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

Cl1s (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 Cl1s→3p σ 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 unfiltered 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±0.01Å.