Full gap opening in single crystalline Fe1-xCoxSi evidenced by high-resolution photoemission

We have investigated high-quality tri-arc-Czochralski grown single crystals of Fe1-xCoxSi by high-resolution photoemission spectroscopy using synchrotron radiation. The Fermi edges of FeSi and Fe0.95Co0.05Si were measured with an energy resolution of 10 meV. The spectra evidence for the first time a full band gap in FeSi. A closing of this gap by doping with 5 at% Co could clearly be established. Band structure calculations with different techniques describe the measured spectra differently well. Agreement with the experiment is achieved by generalized gradient approximation (GGA) method. (c) 2006 Elsevier B.V. All rights reserved.