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Abstract: The electronic structure of Ge x As40− x S60 glasses and amorphous films has been obtained by means of X-ray photoelectron spectroscopy. Core level peaks and valence band spectra in the dependence on the composition as well as on structural changes initiated by illumination and/or annealing have been investigated and discussed. [Copyright &y& Elsevier]

The present paper reports the XPS study of different high sulfur content amorphous oxysulfides thin films MOySz (M=W, Ti), prepared by radio frequency magnetron sputtering in a pure argon or mixed oxygen/argon plasma. Two types of thin layers are analyzed in this work, synthesized with an oxygen partial pressure equal to 0 and 2×10-4 Pa. On the basis of both core peaks and valence bands, several types of sulfur ions were observed and revealed the specific character of such amorphous layers. In order to precise the common features and the differences as a function of the nature of the metal atom, a comparison of the XPS data for the two kinds of thin films has been done. The results are also commented with respect to theoretical calculations (FP-LAPW—code WIEN97) undertaken on crystallized reference compounds. [Copyright &y& Elsevier]

Abstract: We have investigated the reaction mechanisms occurring upon the first discharge/charge cycle of a MnSn2//Li electrochemical cell, by using bulk- and surface-sensitive characterization techniques (X-ray Diffraction, 119Sn Mössbauer spectroscopy, magnetic measurements, X-ray photoelectron and Auger spectroscopies). Compared to other tin-transition metal alloys, MnSn2 displays an original behaviour. Lithium insertion into MnSn2 particles results in a nanocomposite consisting of Li7Sn2 phase, and of Mn nanoparticles which are immediately oxidized at their surface. Lithium extraction from this nanocomposite leads to the formation of magnetic MnSn2 particles and to our knowledge it is the first time such a mechanism is observed in tin-based intermetallic electrode materials due to electrochemical reaction with Li. The solid electrolyte interphase (SEI) is formed at the beginning of the first discharge and its thickness slightly increases upon further lithium insertion. A partial re-dissolution process occurs upon lithium extraction from the material, while its chemical composition is very stable over the whole cycle. [Copyright &y& Elsevier]

Abstract: The present paper deals with a fine physico-chemical analysis of some hybrid materials combining an inorganic layered double hydroxide phase (LDH) with an organic benzene derivative entity R′-C6H4-R with R = –SO3 −, –CO2 − and R′ = –H, –OH. The main topic of this work is, in a nanoscale, to propose a way to approach the understanding of the interactions between inorganic and organic sub-systems. The role of the anionic headgroup R is discussed in term of reactivity with the mineral support. The classical expertise of materials via the PXRD technique puts into light an effective LDH interlayer space enlargement with the organics incorporation and a minimum angle of inclination for every organics within the LDH matrix. The originality of this study is to use the X-Ray Photoelectron spectroscopy (XPS) as a local probe of the chemical environments of the headgroup of the organic entities. In a parallel way, some quantum calculations (by using molecular and periodical codes) are carried out to best appreciate the electronic and structural evolutions before and after the intercalation step. A specific reactivity of the –SO3 − group compared with the –CO2 − one is evidenced. Moreover, a correlation at the first order is then set up between the net charges of atoms and the XPS binding energies of their core levels. [Copyright &y& Elsevier]

Abstract: Ag y V2O5-type thin films have been deposited by radiofrequency (rf) magnetron co-sputtering either in a pure argon or in a mixed argon/oxygen atmosphere with 14% oxygen partial pressure using a metallic Ag target and a V2O5 target. The silver content in the thin films has been controlled by simply varying the rf power ratio applied to the two targets. We have investigated the influence of the dopant on the thin film composition, the structure and the morphology as well as on their electrochemical performances compared to undoped V2O5 thin films prepared in the same sputtering conditions. The thin films have been analyzed by various characterization methods such as Rutherford Backscattering Spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy, X-ray diffraction, Scanning Electron Microscopy and electronic conductivity measurements. Electrochemical characterization has been carried out on two peculiar compositions: Ag0.32V2O4.6 (obtained in absence of oxygen) and Ag0.26V2O5 (prepared under PO2 =14%). Furthermore, the redox processes occurring during lithium insertion and de-insertion have been investigated by using XPS. The Ag0.32V2O4.6 thin film is amorphous and dense with a smooth surface and shows a good cycling stability as well as discharge capacity values similar to thus obtained for an amorphous V2O5 thin film prepared in absence of oxygen. The Ag0.26V2O5 thin film is amorphous, porous and shows improved discharge capacities compared to crystallized V2O5 thin films, probably due to the additional participation of silver ions to the redox processes. Nevertheless, a continuous capacity fading is observed, as already mentioned for porous crystallized V2O5 thin films. [Copyright &y& Elsevier]

Abstract: Sputtered vanadium pentoxide thin films have been used as positive electrode in lithium microbatteries and extensively studied after cycling over the 31st galvanostatic cycles by two complementary techniques, especially well-adapted for thin films analysis: X-ray photoelectron spectroscopy and atomic force microscopy. This study is mainly focussed on the characterization of the surface film (solid electrolyte interface-type) which is formed during subsequent discharges and charges and especially on its composition and its morphology that are changing during cycling. First, the growth of a surface layer between the positive electrode and the liquid electrolyte has been evidenced upon the discharge as well as its partial dissolution upon the charge. Secondly, the chemical and topographic changes of this interfacial layer at various stages of cycling are discussed in correlation with the evolution of the discharge capacity over cycles. [Copyright &y& Elsevier]

Abstract: Research into new negative electrode materials as an alternative to carbonaceous materials brings new questions about electrode/electrolyte interface mechanisms. For graphite, these mechanisms have great importance on the ageing phenomena. What about intermetallic alloys, such as Cu–Sn systems? The nature of the electrode and its potential of lithium ions uptake (different from graphite) may have a great influence on the passivation film formed at the surface of the electrode. In this paper, we report on the XPS study of the electrode/electrolyte interface of a Cu6Sn5-based electrode. The main difference with graphite is not the nature and composition of the passivation layer, but its poor dependence on the electrochemical reaction during cycling. [Copyright &y& Elsevier]