DENSITY-OF-STATES IN QUASI-CRYSTALS AND APPROXIMANTS - TUNNELING EXPERIMENT ON BARE AND OXIDIZED SURFACES

Tunneling spectroscopy studies on oxidized and bare surfaces of icosah edral i-AlPdRe, i-AlCuFe, and approximant alpha-AlMnSi phases reveal s pecific features of the density of states (DOS) close to the Fermi lev el as compared to the crystalline nonapproximant omega-AlCuFe phase. T he Fermi energy lies in the middle of a narrow pseudogap of about 50 m eV width. For higher energies, the DOS exhibits a square root energy d ependence attributed to electron-electron interaction effects. The DOS differs from the linear muffin tin orbital calculated DOS and the pos sible roles of electron scattering and inhomogeneous electronic struct ure close to the surface are discussed.