Jacky Vigneron

High resolution XPS studies of Se chemistry of a Cu(In, Ga)Se2 surface

Chemistry of co-evaporated Cu(In, Ga)Se2 (CIGS) surfaces submitted or not to chemical treatments was investigated by high resolution XPS. The surface analysis allowed us to compare the surface composition with the bulk one as a function of the treatments. We also studied too several standard compounds as Cu2−xSe, In2Se3, ZnSe, Se0 and CdSe. A Se XPS signal specific of the CIGS surfaces was identified. In this paper, we present a detailed study of Se signal in CIGS and show of the different spectroscopic contributions can be separated using standards information. Then, we discuss the chemical origin of these signals and the implications for the device processing.

Polypyridyl ruthenium complexes as coating agent for the formation of gold and silver nanocomposites in different media. Preliminary luminescence and electrochemical studies

Three polypyridyl ruthenium complexes, [(phen)2Ru(2,2′-p-phenylene-bis(imidazo[4,5-f][1,10])phenanthroline)](X)2 (1·X2), [(phen)2Ru((4-pyridine)oxazo[4,5-f][1,10]phenanthroline)](X)2 (2·X2) and [(phen)2Ru((3-thiophene)imidazo[4,5-f][1,10]phenanthroline)](X)2 (3·X2), X− = PF6− or Cl−, have been used to functionalize and stabilize gold and silver nanoparticles in aqueous and non aqueous (acetonitrile) media. Direct interaction between the metallic nanoparticles and the ruthenium complexes was ensured by bidentate chelating phenanthroline (1), monodentate pyridine (2) or monodentate thiophene (3) groups. The influence of several parameters was studied in order to control the size, shape and stability of the nanocomposites thus formed: the nature of the metallic nanoparticles, the nature of the coating ruthenium complex, the ratio R = [Mn+]/[Ru2+] (M = Ag or Au) and the solvent. The colloidal solutions have been characterized by UV-Vis spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Preliminary electrochemical and luminescence measurements have shown the influence of the metallic nanoparticle on the properties of the ruthenium complexes.

Chemical elaboration of well defined Cu(In,Ga)Se2 surfaces after aqueous oxidation etching

Abstract The present work is an attempt to prepare well defined surfaces of Cu(In,Ga)Se2 (CIGS) thin films in order to answer to basic questions about the relationship between bulk and surface composition. The approach is to use an oxidative etch with an aqueous bromine solution, known to lead to specular surfaces. The CIGS surface is then analyzed by mechanical profilometry, SEM and XPS, allowing for determination of the surface roughness and the nature of surface species. After short time bromine etch, a Se0 film is formed on the CIGS surface which can be completely removed by KCN treatment, leaving a CIGS specular surface. An highlight result is that under specific conditions, the surface composition is close to the stoichiometry of the Cu(In,Ga)3Se5 copper deficient phase. This is the first time that such a study is conducted on technology relevant thin polycrystalline CIGS film. It is expected that the method described will help conducting experiments (e.g. Angle resolved XPS, SIMS, etc.) with an improved resolution.

Thin anodic oxides on n-InP studied by photocurrent transients and surface analysis

Investigation of semiconductor/electrolyte interface modified by superficial oxides has been performed with photocurrent transients and surface analysis. Studies of the photocurrent transients before and after the modification of the semiconductor surface exhibit the electrical properties of the interface, whereas XPS analysis gives access to the chemical aspect. This work evidenced a correlation between the level of photocurrent, the surface oxidation and the texture (porosity, thickness) of the oxide layer.

Manganese(III)-Containing Wells–Dawson Sandwich-Type Polyoxometalates: Comparison with their Manganese(II) Counterparts

We present the synthesis and structural characterization, assessed by various techniques (FTIR, TGA, UV-vis, elemental analysis, single-crystal X-ray diffraction for three compounds, magnetic susceptibility, and electrochemistry) of five manganese-containing Wells-Dawson sandwich-type (WDST) complexes. The dimanganese(II)-containing complex, [Na(2)(H(2)O)(2)Mn(II)(2)(As(2)W(15)O(56))(2)](18-) (1), was obtained by reaction of MnCl(2) with 1 equiv of [As(2)W(15)O(56)](12-) in acetate medium (pH 4.7). Oxidation of 1 by Na(2)S(2)O(8) in aqueous solution led to the dimanganese(III) complex [Na(2)(H(2)O)(2)Mn(III)(2)(As(2)W(15)O(56))(2)](16-) (2), while its trimanganese(II) homologue, [Na(H(2)O)(2)Mn(II)(H(2)O)Mn(II)(2)(As(2)W(15)O(56))(2)](17-) (3), was obtained by addition of ca. 1 equiv of MnCl(2) to a solution of 1 in 1 M NaCl. The trimanganese(III) and tetramanganese(III) counterparts, [Mn(III)(H(2)O)Mn(III)(2)(As(2)W(15)O(56))(2)](15-) (4) and [Mn(III)(2)(H(2)O)(2)Mn(III)(2)(As(2)W(15)O(56))(2)](12-) (6), are, respectively, obtained by oxidation of aqueous solutions of 3 and [Mn(II)(2)(H(2)O)(2)Mn(II)(2)(As(2)W(15)O(56))(2)](16-) (5) by Na(2)S(2)O(8). Single-crystal X-ray analyses were carried out on 2, 3, and 4. BVS calculations and XPS confirmed that the oxidation state of Mn centers is +II for complexes 1, 3, and 5 and +III for 2, 4, and 6. A complete comparative electrochemical study was carried out on the six compounds cited above, and it was possible to observe the distinct redox steps Mn(IV/III) and Mn(III/II). Magnetization measurements, as a function of temperature, confirm the presence of antiferromagnetic interactions between the Mn ions in these compounds in all cases with the exception of compound 2.

Cathodic decomposition of InP studied by XPS

Abstract The cathodic decomposition of InP at pH 9 was studied by cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). Under cathodic conditions, the modified surface layer consists mainly of elemental indium (In). In the anodic range, In is converted into In(OH)3. The subsequent cathodic reduction of In(OH)3 to In does not take place to completion, and the amounts of In(OH)3 and In increase irreversibly during cyclic potential scanning.

Porous Anodic Etching of p ‐ Cd1 − x Zn x Te Studied by Photocurrent Spectroscopy

Anodic treatment of p-Cd 1-x Zn x Te (x=0,0.05, and 0.12) in 0.5 M H 2 SO 4 leads to the formation of a network of pores which can extend more than 100 μm below the top surface. Photocurrent spectroscopy reveals the presence of Te° on the surface of the pores. The Te° film is on average thin (≤5 A), in contrast to the thicker film obtained by photoanodic etching of n-CdTe. The photocurrent spectra arc affected not only by the absorbance of Te°, hut also by recombination in the porous layer.

A multiscale approach to assess the complex surface of polyurethane catheters and the effects of a new plasma decontamination treatment on the surface properties.

Polyurethane catheters made of Pellethane 2363-80AE® were treated with a low temperature plasma developed for the decontamination of reusable polymer devices in hospitals. We investigated the modifications of the polymer surface by studying the topographic modifications, the chemical modifications, and their consequences on the wettability and bacterial adhesion. This study showed that plasma treatment modified the topography and grafted oxygen and nitrogen species onto the surface, resulting in an increase in the surface polarity. This effect could be correlated to the number of nitrogen atoms interacting with the surface. Moreover, this study demonstrated the significance of multiscale heterogeneities, and the complexity of industrial medical devices made from polymers. Their surface can be heterogeneous, and they contain additives that can migrate and change the surface composition.

A general route to nanostructured M[V3O8] and Mx[V6O16] (x = 1 and 2) and their first evaluation for building enzymatic biosensors

In order to develop novel electroactive hosts for biosensor design, the possibility to use nanostructured vanadate phases as alternatives to well-known V2O5 gels was studied. For this purpose, the formation of M[V3O8] and Mx[V6O16] (x = 1 and 2) oxides by the sol–gel process has been studied over a wide range of cations (M+ = Li+, Na+, K+, Cs+, and NH4+; M2+ = Ca2+, Mg2+ and Ba2+). By a combination of XRD, 51V NMR and SEM studies, it was possible to evidence the influence of the nature and hydration state of cations on the size and morphology of the resulting particles as well as on the kinetics of their formation. On this basis, K2[V6O16] was evaluated for glucose oxidase encapsulation, either via impregnation or co-precipitation methods. When compared to V2O5, these novel bioelectrodes exhibit higher stability under pH conditions of optimum enzymatic activity, as well as better sensitivity, and reproducibility for glucose detection via amperometric titration.

Photodissolution of n-GaAs electrodes under laser illumination: control of the etching profile

The etching profiles of n-GaAs electrodes are controlled under laser illumination and anodic polarization. Depending on the incident light power and pH of the solution two etching profiles are obtained: at strong alkali or acid pH the photon flux limits the photodissolution of GaAs. The etching profile is Gaussian, reproducing the photon distribution of the laser. This etching profile is associated with an immediate and constant photocurrent. At intermediate pH, the growth of an oxide layer limits the photodissolution of n-GaAs. Therefore we obtained a flat bottom etching profile related to a decrease of the photocurrent to a steady state.