Scanning Electron Microscopy Inspection Research Articles

On fatigue crack growth mechanisms of MMC: Reflection on analysis of ‘multi surface initiations’

This work attempts to examine the mechanisms of fatigue when cracks synergetically initiate in more than one site at the specimen surface. The metal matrix composites (MMC) i.e. silicon carbide particles reinforced aluminium matrix composites (Al/SiC p–MMC), seem to be good candidates to accelerate fatigue failures following multi surface initiations (MSI). Closure effects of MSI mechanisms on the variation of fatigue behaviour are explored for various stress states. Experiments were carried out using non pre-treated and pre-treated specimens. Using an Equivalent Ellipse Method (EEM), it is shown that the aspect of surface finish of specimen plays an important role on crack growth. Scanning Electron Microscope (SEM) inspections have lead to distinguishing the initiation regions from propagation regions and final separation regions. It is also revealed that the total lifetime of specimens is sensitive to heat treatment. Moreover, it is found that the appearance of MSI in cycled materials is more probable at high level of fatigue loads.

Experimental verification of super-resolution optical inspection for semiconductor defect by using standing wave illumination shift

Semiconductor design rules and process windows continue to shrink, so we face many challenges in developing new processes such as the less 100-nm design rule and the 300-mm wafer. The challenges have become more difficult, and the next generation of defect inspections is urgently needed. Optics and electron beams have been primarily used for the detection of critical defects, but both technologies have disadvantages. The optical inspection is generally not sensitive enough for defects at 100 nm or less, while the scanning electron microscopy inspection has low throughput because it takes a long time to scan 300 mm. To find a solution to these problems, we have proposed a novel optical inspection method for the critical defects on the semiconductor wafer. First, we carried out theoretical examinations and computer simulations. As a result, the proposed method makes it possible to observe a structure with robustness and higher resolution beyond the Rayleigh limit. Second, we developed an apparatus for the basic experiment and carried out the super-resolution experiment using a line and space sample. As a result, the sample structures were clearly resolved beyond the Rayleigh limit and defects on the sample surface were detected with super-resolution.

Thermal Stability Improvement of NiSi on Gate by High Dosage Germanium Implantation

The thermal stability of nickel silicide (NiSi) on source/drain and gate is one of the important research topics in complementary metal oxide semiconductor technology. Here we report the effects of germanium-ion implantation (Gel/I) on the thermal stability of NiSi on poly-Si gates. Scanning electron microscope inspections and thin-film X-ray diffraction results show that agglomeration and NiSi 2 transformation can be suppressed by high dosage Ge implanted on poly-Si gates. The allowable process temperature of NiSi formation can be increased by 100°C.

Accurate determination of the functional hole size in photonic crystal slabs using optical methods

Control and repeatability in the fabrication of two-dimensional photonic crystal (PhC) slabs is becoming increasingly important as the technology matures towards practical applications. A key problem in this respect is the determination of the actual hole size in finished devices. We have developed an optical method for measuring the hole size in PhC slabs as an alternative to the inspection of scanning electron microscope (SEM) images. The optical method relies on determining the cut-off frequency of W1 PhC waveguides, which is easily measured and compared to calculations as a function of hole size. We show that the typical error in the measurement of hole diameter is approximately 2%, or 5 nm. This level of accuracy is a significant improvement over current methods, which rely on the inspection by SEM. SEM inspection can introduce large systematic errors because different electron detectors, and even different settings of the same detector, will provide differing contrasts between a hole and its edge. Such errors can be of the order of 20 nm, or as much as 5–10% of the absolute hole diameter. Furthermore, our method provides the functional or effective hole size, which determines the photonic function of the device, and which may be different from the physical hole size.

Correlation of the tribological behaviors with the mechanical properties of poly-ether-ether-ketones (PEEKs) with different molecular weights and their fiber filled composites

The tribological behaviors of three poly-ether-ether-ketones (PEEKs) with different molecular weights and their SCF (short carbon fiber)/graphite/PTFE (polytetrafluoroethylene) filled composites were examined using a block-on-ring apparatus under dry sliding conditions. Tensile tests, hardness measurements and dynamic mechanical thermal analysis (DMTA) of the PEEK based materials were also performed. The tribological behaviors of PEEK based materials were correlated with their mechanical properties and the tribological mechanisms were discussed based on scanning electron microscope (SEM) inspections of worn surfaces and wear debris. Under a low apparent pressure, a high material ductility seems to reduce the wear rate of pure PEEK through alleviating the microcutting effect exerted by the protruding regions of the counterpart. Under a high pressure, however, a high stiffness seems to improve the wear resistance of pure PEEK by reducing the plastic flow occurring in the PEEK surface layer. After incorporating SCF/graphite/PTFE fillers, the wear rate of PEEK was decreased significantly. Thinning and cracking of SCF are supposed to be the important factors determining the tribological behaviors of the composites.

Unravelling the microbial role in ooid formation – results of an in situ experiment in modern freshwater Lake Geneva in Switzerland

ABSTRACTThe microbial role in the formation of the cortex of low‐Mg calcite freshwater ooids in western part of Lake Geneva in Switzerland has been suggested previously, but not demonstrated conclusively. Early work mostly concentrated in hypersaline milieus, and hence little is known about their genesis in freshwater environments. We designed an in situ experiment to mimic the natural process of low‐Mg calcite precipitation. A special device was placed in the ooid‐rich bank of the lake. It contained frosted glass (SiO2) slides, while quartz (SiO2) is the most abundant mineral composition of ooid nuclei that acted as artificial substrates to favour microbial colonization. Microscopic inspection of the slides revealed a clear seasonal pattern of carbonate precipitates, which were always closely associated with biofilms that developed on the surface of the frosted slides containing extracellular polymeric substance, coccoid and filamentous cyanobacteria, diatoms and heterotrophic bacteria. Carbonate precipitation peaks during early spring and late summer, and low‐Mg calcite crystals mostly occur in close association with filamentous and coccoid cyanobacteria (e.g. Tolypothrix, Oscillatoria and Synechococcus, Anacystis, respectively). Further scanning electron microscope inspection of the samples revealed low‐Mg calcite with crystal forms varying from anhedral to euhedral rhombohedra, depending on the seasons. Liquid cultures corroborate the in situ observations and demonstrate that under the same physicochemical conditions the absence of biofilms prevents the precipitation of low‐Mg calcite crystals.These results illustrate that biofilms play a substantial role in low‐Mg calcite ooid cortex formation. It further demonstrates the involvement of microbes in the early stages of ooid development. Combined with ongoing microbial cultures under laboratory‐controlled conditions, the outcome of our investigation favoured the hypothesis of external microbial precipitation of low‐Mg calcite as the main mechanism involved in the early stage of ooid formation in freshwater Lake Geneva.

Structural characterization of single crystals of sodium titanate nanowires prepared by hydrothermal process

Na 2Ti 6O 13 nanowires have been synthesized using a simple hydrothermal reaction at 130 °C between TiO 2 particles and NaOH aqueous solution. Subsequently the samples were annealed at 500 °C in air for 24 h. Field emission scanning electron microscope(FEG-SEM) and low-magnification transmission electron microscope(TEM) inspection showed wire-like structures with uniform diameters and high contrast, indicating the formation of single crystals. High-resolution transmission electron microscope(HRTEM) and 2-D fast Fourier transform confirmed that the annealed structures correspond to hexatitanate single crystals with diameters between 20 and 120 nm and lengths ranging from 500 nm to 1 μm. Structural characterization was performed by X-ray diffraction(XRD) and Raman spectroscopy. Annealed samples presented diffraction patterns and Raman vibrational spectra corresponding to the sodium hexatitanate indexed as Na 2Ti 6O 13. FEG-SEM and TEM inspection of the synthesized samples without annealing showed belt- and tube-like structures with diameters between 10 and 60 nm and several micrometers in length. However, their crystalline structure could not be determined using the same techniques applied to the annealed samples.

Effects of Sulfur Level and Anisotropy of Sulfide Inclusions on Tensile, Impact, and Fatigue Properties of SAE 4140 Steel

During metal forming processes such as rolling and forging, deformable manganese sulfide (MnS) inclusions become elongated. Such elongated MnS inclusions can have considerable adverse effects on mechanical properties, if the inclusions are not aligned with the loading direction. The objectives of this study were to evaluate and compare fatigue, monotonic tensile and CVN impact behavior of SAE 4140 steel with high (0.077% S), low (0.012% S) and ultra low (0.004% S) sulfur contents at two hardness levels (40 HRC and 50 HRC). The longitudinally oriented samples at 40 HRC, where MnS inclusions were oriented along the loading direction, did not exhibit any significant sensitivity of tensile or fatigue properties to the sulfur content. For the transversely oriented MnS inclusions, however, the monotonic tensile test results indicate very low ductility of the high sulfur material at both hardness levels, where specimens failed shortly after yielding. The yield strength of the materials, however, did not differ significantly with the sulfur content. With regards to fatigue strength, the high sulfur material had up to 25% lower fatigue strength than the ultra low sulfur material under transverse loading. The scanning electron microscopy (SEM) inspection of failed fatigue test specimens revealed that the fracture topography of the high sulfur material were very rough and jagged, indicating several cracks originating from MnS inclusions. The fracture surfaces of the other two materials with lower sulfur content exhibited typical fatigue fracture surfaces with clear initiation and final fracture regions.

Performance of tubular SrFe(Al)O 3− δ–SrAl 2O 4 composite membranes in CO 2- and CH 4-containing atmospheres

The stability and oxygen permeability of dense tubular membranes, made of (SrFeO 3− δ ) 0.7(SrAl 2O 4) 0.3 (SFSA) composite by cold isostatic pressing, were assessed under air/CO 2 and air/(CH 4 + CO 2) gradients at 973–1173 K. Mixed-conducting SFSA, comprising SrFe(Al)O 3− δ perovskite-like and SrAl 2O 4-based phases, was selected as a model membrane material for the natural gas conversion reactors due to its attractive oxygen transport, catalytic and thermomechanical properties. As partial dissolution of SrAl 2O 4 in the perovskite-like component leads to strontium deficiency of the perovskite phase, the composite exhibits an improved stability with respect to interaction with CO 2, although thermogravimetric analysis showed that carbon dioxide adsorption on SFSA is still significant. No degradation was revealed in the course of oxygen permeation tests during 200–300 h with subsequent scanning electron microscopy inspection. However, contrary to that observed for SFSA powders, methane conversion in the tubular SFSA membranes without surface modification results in predominant total combustion caused by the slow kinetics of the reforming reactions. Significantly higher conversion efficiency and synthesis gas yields were achieved passing the pre-reacted gas mixtures into an additional reactor with Pt/LaNiO 3/Al 2O 3 catalyst bed at the tubular membrane outlet.

Properties of graphene produced by the high pressure–high temperature growth process

The authors report on a new method for the synthesis of graphene, a mono-layer of carbon atoms arranged in a honey comb lattice, and the assessment of the properties of obtained graphene layers using micro-Raman characterisation. Graphene was produced by a high pressure–high temperature (HPHT) growth process from the natural graphitic source material by utilising the molten Fe–Ni catalysts for dissolution of carbon. The resulting large-area graphene flakes were transferred to the silicon–silicon oxide substrates for the spectroscopic micro-Raman and scanning electron microscopy inspection. The analysis of the G peak, D, T+D and 2D bands in the Raman spectra under the 488 nm laser excitation indicate that the HPHT technique is capable of producing high-quality large-area single-layer graphene with a low defect density. The disorder-induced D peak ∼1359 cm−1 while very strong in the initial graphitic material is completely absent in the graphene layers. The proposed method may lead to a more reliable graphene synthesis and facilitate its purification and chemical doping.

Thermal approach of defects generation on copper/organic dielectric interface due to SEM inspections

Scanning electron microscopy (SEM) sometimes induce defects on samples during imaging. We study in this article the thermal effects of SEM views on the Cu/BCB interface, in focused ion beam (FIB) cross sections. Electrons can lead to local thermal power dissipation due to their deceleration and create delamination. A TEM lamella sample preparation method was also found to avoid this kind of delamination. In this case, the thermal dissipated power could be reduced due to the fact that a big part of the incoming electrons could go through the sample without interactions. Several thermal simulations (2D/3D) were carried out to estimate the field of temperatures under electron beam and to explain the Cu/BCB interface delamination.

A novel method for nanoprecision alignment in wafer bonding applications

Wafer bonding has been identified as a promising technique to enable fabrication of many advanced semiconductor devices such as three-dimensional integrated circuits (3D IC) and micro/nano systems. However, with the device dimensions already in the nanometre range, the lack of approaches to achieve high precision bonding alignment has restricted many applications. With this increasing demand for wafer bonding applications, a novel mechanical passive alignment technique is described in this work aiming at nanoprecision alignment based on kinematic and elastic averaging effects. A number of cantilever-supported pyramid and V-pit microstructures have been incorporated into the outer circumference area of the to-be-bonded Si chips, respectively. The engagement between the convex pyramids and concave V-pits and the compliance of the support cantilever flexures result in micromechanical passive alignment which is followed by direct bonding between the Si chips. The subsequent infrared (IR) and scanning electron microscopy (SEM) inspections repeatedly confirmed the achievement of alignment accuracy of better than 200 nm at the bonding interface with good bonding quality. The impact and potential applications of the developed alignment technique are also discussed.

The influence of smear layer in lateral channels filling

This in vitro study evaluated the ability of a warm gutta-percha obturation system Thermafil to fill lateral channels in presence/absence of smear layer. Forty single-rooted extracted human teeth were randomly divided into two groups for which different irrigation regimens were used: group A, 5 ml of 5% NaOCl + 2.5 ml of 3.6% H(2)O(2); group B, 5 ml of 5% NaOCl 5% + 2.5 ml of 17% ethylenediamine tetraacetic acid. A conventional crown-down preparation technique was employed. Obturation was performed using epoxy resin-based cement (AH Plus) and a warm gutta-percha plastic carrier system (Thermafil). Specimens were cleared in methyl salicylate and analyzed under a stereomicroscope to evaluate the number, length, and diameter of lateral channels. Lateral channels were identified in both groups at medium and apical thirds. Additional samples were prepared for scanning electron microscopy inspection to confirm the presence of smear layer in group A, and the absence of smear layer in group B. All lateral channels resulted filled in both groups. No statistically significant differences regarding number, length, and diameter were observed between the two groups. Smear layer did not prevent the sealing of lateral channels.

Thermal stability of NiPt- and Pt-silicide contacts on SiGe source/drain

NiPt (10% Pt) and Pt were investigated as alternatives to Ni for contact formation to SiGe (20%) source/drain. The germanosilicide phase formation and morphology were studied by means of sheet resistance measurements, X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) inspection. From isothermal anneals it is found that NiPt- and Pt-germanosilicide have better thermal stability compared to Ni-germanosilicide. Improved thermal stability is observed for Ni-, NiPt- and Pt-germanosilicide on B doped SiGe as compared to undoped SiGe. The degradation mechanism of NiPt- and Pt-germanosilicide films on SiGe is morphological degradation while the film is still in the mono-(germanosilicide) phase.

Spectroscopic study of carbonaceous dust particles grown in benzene plasma

Carbonaceous dust particles have been synthesized from benzene using an rf glow discharge. Scanning electron microscope inspection revealed that the plasma-synthesized dust particles can be classified into two types. Shell-structured dust particles showed a wide size distribution from 3 to40 μm. The other type, with different degrees of aggregation, appeared to be dense and spherical with a very distinctive yellow color and size distribution from 100 nm to 2 μm. Analyses using micro-Raman and Fourier transform infrared microscopy indicated that the main components of the dust particles are polyphenyls and hydrogenated amorphous carbon (HAC). The luminescence background in Raman spectra and the infrared C–H stretching vibrational features observed around 3.4 μm for the dust particles are attributed to HAC. The formation mechanisms and spectroscopic characterization of carbonaceous dust particles are discussed.

Acetone and ethanol solid-state gas sensors based on TiO2 nanoparticles thin film deposited by matrix assisted pulsed laser evaporation

Matrix assisted pulsed laser evaporation (MAPLE) is a new promising laser-based technique thought for polymer or biomaterial thin films deposition. In this work, the MAPLE technique has been used for the deposition of titania (TiO 2 ) nanoparticle thin films to be used for gas sensor applications. For this purpose, an aqueous solution of TiO 2 nanoparticles, synthesized by a novel chemical route, was frozen at the liquid nitrogen temperature and introduced in a vacuum chamber to be irradiated with a pulsed ArF excimer laser. The volatile solvent was pumped away while the TiO 2 nanoparticles were deposited on Si and Al 2 O 3 substrates. A uniform distribution of TiO 2 nanoparticles with an average size of about 10 nm was obtained, as demonstrated by high resolution scanning electron microscopy (SEM-FEG) inspection. We realized gas-sensing devices based on resistive transduction mechanism by using the TiO 2 nanoparticles thin films deposited by the MAPLE technique onto suitable rough alumina substrates equipped with interdigitated electrical contacts (IDC) and heating elements. Electrical characterization measurements were carried out in controlled environment. The results of the gas-sensing tests towards low concentrations of ethanol and acetone vapors are reported. Typical gas sensor parameters (gas responses, response/recovery time, sensitivity, and low detection limit) towards ethanol were extracted and compared with to the corresponding parameters towards acetone.

Using Scanning Electron Microscopy to Detect the Ultrastructural Variations in Eggshell Quality of Fayoumi and Dandarawi Chicken Breeds

An experiment was conducted to evaluate egg quality and ultrastructural measurements of eggshell in two Egyptian local breeds of chicken (Fayoumi and Dandarawi). A total of 162 females representing the two breeds were randomly assigned to the current experiment. They were housed in individual cages placed in an open-sided house under the same environmental, managerial and hygienic conditions. Maturation measurements including body weight and age at sexual maturity were determined. Also, egg production (number and weight) was recorded for the first 3 months of production cycle to calculate egg mass. To as sess egg quality parameters (internal and external), a total of 90 eggs were randomly collected from each breed at 26 weeks of age. In addition, eggshell samples were prepared to investigate ultrastructural variations using scanning electron microscopy (SEM). The current results revealed that Fayoumi breed had a better performance at sexual maturity compared to Dandarawi one. Inferior egg production parameters during the first 3 months of laying cycle were associated with Dandarawi breed. With respect to internal egg quality, there were no significant differences between Fayoumi and Dandarawi breeds for liquid components as a percentage of egg weight. In addition, Haugh unit and yolk index as indicators to the quality of albumen and yolk, did not exhibit a difference between breeds. Regarding eggshell quality traits, it could be noticed that Fayoumi breed significantly increased specific gravity and eggshell strength compared to Dandarawi one. In terms of ultrastructural measurements of eggshell, SEM inspection revealed that eggshell of Fayoumi breed had a higher effective thickness (palisade layer) compared to Dandarawi one. On the other hand, the length of mammillary layer (absolute or relative) was significantly lower in eggshells of Fayoumi hens compared to those of Dandarawi counterparts. Type B bodies, which are rounded and located among mammillary caps, were more frequent in eggshell of Dandarawi breed resulting in poor shell quality. However, Fayoumi breed had good rounded caps and early fusion as compared to Dandarawi one. The incidence of mammillary alignment and erosion were more common in eggshell of Dandarawi breed suggesting poor shell strength. In conclusion, Fayoumi breed had genetically not only better egg production and egg quality but also good ultrastructural formation of eggshell compared to Dandarawi breed.

Glass-Alumina Functionally Graded Materials Produced by Plasma Spraying

The present work was focused on glass-alumina functionally graded materials. The samples, produced by plasma spraying, were built as multi-layered systems by depositing several layers of slightly different composition, since their alumina and glass content was progressively changed. After fabricating the graded materials, several, proper characterization techniques were set up to investigate the gradient in composition, microstructure and related performances. A particular attention was paid to the observation of the graded cross sections by scanning electron microscopy, which allowed to visualize directly the graded microstructural changes. The scanning electron microscopy (SEM) inspection was integrated with accurate mechanical measurements, such as systematic depth-sensing Vickers microindentation tests performed on the graded cross sections.

The effects of magnesium particles in posterolateral spinal fusion: an experimental in vivo study in a sheep model

Magnesium has recently become a material of interest as a biocompatible and biodegradable implant metal. Authors of several reports have noted the potential bone-cell activating or bone-healing effect of high Mg ion concentrations. The classic method for achieving intertransverse process fusion involves using an autologous iliac crest bone graft. Several studies have been performed to investigate enhancement of this type of autograft fusion. To the authors' knowledge, no research has been conducted in which the efficacy of pure Mg particles in posterolateral spinal fusion has been investigated. The objective of this study was to determine whether Mg particles enhance the effectiveness of intertransverse process lumbar fusion in a sheep model. Sixteen skeletally mature female sheep were subjected to intertransverse process spinal fusions with pedicle screw fixation at L2-3 and L5-6. Each animal was given a 5-cm3 bone autograft at one fusion level, and a combined 5-cm3 bone autograft with the addition of 1 cm3 Mg at the other level. Six months after surgery, bone formation was evaluated by gross inspection and palpation, and by radiological, histological, scanning electron microscopic, and x-ray diffraction analyses. Radiological results were graded from 0 to 4 according to the status of the bridging bone, which was determined by evaluating both x-ray films and computed tomography scans. The quality of the spinal fusion was assigned a histological score of 0 to 7, in which a score of 0 represented an empty cleft and a score of 7 represented complete bridging of bone between the transverse processes. The trabecular bone formation at each fusion level and the Ca hydroxyapatite crystalline structure in core biopsy specimens were evaluated using scanning electron microscopy and x-ray diffraction analyses, respectively. The rate of rigid bone fusion, according to both palpation and radiological assessment, in the combined Mg and autologous bone treatment group was higher (81.25%) than in the autograft bone treatment group (62.5%), but this difference was not statistically significant. The quality of bone fusion, according to the histological grading system and scanning electron microscopy inspection, was higher in the bone fusion segments of the Mg and autologous graft combined group than in the group with autograft-only arthrodesis, and this difference was statistically significant. The x-ray diffraction analyses further confirmed the effect of Mg in promoting the formation of the crystalline portion of the bone (hydroxyapatite). Based on the results of this study, adding Mg particles to autologous corticocancellous bone in a posterolateral intertransverse process fusion enhances the quality of bone formation. However, radiological findings did not reveal a statistically significant effect of Mg on the rate of solid bone fusion formation between the two transverse processes.

Field emission characteristics of polymethyl methacrylate polymer thin film

Polymethyl methacrylate (PMMA) thin films were prepared by spin coating using chloroform solvent. The field emission current versus applied field characteristics were tested. Stable field emission was observed after a switch-on process. The field emission properties of PMMA film exhibit vacuum gap dependence characteristics. The scanning electron microscope inspection reveals that after emission process microwhiskers were formed at the surface. The gap dependence of the field emission properties was explained. It is proposed that the high field during the switch-on process leads to the formation of the microwhiskers.