Multipak software

A PHI 5000 VersaProbe instrument (Physical Electronics, Chanhassen, MN, USA) was used for survey, scan and high resolution XPS. The powder was dried in oven at 100 °C for 24 h at atmospheric pressure before analysis and thereafter placed in the XPS pre-chamber overnight, in order to avoid anomalous outgassing during the XPS characterization, performed in UHV conditions (10⁻⁸ Pa). A monochromatic Al K-alpha X-ray source (1486.6 eV energy, 15 kV voltage and 1 mA anode current, and a power of 25.2 W were used for analysis. Different pass energy values were employed: 187.85 eV for survey spectra and 23.5 eV for high resolution peaks. Analyses were carried out with a take-off angle of 45° and with a 100 μm diameter X-ray spot size on a square area of 1400 × 1400 μm², with the aim to have a good average and better statistics of powder behavior. A double beam (electron and argon ion gun) neutralization system, dedicated to reduce the charging effect on samples, was also employed during data acquisition. All binding energies (BE) were referenced to the C1s line at 284.8 eV. Spectra were analyzed and peak deconvolution was performed using Gauss–Lorentz curves by MultiPak software (version 9.6.0, Physical Electronics, Chanhassen, MN, USA).

XPS spectra were collected with a PHI 5600/ESCA system equipped with a monochromatic Al Kα radiation source (hν = 1486.6 eV). High-resolution XPS spectra were deconvoluted with MultiPak software (Physical Electronics) by centering the C-C peak to 284.5 eV, constraining peak centers to ±0.1 eV the peak positions reported in previous literature^{36 (link)}, constraining full width at half maxima (FWHM) ≤ 1.5 eV, and applying Gaussian-Lorentzian curve fits with the Shirley background. AFM images were collected with an MFP-3D system (Asylum) in tapping mode with an NCL-20 AFM tip (force constant = 48 N/m, Nanoworld). Optical properties of the GQDs were studied with absorbance spectroscopy (UV-3600 Plus, SHIMADZU), photoluminescence spectroscopy (Quantamaster Master 4 L-format, Photon Technologies International), and excitation-emission profiles (Cary Eclipse, Varian). MALDI-TOF mass spectra were acquired on an Autoflex Max (Bruker) with a 355-nm laser, in the positive reflectron mode. Samples were added to CHCA matrix.

The photoemission studies XPS (X-ray Photoemission Spectroscopy) were performed on PHI5700/660 Physical Electronics (Chanhassen, Minnesota, USA) spectrometer using Al Kα monochromatic X-ray source with energy 1486.6 eV. All photoelectron spectra were calibrated against the peaks of Au4f_7/2 at 83.98 eV, Ag3d_5/2 at 368.27 eV and Cu2p_3/2 at 932.67 eV of binding energy. The thin film ZrO₂ surface was cleaned in a measuring chamber by using low energy E = 0.7 keV argon ion beam applied at time 1 min. The electronic structure of the ZrO₂ film was tested both for “as received” and ion beam treatment surfaces. The test of the surfaces of the film was carried out at a take-off angle of 45°. The electron float gun was used for the compensation of positive surface charge, which may appear on the insulator materials’ surface. The XPS measurement was carried out for the core lines of O1s, Zr3d, C1s, and valence band region. Atomic concentration calculations and fitting process were performed with the use of Multipak software and SimPeak software from Physical Electronics.

Measurements were carried out using a PHI Quantera SXM instrument (Physical Electronics, Chanhassen, USA) equipped with a 180 hemispherical electron energy analyzer and a monochromatized Al Kα (1486.6 eV) source operated at 15 kV and 4 mA. The analysis spot had a diameter of 200 μm and the detection angle relative to the substrate surface was 45°. Standard deviations were calculated from measurements performed on two different areas. Data were analyzed using the Multipak software (version v.9.6.0, Physical Electronics). The depth probed by XPS analysis is between 5–10 nm.

XPS characterization was carried out using a scanning microprobe PHI 5000 VersaProbe II, purchased from Physical Electronics (Chanhassen, MND, USA), equipped with a micro-focused monochromatized AlKα X-ray source. Specimens were analyzed in HP mode using an X-ray take-off angle of 45°. The instrument base pressure was set at about 10⁻⁹ mbar. Scanned areas of 1400 × 200 μm were acquired. Pass energy values equal to 117.4 and 29.35 eV were recorded in the FAT mode for survey scans and high-resolution spectra, respectively. For high-resolution spectra curve fitting, MultiPak software (version 9.9.0.8, Physical Electronics, Chanhassen, MN, USA) was used. The carbon C1s correction was performed by setting as reference charge (284.8 eV) the adventitious carbon.

The chemical composition of the surface was investigated by XPS analyses with a PHI 5000 Versa Probe II spectrometer (Physical Electronics) equipped with a monochromatic Al Kα X-ray source (1486.6 eV), operated at 15 kV and 24.8 W, with a spot size of 100 µm. Survey (0–1200 eV) and high-resolution spectra (C1s, O1s, Ca2p, P2p, and Nb 3d) were recorded in FAT mode at pass energy of 187.85 and 29.35 eV, respectively. Surface charging was compensated using a dual beam charge neutralization system. All spectra were collected at an angle of 45° with respect to the sample surface. The hydrocarbon component of C1s spectrum was used as an internal standard for charging correction and it was fixed at 284.8 eV. Spectra were processed with MultiPak software (Physical Electronics). Atomic concentrations were determined from the high-resolution spectra after subtracting a Shirley-type background, using the Scofield sensitivity factors set in the MultiPak software.

The surface chemical analysis of the samples was performed using a PHI TFA XPS from Physical Electronics, Chanhassen, MN, USA. The base pressure in the XPS analysis chamber was approximately 6 × 10⁻⁸ Pa. The samples were excited with X-rays over a 400 µm area with monochromatic AlKα_1,2 radiation at 1486.6 eV, operating at 200 W. Photoelectrons were detected with a hemispherical analyzer (Physical Electronics, Chanhassen, MN, USA), positioned at an angle of 45° to the sample surface. A detection depth was approximately a few nm. Spectra were measured at least at two different locations on each sample. Survey spectra were taken at a pass-energy of 187 eV and a 0.4 eV energy step. High-resolution spectra were acquired at a pass-energy of 23.5 eV and a 0.1 eV energy step. An additional electron gun was used to compensate the surface charge accumulation during the measurement. Binding energy was calibrated by setting the C1s peak at 284.8 eV. The MultiPak software (Physical Electronics, Chanhassen, MN, USA) was used to calculate the surface elemental concentrations from the survey scan spectra.