Structure of the  Cl-passivated Ge(111) surface determined using X-ray absorption and first principles  calculations

Z.H. Lu^a, T. Tyliszczak^b, A.P. Hitchcock^b and M.W.C. Dharma-wardana^c

^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.