resolved photoemission spectroscopy, and with the extended photoemission fine structure technique.The surface core-levels and surface states on the Si(111)-(7 x 7) surface have been used to examine submonolayer deposits of Ge onto this surface. Knowledge of the initial stages of interface formation in these systems is important due to their application in heterostructure device physics. The decomposed Si-2p and Ge-3d core levels and angle-integrated valence band spectra have been analyzed as a function of Ge coverage and annealing temperature. The results support the assignment of the lower binding energy component in both the Si-2p and Ge-3d cores to adatom emission. The implications with respect to adatom-to-rest-atom charge transfer are discussed.Lead adlayers on the (111) surfaces of Si and Ge have been examined as well. The surface phase diagram of Pb on these substrates exhibits interesting properties which arise in part due to the differing degrees of lattice matching ($\sim$4% for Pb/Si, $<$1% for Pb/Ge) and the nature of the clean surface reconstructions ((7 x 7) vs. c(2 x 8)). Atomically abrupt interfaces are insured for these systems since Pb is insoluble in these surfaces even for temperatures well beyond the Pb melting point (340$\sp\circ$C). Thus, they are considered ideal systems to study with regard to metal-semiconductor interface formation and interface-dependent Schottky barrier studies, in contrast to reactive systems where intermixing usually occurs. This lack of interdiffusion has also allowed studies of the 2D melting of the Pb overlayers. The growth, desorption, Schottky-barrier heights, and atomic structure of the Pb-induced phases on Si and Ge are investigated via synchrotron radiation photoemission spectroscopy, along with other techniques such as reflection high-energy electron diffraction and Auger electron spectroscopy (AES). Examining the differences between these closely related systems nicely illustrates the complex interrelationship between the atomic and electronic structure of reconstructed surfaces.U of I OnlyETDs are only available to UIUC Users without author permissio