Structural study of C2D6 thin films adsorbed on MgO (100)

Abstract

The structure of C₂D₆ thin films adsorbed on high homogeneous MgO (100) powder surface have been investigated by means of neutron diffraction techniques at 10 K. Neutron diffraction spectra have been recorded for three different coverages. Two bi-dimensional solids S₁ and S₂ have been determined, respectively for a coverage θ =0.7 layer and θ =1.2 layer. In agreement with LEED measurement, the S₂ phase presents the commensurability C(x2)R45° with the MgO (100) surface. The S₁ phase also presents a commensurate structure with the substrate lattice but its commensurability is weaker than that of S₂. The (2D) solid phase, measured at an intermediate coverage θ =1.0 layer is a mixture of S₁ and S₂. For both solid phases, unit cell, location and orientation of molecules within are determined. The commensurate cell of the S₁ solid with the MgO (100) surface is given.