Analysis of X-ray photoelectron spectra of silicon-based polymers by deMon density functional calculations using model molecules

The X-ray photoelectron spectra (XPS) of seven silicon-based polymers[ (-Si(CH3)(2)-)(n) (PDMS), (-Si(C6H5)(CH3)-)(n) (PMPS), (-Si(n-C6H13)(2)-)(n) (PDHS), (-Si(CH3)(2)-O-)(n) (PDMSO), (-Si(C6H5)(CH3)-O)(n) (PMPSO), (-Si(CH3)(C6H5)-CH2-)(n) (PMPSM), and (-Si(C6H5)(2)-CH2-)(n) (PDPSM)] in XPS were analyzed by deMon density-functional calculations using model molecules. Calculated Al-K-infinity valence photoelectron spectra were obtained using Gaussian lineshape functions of an approximate linewidth (0.10I(k)): I-k=I-k-WD, as in previous works. The vertical ionization potential I-k was calculated by restricted diffuse ionization (rDI) model. The theoretical spectra showed good agreement with the observed spectra of the polymers between 0-40eV. The core-electron binding energies (CEBEs) of Cls, Ols and Si2p of the model molecules were calculated by unrestricted generalized-state (uGTS) models. The difference between calculated and the observed CEBEs for Cls reflected WDs of the polymers.