bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser microprobe mass analysis (LAMMA) and adsorption study of aliphatic alkylammonium ions and alkylamines on asbestos fibre surfaces
Authors: De Waele J. K. , Verhaert I. , Vansant E. F. , Adams F. C.
Published: December 2004

The adsorption–desorption behaviour of aliphatic alkylamines for asbestos was studied. A high affinity and strong adsorption characteristics, controlled by Van der Waals interaction and steric hindrance were obtained. For the RnNH4−nCl (1 ⩽ n ⩽ 4) doped asbestos fibres, the laser microprobe mass analysis (LAMMA) technique was used to analyse selectively the individual asbestos surface loadings. Only for quaternary (and tertiary at higher concentrations) ammonium products, could a semi‐quantitative picture of the organic asbestos surface covering be observed.
The reactive behaviour of the BCL3/H2/steel system
Authors: Than E. , Luthardt M. , Marx G. , Finster J. , Meisel A.
Published: December 2004

For the description of reactions between solids and gases it is important to investigate the compositional changes in the surface of the solid as a function of temperature and reaction time. Conventional methods of surface analysis cannot be applied in such investigations under atmospheric pressure. We have used the techniques of thermal analysis by emission spectrography (TESG) and of X‐ray photoelectron spectroscopy (ESCA). Work with aggressive gases under atmospheric pressure was done in a special reactor, connected by a vacuum‐lock directly to the ESCA spectrometer. Thus we have been able to establish characteristic reaction temperatures in the BCl3/H2/steel system and to assign them to certain surface changes. From that a model for the initial phase of the formation of the boride layer on a plain carbon steel has been derived.
XPS surface and bulk studies of heat treated palladium in the presence of hydrogen at 150°C
Authors: Moddeman W. E. , Bowling W. C. , Carter D. C. , Grove D. R.
Published: December 2004

Palladium metal powders used for hydrogen isotope pumping were studied for their bulk and surface chemistry changes during cleaning with hydrogen gas at 150°C. Cleaning is necessary to promote rapid hydriding and dehydriding and to prevent contaminant ingrowth in the process gas during use. These studies show that heating the powders in vacuum at moderate temperatures (150°C) in a reducing environment removes surface oxide, leaves a predominately palladium metal surface which presents no significant barrier to hydrogen absorption or desorption, and shows no loss in surface area and pourability. A surface model of PdO is given and XPS results show that the water‐forming reaction is the mode of PdO reduction. Thermodynamic data are discussed which support the above results.
Ignition mechanism of the titanium–boron pyrotechnic mixture
Authors: Burke A. R. , Brown C. R. , Bowling W. C. , Glaub J. E. , Kapsch D. , Love C. M. , Whitaker R. B. , Moddeman W. E.
Published: December 2004

Titanium–boron pyrotechnic reactions are essentially gasless, are very exothermic, and are known to initiate only at extremely high temperatures. The reactants are stable in normal laboratory environments and require no special sample handling, such as inert storage. These factors make the titanium–boron mixture ideal for one‐shot thermal heat source applications. Mound has been investigating energetic material ignition properties for a number of years. Pyrotechnic mixtures of TiHx/KClO4 have revealed that the surface composition of the titanium fuel was TiO2 and its presence on the fuel's surface controls the TiHx + KClO4 reaction. In the present study the surface chemistry of titanium and of boron have been examined before ignition. To understand the effect of temperature on the reactants and the mixture, titanium powder, boron powder, and blends were analyzed at ambient and elevated temperatures. XPS, TG and DTA results presented will show that the oxide on boron is the controlling factor in the ignition mechanism of the titanium–boron pyrotechnic reaction.
Morphological and chemical changes in palladium alloy gauzes used for platinum recovery in high‐pressure ammonia oxidation plants
Authors: Fierro J. L. G. , Palacios J. M. , Tomás F.
Published: December 2004

Scanning electron microscopy (SEM) combined with energy dispersive x‐ray analysis (EDX) and x‐ray photoelectron spectroscopy (XPS) have been used to study platinum recovery by catchment on palladium alloy gauzes placed at the outlet of high‐pressure plants for ammonia oxidation. It has been found that Pt evaporated from the Pt–Rh catalyst gauzes is efficiently recovered by a pack of Pd gauzes situated downstream. During this process important geometrical, morphological and chemical changes take place. In general, the wire diameter increase depends on the gauze position in the pack and also on the initial wire diameter. This diameter increase, due to Pt alloying, is accompanied by deep recrystallization and faceting. Chemical analysis by both EDX and XPS revealed that the Pt/Pd ratios depend markedly on the position in the catchment pack, and also on the orientation with respect to the stream (front or back face). In addition, nodular Rh2O3particles randomly distributed over the Pd alloy surface have been observed. An explanation for these features is given.
Damage and recovery by electron and ion beam irradiation during AES analysis of silicon oxynitrides
Authors: Bender H. , Chen W. D.
Published: December 2004

Damage and recovery induced by electron and ion beam irradiation during AES analysis of silicon nitride and oxynitrides are discussed. The results show that after prolonged electron beam irradiation, a damage peak is induced in the Si LVV spectrum. The initial incubation time decreases for higher electron current densities and for higher O/N rations. The electron beam‐induced damage is irreversible. The silicon nitride and oxynitrides are very susceptible to damage by energetic ion impact. However, this damage is reversible: the surface can be recovered by irradiation with an electron beam in the ultra‐high vacuum system when the electron current density is kept low. The damage recovery is related to the irradiation time, the current density and the beam energy, as well as to the preparation method of the layers. The degree of damage and recovery are characterized by the fraction of ‘covalent’ silicon and silicon nitride obtained from factor analysis of the Si LVV spectrum. The mechanism of the damage and recovery will be discussed.
The effect of thin titanium oxide layers on the wettability of thin‐film nickel metallization
Authors: Thomas Iii J. H. , , Hitch T. T.
Published: December 2004

Monolayer thickness TiO2contamination layers are shown to be detrimental to reflow soldering of thin‐film nickel, which is a part of the Al‐Ti‐Ni metallization system used in backplane metallization of silicon chips. Measurements based on real‐time flow of Pb‐Sn(10 wt.%)‐Ag(2 wt%) alloy solder show that the presence of approximately one monolayer of TiO2plus NiO on Ni raises the temperature at which solder begins to flow in the forming gas (10% H2) by 100°C over that of a clean NiO native oxide layer on Ni. Surface chemistry was determined using x‐ray photoelectron spectroscopy and Auger electron spectroscopy. Solder pool area measurements as a function of solder temperature were used to determine qualitatively the wettability of a surface. Poorly wetting surfaces show a negative slope. In this study, the slope was negative at equivalent Ti coverages, as determined by Rutherford back‐scattering analysis, of 0.65 nm or greater. The wettability of the surface appears to be controlled by TiO2at 0.65 nm or above and may be related to the ability of the forming gas to reduce the surface oxide sufficiently at the soldering temperature to permit flow. Therefore, small amounts of Ti that may diffuse through the nickel layer of the three‐metal thin‐film metallization system can have significant effects on the wettability of the Ni surface.
Effects of SO2 deposition on painted steel surfaces
Authors: Davis G. D. , Shaw B. A. , Arah C. O. , Fritz T. L. , Moshier W. C. , Simpson T. C. , Moran P. J. , Zankel K. L.
Published: December 2004

The effects of 1 ppm SO2 with high humidity on alkyd‐painted steel was investigated using x‐ray photoelectron spectroscopy (XPS) and adhesion tensile tests. The SO2 caused a spotted discoloration on the specimens on which dew is allowed to dry and accelerated the loss of adhesion between the primer and the steel. The brown spots are characterized by a high S content and form in areas where the condensed dew becomes more concentrated in H2SO3 or H2SO4 as it evaporates. Specimens not exposed to dew also have high S concentration on the surface, but do not discolor. High humidity alone caused a loss of adhesion at the primer–metal interface, but SO2 increased the rate of this de‐adhesion. Such a loss of adhesion decreases the protection provided by the paint system and the presence of Fe on both sides of some failures indicated that the substrate was beginning to corrode.
Depth profiles of Ag/Si(111) thin‐film interface regions
Authors: Chambers G. P. , Sartwell B. D.
Published: December 2004

The metal/semiconductor interface region of in situ deposited Ag thin films prepared on a Si(111) substrate has been investigated using AES sputter depth profiling in conjunction with proton‐induced x‐ray emission (PIXE). Interface regions have been modeled with the interface analysis program LOGIT, developed at the National Institute of Standards and Technology (NIST). Values for the parameters obtained from this model indicate that the rate of ion beam sputtering through samples prepared without simultaneous low‐energy ion activation tended to be noticeably greater than the rate of sputtering through samples prepared with simultaneous ion activation. Further, we found that one effect of the ion beam is temporarily to shift the fractional Ag surface coverage to higher values. The likely mechanism for this shift is sputter redeposition by the ion beam of Ag atoms from large nucleated Ag islands, transporting them to open areas between islands. These results support conclusions from an earlier study, which found that the effect of low‐energy simultaneous ion beam activation during thin‐film deposition was to shift the mode of growth of Ag on an Si(111) substrate from an SK (layer‐plus‐island) to an FM (layer) growth mode, to a degree dependent on the conditions of simultaneous ion co‐bombardment.
Deposition of MgO/Au cermet films by triode sputtering and their characterization
Authors: Ritz Victor H.
Published: December 2004

Cermet films, which consist of a mixture of insulator and metal microcrystals, have been suggested as a way to achieve high secondary‐electron emission with good electrical conductivity in cathodes for high‐power microwave tubes. We have radio frequency (rf) sputtered 75% MgO and 25% Au (mol.%) films, 4000 Å thick, from composite targets in a turbopumped ultrahigh vacuum system. A triode sputtering source operated at 1.8 mTorr Ar pressure provided high deposition rates (60 Å min−1) over the surface of a cylindrical cathode that was rotated slowly to insure uniform deposition. The low pressure of the triode sputtering source enabled one to operate in a region of the Thornton structure‐zone diagram (J. Vac. Sci. Technol. 11, 666 (1974)) conductive to the formation of densely packed grains (zone T). The cathode substrate was sputter‐etched before film deposition to remove the surface oxide and contamination, and the deposited cermet was lightly sputtered afterwards with low‐energy Ar ions to enhance the surface MgO concentration by preferential sputtering. The resulting films were characterized by AES and SEM as to their bulk chemical composition, surface contamination, film morphology and thickness. The deposition rate in a geometry in which a small, relatively inexpensive, disk‐shaped target was used to coat a larger cylindrical substrate could be approximated by correcting an average planar deposition rate for the difference in areas. The films showed no evidence of a porous columnar structure but were finely grained and densely packed. Films deposited on Type 304 stainless‐steel substrates adhered well and passed simple adhesive tape tests. The films were the same composition as the sputtering target, with no bulk C contamination or impurity migration from the substrate.
Characterization of nitrogen distribution profiles in fcc transition metal nitrides by means of Tc measurements
Authors: Lengauer Walter
Published: December 2004

The suitability of characterizing the nitrogen distributions in near‐surface regions of compact samples of TiN, ZrN, HfN, VN and NbN by means of a series of inductive Tc measurements with successive etching was investigated. The distribution profiles could be determined for TiN, ZrN and VN with an accuracy exceeding that of established microanalytical tools. One problem encountered in the characterization process was the non‐isotropic removal of layers. For HfN and NbN, nitrogen profile measurements were not possible because of the intrinsic Tc behaviour.
Water interactions in Al/PET
Authors: Chtaïb M. , Peremans A. , Novis Y. , Caudano R. , Butaye L. , Adams F. , Lutgen P. , Feyder G.
Published: December 2004

Two cases of water interaction with virgin PET and with metallized (Al) PET were studied using thermal desorption spectroscopy (TDS) and dynamic secondary ion mass spectrometry (SIMS), respectively. On the one hand, the TDS approach tends to show that the water is weakly bound to the polyester (∼ 10 kcal mol−1); on the other hand, the SIMS study performed on metallized PET shows an enhancement of the water concentration around the interface. These results are discussed in order to elucidate the presence of such moisture and its influence on the metal/polymer adhesion and corrosion.
XPS investigation of anodic oxides grown on p‐type InP
Authors: Faur Maria , Faur Mircea , Jayne D. T. , Goradia M. , Goradia C.
Published: December 2004

Chemical composition of anodic oxides grown on lightly doped p‐type InP have been investigated by XPS. Anodization was performed in the constant current density (Jc) mode using an ortho‐phosphoric acid solution mixed with acetonitrile (ACN). The electrolyte was chosen after experimentation on the effect of the anodization parameters (electrolyte, viscosity of the electrolyte and pH,Jcand illumination level) and annealing conditions on the uniformity and stability of the oxide and the contamination level, as determined by SEM/EDAX, SIMS and XPS. Based on our XPS investigation, it appears that the inhomogeneity with depth of the anodic oxides grown on p‐type InP is strongly dependent on the growth conditions. Depending on the anodization procedure, the anodic oxide appears complex and the presence of In(OH)3, In2O3, InPO4, In(PO3)3, In(PO3)4and other non‐stoichiometric In(POy)xcompounds have been identified. Depending on the anodization conditions, it appears that both amorphous and crystalline phosphorus‐rich condensed phosphates, of interest for surface passivation of InP, can be grown on p‐type InP.
Interpretation of surface textural changes in SrTiO3 ex‐oxalate samples using XPS and IR spectroscopies
Authors: Munuera G. , Gonzalez‐Elipe A. R. , Espinos J. P. , Lopez‐Molina E.
Published: December 2004

XPS, IR and x‐ray diffraction (XRD) have been used to study high‐surface‐area ‘ex‐oxalate’ polycrystalline SrTiO3 materials. Changes of surface area and pore size distribution are induced during lixiviation with a 0.1 M HCl solution, which removes carbonate impurities. The study shows the presence in the original sample of a microcrystalline SrCO3 phase at its surface and isolated CO species, these latter remaining even after outgassing at 773 K for 15 h. However, a complete elimination of the SrCO3 and other carbonate species at the surface is achieved by heating the acid‐lixiviated sample at 773 K, although carbonate species still remain in the bulk of the SrTiO3 material after this treatment. The usefulness of the combined use of XPS and IR for the characterization of surface and bulk species in this type of powdered material is pointed out during this study.
Spectral properties of the Al and Mg Kα1 lines determined by the PAX method
Authors: Richter K. H.
Published: December 2004

The Lorentzian widths and the spin‐orbit separation of the Al and Mg Kα1 lines have been studied, using photoelectron spectroscopy for the study of x‐rays10 and neon and argon as converter atoms. The natural widths of the title lines have been determined. The recommended properties of the Al and Mg Kα1 lines are collected in Table 3.
Study of surface passivation of InP
Authors: Faur Mircea , Faur Maria , Jenkins Phillip , Goradia Manju , Bailey Sheila , Jayne Douglas , Weinberg Irving , Goradia Chandra
Published: December 2004

The effects of various surface preparation procedures, including chemical treatments in HF, HNO3,o‐H3PO4and H2SO4solutions and anodic oxidation, on the passivating properties of InP have been investigated in order to optimize the fabrication procedures ofn+porp+nInP solar cells made by thermal diffusion. The InP substrates used in this study werep‐type Cd‐doped to a level of 1.7 × 1016cm−3, Zn‐doped to levels of 2.2 × 1016and 1.2 × 1018cm−3andn‐type S‐doped to 4.4 × 1018cm−3. The passivating properties have been evaluated from photoluminescence (PL) data; good agreement was found between the level of surface passivation and the composition of different surface layers as revealed by x‐ray photoelectron spectroscopy (XPS) analysis.
Determination of the atomic mixing layer in sputter profiling of Ta/Si multilayers by TEM and AES
Authors: Hofmann S. , Mader W.
Published: December 2004

Sputter‐deposited multilayers of Si and Ta with a nominal period length of a double layer (Ta + Si) of 20 nm were studied with AES depth profiling and with transmission electron microscopy (TEM). The asymmetric shape of the measured Si layer profiles was fitted to model calculations based on preferential sputtering of Si and an atomic mixing zone length of 4 nm for 3 keV Ar+ ions at a 36° incidence angle. TEM images of cross‐sections of the original sample show sharp Si/Ta and Ta/Si interfaces, with a width of ∼ 0.5 nm. The atomic mixing zone length of the sputter‐profiled sample was observed directly by TEM and was determined to be 4.0 nm, in accordance with the AES profile evaluation. It is concluded that the observed asymmetric broadening of the shape of the measured AES sputtering profiles is due mainly to atomic mixing and is enhanced by preferential sputtering of Si.
XPS analysis of passive films on the amorphous alloy Fe70Cr10P13C7: Effect of the applied potential
Authors: Rossi A. , Eisener B.
Published: December 2004

Passive films formed in 1N HCI at different potentials on mechanically polished samples of the alloy Fe70Cr10P13C7 were studied by XPS surface analysis. The thickness of the films increases with the applied potential; at 0.4 V/SCE (saturated calomel electrode) a discontinuity is observed. The passive films are enriched in chromium oxyhydroxide; phosphates are incorporated in notable amounts. The substrate underneath the film is enriched in phosphorus. The outstanding corrosion resistance of this alloy may thus be attributed to this enrichment of phosphorus underneath the film, reducing to a great extent the ionic conductivity of the interface, and to the incorporation of phosphates in the passive film.
Calibration of a basic secondary ion mass spectrometer, by means of elastic recoil detection, for hydrogen isotopes implanted into graphite
Authors: Paynter R. W. , Turgeon S. , Sabet‐Sharghi R. , Leblanc L. , Pageau J. F. , Ross G. G.
Published: December 2004

A secondary ion mass spectrometer equipped with a low‐resolution argon ion source and a small quadrupole ion mass analyser was calibrated for moderate to high concentrations of hydrogen and deuterium in graphite. The polished graphite samples were implanted with hydrogen isotope ions of 1 or 2 KeV energy. The depth profiles of the implanted hydrogen were determined by means of elastic recoil detection (ERD) and compared with those obtained by SIMS. Linear correlations were found between the peak D+/C+ or CH+/C+ ratio and the maximum D or H concentration determined by ERD, as well as between the integral of the SIMS profile curves and the total quantity of hydrogen isotope.
SIMS imaging studies of the corrosion of alloy 800 and alloy 600 surfaces under secondary side boiler conditions
Authors: McIntyre N. S. , Davidson R. D. , Weisener C. G. , Taylor K. R. , Gonzalez F. C. , Rasile E. M. , Brennenstuhl A. M.
Published: December 2004

The nickel‐rich superalloys Alloy 600 and Alloy 800 have been corroded in mildly alkaline deuterated aqueous conditions typical of secondary coolant circuits in a nuclear power station. The oxide films and substrates of these alloys have been analysed by imaging SIMS depth profiling, which makes it possible to describe elemental distribution in all three dimensions. The measurement of the distribution of the secondary ions NiO−, FeO− and CrO− appears useful for detailing the behaviour of nickel, iron and chromium within oxidized phases. The measurement of D− distribution outlines the extent of oxide hydration. For Alloy 800, evidence of sodium migration into the grain boundaries of the alloy substrate is found. For Alloy 600, no grain boundary sodium ingress can be identified under comparable corrosion conditions.
Separation of sample geometry and material effects within the secondary electron cascade: Preliminary results for gold
Authors: Crone M. , Barkshire I. R. , Prutton M.
Published: December 2004

Experimental results are reported for the energy‐analysed angular distributions of the secondary electron cascade with energies from 200 eV up to 2450 eV using an incident beam energy of 20 keV and samples of Au and Au on Si. These angular distributions are compared to those of the Auger electron emission of the same samples. The dependence of the shape of the secondary electron cascade on the angle of incidence and the take‐off angle to the analyser is examined. In the case of Au, the results are reported for a bulk and a layered specimen consisting of a thin Au film on an Si substrate. It is concluded for these samples that the contributions of the sample geometry and atomic number to the shape of the electron spectrum can be separated within a power law description of the secondary electron cascade.
Scanning probe microscope imaging of polyaniline thin films in non‐contact mode
Authors: Porter T. L. , Sykes A. G. , Caple G.
Published: December 2004

The structure of electropolymerized thin films of polyaniline has been studied using the techniques of contact and non‐contact scanning probe microscopy (SPM). Films exposed to Ir+ cations in solution, as well as unexposed films, were examined. Contact‐mode SPM images of these films reveal only a diffuse, amorphous surface structure in both types of film, while non‐contact SPM images indicate an intricate, nanometer‐scale domain structure. Film growth is in a layer‐by‐layer mode, with each layer consisting of small polymer bundles of average dimension 1000 ± 75 Å. The Ir+ incorporation in these films does not involve a restructuring of the film morphology. The relevance of the microscopic domain structure to models describing conduction mechanisms in these films is also discussed.
Applications of focused ion beams in microelectronics production, design and development
Authors: Stevie F. A. , Shane T. C. , Kahora P. M. , Hull R. , Bahnck D. , Kannan V. C. , David E.
Published: December 2004

Focused ion beam (FIB) systems using gallium liquid metal ion sources can remove material with a lateral resolution below 50 nm and can produce metal deposition at a similar resolution with ion beam‐enhanced chemical vapour deposition. These capabilities have resulted in many valuable applications for the microelectronics industry. Circuit modifications are possible because existing connections can be severed and reconnected to different locations. Testing of circuitry can be enhanced by isolation of specific circuits, removal of overlayers and by creation of probe pads where desired. Grain sizes can be determined from secondary electron images by the delineation of individual grains due to orientation‐dependent channeling of the ion beam. Secondary ion mass spectrometry analyses of small areas can provide ion images, elemental identification of small areas and endpoint detection with depth profiles. Scanning electron microscopy and transmission electron microscopy sections are prepared routinely using the FIB. These FIB‐prepared sections are notable because specific features, such as defects, can be exposed and a range of materials including silicon, indium phosphide, gallium arsenide and even metal layers can be cut without distortion. Transmission electron micrographs of superior quality have been obtained with a large area of very uniform thickness that permits identification of features such as areas under stress.
Surface characterization of SiC mirrors exposed to fast atomic oxygen
Authors: Raikar Ganesh N. , Gregory John C. , Partlow William D. , Herzig Howard , Choyke W. J.
Published: December 2004

Two chemical vapor deposited silicon carbide (SiC) mirrors were exposed to the 5 eV fast atomic oxygen environment in low Earth orbit on NASA's Long Duration Exposure Facility (LDEF) which remained in space for nearly 6 years. The samples were characterized using the techniques of x‐ray photoelectron spectroscopy (XPS), ellipsometry, and reflectance measurements. The normal‐incidence optical reflectance of the atomic‐oxygen‐exposed portion of one sample degraded considerably over the 60–160 nm span. The XPS results showed the presence of SiO2‐like species, the thickness varying from 1 to 8 nm depending upon the location of the samples on the spacecraft. The XPS results are in good agreement with those from ellipsometry measurements.
Angle‐resolved XPS study of plasma‐treated teflon PFA surfaces
Authors: Shi M. K. , Martinu L. , Sacher E. , Selmani A. , Wertheimer M. R. , Yelon A.
Published: December 2004

Teflon PFA (polytetrafluoroethylene‐co‐perfluoroalkoxy vinyl ether) was treated by a low‐pressure microwave (2.45 GHz) plasma in O2, N2, H2, He and their mixtures. X‐ray photoelectron spectroscopy measurements showed ablation of fluorine and incorporation of new O‐ and N‐containing groups into the surface. Among the different gases, H2 is the most efficient for defluorination, N2 + H2 for surface functionalization, while O2 showed the least performance for both effects. Plasma treatments using N2 + H2 and O2 + H2 resulted in intermediate defluorination, i.e. between those in the pure gases, and sequential treatment by He/(N2 + H2) showed an additive effect of He and N2 + H2 alone. Angle‐resolved XPS measurements revealed a pronounced gradient in the near‐surface composition following H2, N2 + H2 and He/(N2 + H2) plasma treatments, in contrast to a more uniform depth distribution upon O2, N2 and He exposures. The surface modification of Teflon PFA leads to an enhanced adhesion of metals such as Cu, Ag and Au.
Experimental requirements for surface charge spectroscopy (SCS) measurements. Examples of SCS measurements on high‐ and low‐resistivity Si samples
Authors: Ermolieff A. , Charrasin V. , Marthon S. , Piaguet J. , Deleonibus S.
Published: December 2004

The surface charge spectroscopy (SCS) method investigated by x‐ray photoelectron spectroscopy is used with structures such as semiconductors covered with a thin dielectric layer to estimate the electrical quality of the dielectric film and to determine approximately the breakdown voltage of the dielectric and the interface state density between the semiconductor and the insulator.

The experimental conditions for SCS measurements were investigated and the most important error sources, inducing imprecise or wrong results, were established.

Because of the nature of the sample, binding energy reference is one of the most important points for validity of these measurements. The effects on the determination of the Si 2p photoelectron line position due to bad electrical contact between the spectrometer and the semiconductor, with and without its native oxide film, were studied.

Surface potential modifications when low‐energy flood gun electrons are injected into the dielectric surface were also studied as a function of semiconductor resistivity. Because it is often necessary in SCS measurements to bias the sample, this point was also considered.

Three SCS measurements are reported, two on similar low‐resistivity samples to check reproducibility of the measurements and one on a high‐resistivity sample. It is shown that the determination of the interface state density is uncertain in the case of high‐resistivity samples and how confident it is possible to be in the SCS results.

Two examples of erroneous experiments are also given to illustrate the consequences of inadequate experimental conditions.

It is also pointed out that the SCS method gives information on the electrical properties of very thin dielectric film.
Characterization of MgO layers on different alumina and glass substrates by grazing incidence diffractometry and grazing incidence X‐ray reflectometry
Authors: Wulff H. , Klimke J. , Gerova E.
Published: December 2004

Magnesium oxide thin films were deposited at an average evaporation rate of 1.8 nm s−1 onto different crystalline alumina substrates and amorphous float glass. The deposits were made in an electron‐beam evaporator at substrate temperatures between 25°C and 190°C under different oxygen partial pressures. Films of 0.1, 0.5 and 1 μm thickness were deposited. These coatings were investigated by grazing incidence diffractometry (GID) to vary the depth of penetration. For films 0.1 μm thick the additional use of grazing incidence x‐ray reflectometry (GIXR) was possible. The deposite films were polycrystalline with different 〈100〉 textures depending on the substrate temperature. All the MgO thin‐film reflexes measured were strongly broadened compared with the reflexes of a standard polycrystalline MgO material. The crystal size and the microstrain of the MgO coatings were calculated by profile analysis using the Fourier transformation method. It was demonstrated that the x‐ray profiles of the MgO reflexes are influenced by the roughness of the substrate surface. Only small gradients were found in the particle sizes and microstrains within the deposited films. The oxygen partial pressure did not significantly influence the film properties measured by GID. The GIXR roughness and mass density measurements agreed with the results of GID. Magnesium oxide films deposited at higher temperatures show a diminished crystallinity and less interface roughness.
XPS investigation of surface oxidation and reduction in nanocrystalline CexLa1 − xO2 − y
Authors: Trudeau M. L. , Tschöpe A. , Ying J. Y.
Published: December 2004

Inert gas condensation was used to generate nanocrystalline La‐doped CeO2 − x. Non‐stoichiometric CeO2 − x‐based materials were found to be excellent catalysts in recent studies for the selective reduction of SO2. To understand better the stoichiometry‐related catalytic properties, the surface chemistry of nanocrystalline La‐doped CeO2 − x was investigated through in situ oxidation‐reduction thermal treatments. Oxidation in CO2 and reduction in H2 atmospheres were performed between 30°C and 600°C in a reaction chamber connected to a x‐ray photoelectron spectrometer analytical chamber. Curve fitting and target factor analysis were used to obtain a semi‐quantitative measurement of the transformation between +3 and +4 oxidation states during these reactions. Target factor analysis was found to be a very useful tool for analyzing the contributions corresponding to Ce+3 and Ce+4.
Surface structure and properties of polymers irradiated with hyperthermal atomic oxygen
Authors: Kleiman J. I. , Gudimenko Y. I. , Iskanderova Z. A. , Tennyson R. C. , Morison W. D. , McIntyre M. S. , Davidson R.
Published: December 2004

Surface properties of Kapton® were analysed after different exposures to ground state fast atomic oxygen (FAO) and vacuum ultraviolet radiation in the atomic oxygen beam facility at the University of Toronto Institute for Aerospace Studies. X‐ray photoelectron spectroscopy, scanning electron microscopy and contact angle measurements were used to characterize the chemical and physical changes to the surfaces of the materials analysed. The most important changes in the surface chemistry of Kapton induced by the various exposures to FAO were oxidative degradation of the polymer and substantial changes in supermolecular organization and morphology of the surface layer. A very weak adhesion of the rough top layer to the original Kapton has been observed after an atomic oxygen irradiation with a total fluence of 1.3 × 1021 atoms cm−2, which is comparable to some low earth orbit (LEO) exposures. Comparison was made between pristine samples and the cleaned surface of samples that had been exposed in the atomic oxygen beam facility and in the LEO environment. An ageing effect was observed in the surface layer of exposed samples after a prolonged storage. For several polymer materials, a correlation was found between the erosion yield when exposed to FAO and the dispersion component of the surface tension of the pristine material.
Germanium behaviour during the low‐temperature plasma‐assisted oxidation of SiGe alloys
Authors: Tételin C. , Wallart X. , Nys J. P. , Vescan L.
Published: December 2004

In this paper, we investigate the germanium behaviour during the low‐temperature plasma‐assisted oxidation of strained epitaxial Si1 − xGex (x = 0.1, 0.2) layers. For an oxidation temperature of 500°C and an oxide thickness between 80 and 200 Å, using Auger depth profiling, we find that the oxidation process leads to the formation of a pure SiO2 top layer and the rejection of Ge at the oxide/alloy interface. Taking into account in a suitable way the broadening effect affecting the Auger profiles, we show that a pure Ge layer is formed at the interface.
XPS and SEM characterization of hydrated cerium oxide conversion coatings
Authors: Hughes A. E. , Taylor R. J. , Hinton B. R. W. , Wilson L.
Published: December 2004

Cerium‐rich conversion coatings have been deposited onto aluminium 2024‐T351 alloy by immersion into a solution containing 10 g L−1 CeCl3 and 1% H2O2 in a process described as ‘cerating’. Prior to deposition the alloy had been prepared either by using a standard chemical pretreatment used for aerospace alloys before conversion coating or by polishing. X‐ray photoelectron spectroscopy and scanning electron microscopy have been used to characterize these cerium‐containing conversion coatings. It was found that, during deposition, hydrated cerium oxide initially covered the intermetallics present in the alloy surface and then covered the surface generally. Deposition continued over the intermetallics throughout the conversion coating process, resulting in thick, heavily‐cracked regions considerably greater than the average thickness of the film (>0.3 μm). Elsewhere the coating was generally up to 0.2 μm thick, and appeared to comprised of deposited particles around 100 nm in size.
The effect of aromatic plasticisers on the photo‐dehydrochlorination of poly(vinyl chloride)
Authors: Biggin I. S. , Gerrard D. L. , Williams G. E.
Published: December 2004

A comparison has been made of the effect of ultraviolet and solar radiation on plasticised and unplasticised PVC. It has been shown that, when the polymer, plasticised with either a phthalate or trimellitate ester, is exposed to short‐wavelength ultraviolet radiation (<292 nm), the photodehydrochlorination of the polymer is retarded by the plasticiser. It has also been shown that, when longer‐wavelength radiation is used, the dehydrochlorination is accelerated by the plasticiser. In each case, the effect of the trimellitate is greater than that of the phthalate. Possible mechanisms for the reactions at both long and short wavelengths are considered, and the role of the plasticiser is explained in terms of its electronic absorption spectrum.
PVC and other major plastics in the European economy
Authors: Claus P. G.
Published: December 2004

Following a decade of strong development of plastics consumption, the European market and the production of European manufacturers have fallen back into stagnation since the oil crisis of 1973, followed by the second oil‐price explosior. of 1979. The author presents the reasons of the economic recession prevaling in the European plastics industry for a number of years, notwithstanding the temporary upsurge of 1979, in a review of aspects relative to internal economic government policies in Europe, relative to external trade and relative to the Community's policies towards Third World countries. Prospects for the European plastics industry are considered as a function of economic and industrial government policies in Europe, of development in third countries, and of new approaches by the European industry. The various aspects considered are illustrated in particular by the case of PVC, a typical representative of the major plastics reviewed.
Reasons for PVC bottle development in France
Authors: Decroly Pierre
Published: December 2004

The French PVC‐bottle market represents a consumption of 140,000 tons per year, much more than in other countries; in 1960, this consumption was practically nil. The technical ability to produce bottles suitable for the packaging of food products allowed the first general penetration of PVC in the bottle market. One may eventually observe bit differences from country to country in Europe. In the case of France, it clearly appears that it is the technical and legal possibility to use PVC to bottle mineral waters that had provoked the skyrocketing production of bottles from this material. We will analyze the technical, economical, and sociological reasons that have allowed this development to occur, and examine why other market sectors could not be reached by PVC bottles and why the evolutions were not the same in various countries; future trends will also be outlined.
Predicting heat buildup due to the sun's energy
Authors: Rabinovitch Elvira B. , Quisenberry Joseph G. , Summers James W.
Published: December 2004

PVC building products such as siding, windows, and roofings are exposed to the sun. Absorption of the sun's energy leads to a temperature rise, which may cause dimensional control problems, such as expansion and, in severe cases, distortion of the PVC products. The amount of heat buildup in the product depends on the color and/or pigment system of the PVC compound. Generally, the darker the color, the more the sun's energy is absorbed and the higher the temperature heat buildup. Because of the growing demand for darker colors of PVC building products, a test for measuring temperature rise to predict performance of the product in actual use is needed. A laboratory test method for predicting maximum heat buildup due to the sun is described in this paper. The effects of the sample thickness and gloss, carbon black and titanium dioxide levels, and the distance of an infrared heat source from the sample on the heat buildup are also presented in the paper.
A study of the variables affecting bubble stability in poly (vinyl chloride) plastisols
Authors: Harrell E. R. , Kim J. S. , Gall G. A.
Published: December 2004

The formation of stable air bubbles during processing is one of the most critical problems encountered in many PVC plastisol applications (often referred to as the “air release problem”). Stable bubbles can lead to both cosmetic and structural defects in finished products. Analysis of the air release problem has been difficult not only because air release is affected by many variables (some of which are interrelated), but also because no air release test has been universally accepted as being reliable. This paper presents a comparison of some of the more commonly used air release tests of the PVC plastisol industry, i.e., the Huff ring test, air injection by syringe, and air entrapment by stirring. Our investigation indicates that results obtained from these air release tests strongly depend upon test procedure, test environment, plastisol age, and even the amount of plastisol in the test container. Among the test methods which were examined, air entrapment by stirring was found to be the most convenient and reliable. Possible causes for the observed discrepancies among the tests and data scatter within each test are discussed in terms of variables which affect bubble stability, such as bubble size, rheology, film stress distribution, surface tension, and the Marangoni effect.
Rheology of poly(vinyl chloride) formulations from melt flow index measurements
Authors: Shenoy A. V. , Saini D. R. , Nadkarni V. M.
Published: December 2004

A knowledge of the complete flow curve, or rheogram, of a PVC formulation depicting the variation of the melt viscosity over industrially relevant ranges of shear rate and temperature is essential in the design of polyer‐processing equipment, process optimization, and troubleshooting. These data are generated on sophisticated rheometers that are beyond the financial and technical means of most PVC processors. The only flow parameter that can be readily measured on an inexpensive apparatus is the melt flow index of the resin‐mix. In the present work, a method has been proposed to estimate the rheograms of a PVC formulation at temperatures relevant to its processing conditions with the use of a master curve, knowing the melt flow index and glass‐transition temperature of the formulation. A master curve that coalesces rheograms of different PVC formulations at various temperatures has been generated and proposed as a tool for estimating the flow curve.
The lubrication mechanism of calcium stearate/paraffin wax systems in PVC compounds
Authors: Rabinovitch Elvira B. , Lacatus Emilia , Summers James W.
Published: December 2004

The lubrication mechanism in PVC was studied using calcium stearate and paraffin wax lubricants. Based on the results of the differential thermal analyses, percent haze, microscopy, metal release, Brabender fusion, and extrusion studies we have developed a new theory of PVC lubrication based on molecular structure. Lubricants containing polar groups, which preferentially wet the metal surface in the presence of PVC, such as calcium stearate, are excellent metal lubricants. Non‐polar lubricants which do not wet the metal surface, such as paraffin wax, allow PVC to stick to the metal surface. However, these lubricants work in combination with the metal wetting lubricants to make the lubricant layer more fluid, providing a better lubricating system than either lubricant alone. Lubrication between PVC primary particle flow units is similar to that at the metal surface with the polar PVC surface acting in a similar manner as the metal surface. We find the common classification of lubricants as internal or external to be deficient in explaining performance.
Lubricant behavior in rigid PVC rheology
Authors: Vismara Hugo R. , Capiati Numa J.
Published: December 2004

Capillary rheometry was carried out on lubricated suspension PVC resin at a temperature of 180°C and a shear rate range of 1.5 to 350 sec−1 to specify lubrication efficiency. Correction and discussion for the effects of pressure, non‐Newtonian behavior and viscous heating were done. An indication that the lubricant is localized in the resin free volume appears from pressure coefficient variation. Corrected capillary rheometry showed to be sensitive for low lubricant concentrations (0.3 to 2 Phr) similar to those used in commercial compounds.
Effect of processing on fracture toughness and fatigue crack propagation in unplasticized polyvinyl chloride (uPVC)
Authors: Mai Y. W. , Kerr P. R.
Published: December 2004

The effect of processing on the fracture toughness and fatigue crack propagation rates in unplasticized PVC pipes, both along and perpendicular to the extrusion direction, is evaluated in this paper. The methylene chloride test is used to distinguish between well processed and poorly processed pipes. Well processed pipes have higher fracture toughness under monotonic loading test conditions. However, under impact conditions processing has no significant effects on notched Charpy fracture toughness. For the well processed pipes, there is no directional effect on the fatigue crack propagation rates. For the poorly processed pipes, fatigue crack growth is faster in the extrusion direction, but slight improvement in the processing level removes this difference. Generally, fatigue in the longitudinal direction is independent of the level of processing, but in the transverse (extrusion) direction it is quite sensitive to variations in processing.
Barium/cadmium for the stabilization of rigid vinyl for exterior applications
Authors: Bredereck Peter
Published: December 2004

The highly developed synergistic Ba/Cd stabilizer system for rigid vinyl use in exterior applications is the result of long lasting efforts in this field. By itself, cadmium carboxylate is ineffective because developing cadmium chloride acts as a strong Lewis acid and accelerates the decomposition of PVC. Barium carboxylate converts cadmium chloride formed back into the cadmium carboxylate. Addition of a chelating agent decidedly improves the stability of PVC. A certain ratio of Ba/Cd stabilizer must be retained; best ratio is 6 to 1. The addition of epoxidized soybean oil further improves both heat and light stability of these systems. More than 20 years performance of these formulations has been applied successfully. Increased stability of colored window profiles is effected with the addition of 0.5 parts of a UV absorber. Recommended pigmentations for masstone colored and tinted shades are provided in addition to formulations for white titanium dioxide pigmented profiles.