Auger Scanning Electron Microscopy Research Articles

Anodic Oxidization of Aluminum at High Current Densities and Mechanism of Film Formation

Galvanostatic anodization of aluminum at high current densities (100, 150, 200 mA cm−2) was studied. The growth rates of the synthesized anodic aluminum films were 1-3 μm/min. Films with ordered pores or with a fractal surface were also prepared. Consequently, nonlinear anodization and hypothesis for film formation are proposed and applied to elucidate experimental results. Transmission electron microscopy (TEM) and scanning Auger electron microscopy (SAM) were applied to acquire supplementary experimental results to support the proposed hypothesis. TEM shows that initial oxygen bubbles were collected on the boundary of neighboring hexagonal cells, channels for bubble liberation were located in the center of hexagonal cells. By profiling on SAM, depth profiles of Al and O atoms in the film were obtained, and the assumption that oxygen evolution plays positive roles in ion transfer during anodizing was supported indirectly. Although the validity of the hypothesis needs further testing, some points of the assumption are supported. © 2004 The Electrochemical Society. All rights reserved.

Identification of the segregation layer and its effects on the activated sintering and ductility of Ni-doped molybdenum

Previous literature has shown that the sintering temperature of molybdenum compacts can be decreased significantly through activated sintering by adding a small amount of nickel. This nickel doping, however, reduces the ductility of the material. A number of studies have postulated mechanisms to explain this enhanced sintering and embrittlement, but little direct evidence has been reported to date. In this study, the use of a field emission transmission electron microscope and a scanning Auger electron microscope has identified a δ-NiMo intermetallic compound film, about 2 nm thick, at the grain boundaries. An experiment focusing on the Mo/Ni-Mo diffusion couple shows that the δ-NiMo layer at the grain boundaries serves as a short-circuit diffusion path and causes the activated sintering of Ni-doped molybdenum. This compound is, however, intrinsically brittle and thus is the root cause of the embrittlement problem of Ni-doped molybdenum.

Characterization of aluminum–organic‐stabilized platinum–colloid networks with electron and photon spectroscopies

AbstractWe have measured and interpreted the ultraviolet (HeI) and X‐ray photoelectron spectra and the metastable impact electron spectra (MIES) from aluminum–organic‐stabilized platinum–colloids and colloid networks, deposited on silicon substrates and characterized by X‐ray photoelectron spectroscopy, scanning Auger electron microscopy and transmission electron microscopy. MIES, in particular, gives information on the electronic structure of the spacer molecules interconnecting the colloids.In addition, changes in the electronic structure of the platinum clusters that are induced by different spacer molecules were identified by means of X‐ray absorption near‐edge structure measurements at the platinum LIII‐edge of these materials. This combination of techniques was also employed to follow the chemical changes that occur upon heating of the network in situ. It turns out that the thermal decomposition of the network is driven by the disintegration of the spacer molecules. Moreover, less sintering of the colloidal particles occurs in the networked systems than in unconnected particles. Most of the networked platinum–particles are still present in their original shape even after the destruction of spacer molecules. This observation could be linked to the encapsulation of these platinum particles into an (AlO) protecting shell. Copyright © 2003 John Wiley & Sons, Ltd.

Surface metallization of alumina ceramics by pulsed high energy density plasma process

Surface metallization of alumina ceramics was carried out by pulsed high energy density plasma (PHEDP). A layer of copper film was deposited on the surface of alumina ceramics. Scanning auger electron microscopy (SAM) analysis revealed that copper diffused deep into the alumina substrate. Bonding of alumina and copper film was good. The reaction between copper and alumina was studied by X-ray diffraction (XRD) analysis. A copper aluminum oxide unstable at high temperature and very difficult to be synthesized, cubic phase CuAl 2O 4, was detected. A kinetics complexity in reaction of PHEDP and ceramics was discussed. An adiabatic model was used to describe heating and quenching of the PHEDP processing and analyze the interaction between PHEDP and alumina ceramics. The experimental results suggest that PHEDP method is a useful technology for various metal–ceramics bonding.

Crystallinity effects on primary beam and Auger electron signal intensities observed for graphite

This paper shows the experimental outcomes of a study of crystallinity dependent diffraction effects on both elastically-scattered and Auger electrons produced from highly-oriented pyrolytic graphite (HOPG) using a commercial scanning Auger electron microscope (SAM). This system is equipped with a coaxial cylindrical mirror analyser (CMA). Scanning electron images (SEM), backscattered electron images (BSE), Auger maps and the Auger spectra, using a range of relatively low incident electron energies, are obtained and analysed in detail. It is shown that the regional contrast shown in the SEM and BSE images and in the Auger maps, in the electron energy range used, is formed predominantly by forward focusing along the close-packed 〈2 1 ̄ 1 ̄ 2〉-type atomic chains of the graphite lattice. The intensity of the exiting electrons received by the CMA can be interpreted as a convolution of the diffraction of both incident and exiting electrons, e.g. that of the exiting elastically scattered electrons can vary by up to 50% on changing the incident direction of the primary beam and the orientation of the specimen. Increasing the energy of incident beam enhances forward focusing and increases the contribution from diffraction along the secondary close-packed atomic chains, e.g. the 〈3 3 04〉-type atomic chains present. The carbon (KLL) Auger electrons produced are found to behave in a way similar to the primary electrons in regard to the diffraction process but with less marked diffraction evident.

Control of frictional force on coating films of boron nitride–copper complex in ultra high vacuum

Boron nitride–copper complex (BN/Cu) films were synthesized using a magnetron co-sputtering method using different discharge times. The frictional force of the coating films of BN/Cu was observed with a vacuum-friction measuring system with variable vacuum pressure. Scanning auger electron microscopy and contact angle measurements were carried out in order to characterize the BN/Cu films. Two elements of surface energy were estimated from the contact angle of two solutions. Frictional coefficients as low as 0.1 were achieved for the BN/Cu films under ultra high vacuum (UHV) conditions. It was found that alteration of the composition of boron nitride with copper in the mixture under different discharge times was effective in controlling the frictional force on the film surface under UHV.

Surface potential measurement with high spatial resolution using a scanning Auger electron microscope

The microscopic surface potential distributions were measured from the onset energies of secondary electron spectra using a scanning Auger electron microscope. The spatial resolution is several tens of nanometers and a sensitivity of the surface potential measurement is 0.05 eV. We demonstrated the calibration of the instrument for local surface potential analysis based on the onset energy measurement of the secondary electron spectrum. Several applications of this technique for Ni polycrystal grains of different orientations, and a potential profile along the p–n junction of a light-emitting diode were demonstrated.

Surface electromigration of In on vicinal Si(0 0 1)

Surface mass transport of In film on vicinal Si(0 0 1) has been systematically investigated by a scanning Auger electron microscopy (SAM), low energy electron diffraction (LEED) and atomic force microscopy (AFM). It was observed that the temperature dependence of the mass transport shows the critical phenomenon. Above a critical temperature T c, surface electromigration of the In film toward the cathode side dominated the surface mass transport on the vicinal Si(0 0 1) surface. The LEED and AFM observations revealed that the In film surface on the vicinal Si(0 0 1) consists of 3×4 terraces and (3 1 0) facets. The area ratio of the facet to the terrace exhibited abrupt an increase at T c. It is believed that the change of the mass transport is related to the abrupt change of the area ratio of the facet to the terrace. Both the critical temperature T c and the spread due to the surface electromigration of the In film depended on the configuration of the DC current direction and the step edge.

Electrodeposition of Multilayered Ni–Cr Films from Sulfate–Oxalate Electrolytes

As shown by scanning Auger electron microscopy and Auger electron spectroscopy, multilayered Ni–Cr thin films can be deposited under the action of periodic currents from sulfate–oxalate solutions containing nickel and chromium ions. The chromium-rich layers have an amorphous structure. In the nickel/chromium interphase region, the carbon content is elevated. Nickel layers contain admixtures of a hydroxide nature.

Chemical, morphological and accumulation phenomena in ultrashort-pulse laser ablation of TiN in air

Ultrashort-pulse laser ablation (τ=130 fs, λ=800 nm, repetition rate 2–20 Hz) of titanium nitride was investigated for laser fluences between 0.3 and 4.5 J/cm2 using the direct focusing technique in air. The influence of the laser pulse number and the peak fluence was investigated by means of several surface analytical techniques (optical microscopy, dynamic friction atomic force microscopy, scanning Auger electron microscopy and small-spot electron spectroscopy for chemical analysis). The correlation of the results about optical, physical and chemical properties of the irradiated areas allows us to propose a simple oxidation model, which explains different observed phenomena associated with surface damage such as mound formation and crater widening and clarifies the incubation behavior reported earlier for this material.

Synthesis and characterization of boron carbon nitride films by radio frequency magnetron sputtering

Boron carbon nitride (BCN) films were deposited on silicon substrates by radio frequency (r.f.) (13.56 MHz) magnetron sputtering from hexagonal boron nitride (h-BN) and graphite targets in an Ar–N 2 gas mixture of a constant pressure of 1.0 Pa. During deposition, the substrates were maintained at a temperature of 400°C and negatively biased using a pulsed voltage with a frequency of 330 kHz. Different analysis techniques such as X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD) and scanning Auger electron microscopy (SAM) were used for characterization. In addition, the mechanical and tribological properties of the films were investigated by nano-indentation and micro-scratching. The carbon concentration in the films could be adjusted by the coverage area of a graphite sheet on the h-BN target, and decreased with increasing bias voltage. It was found that the ternary compound films within the B–C–N composition triangle possessed a less ordered structure. BN, BC and CN chemical bonds were established in the films, and no phase separation of graphite and h-BN occurred. At zero bias voltage, amorphous BC 2N films with atomically smooth surface could be obtained, and the microfriction coefficient was 0.11 under a normal load of 1000 μN. Hardness as determined by nano-indentation was usually in the range of 10–30 GPa, whereas the Young’s modulus was within 100–200 GPa.

Surface analytical studies of metal dusting of iron in CH4-H2-H2S mixtures

The metastable iron carbide, cementite (Fe 3 C), occurs as an intermediate phase during the high temperature corrosion process called metal dusting. The kinetics and thermodynamics of metal dusting of iron have been studied by Grabke et al. [1-5] using CO-H 2 -H 2 O and CH 4 -H 2 gas mixtures. H 2 S additions to carburising atmospheres impede the carbon transfer and retard the onset of metal dusting [6-14], thus allowing to study the early stages of the process. In this work the metal dusting process was studied in CH 4 -H 2 -H 2 S atmospheres at 700°C. Segregation experiments and surface analyses showed that S segregates on iron surfaces as well as on cementite surfaces. By means of Auger electron spectroscopy (AES), scanning Auger electron microscopy (SAM) and energy dispersive X-ray analysis (EDX) it was shown that coke contains graphite, cementite and iron particles with adsorbed sulphur.

CEMS study of iron disilicide formation by iron ion implantation into silicon

Doses from 2 × 10 15cm –2 to 2 × 10 17cm −2 of 57Fe ions were implanted with 40 keV into n-type Si(1 1 1) at 350°C. The iron concentration profiles reach peak maximum concentrations from 0.3 at.% for the lowest dose up to about 34 at.%. For the highest dose a plateau-like profile is formed due to the effect of sputtering. The phase formation of the iron disilicides was studied by 57Fe conversion electron Mössbauer spectroscopy. Depending on the implanted dose two different regions of phase formation are found. For doses ⩽1 × 10 16 cm −2 only the metastable γ-FeSi 2 is present whereas at values ⩾2 × 10 16 cm −2 a mixture of α- and β-FeSi 2 is formed. The phase composition in this second region is dose dependent and with increasing iron content an enlarged fraction of the β-phase is found. At the highest dose of 2 × 10 17 cm −2 mostly β-FeSi 2 and no α-FeSi 2 is present. But additionally to the β-FeSi 2 a second component occurs in the Mössbauer spectrum which is observed for the first time. With respect to the iron concentration this subspectrum could be attributed to a new metastable state of the mono silicide. Different annealings of the as-implanted samples at 900°C and 1150°C lead to the formation of the pure β- and α-FeSi 2, respectively. Additionally to the measurements of the concentration profiles investigations of the lateral element distributions in the layers were performed with scanning Auger electron microscopy. It can be concluded that during the annealing at 1150°C precipitates of the α-FeSi 2 grow in the Si matrix.

Determination of titanium distribution on the catalyst surface of industrial supported Ziegler catalysts by means of scanning auger electron microscopy

Scanning Auger electron microscopy (SAM), which is one of the best surface analytical methods, was applied to achieve basic understandings of the surface distribution of titanium species on supported Ziegler catalysts. Three different types of supported Ziegler catalysts were prepared by grinding MgCl2 with TiCl4 (Cat-A), by grinding MgCl2 with ethyl benzoate (EB) followed by the reaction with TiCl4 (Cat-B), and by reacting TiCl4 with a mixture of Mg(OEt)2 and dibutyl phthalate (DBP) (Cat-C). The SAM analysis revealed that the titanium species were scattered over the surface of Cat-A, while the distribution of the titanium species was rather even on the surface of Cat-B. In the case of Cat-C, the titanium species were found to exist evenly on the surface, and all particles of the catalyst showed a similar tendency. Hence, the influence of the preparation method of the catalyst on the distribution of the titanium species is clearly observed by SAM. Models of the catalyst particles obtained by different preparation methods were proposed on the basis of the results.

Determination of titanium distribution on the catalyst surface of industrial supported Ziegler catalysts by means of scanning Auger electron microscopy

Scanning Auger electron microscopy (SAM), which is one of the best surface analytical methods, was applied to achieve basic understandings of the surface distribution of titanium species on supported Ziegler catalysts. Three different types of supported Ziegler catalysts were prepared by grinding MgCl 2 with TiCl 4 (Cat-A), by grinding MgCl 2 with ethyl benzoate (EB) followed by the reaction with TiCl 4 (Cat-B), and by reacting TiCl 4 with a mixture of Mg(OEt) 2 and dibutyl phthalate (DBP) (Cat-C). The SAM analysis revealed that the titanium species were scattered over the surface of Cat-A, while the distribution of the titanium species was rather even on the surface of Cat-B. In the case of Cat-C, the titanium species were found to exist evenly on the surface, and all particles of the catalyst showed a similar tendency. Hence, the influence of the preparation method of the catalyst on the distribution of the titanium species is clearly observed by SAM. Models of the catalyst particles obtained by different preparation methods were proposed on the basis of the results.

Analysis of the surface of lithium in organic electrolyte by atomic force microscopy, Fourier transform infrared spectroscopy and scanning auger electron microscopy

The surface of lithium has been analyzed in a dry-air atmosphere and in 1 M LiClO4/PC by in situ AFM observation and FTIR spectroscopy. High-resolution AFM discloses the nano-structure of the lithium surface which consists of grain boundaries, many ridge-lines, and flat areas. After immersing lithium in LiClO4/PC, these lines swelled and large particles appeared. The surface chemistry of lithium has been examined by ex situ XPS and SAM. It is found that Li2CO3 and Li2O localize on the ridge-lines and the grain boundaries. The morphological change due to lithium deposition occurs as a formation of particles on the ridge-lines and the grain boundaries.

Determination of titanium distribution on the catalyst surface of industrial supported Ziegler catalysts by means of scanning Auger electron microscopy

Determination of titanium distribution on the catalyst surface of industrial supported Ziegler catalysts by means of scanning Auger electron microscopy

Effects of mercury electrodeposition on the surface degradation of microlithographically fabricated iridium ultramicroelectrodes

The surface degradation of a microlithographically fabricated array of 10 mm diameter iridium ultramicroelectrodes (UME) was investigated using atomic force microscopy (AFM), Auger scanning electron microscopy (SEM), and stripping voltammetry. Micrometer-size accumulations could be observed on the iridium surface after mercury was electrochemically deposited and stripped approximately five times in a perchloric acid media with a Ag AgCl 3M NaCl reference electrode. AFM images of the accumulations revealed that they were pyramidal in shape and had a tendency to form in clusters. Elemental analysis of the clusters with Auger SEM identified them as mercury and a small amount of chloride. The accumulations were determined to be mercurous chloride (Hg2Cl2) with the chloride contamination resulting both from leakage of the reference electrode and the decay of the perchloric acid. During subsequent depositions of mercury, chloride ions were eliminated by using a nitric acid media and a polyurethane solid state reference electrode. With chloride eliminated, mercury could be electrodeposited and stripped at least ten times on the iridium UME array without any visible surface degradation. © 1998 Elsevier Science S.A. All rights reserved.

Failure analysis of microfabricated iridium ultramicroelectrodes in chloride media

This study investigates the failure mechanisms for an electrochemical sensor consisting of an array of microlithographically fabricated iridium ultramicroelectrodes (UME) on a silicon wafer. It has been noted that the use of these sensors during voltammetric determination of heavy metal ions in the presence of >0.1 M Cl − results in loss of response and general failure of the sensor. The addition of Hg or Ag to the Cl containing solution caused massive accumulations on the exposed Ir surfaces, which were identified using auger scanning electron microscopy (SEM). Under analytical conditions this failure does not appear to be due to migration of Cl − but to the penetration of Cl − through pin-holes in the insulating layer and subsequent reaction with the Al interconnect traces on the chip. Consequently, the Al traces dissolved and hydrogen gas was evolved. This reaction generates a potential which is transmitted to exposed Ir and consequently metal ions present in the solution are then reduced onto these surfaces. Several insulating layers, SiO 2 (5000 Å) and Si 3N 4 (1500, 2500 and 5000 Å) were also used, but failure occurred with all. It is critical that either sub-micron sized pin-holes during the fabrication process be better controlled or that the Al interconnect traces be replaced by Au. The use of Au however may still allow these unwanted micron-sized UMEs to interfere with the electrochemical analysis.

New development of a high-resolution scanning ESD system for two-dimensional images of hydrogen and its applications

Currently, many people have focused their study of hydrogen behaviors on solid surfaces because this plays an important role in surface physics and chemistry. Hydrogen is detected easily by a time-of-flight type electron-stimulated desorption spectroscopy (TOF-ESD). Very recently, we have developed way to measure a two-dimensional distribution of hydrogen with high-resolution of less than 1 μm using a thermal field emission (TFE) electron gun. The high detection efficiency of the TOF-ESD system allows various ESD measurements including two-dimensional analysis. This method is complementary to scanning Auger electron microscopy (SAM), since SAM is insensitive to hydrogen but is able to analyze surface concentration for most elements. In this article, we show some results obtained by our TOF-ESD system using a LEED gun and a LaB 6 gun and recent progress using a TFE gun.