[en] We report our investigation of the dependence of the profile extracted from ARXPS data on the value of the regularization parameter α. We argue that a choice based upon the L-curve criterion, which does not require knowledge of the variances in the data, is less satisfactory than an approach based on choosing α such that χ²/N = 1

[en] X-ray photoelectron spectroscopy (XPS) depth chemical and phase profiling of air-oxidized niobium nanofilms has been performed. It is found that oxide layer thicknesses depend on the initial thickness of the niobium nanofilm. The increase in thickness of the initial Nb nano-layer is due to increase in thickness of an oxidized layer.

[en] Competitive adsorption of As(V) and Sb(V) at environmentally relevant concentrations onto ferrihydrite was investigated. Batch experiments and XPS analyses confirmed that in a binary system, the presence of Sb(V) exhibited a slight synergistic effect on As(V) adsorption. XPS analyses showed that As(V) and Sb(V) adsorption led to obvious diminishment of Fe–O–Fe and Fe–O–H bonds respectively. At pH of 9, a more significant decrease of Fe–O–Fe was observed in the binary system than that in a single system, indicating that As(V) displayed an even stronger interaction with lattice oxygen atoms under competitive conditions. Basically, ionic strength demonstrated a negligible or positive influence on As(V) and Sb(V) adsorption in binary system. Study of adsorption sequence also indicated that the presence of Sb(V) showed a promotion effect on As(V) adsorption at neutral pHs. Considering that co-contamination of As and Sb in waters has been of great concern throughout the world, our findings contributed to a better understanding of their distribution, mobility, and fate in environment.

[en] Sorption of pertechnetate on pyrrhotite Fe_nS_n+1 (I) and stibnite Sb₂S₃ (II) from distilled water was evaluated. The distribution coefficients were found to be 185 and 223 cm³/g, respectively. The XPS study of the chemical state of ⁹⁹Tc absorbed on the surface of pyrrhotite and stibnite from aqueous solution of potassium pertechnetate (KTcO₄) was carried out. It was found that Tc(IV) ions are present mostly on the surface of the studied samples, their concentration was 5.7 times higher on the surface of pyrrhotite compared to that on the surface of stibnite. A 13% admixture of Tc(VII) ions on the surface of pyrrhotite was observed.

[en] Highlights: • Method to obtain wide ranges of water contact angles (CA) ∼5° to ∼149° proposed. • Reported effect of length of silicon nanowires and/roughness on final water CA. • Reported how nanoscale variation in PDMS thickness effects hydrophobic recovery. • Studied evolution of water CA vs. time for PDMS coated Si/Si nanowire samples. The ability to modify the contact angle (CA) of water on silicon has applications ranging from thermal management of electronics to miniaturized biomedical devices. Here, we report ∼30 ± 1° variation in superhydrophobic CA on silicon nanowires (NWs) coated with few nm of polydimethylsiloxane (PDMS), using a simple and stable plasma treatment. The variation in CA arises from choosing NWs of different lengths. We characterize the surfaces using a combination of X-ray photoelectron spectroscopy and other techniques. Together with CA available from similar treatment on bulk silicon, it is possible to non-lithographically create regions of diverse CA, from ∼5 to 149 ± 1°.

[en] Highlights: • The efficient passivation of in situ NH₃-plasma pre-treatment on SiC has been investigated by XPS. • PEALD has been performed to deposit HfO₂ on SiC with in situ NH₃-plasma pre-treatment. • The passivated interfacial layer can regulate the band alignments between HfO₂ and SiC. -- Abstract: The efficient passivation of in situ NH₃-plasma pre-treatment and its regulation of the band alignment between HfO₂ and 4H-SiC have been investigated by XPS. With in situ NH₃-plasma passivation by PEALD, a VBO of 0.72 eV and a CBO of 1.54 eV can be obtained across the HfO₂/4H-SiC interface. The Si-O bonds components reduction in the passivated interface layers will lead to band bending or band shift at the interface and regulate the band alignments between HfO₂ and 4H-SiC. The physical mechanism investigation of band alignments can be a cornerstone for the application of HfO₂/4H-SiC heterojunctions in the high-power devices.

[en] It is shown that both sp² and sp³ hybridized structures form in samples modified with fullerene and prepared by fusion, which is indicative of the carbon nanostructure formation. In the samples modified with graphite and prepared by fusion, only graphite-like structures form

[en] We report in this paper an original way to covalently bind the macrocyclic ligand, 1,4,8,11-tetraazacyclotetradecane (cyclam), through diazonium salt chemistry, on the surface of carbon screen-printed electrodes (SPEs). The in situ synthesis of the diazonium salt obtained from the amine precursor derived from the cyclam and its electrografting are described. X-ray Photoelectron Spectroscopy was used to characterize this functionalized surface. Owing to the strong cyclam–Cu(II) affinity, the so called SPE-cyclam can be used as electrochemical sensors for Cu(II) determination at trace levels. The influence of electroanalysis parameters such as the accumulation time and the pH of the medium were investigated. An interference study was carried out with numerous metallic cations and few interference was found for Cu(II) quantification. The described method provided a limit of detection and a limit of quantification of 1.3 × 10"−"8 M and 4.0 × 10"−"8 M, respectively. Interference study and performances show that SPE-cyclam could be considered as efficient sensors for environmental analysis.

[en] Highlights: → Using X-ray photoelectron spectroscopy, we have studied the Mn 2p, Ca 2p, and Pr 4d core levels of Pr_1-xCa_xMnO₃ (x = 0.2, 0.33, 0.4 and 0.84) as a function of x at room temperature as well as 77 K. → Suppression of chemical potential shifts have been observed at 77 K compared to that of room temperature spectra. → We have discussed this result by considering the concept of phase separation. - Abstract: We have studied the Mn 2p, Ca 2p, and Pr 4d core levels of Pr_1-xCa_xMnO₃ (x = 0.2, 0.33, 0.4 and 0.84) as a function of x using X-ray photoelectron spectroscopy both at room temperature as well as 77 K. Suppression of chemical potential shifts have been observed at 77 K compared to that of room temperature spectra. We have discussed this result by considering the concept of phase separation.

[en] The third international workshop on hard X-ray photoelectron spectroscopy (HAXPES 2009) was held at Brookhaven National Laboratory, Upton, New York, from May 20-22, 2009. This three-day workshop brought together approximately 100 scientists from 14 countries to discuss progress and future prospects for this rapidly developing field of research. The conference was sponsored by the National Synchrotron Light Source, the National Synchrotron Light Source-II Project, Brookhaven National Laboratory Condensed Matter Physics and Materials Science Department, and the National Institute of Standards and Technology.