Valence band structure of PDMS surface and a blend with MWCNTs: A UPS and MIES study of an insulating polymer

•Valence electron spectroscopy was performed on an insulating polymer using different charge compensation methods.•MWCNT were embedded in PDMS and found to be the most effective method for reducing the charging of the insulating polymer.•The valence band spectrum of PDMS was obtained via MIES and UPS.•Ion scattering spectroscopy was used to determine the concentration depth profile of the PDMS in the sample. The use of polydimethylsiloxane (PDMS) is increasing with new technologies working toward compact, flexible and transparent devices for use in medical and microfluidic systems. Electronic characterization of PDMS and other insulating materials is difficult due to charging, yet necessary for many applications where the interfacial structure is vital to device function or further modification. The outermost layer in particular is of importance as this is the area where chemical reactions such as surface functionalization will occur. Here, we investigate the valence band structure of the outermost layer and near surface area of PDMS through the use of metastable induced photoelectron spectroscopy (MIES) paired with ultraviolet photoelectron spectroscopy (UPS). The chemical composition of the samples under investigation were measured via X-ray photoelectron spectroscopy (XPS), and the vertical distribution of the polymer was shown with neutral impact collision ion scattering spectroscopy (NICISS). Three separate methods for charge compensation are used for the samples, and their effectiveness is compared.