Quantitative XPS Analysis of PEG-Modified Silicon Surfaces

Poly(ethylene glycol) (PEG) films were covalently coupled to silicon surfaces using a solution phase and a vapor phase technique. These methods are targeted for creating nonfouling PEG films on silicon bio-microsystems. We used X-ray photoelectron spectroscopy (XPS) to better understand and analyze PEG functionalized silicon surfaces. Elemental surface composition was obtained from survey spectra for various PEG modified surfaces. Further, high-resolution C-1s scans were taken to ensure the presence of the characteristic C−O bond, which confirms the coupling of PEG on the silicon surface. Percent C−O was analyzed theoretically to better understand the formation of thin PEG films on silicon surfaces. Also, the thickness of the PEG film was estimated using the standard overlayer model.