Electron Spectroscopy For Chemical Analysis Measurements Research Articles

Anomalous diffusion effects in ion implanted MgO single crystals

The effects of niobium and rubidium ion implantation on monocrystalline (100) MgO slices have been investigated using Rutherford backscattering spectrometry in channeling geometry (RBS), electron spectroscopy for chemical analysis (ESCA) and optical absorption measurements. Analysis of the implantation profiles have been performed on samples implanted at 300 K with energies of 150 and 320 keV and doses ranging from 2 × 10 15 to 2 × 10 17 ionscm −2. For doses above 10 16 ionscm −2, the implantation profiles differ significantly from theoretical predictions of the “TRIM” code and exhibit a marked depth diffusion effect of implanted particles. Moreover, a particularly high fraction (between 60 and 95%) of implanted atoms in substitutional sites is evidenced. It has to be noticed that even for the highest doses the amorphization of the implanted layer does not occur. The different chemical states of atoms in the implanted layers investigated by ESCA and optical measurements have been correlated with RBS results in order to precise the anomalous diffusion effects of implanted species.

Surface oxidation by microwave-induced plasma of candidate composite materials for space shuttle protection

Oxidation resistance of composite materials (SiC/SiC, C/SiC and C/C) which can be used to protect shuttles is studied in oxygen microwave-induced plasmas (MIP). These plasmas contain the same energetic species (electrons, ions, radicals, excited atoms or molecules) as those produced by the shock wave resulting from re-entry into the atmosphere. The plasma is sustained in a silica tube located in a resonant cavity and microwave energy is supplied by a generator operating at 2450 MHz with variable power from 15 to 1000W. Experiments are conducted at pressures from 100 to 1000 Pa with temperature ranging from 1100 to 1300 °C. The atomic oxygen flow rate is about 6.1019 at sec−1 cm−2. The wafers are exposed to the plasma for 10 to 25 h for periods of 15 or 30min. Kinetic behaviour of the material is studied by gravimetry and surface characteristic modifications are analysed by BET Krypton isotherms at 77 K and electron spectroscopy for chemical analysis (ESCA). Gravimetric results, measurements of specific surface area by krypton adsorption and ESCA analysis show that the samples of SiC/SiC and C/SiC are quite resistant to the oxygen plasma even after 25 h exposure. The mass loss is small and the specific surface area (BET) increases but is always lower than 1 m2 g−1. ESCA analysis shows that the surface evolves by change of the superficial silicon carbide into silica. The C/C samples behave quite differently: without any protection they disappear in less than 5 min. With an antioxidant protective layer, this material can be oxidation resistant. The BET and ESCA measurements show that the attack leads to a sintering of the silica which gathers on the fibres, reducing the protection of the matrix.

Electrical conductivity of plasma-polymerized organic thin films: Influence of plasma polymerization conditions and surface composition

An attempt has been made to prepare plasma-polymerized organic thin films with considerably high electrical conductivity at room temperature without doping. As the starting monomer, 3,4,9,10-perylenetetra-carboxylic dianhydride (PTCDA) was specifically used. The conditions of plasma polymerization have been found to significantly influence the electrical conductivity of the prepared samples. ESCA (electron spectroscopy for chemical analysis) measurements have suggested a possible important role for nitrogen, when it is used as a carrier gas, as it may be incorporated in the skeleton of the samples and cause an increase in the electrical conductivity.

化学蒸着した珪化タングステン薄膜と多結晶シリコンとの密着性の評価

It is not easy to evaluate thin film/substrate adhesion and to characterize the thin film/substrate interface when adhesion is strong. For this purpose, a new method (scratch-ESCA test), which is a combination of the scratch test, the peeling (by adhesive tape) test, and the ESCA (electron spectroscopy for chemical analysis) measurement, has been developed and is applied to the study of CVD (Chemically vapor deposited) WSix (tungsten silicide)/poly (polycrystalline) Si adhesion. In addition to the conventional adhesion evaluation by the scratch test, it is possible to evaluate adhesion by measuring (with ESCA) the amount of WSix film peeled off from poly Si by an adhesive tape after the scratch test. At the same time, WSix/poly Si interface can be characterized from the results of this ESCA measurement.The results of the above adhesion evaluation are found to have a good correlation with the tendency of WSix films to delaminate or peel during semiconductor device manufacturing processes. The interface characterization by ESCA shows that the WSix adhesion is affected by the presence of such elements as F, O, C and N at this interface.It is believed that this scratch-ESCA test will be a powerful tool for the adhesion evaluation of well-adhering thin films, determination of various factors influencing adhesion, and characterization of interfaces in general.

Microstructure of poly[polytetrahydrofuran‐block‐poly(sebacoylchloride‐alt‐hexamethylenediamine)] and its role in blood compatibility

AbstractThe microstructure of poly[polytetrahydrofuran‐block‐poly(sebacoyl chloride‐alt‐hexamethylenediamine)]s 1–4, containing polytetrahydrofuran (PTHF) blocks of various molecular weights, and their blood compatibility were studied. These multiblock copolymers were prepared by interfacial polycondensation. The characterization of these copolymers was carried out by means of transmission electron microscopy (TEM), differential scanning calorimetry (DSC), dynamic mechanical measurements, wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS), and electron spectroscopy for chemical analysis (ESCA). The TEM observation revealed the formation of a spherulitic structure at the copolymer surfaces, which is closely related to the homopolymer, polyamide (PA) 610. The DSC and dynamic mechanical measurements indicate the presence of distinct phase separation between PTHF and PA 610 blocks, and of the PTHF block in the copolymer being partially crystallized. The WAXD and SAXS indicate the formation of microstructures composed of crystalline and amorphous phases in the copolymer. Moreover, ESCA measurements verify that the surface chemical composition of the copolymer is identical to their bulk composition. Blood compatibility of these copolymers was evaluated by estimating platelet adhesion on the copolymer surfaces. Platelet adhesion was found to be affected by the PA 610 crystallinity, including the size and distribution of the crystalline phase in the case of the copolymers in which the PTHF blocks are completely amorphous (M̄n = 980). On the contrary, platelet adhesion at the copolymers in which the PTHF blocks are partially crystallized (M̄n ≥ 1560) depends upon the crystallinity of both PA 610 and PTHF, including the balance of crystalline (PA 610 and PTHF) and amorphous (mainly PTHF) phases. This result suggests that the balance of the crystalline and amorphous phase distribution in the copolymer is the most determinative factor for suppressing platelet adhesion at the copolymer surface.

Quantitative chemical analysis by ESCA

Abstract Electron spectroscopy for chemical analysis (ESCA) can be used as a quantitative tool for the determination of the chemical composition of the surface region of a solid if certain parameters are known. The least well known is the electron mean free path. We present values of the electron mean free path for inelastic scattering as a function of energy for all elemental solids (with the exception of the rare earths and the actinides) and we give formulae for the calculation of the mean free paths for compounds. It is shown that this information makes it possible to deduce from ESCA measurements the relative concentration of atoms or molecules distributed homogeneously in the surface region of a material.