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Chiang, Tai-Chang Samsavar, Amin 2011-06-01T14:43:01Z 2011-06-01T14:43:01Z 10000-01-01 1990 "The clean and reacted surfaces of Si(111)-(7x7), Si(100)-(2x1), Ge(111)c( 2x8), and Ge(100)-(2x1) have been studied to better understand the nature of these elemental-semiconductor surfaces. By carefully monitoring the adsorbateinduced changes in the electronic properties at the surface via spectroscopic methods such as photoemission, and by studying the resulting surface structures by scanning tunneling microscopy (STM), a quantitative description of the interaction and reaction between adsorbate and surface can be obtained. The photoemission method allows a distinction between atoms in different layers and in inequivalent sites by their binding energy shifts. By comparison with structural models and reference samples the number of atoms in each distinct chemical configuration can be determined. An adsorbate-induced chemical shift can be correlated with electronegativity differences between substrate and adsorbate atoms. In particular, studies of noble-metal interfaces with the (100) faces of Si and Ge demonstrate this novel combined application of photoemission and STM. The (111) faces of Si and Ge reconstruct to exhibit rather complex chemisorption geometries which are generally not well understood. For clean Si(111)-(7x7), there are three distinct surface sites giving rise to three different chemical environments. To establish the correlation between various surface-shifted components of the core levels and the surface sites, several experiments were designed and performed. The main idea behind these experiments has been to selectively replace atoms or saturate the dangling bonds of a certain surface site by adsorbate atoms, using the noble metalsemiconductor interface as the model system to test this basic approach. Results for other interface systems such as Sb, Sn and NH3 with these semiconductors are also presented for comparison. These studies indicate that the ""adatoms"" on the clean Si(lll)-(7x7) surface are directly responsible for the metallic surface state in the valence band. Additionally these adatoms exhibit a core level shift of -0.77 eV relative to the bulk atoms." Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-01T14:43:01Z No. of bitstreams: 1 1990_samsavar.pdf: 4985026 bytes, checksum: 68b074ec180427d57e0b145abf2035c9 (MD5) Made available in DSpace on 2011-06-01T14:43:01Z (GMT). No. of bitstreams: 1 1990_samsavar.pdf: 4985026 bytes, checksum: 68b074ec180427d57e0b145abf2035c9 (MD5) Previous issue date: 1990 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-06-01T14:43:01Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:12:39-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Thesis U of I Only 3478195 http://hdl.handle.net/2142/25096 en 1990 Amin Samsavar elemental-semiconductor surfaces scanning tunneling microscopy (STM) absorbate and surface interactions Photoemission and scanning tunneling microscopy investigation of elemental-semiconductor surfaces Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.