The small peak existing at 152.2 eV KE was referred to an Auger peak of sulfur (S) contamination by Vaughan et al. Since the O2s bands are closer in energy to Zr4p than with Zr4s, the overlap of O2s wave function with Zr4p is much stronger than Zr4s and can explain the non-equal shift in Auger transitions. This difference suggests a variation in the interactions between Zr-O and O-O with increasing oxygen content 30. The M 45(O)N 1(O)N 23(O) and M 45(O)N 23(O)N 23(O) are shifted of about 3.6 and 5.6 eV respectively. In order to investigate the valence band behaviour and the Auger transitions of ZrO x as a function of oxygen incorporation, several thin film samples were prepared with magnetron sputtering under different argon/oxygen atmosphere that led to various \(\frac\) = 1.3 film. Based on Auger transition corrections, an attempt to correlate the obtained results with the structural properties of ZrO x will be presented. Auger transitions involving valence bands could therefore be used as a reference for charge correction of the XPS spectra and give a better understanding of the evolution of the valence bands upon oxidation. The study of Auger, core-level and valence spectra using XPS and Ultraviolet Photoelectron Spectroscopy (UPS) of the ZrO x films showed that the variation of the oxidation state do not influence the position of the O2p bands but rather the band edge of the upper valence band. In Figure 3, we see high energy resolution spectra acquired from the copper samples, A. The ability to detect and quantify this shift makes XPS such a powerful analytical technique. This method allowed us to avoid the charging effect and to eliminate the contribution of the substrate to the measured signal. peaks in finer detail, then we see that even for the same element, the peak energy may shift depending on the surface chemistry. In the current investigation, the oxidation state of the films as well as their thicknesses have been controlled directly by reactive magnetron sputtering.
This large range between reported values has been puzzling both experimentalists and theoreticians and no clear explanation has been given up-to date 19.Īlthough previous studies already addressed surface oxidation of metallic Zr under various oxygen atmosphere using photo-electron spectroscopy techniques 20, 21, 22, 23, they did not provide a full interpretation of the valence behaviour of ZrO x films. As an example, we mention that the reported band gap value of ZrO 2 varied from 3.8 to 5.8 eV for the monoclinic phase depending on the measurement techniques 15, 16, 17, 18. Indeed, the build-up of static charges at the surface for thicknesses above 5 nm can randomly shift the measured spectra 13, 14 depending on the thickness, micro-structure of the film and exposure time to X-ray photoelectron spectroscopy (XPS) excitation. Using photo-electron spectroscopy techniques to study the properties of such an insulator is a challenging task.
ZrO 2 still attracts attention of other fields, thus the understanding of its electronic behaviour is crucial for the development of various technology sectors. EDS analysis of cross-sections revealed a gradual P reduction up to 50% towards the inner part of the membrane.Zirconium dioxide (ZrO 2) has been studied extensively due to its physical and chemical properties, whether in high temperature fuel cells 1, 2, 3, gas sensors 4, 5, 6, protective coating for metal anti-corrosion 7, 8, 9, or insulator on metal-oxide semiconductor devices 10, 11, 12. The introduction of a neutralization step led to a reduction of P content, which pointed out to the presence of phosphates ionically bound to protonated amines, in addition to phosphate esters. High-resolution XPS spectra regarding C1s, O1s, N1s and P2p are discussed. The phosphate content increased with the reaction time, as shown by XPS and ATR-FT-IR, a P/N atomic ratio of 0.73 being obtained after 48 h of treatment. Cross-sections were analyzed by SEM fitted with EDS.
Surface characterization was performed by XPS, ATR-FT-IR, and SEM. Phosphorylation was carried out at room temperature using the H3PO4/Et3PO4/P2O5/butanol method. Additionally, the negatively charged phosphate functionalities, together with the positively charged amine groups from chitosan, are expected to provide chitosan with an amphoteric character, which may be useful as a combinatorial therapeutic strategy, by simultaneously allowing the immobilization of signalling molecules like growth factors. Phosphate groups chelate calcium ions, thus inducing the deposition of an apatite-like layer known to improve the osteoconduction of polymer-based implants. Phosphorylation may be of particular interest in materials for orthopaedic applications, due to the cation-exchange properties of phosphate functionalities.
In the present work, the surface of chitosan membranes was modified using a phosphorylation method carried out at room temperature.