Papers by Keyword: XPS

Abstract: We report on time-dependent Positron annihilation induced Auger Electron Spectroscopy (PAES) study on 0.5 monolayers (ML) Ni on polycrystalline Pd accompanied by complementary X-ray induced Photoelectron Spectroscopy (XPS). The normalized PAES spectra showed a significant decrease in the Ni intensity and an increase in the Pd intensity as a function of time. To rule out varying influence on the elements e.g. from surface contaminates due to the residual gas, a time-dependent XPS analysis was performed on pure Ni and Pd as well as to analyze the main contaminants C and O. The O fraction was found to be constant within the measurement time and the time constants for C significantly differ from those of Ni and Pd in the PAES data. Consequently, it was concluded that the PAES data show a superposition of C contamination and structural changes at the surface of Ni/Pd.

Abstract: The liquid lead-bismuth eutectic (LBE) alloy is of great interest for applications in future nuclear reactors. The structure and clustering of alloying elements have been investigated on an extended range of temperature (125-720 °C) by high temperature X-ray diffraction (HT-XRD), XPS and scanning photoemission microscopy (SPEM) at the ELETTRA synchrotron in Trieste. After melting the short-range order in liquid metal corresponds to a cuboctahedral arrangement of atoms that progressively evolves towards an icosahedral one as temperature increases. Such process, which is completed around 720 °C, is accompanied by a micro-chemical re-arrangement of atoms with changes of cluster size and composition. At high temperature the atom distribution results to be more homogeneous and the average size of clusters noticeably smaller.

Abstract: The beta-phase of Zn₄Sb₃ has been regarded as a very promising thermoelectric material since middle nineties, owing to its unique merit: intermediate temperature region (200-400 °C), made of cheap, non-toxic and abundant elements and high thermoelectric property. However, the thermal stability of Zn₄Sb₃ seems to be an inherent obstacle for the practical application during the working temperatures. Herein, magnesium doped Zn-Sb semiconductor (Mg_0.04Zn_3.96Sb₃) was investigated thoroughly in-situ during thermal annealing up to 600 K, whilst both microstructure and electronic structures were recorded via the combination of synchrotron-based two dimensional X-ray diffraction techniques and the X-ray photoemission spectroscopy. While the time-resolved grazing incidence XRD reveals the preserved crystal structures during thermal annealing to 600 K, XPS measurement demonstrate the robustness of electronic structures. On basis of these findings, it was concluded in the end that the doping of magnesium significantly improves the thermal stability of zinc-antimonite compounds and introduces minor influence on the electronic structure of Zn-Sb alloy. Our study may propose an effective approach towards the wild application of Zn₄Sb₃ related thermoelectric materials.

Abstract: We discuss several mechanistic approaches and experimental data for improving post-CMP cleaning of W plugs with TiN as barrier liner, and dielectric substrates SiO₂ and Si₃N₄ for use at the 10 nm technology node (metal pitch of 40 nm). Particle charge in the low pH, W CMP slurries are usually positive, and the W surface is always negatively charged at pH >3. Therefore, a strong electrostatic attraction is expected to occur between the W surface and the residual particles during post-CMP cleaning. Two main approaches were chosen to break down the strong particles-W surface post-CMP electrostatic interactions, as well as particles dispersion and prevention of redeposition: (1) using cleaning additives able to adsorb at the W surface and reverse the W surface charge; (2) using organic additives to reverse the particle charge. The latter approach results in two strongly negative charged surfaces, which are able to repulse each other, and leads to the best cleaning.

Abstract: A study was conducted on the corrosion behavior and characteristics of the passive oxide film of Fe-Mn-Si-Cr-Ni-(Co) shape memory stainless steels (SMSS) in a concentrated nitric acid (HNO₃) solution, based on potentiodynamic polarization, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses. The results indicated that Fe-Mn-Si-Cr-Ni-(Co) SMSSs exhibit a passive behavior similar to that of 304L austenitic stainless steel (304L SS). However, unlike 304L SS, their high silicon (Si) content renders them insensitive to intergranular attack in highly oxidizing environments. The XPS analysis also indicated that Si appears to be the main element responsible for the high protectiveness afforded by the passive film formed on Fe–Mn–Si–Cr–Ni–Co SMSS.

Abstract: Kenaf fibers were immersed in 6% solution of sodium hydroxide (NaOH) for 1, 2, 3, 4 and 5 hours. The treated fibers were characterized with X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The XPS results showed that the alkali treatment increased the proportion of oxygen atoms on the fiber surface as indicated by the increase in oxygen-carbon ratio. An increase in C2 peak (C-OH bonds) was also observed suggesting the present of cellulose on the fiber surface. The decrease in C1 peak (C-C bonds) suggested that lignin was removed from the fiber surface following the alkali treatment. Scale-like structures were observed from the AFM topographic images to indicate the presence of cellulose microfibrils in the primary cell wall of the treated fiber. Alkali treated fiber surface showed lower mean surface roughness than the untreated fiber indicating smoother fiber surface. The fiber surface became relatively smooth after the alkali treatment due to the removal of non-cellulosic layer.

Abstract: The purpose-built pyrolysis system based on an ultrasonically generated aerosol has been successfully used for deposition of highly transparent and conductive undoped tin (IV) oxide thin films. The morphological, structural, optical and electrical properties as well as electronic structures of the films for different concentrations of SnCl₄.5H₂O used as the starting precursor were investigated. FE-SEM displayed the substrate surfaces were uniformly covered with the film. The film thickness varied with the precursor concentration. XRD patterns showed the deposited films were a tetragonal phase and presented random orientations. The optical transmission spectra of all films revealed highly transmittance in the visible region. Refractive index of the films was between 1.85 and 2.0. XPS spectra for the Sn 3d_5/2 and Sn 3d_3/2 confirmed that the films were composed of SnO and SnO₂ phases. The non-stoichiometric composition decreased with increasing concentration of the precursor. The films deposited with 0.30 M showed the highest conductivity and carrier concentration of 17 W^-1cm^-1 and 9.5 x 10¹⁹ cm^-3, respectively. The disagreement of relation between XPS and Hall measurement suggested the higher carrier concentration arose from incorporation of residual chlorine from the solution precursor during deposition into the films. The interstitially incorporated chlorine considerably influenced the electrical properties of the films.

Abstract: The Sirius Project is an initiative of the Brazilian Synchrotron Light Laboratory - LNLS (CNPEM - MCTI), for the design, construction and operation of a new synchrotron radiation source 3rd generation, with high brightness and energy of the electrons of 3.0 GeV. Among many other components there will be built 80 ceramic cameras embedded in special magnets, whose function is to act to correct the orbit of the electron beam in the storage ring. The ceramic chamber is crucial for this application because this material is transparent to the magnetic field generated in the electro magnet and thus acts directly on the electron beam. The difficulty of these constructive components lies in the fact that, the ceramic components must be attached to metal components will join vacuum chambers that make up the ring, and then must present excellent mechanical and vacuum tight. The process of chemical bonding between the ceramic and metal components is performed by brazing in high vacuum. After brazing, a film is deposited of copper with 7 micrometers thickness. The objective of this paper is to describe the process of film deposition and brazing of copper and the excellent results obtained in the production, mechanical characterization, microstructural and tightness.

Abstract: The absorbed liquids in the substrate material may have a potential influence on atmospheric pressure plasma treatment. In order to investigate how the influence of ethanol pretreatment affects atmospheric pressure plasma treatment, nylon 6 films were treated by helium/oxygen plasma using atmospheric pressure plasma jet (APPJ). Water contact angle of the ethanol pretreated samples was close to that of the control. Scanning electron microscopy (SEM) showed that the ethanol pretreated sample surface had a little change on the surface. X-ray photoelectron spectroscopy (XPS) showed that the carbon component decreased and the oxygen component increased after plasma treatment. With the ethanol pretreatment, the T-peel strength values for the samples were similar to that of the control.

Abstract: Structural investigations of Si quantum dots (QDs) grown by CVD on two different heterostructures: AlN/Si (111) and 3C-SiC/Si (100) are conducted. The Si QDs have been grown using silane as precursor, diluted in hydrogen, at fixed temperature and pressure (830°C - 800mbar). High densities of dots can be obtained (up to 10¹¹ cm^-2) with typical heights below 10nm. The kinetic of deposition lets suppose the presence of an initial wetting layer before the dots formation. Different durations are required for nucleating dots on AlN and 3C-SiC. Si QDs on AlN present a luminescence band which can be attributed to quantum confinement.