Date of Award
Doctor of Philosophy
Physics and Astronomy
D. W. Lynch
A reflectance-difference spectroscopy (RD) system was designed and built. Automatically controlled by a computer (PC), the system was used to study the anisotropic optical response of the (110) surfaces of Ag and Cu. Four Ag(110) surfaces were prepared, one epitaxially-grown single-crystalline thin film surface and three chemically etched single crystal surfaces. The RD spectra show all surfaces have very similar anisotropic peaks around 3.8 eV and 3.9 eV. This anisotropy is produced by the surface layer of atoms and is sensitive to the details of the electronic band structure. The peak structures can be attributed to transitions between surface-modified bulk-like states. The origin of this optical anisotropy can be understood as splitting of bulk bands near the high-symmetry point L in the Brillouin zone, due to the surface perturbation. Surface states and surface resonances are expected to have the largest splitting. Optical anisotropy in the Drude region below the lowest interband absorption was also observed in the RD spectra, which is due to the anisotropy of the Drude parameters on the surface. Furthermore, the RD spectra show surface plasmon (SP) peaks below 3.6 eV in the intraband transition range. These SP peaks can be excited by surface roughness, which was verified by the observed SP peak for a vicinal surface of Ag(110), cut 1° off the (110) face along the (001) direction. Because of the similarity of the electronic band structures of Ag and Cu, the RD spectra on (110) surfaces of Cu were measured. As for Ag, the RD spectra of Cu showed anisotropic structures, too. The anisotropy can be interpreted with the same model as for Ag, but involving the X point as well as L by considering the splitting of bulk bands on the surface.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Chen, Zai, "Optical anisotropy of (110) surfaces of Ag and Cu " (1994). Retrospective Theses and Dissertations. 10686.