Multipak

The chemical surface compositions were analyzed by high-resolution X-ray photoelectron spectroscopy (XPS) using a PHI VersaProbe II (Ulvac-phi, Inc., Chigasaki, Japan) with a monochromatic Al-Kα source, and photon energy of 1486.6 eV. The X-ray source used had a power of 100 W, whereby the sample surface was scanned with a beam size of 100 µm over an area of 1400 × 200 µm². High-resolution spectra of the coated and uncoated samples (n = 6) were recorded with a pass energy of 46.95 eV and a step size of 0.1 eV, with a constant electron take off angle of 45°. The spectrometer was calibrated to the copper and gold reference lines (932.62 eV and 83.96 eV), whereas the minimum detector resolution measured at the silver peak Ag (3d5/2) was 0.6 eV, with a pass energy of 23.5 eV. The measurements were obtained at room temperature and a base pressure of 2 × 10⁻⁶ Pa. To avoid charging effects, all measurements were carried out with charge compensation by utilizing a cold cathode electron flood source and low-energy argon ions. All spectra were shifted to the carbon peak (C1s) to 284.6 eV. The data analyses were performed using the software MultiPak (version 9.9.0.8, Ulvac-phi, Inc., Chigasaki, Japan).

The samples were analyzed using a TFA XPS spectrometer (Physical Electronics Inc., Chanhassen, MN, USA) equipped with a monochromated Al-Kα X-ray source under ultra-high vacuum. The high-energy-resolution spectra of the characteristic peaks for elements Fe 2p, Fe 3p, O 1s, N 1s, and C 1s were recorded over a narrow energy range. The spectra were analyzed using MultiPak, Physical Electronics Inc., Chanhassen, MN, USA.

X-ray photoelectron spectroscopy (Quantera II, Physical Electronics, Chanhassen, MN, USA) was used to further elucidate the chemical composition of the surface of the samples. Survey scans were taken at a pass energy of 140 eV, after which atomic percentage concentrations were calculated from the elemental peak area. Results were averaged after 10 measurement cycles. Prior to measurements, samples were sputtered at 500 V for one minute to remove surface contamination. Ion and electron guns were turned on during measurements to neutralize the surface charge build-up of the non-conductive samples. Data analysis was performed using the MultiPak software (Version 9.6, Physical Electronics, Chanhassen, MN, USA).

XPS spectra of the pristine PDA and LAPDA films were obtained using Phi 5600 XPS (Perkin Elmer, USA) to analyze atomic compositions. A monochromatic X-ray source (Al Kα) was used for the data collection. To avoid the effect of surface charging, the neutralizer was applied simultaneously to the surfaces with a constant current (~1 µA). The at.%s were calculated by deconvolution of the XPS spectra with MATLAB-based software (MultiPak) provided by Physical Electronics, Inc.