Structure of the Cl-passivated Ge(111) surface determined using X-ray absorption and first principles calculations
Z.H. Lua, T. Tyliszczakb, A.P. Hitchcockb and M.W.C. Dharma-wardanac
aDepartment of Metallurgy and Materials Science,
University of Toronto, Toronto, ON M5S 3E4, Canada
bBrockhouse Institute for Materials Research, McMaster University, Hamilton, ON L8S 4M1, Canada
cInstitute for Microstructural Sciences, Ottawa, ON K1A 0R6, Canada
Received 3 May 1999, accepted for publication 30 August 1999
Cl 1s (K-shell) near-edge and extended X-ray absorption fine structure spectroscopy (EXAFS), and first-principles calculations have been used to quantify the Ge(111)-Cl surface structure. Cl passivation is achieved in ambient atmosphere by wet chemical methods. Strong polarization, observed both in the Cl 1s -> 3p s-resonance and in the extended fine structure region, proves that Cl forms a stable monochloride structure with Cl bonded to Ge in the atop position. A stable atop Cl-Ge monochloride structure was also found in our theoretical calculations. The calculated Ge(111)-Cl surface structure was used to refine the structural parameters by matching Feff calculations to the un-filtered experimental EXAFS signal. Excellent agreement between theory and experiment was found with the atop monochloride structure with a Ge-Cl bond-length of 2.17 ±0.01 Å. 1999 Elsevier B.V. All rights reserved.
Keywords: Germanium, Surface structure, SEXAFS, Ab initio quantum chemical methods and calculation.