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

Cl 1s (K shell) near-edge and extended X-ray absorption fine structure spec troscopy (EXAFS), and first-principles calculations have been used to quant ify 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 sigma resonance and in the extended fine structure region, p roves 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 fou nd in our theoretical calculations. The calculated Ge(111)-Cl surface struc ture was used to refine the structural parameters by matching Feff calculat ions to the unfiltered experimental EXAFS signal. Excellent agreement betwe en theory and experiment was found with the atop monochloride structure wit h a Ge-Cl bond length of 2.17+/-0.01 Angstrom. (C) 1999 Elsevier Science B. V. All rights reserved.