Scanning Electron Microscopy Microprobe Analysis Research Articles

Fission gas release from irradiated mixed-oxide fuel pellet during simulated reactivity-initiated accident conditions: Results of BZ-3 and BZ-4 tests

Fission gas release from high-burnup mixed-oxide (MOX) fuel pellet with Pu fissile contents of 4.1% during reactivity-initiated accident (RIA) was estimated based on radial Xe concentration profiles in fuel pellet using scanning electron microscopy/electron probe microanalysis (SEM/EPMA) before and after pulse irradiation tests called BZ-3 and BZ-4. The tests were conducted at the Nuclear Safety Research Reactor (NSRR) in Japan Atomic Energy Agency (JAEA). The depression of Xe concentration in the Pu-spot and the crack formation in the peripheral region of fuel pellet were observed after BZ-3 and BZ-4. This kind of cracks was considered to promote the release of the fission gas retained in the Pu-spot. Based on the EPMA results and the effect of the crack formation, the amounts of the release of the gas retained in Pu-spot was estimated to be 0.13 and 0.04 in BZ-3 and BZ-4 tests, respectively. Moreover, taking account of the release of the gas accumulated in the grain boundary in Pu-spot-excluded region and the release of the gas dissolved in the matrix, the total amount of fission gas release was evaluated as 0.33–0.43 and 0.15–0.27 in BZ-3 and BZ-4 tests, respectively. Comparing the results of the fission gas release with the results of rod-puncture test, it was suggested that fission gas release from not only the Pu-spot but also the Pu-spot-excluded region.

Zn/La Mixed Oxides Prepared by Coprecipitation: Synthesis, Characterization and Photocatalytic Studies.

Mixed oxides containing zinc and lanthanum were prepared by coprecipitation in alkaline medium, followed by calcination at 400 °C. The initial precipitation product and the calcined form were characterized by Brunauer–Emmett–Teller (BET) method adsorption of nitrogen at −196 °C, Scanning Electron Microscopy/Electron-Probe Microanalysis (SEM/EPM), Ultraviolet—Diffuse Reflectance Spectroscopy (UV-DRS) and Infrared (IR) spectroscopy. The band gap slightly changes from 3.23 eV to 3 eV by calcination. The photocatalytic performance of the solids were investigated in diluted aqueous medium, by using clofibric acid (CA), a stable and toxic molecule used as precursor in some pesticides and drugs, as test compound, possibly found in the wastewaters in low concentrations. The effects of the degradation extent, determined by high performance liquid chromatography (HPLC) and total organic carbon (TOC) measurements, were investigated at different initial concentrations of CA. Within about 60 min the CA degradation is almost total at low concentration values (3 ppm) and reaches over 80% in 180 min for an initial concentration of 50 ppm. Moreover, the CA removal performance of photocatalyst remains excellent after three cycles of use: the removal yield was practically total after 60 min in the first two cycles and reached 95% even in the third cycle.

Experimental Study on the Thermodynamics of the CaO-SiO2-Ce2O3 System at 1873 K

The phase relations in the CaO-SiO2-Ce2O3 system under the reducing atmosphere at 1873 K were determined by the conventional equilibrium and quenching method combined with scanning electron microscopy-electron probe microanalysis (SEM-EPMA) and X-ray diffraction (XRD) measurements on the quenched samples. Based on these analyses, a large part of the isothermal phase diagram was constructed. Furthermore, the thermodynamic activities of Ce2O3 in the melts at 1873 K were measured by the chemical equilibrium method. Using the measured activity data, an empirical formula to estimate the activity coefficient of Ce2O3 was proposed based on the regular solution model. It was found that, for the melts with the same Ce2O3 contents, the thermodynamic activities of Ce2O3 increase gradually with the rise of basicity (the ratio of CaO to SiO2) of the melts. This implies that, from the thermodynamic point of view, the increase of basicity is favorable to the enrichment and precipitation of Ce-containing mineral phases.

Bioactivity and biomineralization ability of calcium silicate-based pulp-capping materials after subcutaneous implantation.

To evaluate the abilities of three calcium silicate-based pulp-capping materials (ProRoot MTA, TheraCal LC and a prototype tricalcium silicate cement) to produce apatite-like precipitates after being subcutaneously implanted into rats. Polytetrafluoroethylene tubes containing each material were subcutaneously implanted into the backs of Wistar rats. At 7, 14 and 28days post-implantation, the implants were removed together with the surrounding connective tissue, and fixed in 2.5% glutaraldehyde in cacodylate buffer. The chemical compositions of the surface precipitates formed on the implants were analysed with scanning electron microscopy-electron probe microanalysis (SEM-EPMA). The distributions of calcium (Ca) and phosphorus (P) at the material-tissue interface were also analysed with SEM-EPMA. Comparisons of the thicknesses of the Ca- and P-rich areas were performed using the Friedman test followed by Scheffe's test at a significant level of 5%. All three materials produced apatite-like surface precipitates containing Ca and P. For each material, elemental mapping detected a region of connective tissue in which the concentrations of Ca and P were higher than those in the surrounding connective tissue. The thickness of this Ca- and P-rich region exhibited the following pattern: ProRoot MTA > prototype tricalcium silicate cement≥TheraCal LC. ProRoot MTA had a significantly thicker layer of Ca and P than the other materials at all time-points (P<0.05), and a significant difference was detected between the prototype cement and TheraCal LC at 28days (P<0.05). After being subcutaneously implanted, all of the materials produced Ca- and P-containing surface precipitates and a Ca- and P-rich layer within the surrounding tissue. The thickness of the Ca- and P-rich layer of ProRoot MTA was significantly thicker than that of the other materials.

Hybrid framework with cobalt–chromium alloy and gold cylinder for implant superstructure: Bond strength and corrosion resistance

PurposeThe aim of this in vitro study was to evaluate tensile bond strengths and corrosion resistance of CoCr alloys joined with gold cylinder by a soldering system in comparison with the conventional cast-joining system. MethodsCoCr alloys joined with gold cylinder by a soldering system using a high-fusing gold solder (CoCr/Solder/Gold cylinder), gold alloy joined with gold cylinder by a cast joining system (Gold alloy/Gold cylinder) and CoCr castings were fabricated. The tensile bond strength and corrosion resistance in 0.9% NaCl solution (pH 7.4 and pH 2.3) were evaluated. Scanning electron microscopy (SEM) of the fractured surface and electron probe microanalysis (EPMA) of the joined interfaces were also performed. ResultsThe tensile bond strengths of the CoCr/Solder/Gold cylinder specimens showed similar values as the Gold alloy/Gold cylinder specimens. SEM observation and EPMA analyses suggested firm bonding between the CoCr alloy and gold cylinder. The released elements from the CoCr/Solder/Gold cylinder specimens were similar to ones from CoCr castings. ConclusionsResults showed that superstructures made of CoCr alloys joined with the gold cylinder using a high-fusing gold solder had sufficient bond strength and high corrosion resistance. These hybrid frameworks with cobalt–chromium alloy and gold cylinder are promising prosthesis for implant superstructures with the low cost and favorable mechanical properties instead of conventional high-gold alloys.

Adsorption of xanthene food additive dyes to cellulose granules

It was found that three kinds of the synthetic food additive dyes, red nr. 3 (erythrosine), nr. 104 (phloxine), and nr. 105 (rose bengal) were adsorbed to the surface of charred cellulose granules and the maximum amounts of adsorption of these dyes were 3.75, 3.42, and 4.74 mg/g cellulose, respectively. Scanning electron microscopy-electron probe micro analysis (SEM-EPMA) showed a coating of the dyes on the surface of charred cellulose granules. Electron spectroscopy for chemical analysis (ESCA) suggested the presence of NH3 + in the surface of charred cellulose granules. Since all three dye compounds have both anionic carboxylate and hydrophobic groups and were released from the surface of charred cellulose granules by 0.1 N NaOH solution, it was surmised that these three food additive dyes were bound to the surface of cellulose granules by both ionic and physical interactions.

Composite coating containing WC/12Co cermet and Fe-based metallic glass deposited by high-velocity oxygen fuel spraying

A composite coating containing WC/12Co cermet and Fe 43Cr 16Mo 16C 15B 10 metallic glass was successfully deposited onto type 304 stainless steel by high-velocity oxygen fuel (HVOF) spraying, and the microstructure and tribological properties were investigated. The microstructure of the coating was characterized by scanning electron microscopy/electron probe micro-analysis (SEM/EPMA) and X-ray diffractometry (XRD). The hardness, adhesion strength and tribological properties of the coating were tested with a Vickers hardness tester, tensile tester and reciprocating wear tester, respectively. The composite coating, in which flattened WC/12Co was embedded in amorphous Fe 43Cr 16Mo 16C 15B 10 layers, exhibited high hardness, good wear resistance and a low friction coefficient compared to the monolithic coating. The addition of 8% WC/12Co to the Fe 43Cr 16Mo 16C 15B 10 matrix increased the cross-sectional hardness from 660 to 870 HV and reduced the friction coefficient from 0.65 to 0.5. WC/12Co reinforcement plays an important role in improving the tribological properties of the Fe 43Cr 16Mo 16C 15B 10 coating.

Relationship between changes in the crystal lattice strain and thermal conductivity of high burnup UO2 pellets

Abstract Two kinds of disk-shaped UO2 samples (4 mm in diameter and 1 mm in thickness) were irradiated in a test reactor up to about 60 and 130 GWd/t, respectively. The microstructures of the samples were investigated by means of optical microscopy, scanning electron microscopy/ electron probe micro-analysis (SEM/EPMA) and micro-X-ray diffractometry. The measured lattice parameters tended to be considerably smaller than the reported values, and the typical cauliflower structure which is often observed in high burnup fuel pellet is hardly seen in these samples. Thermal diffusivities of the samples were also measured by using a laser flash method, and their thermal conductivities were evaluated by multiplying the heat capacity of unirradiated UO2 and sample densities. While the thermal conductivities of sample 2 showed recovery after being annealed at 1500 K, those of sample 4 were not clearly observed even after being annealed at 1500 K. These trends suggest that the amount of accumulated irradiation-induced defects depends on the irradiation condition of each sample. From the comparison of the changes in the lattice parameter and strain energy density before and after the thermal diffusivity measurements, it is likely that the thermal conductivity recovery in the temperature region from 1200 to 1500 K is related to the migration of dislocation.

Sliding wear behaviour of Zr-ion-implanted D3 tool steel

The wear and friction characteristics of zirconium-ion-implanted AISI D3 tool steel have been investigated using pin-on-disc methods. Ion implantation was carried out using a vacuum-arc-based ion implanter to form multicharged zirconium ion beams at a mean ion energy of 130 keV, and the implantation doses investigated were approximately 3.6×10 16, 5×10 16 and 1×10 17 ions cm −2. It was found that Zr implantation decreased both the wear and the coefficient of friction. The beneficial effects of Zr implantation in terms of associated Auger electron spectroscopy, Rutherford backscattering spectroscopy and scanning electron microscopy microprobe analyses are described.

Non-destructive characterization of compositional and textural properties of Etruscan bronzes: a multi-method approach

A combination of conventional analytical techniques, such as X-ray fluorescence (XRF) and scanning electron microscopy-electron probe microanalysis (SEM-EPMA), with novel applications of neutron scattering were employed for a non-destructive study of 6th century BC Etruscan bronze plates discovered almost two centuries ago in a princely chamber tomb in Umbria, Italy. The pieces were used to richly decorate a ceremonial carriage, two war chariots and some furniture. Analytical investigations have been carried out to provide the essential information to correctly assign several fragments in order to recompose the original plates. Analytical responses from XRF and SEM-EPMA, although indicative, were strongly affected by surface alteration and contamination. Rietveld analysis of neutron diffraction profiles emerged for its powerful capability to provide extensive non-destructive, high sensitivity information on bulk alloy composition and phase quantification allowing meaningful comparison among the pieces for the reconstruction of the original plates. In addition, strain and texture analyses demonstrated the capability of the technique to achieve a non-invasive characterization of manufacturing procedures.

Evaluation of Systemic Metal Diffusion after Spinal Pedicular Fixation with Titanium Alloy and Stainless Steel System: A 36-month Experimental Study in Sheep

It is known that titanium alloys cause more extensive local metallosis due to fretting corrosion than stainless steel implants. The aim of the present study was to investigate possible systemic metal releases (Ti, Al, V, Cr, Ni) in sheep where L4-L5 were implanted with titanium alloy (Ti6Al4V, ASTM F 136) and stainless steel (AISI 316 L). 16 sheep were used: 8 were implanted with Ti6Al4V and 8 with stainless steel. At 6, 12, 24 and 36 months, the following examinations were performed: histology, atomic absorption spectrophotometry (AAS) and scanning electron microscopy (SEM), on liver, lung, kidney, brain, spleen and lumbo-aortic lymph nodes. Hair, urine and arteria blood samples were also analysed by AAS before implantation and at sacrifices. A histologic and ultrastructural study was performed on peri-implant tissues, too. Particular attention was paid to avoid contamination from dissection instruments or use of containers. In basal and in samples at 6 and 12 months, no metals were found in blood, urine, hair or other target tissues of the animals implanted with either Ti6Al4V or stainless steel. Regarding Al, V, Co and Ni, negative results in all tissues and body fluids were obtained also at 24 and 36 months. On the contrary, Ti traces were found in lumbo-aortic lymph nodes and lungs of one sheep only (10 and 30 ng/g, respectively) at 24 months. At 36 months, a systemic diffusion of Ti was observed in all tissues of both sheep instrumented with Ti6Al4V (2-16.5 ng/g), except for body fluids and hair. Metal research in target tissues by light and SEM micro-probe analysis provided negative results. Current data suggest that the amount of Ti found in organs after stable pedicular fixation is extremely low and not biologically available. This observation would lead us to exclude the hypothesis of any toxic reaction and such a release seems to be due to the passive diffusion through lymphatic fluids. Additional studies are needed to confirm if this long-term release of Ti particles might cause tissue damage.

Study of Fe-silicalite catalyst for the N 2O oxidation of benzene to phenol

A set of Fe-silicalite samples of MFI structure have been prepared by the hydrothermal technique, followed by steaming and by further chemical treating of the solid. After characterisation by nitrogen adsorption/desorption, X-ray diffraction (XRD), scanning electron microscopy-electron probe micro analysis (SEM-EPMA), the samples have been tested as catalysts for the oxidation of benzene to phenol by N 2O. The best performing catalyst has been studied also by temperature programmed desorption-mass spectrometry and temperature programmed reaction-mass spectrometry (TPD-TPR-MS), after pre-adsorption of both reactants and products. It was found that phenol forms when N 2O is adsorbed first, followed by benzene. Almost no phenol formation was observed when adsorbing benzene before N 2O. Furthermore, on this catalyst N 2O decomposed since 50°C or less, forming gaseous N 2 and adsorbed oxygen, which started to become available for the oxidation of benzene since 100–200°C. However, the so formed phenol remained adsorbed onto the catalyst. It desorbed within the 225–425°C temperature range, with a maximum around 300°C.

A biodegradable hybrid sponge nested with collagen microsponges.

A biodegradable hybrid sponge of poly(DL-lactic-co-glycolic acid) (PLGA) and collagen was fabricated by forming microsponges of collagen in the pores of PLGA sponge. Observation of the PLGA-collagen hybrid sponge by scanning electron microscopy (SEM) showed that microsponges of collagen with interconnected pore structures were formed in the pores of PLGA sponge. The hybrid structure further was confirmed by scanning electron microscopy-electron probe microanalysis (SEM-EPMA), and elemental nitrogen was detected in the microsponges of collagen and on the pore surfaces of PLGA, but not in cross-sections of PLGA regions. The formation of collagen microsponges was dependent on collagen concentration, the effective range of which was from 0.1 to 1.5 (w/v) %. The mechanical strength of the hybrid sponge was higher than that of either PLGA or collagen sponges, in both dry and wet states. The wettability with water was improved by hybridization with collagen, which facilitated cell seeding in the hybrid sponge. Mouse fibroblast L929 cells attached well and spread on the surfaces of the microsponges of collagen in the hybrid sponge. The distribution of cells was spatially uniform throughout the hybrid sponge. Use of the PLGA sponge as a skeleton facilitated formation of the hybrid sponge into desired shapes with high mechanical strength while collagen microsponges contributed good cell interaction and hydrophilicity.

Fabrication of PLGA-Collagen Hybrid Sponge

Abstract A hybrid sponge of biodegradable poly(DL-lactic-co-glycolic acid) (PLGA) and collagen was fabricated by forming microsponges of collagen in the pores of PLGA sponge. Observation of the hybrid sponge by scanning electron microscopy (SEM) showed that microsponges of collagen with interconnected pore structures were formed. The hybrid structure was further confirmed by detecting elemental nitrogen using scanning electron microscopy-electron probe microanalysis (SEM-EPMA). Elemental nitrogen was detected in the microsponges of collagen and on the pore surfaces of PLGA, but not in the cross-sections of PLGA regions. These results indicate that microsponges of collagen were formed in the pores of the PLGA sponge and that the pore surfaces were also coated with collagen.

Recovery of copper through decontamination of synthetic solutions using modified barks

Decontamination of synthetic acetate, chloride, nitrate, and sulfate solutions containing 10, 100, 1,000, 10,000, and 50,000 ppm of copper using chemically treated barks has been studied. Metal percentage removal from solutions depends on the pH, the initial concentration, and, to some extent, the anion. It varies from 40 through 99 pct of the initial metallic ion’s content in the solution. The average retention capacity of the treated bark is about 43 mg of Cu/g of dry modified bark (0.68 mmole/g of dry bark). Extraction of copper cations from the saturated modified bark was made possible with dilute acid. Regeneration of bark for reuse as an ion exchanger was possible. Bark loaded with copper was analyzed by scanning electron microscopy (SEM) and infrared (IR) spectroscopy. Copper was uniformly distributed in the bulk of the bark. No copper segregation was observed. It seems that copper was bound to the acidic (phenolic) sites of the bark. Anions were not detected on the copper-loaded bark with either SEM electron probe microanalysis or IR spectroscopy. Incineration of the bark loaded with copper resulted in ashes containing about 77 pct of copper oxides, while pyrolysis of the same sample led to ashes containing 10 pct of metallic copper and about 85 pct carbon.

Bone-bonding behavior of plasma-sprayed coatings of BioglassR, AW-glass ceramic, and tricalcium phosphate on titanium alloy.

The bone-bonding behavior of three kinds of bioactive ceramics coated on titanium alloy by the plasma-spray technique was investigated. Titanium alloy (Ti-6A1-4V) coated with BioglassR (45S5), apatite-wollastonite containing glass ceramic (AW), or beta-tricalcium phosphate (TCP) was prepared, and rectangular specimens were implanted into the tibial bones of mature male rabbits, which were sacrificed 8 or 24 weeks after implantation. The tibiae containing the implants were dissected out and subjected to detachment tests to measure the failure load. The bone-implant interface was investigated by Giemsa surface staining, contact microradiography, and scanning electron microscopy-electron probe microanalysis (SEM-EPMA). Eight weeks after implantation, the failure loads for implants coated with BioglassR, AW, and TCP were 1.04 +/- 0.94, 2.03 +/- 1.17, and 3.91 +/- 1.51 kg, respectively, and 24 weeks after implantation, the respective failure loads were 2.72 +/- 1.33, 2.39 +/- 1.30, and 4.23 +/- 1.34 kg. Failure loads of AW- and TCP-coated implants did not increase significantly with time. After the detachment test, breakage of the coating layer was observed. Bioactive ceramics can act as stimulants that induce bonding between bone and metal implants. However, failure load of metal implants coated with the bioactive ceramics was lower than that of bulk AW or TCP. It appears impossible to obtain a higher failure load using a bioactive-ceramic coating on titanium alloy. Histologically, the coating layer was found to become detached from the metal implant and the bone tissue bonded to the coating layer. SEM-EPMA observation revealed breakage of the coating layer, although bonding between bone and the coating layer was evident. A Ca-P-rich layer was observed at the interface between bone and the AW coating, and a Ca-P-rich and a Si-rich layer were observed at the interface between bone and the BioglassR coating. For clinical application, it would seem better to use coated metal implants for short-term implantation. However, there is a possibility of breakage of the coating layer because of both dissolution of the bioactive ceramic and mechanical weakness at the interface between the coating layer and the metal implant.

Bone-bonding behavior of three heat-treated silica gels implanted in mature rabbit bone.

Silica gel has been reported to induce apatite nucleation on its surface in vitro and it can act as a stimulant that induces formation of chemical apatite (Ca-P) layers on the surfaces of bioactive glass-ceramics. In this study, apatite formation in response to and the bone-bonding behavior of silica gels implanted in the tibiae of mature rabbits were studied. Implants were made from three silica gels treated at 400, 800, and 1000 degrees C, and the effects of such heat treatment on the above parameters were investigated. The silica gel was made by hydrolysis and polycondensation of tetraethoxysilane in aqueous solution containing polyethylene glycol. Rectangular implants (15 mm x 10 mm x 2 mm) of each heat-treated silica gel were implanted into both tibial bones of mature male rabbits, which were killed 4 or 8 weeks after implantation, and the tibiae containing the implants were dissected out. The bone-implant interfaces were investigated using Giemsa surface staining, contact microradiography, scanning electron microscopy-electron probe microanalysis, and X-ray diffraction. Histologically, no bonding of bone to any of the silica gels was observed at any time postimplantation. Soft tissue was observed at the bone-silica gel interface, but there were no giant foreign body or inflammatory cells. A Ca-P-rich layer was observed only on small areas of the surfaces of the silica gels treated at 400 and 800 degrees C 4 and 8 weeks after implantation. X-ray diffraction analysis confirmed the presence of hydroxyapatite in these Ca-P-rich layers.(ABSTRACT TRUNCATED AT 250 WORDS)

Scanning electron microscopy-electron probe microanalysis study of the interface between apatite and wollastonite-containing glass-ceramic and rabbit tibia under load-bearing conditions after long-term implantation.

Glass-ceramic implants containing oxy- and fluoroapatite [Ca10(PO4)6(O, F2)] and beta-wollastonite (CaSiO3) were studied under load-bearing conditions in a segmental replacement model in the tibia of the rabbit. A 16-mm segment of the middle of the tibial shaft was resected at a point distal to the junction of the tibia and the fibula. The defect was replaced by a 15 mm-long hollow, cylindrical implant that was fixed by intramedullary nailing using Kirschner wire. The implants were 9 mm in diameter and 15 mm long bearing a central hole 3.05 mm in dianeter. The rabbits used were killed 6 months, 1 year, 18 months, and 2 years after implantation. The interface between the bone and the glass-ceramic was investigated by scanning electron microscopy-electron-probe microanalysis (SEM-EPMA). None of the glass-ceramic implants broke, and the glass-ceramic had bonded directly to the bone tissue without any intervening soft tissue. A calcium-phosphorus layer (Ca-P layer) was observed at the glass-ceramic/bone interface. This layer was 30-100 microns thick at 6 months after implantation, 60-110 microns thick at 1 year after implantation, 80-200 microns thick at 18 months, and 120-350 microns thick at 2 years. At the lateral surface of the glass-ceramic uncovered by the bone, the calcium-phosphorus layer was 50-80 microns thick at 6 months after implantation, 250-450 microns thick at 1 year, 300 approximately 400 microns thick at 18 months, and 300 microns thick at 2 years. The thickness of the calcium-phosphorus layer increased moderately after long-term implantation. However, it was difficult to estimate the rate of increase in the thickness of calcium-phosphorus layer.

The properties and performance of (ZrO 2-8wt.%Y 2O 3)/(chemically vapour-deposited Al 2O 3)/(Ni-22wt.%Cr-10wt.%Al-lwt.%Y) thermal barrier coatings

The conventional plasma-sprayed thermal barrier coatings (TBCs) consist of a duplex M-Cr-Al-Y bond coat and thermally insulating ZrO 2-based ceramic top coat. In this study, a new TBC system was attempted in which an intermediate Al 2O 3 layer was interposed between the Ni-22Cr-10Al-1Y bond coat and ZrO 2-8Y 2O 3 top coat (where the compositions are in approximate weight per cent) by the chemical vapour deposition (CVD) process. The performance of the triples ZrO 2-8Y 2O 3/CVD A1 2O 3/M-Cr-A1-Y TBCs was evaluated by thermal cyclic oxidation testing at 1000, 1050, 1100 and 1150°C. The phase and morphology of the Ni-22Cr-10A1-1Y bond coat pre-coated with CVD A1 2O 3, and the oxidation behaviour were analysed by X-ray diffractometry, scanning electron microscopy-electron probe microanalysis and mass gain measurements respectively, to investigate the improvement of this new system. The results of the experiments in this study showed that the TBC specimens with an oxygen diffusion barrier CVD A1 2O 3 layer on the Ni-22Cr-10A1-1Y bond coat exhibited a lower oxidation rate and generally a longer lifetime compared with the conventional TBC specimens. The transport of reacting atoms or ions in CVD A1 2O 3 might involve inward oxygen diffusion.

Photodissolution profile of silver in amorphous chalcogenide GeSe x thin films

Ag photodissolution profile in amorphous GeSe x was investigated by secondary ion mass spectroscopy (SIMS), by Rutherford backscattering (RBS) and also by scanning electron microscopy (SEM). From SIMS measurements, Ag was found to exhibit generally a step-like profile in GeSe x (5.5 < x < 6.4) thin films deposited by plasma enhanced chemical vapor deposition on Si substrate but some samples show an intermediate Ag poor zone. RBS data show two Ag rich regions (one at the surface of the GeSe 5.5 film and the other at the interface GeSe 5.5 /Si) separated by a poor one. In GeSe 4 films evaporated on glass substrate such an anomalous effect is observed for the thin initial Ag layers. GeSe 3 films evaporated on Si substrate exhibit a rather different behavior from SIMS as well as from RBS: Ag photodissolution is very much slower than in GeSe 5.5 and the Ag profile is governed by a diffusion mechanism. SEM microprobe analysis confirms these results.