Scanning Electron Microscopy Inspection Research Articles

Hydroxyapatite/poly(ɛ-caprolactone) double coating on magnesium for enhanced corrosion resistance and coating flexibility

Hydroxyapatite was deposited on pure magnesium (Mg) with a flexible poly(ε-caprolactone) interlayer to reduce the corrosion rate of Mg and enhance coating flexibility. The poly(ε-caprolactone) interlayer was uniformly coated on Mg by a spraying method, followed by hydroxyapatite deposition on the poly(ε-caprolactone) using an aerosol deposition method. In scanning electron microscopy observations, inorganic/organic composite-like structure was observed between the hydroxyapatite and poly(ε-caprolactone) layers, resulting from the collisions of hydroxyapatite particles into the poly(ε-caprolactone) matrix at the initial stage of the aerosol deposition. The corrosion resistance of the coated Mg was examined using potentiodynamic polarization tests. The hydroxyapatite/poly(ε-caprolactone) double coating remarkably improved the corrosion resistance of Mg in Hank's solution. In the in vitro cell tests, the coated Mg showed better cell adhesion compared with the bare Mg due to the reduced corrosion rate and enhanced biocompatibility. The stability and flexibility of hydroxyapatite/poly(ε-caprolactone) double coating was investigated by scanning electron microscopy inspections after the coated Mg was deformed. The hydroxyapatite coating on the poly(ε-caprolactone) interlayer revealed enhanced coating stability and flexibility without cracking or delamination during bending and stretching compared with the hydroxyapatite single coating. These results demonstrated that the hydroxyapatite/poly(ε-caprolactone) double coating significantly improved the surface corrosion resistance of Mg and enhanced coating flexibility for use of Mg as a biodegradable implant.

Micro/Nanostructured Hyaluronic Acid Matrices with Tuned Swelling and Drug Release Properties

Hyaluronic acid (HA) hydrogels were structured in the form of porous monoliths by means of the ice-segregation-induced self-assembly (ISISA) method coupled with freeze-drying. Physical and chemical parameters were explored in order to fine-tune the microstructure and the incidence on both swelling and dissolution behavior in aqueous media. Gentamicin-loaded HA matrices with tuned drug release properties were also prepared; their inherent properties and behavior in solution are discussed in the framework of thermal analysis and scanning electron microscopy inspection.

Friction and wear behaviors of aircraft brake linings material

PurposeThe purpose of this paper is to produce and investigate a reliable and effective aircraft brake lining material.Design/methodology/approachIn total, four different Cu‐based brake lining samples were produced by powder metallurgy. The produced samples were tested in an experimental setup on friction, wear and mechanical performance, then metallographic and scanning electron microscope inspections were performed. Hardness, compression strength and density of copper‐based brake linings were also tested. Moreover, a numerical simulation of the structural reaction of a sample under compression was carried out by using ANSYS.FindingsAccording to tests, suitable aircraft brake lining material composition would be 75% Cu, 5% Fe, 5% Sn, 5% Graphite, 5% SiO2, 5% MoS2.Practical implicationsThe paper will help designers choose the most proper ingredient combination for aircraft brake lining materials.Originality/valueThe paper notes that adding silicon dioxide and graphite forms a porosive structure. In addition, porosity brings a low strength and high wear rate.

Study on the Reliability of Application-Specific LED Package by Thermal Shock Testing, Failure Analysis, and Fluid–Solid Coupling Thermo-Mechanical Simulation

Reliability is essential for large-scale applications of high-power light-emitting diode (LED) devices, modules, and systems for general illumination. In this paper, the reliability of a novel application-specific LED package (ASLP) is investigated by thermal shock testing, failure analysis, and fluid-solid coupling thermo-mechanical simulation. The reliability of the ASLP modules was validated with a dual-bath liquid thermal shock testing from 233 to 398 K. The non-destructive failure analysis was conducted to the catastrophic failure ASLP samples by fluorescent penetrant inspection. The delaminations at the interfaces within the ASLP module were detected. The failure mechanisms were identified by digital optical microscopy and field emission scanning electron microscope inspection after the decapsulation. The experimental results show that fracture failure occurs at the wedge joint of the bonding wire, which leads to the catastrophic failure of the ASLP module. The stress and strain behaviors of the ASLP module, especially the bonding wire under thermal shock loading, were analyzed through thermo-mechanical modeling with the nonlinear time- and temperature-dependent material properties. Significant thermal gradient within the ASLP module during the thermal shock testing was taken into consideration by the fluid-solid coupling transient thermal transfer analysis. The effects of the delaminations detected by the fluorescent penetrant inspection on the reliability of the bonding wire were also examined. It is found the delaminations existing at the interfaces within the ASLP module induce significant plastic strain to the wedge joint and results in fracture failure. The results from the numerical simulation can make a good prediction of the failure mechanism of the ASLP modules under thermal shock loading.

Effective Linewidth Measurement of 45-nm-Half-Pitch Ultraviolet Nanoimprint Lithography Patterns by Scanning Electron Microscope Inspection and Extremely Shallow Si Etching

Resist pattern shrinkage during a scanning electron microscope (SEM) inspection is a critical issue in the measurement of the linewidth or critical dimension (CD) of sub-100 nm polymer patterns. For example, the pattern shrinkages were set to 2.3–4.4 nm for half-pitch (hp) 45–90 nm line and space (L/S) PAK-01 patterns fabricated by UV nanoimprint under SEM conditions to diminish pattern shrinkage. We propose an evaluation method of actual CDs of UV nanoimprint lithography (UV-NIL) patterns by extremely shallow Si etching combined with residual layer removal etching. The method was used to conduct stable measurement without any shrinkage problem by transferring patterns fabricated by UV nanoimprint to the Si substrate. Although the linewidth slightly decreased with etching time, we estimated the linewidths just after the residual layer removal for nominal 45, 65, and 90 nm L/S patterns to be 40.3, 55.1, and 72.1 nm, respectively, by combining the widths determined by SEM with the depths determined by AFM. The method enables us to evaluate linewidth more precisely for finer patterns.

Effective Linewidth Measurement of 45-nm-Half-Pitch Ultraviolet Nanoimprint Lithography Patterns by Scanning Electron Microscope Inspection and Extremely Shallow Si Etching

Effective Linewidth Measurement of 45-nm-Half-Pitch Ultraviolet Nanoimprint Lithography Patterns by Scanning Electron Microscope Inspection and Extremely Shallow Si Etching

Impact of the limitations of state-of-the-art micro-fabrication processes on the performance of pillar array columns for liquid chromatography

We report on the practical limitations of the current state-of-the-art in micro-fabrication technology to produce the small pillar sizes that are needed to obtain high efficiency pillar array columns. For this purpose, nine channels with a different pillar diameter, ranging from 5 to 0.5μm were fabricated using state-of the-art deep-UV lithography and deep reactive ion etching (DRIE) etching technology. The obtained results strongly deviated from the theoretically expected trend, wherein the minimal plate height (Hmin) would reduce linearly with the pillar diameter. The minimal plate height decreases from 1.7 to 1.2μm when going from 4.80 to 3.81μm diameter pillars, but as the dimensions are further reduced, the minimal plate heights rise again to values around 2μm. The smallest pillar diameter even produced the worst minimal plate height (4μm). An in-depth scanning electron microscopy (SEM) inspection of the different channels clearly reveals that these findings can be attributed to the micro-fabrication limitations that are inevitably encountered when exploring the limits of deep-UV lithography and DRIE etching processes. When the target dimensions of the design approach the etching resolution limits, the band broadening increases in a strongly non-linear way with the decreased pillar dimensions. This highly non-linear relationship can be understood from first principles: when the machining error is of the order of 100–200nm and when the target design size for the inter-pillar distance is of the order of 250nm, this inevitably leads to pores that will range in size between 50 and 450nm that we want to highlight with our paper highly non-linear relationship. This highly non-linear relationship can be understood from first principles: when the machining error is of the order of 100–200nm and when the target design size for the inter-pillar distance is of the order of 250nm, this inevitably leads to pores that will range in size between 50 and 450nm.

Dual effect of inorganic polymeric phosphate/polyphosphate on osteoblasts and osteoclasts in vitro

Inorganic polymeric phosphate/polyphosphate (polyP) is a natural polymer existing in both pro- and eukaryotic systems. In the present study the effect of polyP as well as of polyP supplied in a stoichiometric ratio of 2 m polyP:1 m CaCl2 [polyP (Ca(2+) complex)] on the osteoblast-like SaOS-2 cells and the osteoclast-like RAW 264.7 cells was determined. Both polymers are non-toxic for these cells up to a concentration of 100 µm. In contrast to polyP, polyP (Ca(2+) complex) significantly induced hydroxyapatite formation at a concentration > 10 µm, as documented by alizarin red S staining and scanning electron microscopic (SEM) inspection. Furthermore, polyP (Ca(2+) complex) triggered in SaOS-2 cells transcription of BMP2 (bone morphogenetic protein 2), a cytokine involved in maturation of hydroxyapatite-forming cells. An additional activity of polyP (Ca(2+) complex) is described by showing that this polymer impairs osteoclastogenesis. At concentrations > 10 µm polyP (Ca(2+) complex) slows down the progression of RAW 264.7 cells to functional osteoclasts, as measured by the expression of TRAP (tartrate-resistant acid phosphatase). Finally, it is shown that 10-100 µm polyP (Ca(2+) complex) inhibited phosphorylation of IκBα by the respective kinase in RAW 264.7 cells. We concluded that polyP (Ca(2+) complex) displays a dual effect on bone metabolizing cells. It promotes hydroxyapatite formation in SaOS-2 cells (osteoblasts) and impairs maturation of the osteoclast-related RAW 264.7 cells.

Non-Enzymatic and Highly Sensitive H2O2 Sensor Based on Pd Nanoparticle Modified Gold Nanowire Array Electrode

A non-enzymatic hydrogen peroxide (H2O2) sensor based on a vertically aligned gold nanowire array electrode modified with palladium nanoparticles (PdNP/AuNAE) has been fabricated. PdNP have been deposited onto the AuNAE surface by a hydrothermal reduction method using a borohydride technique. Scanning electron microscope inspection (SEM) has revealed granular Pd particles deposited on the surface of the nanowires. X-ray diffraction (XRD) peak analysis has determined an average crystallite size of 3 to 5 nm for PdNP. The catalytic behavior of PdNP/AuNAE has been studied using amperometry and voltammetry which showed a linear response up to 2 mM of H2O2 with a sensitivity of 530 μA mM−1 cm−2 at 20°C. This electrode can detect 5 μM (S/N = 3) of H2O2 at normal conditions without using any enzyme or mediator. A high selectivity toward H2O2 (up to 97%) has been obtained using this electrode platform in the presence of common electrochemical interferences such as ascorbic acid, uric acid, acetaminophen and dopamine.

Miniaturization of grayscale images

Printing of binary patterns onto substrates has been the strength of resist-based binary lithography that has advanced the semiconductor industry. When patterning grayscale structures however, grayscale-lithography processes that are often difficult to use are considered. Here, we describe a process using binary-lithography to create arbitrary grayscale patterns. Particularly, we demonstrate a novel algorithm for the miniaturization of grayscale images that preserves grayscale information when imaged in a scanning electron microscope (SEM). The brightness level of each pixel was adjusted by controlling the density of nanometer-scale pixel elements. Using 17 shades of gray, we demonstrate the electron-beam lithography patterning of an M.C. Escher mezzotint and the Lena image with pixel elements consisting of 10-nm-diameter nanoposts spaced by gaps as small as 10 nm. The patterned images were tens of microns in size and faithfully reproduce the original images under SEM inspection. The process described could find applications in the fabrication of deep sub-wavelength elements with gradually varying dimensions in nanophotonic devices, and in creating grayscale images as anti-counterfeit features on substrates.

GaN directional couplers for integrated quantum photonics

Large cross-section GaN waveguides are proposed as a suitable architecture to achieve integrated quantum photonic circuits. Directional couplers with this geometry have been designed with aid of the beam propagation method and fabricated using inductively coupled plasma etching. Scanning electron microscopy inspection shows high quality facets for end coupling and a well defined gap between rib pairs in the coupling region. Optical characterization at 800 nm shows single-mode operation and coupling-length-dependent splitting ratios. Two photon interference of degenerate photon pairs has been observed in the directional coupler by measurement of the Hong-Ou-Mandel dip [C. K. Hong, et al., Phys. Rev. Lett. 59, 2044 (1987)] with 96% visibility.

Summary of: Sealing ability of mineral trioxide aggregate, glass ionomer cement and composite resin when repairing large furcal perforations

Objective To evaluate the sealing ability of different repair materials and the pathway of bacterial penetration after closure of large pulp chamber floor perforations. Materials and methods Perforations were made in the furcation area of extracted human molars and sealed with either mineral trioxide aggregate (MTA), glass ionomer cement or resin composite. The bacterial leakage method was used with Enterococcus faecalis as microbial tracer. The time of leakage (in days) was recorded for each specimen. Statistical analysis of bacterial leakage was performed using the survival analysis and pairwise comparison of groups. A p-value less than 0.05 was considered statistically significant. Leaking specimens were prepared and inspected for the presence of bacteria by a scanning electron microscope (SEM). Results The percentage of leaking samples was significantly higher in resin composite than in the other groups and the negative control group (p <0.05). SEM inspection revealed the presence of bacteria in all leaking specimens. Bacteria were observed along the filling-dentine interface as well as in dentinal tubules at some distance from the filling. Conclusions The resin composite material leaked significantly more than the MTA and glass ionomer cements when used to repair large furcation perforations. Bacteria could penetrate into dentine even at a distance from the perforation filling.

Sealing ability of mineral trioxide aggregate, glass ionomer cement and composite resin when repairing large furcal perforations

To evaluate the sealing ability of different repair materials and the pathway of bacterial penetration after closure of large pulp chamber floor perforations. Perforations were made in the furcation area of extracted human molars and sealed with either mineral trioxide aggregate (MTA), glass ionomer cement or resin composite. The bacterial leakage method was used with Enterococcus faecalis as microbial tracer. The time of leakage (in days) was recorded for each specimen. Statistical analysis of bacterial leakage was performed using the survival analysis and pairwise comparison of groups. A p-value less than 0.05 was considered statistically significant. Leaking specimens were prepared and inspected for the presence of bacteria by a scanning electron microscope (SEM). The percentage of leaking samples was significantly higher in resin composite than in the other groups and the negative control group (p<0.05). SEM inspection revealed the presence of bacteria in all leaking specimens. Bacteria were observed along the filling-dentine interface as well as in dentinal tubules at some distance from the filling. The resin composite material leaked significantly more than the MTA and glass ionomer cements when used to repair large furcation perforations. Bacteria could penetrate into dentine even at a distance from the perforation filling.

Localization of burn mark under an abnormal topography on MOSFET chip surface using liquid crystal and emission microscopy tools

This article focuses on the localization of burn mark in MOSFET and the scanning electron microscope (SEM) inspection on the defect location. When a suspect abnormal topography is shown on the die surface, further methods to pin-point the defect location is necessary. Fault localization analysis becomes important because an abnormal spot on the chip surface may and may not have a defect underneath it. The chip surface topography can change due to the catastrophic damage occurred at layers under the chip surface, but it could also be due to inconsistency during metal deposition in the wafer fabrication process. Two localization techniques, liquid crystal thermography and emission microscopy, were performed to confirm that the abnormal topography spot is the actual defect location. The tiny burn mark was surfaced by performing a surface decoration at the defect location using hot hydrochloric acid. SEM imaging, which has the high magnification and three-dimensional capabilities, was used to capture the images of the burn mark.

Failure analysis of shear pins in wind turbine generator

This paper examines the failure of shear pins that connect gearbox and generator in a wind turbine generator. Chemical and micro-structural together with hardness measurements have been performed to check any deviation in the material specification. The failure mechanism is analyzed by both visual and Scanning Electron Microscope (SEM) inspection on the fractured surface. Finite Element Analysis (FEA) of shear pin is carried out to determine the root cause for its failure. The neck diameter of shear pin is optimized for the safe operation of the wind turbine. It is inferred from the observations based on fractography study on the fractured surface of the shear pins that the misalignment between the driving and the driven elements in the wind turbine leads to low cyclic fatigue growth.

Structural, electrical, and optical characterizations of laser deposited nanometric iron oxide films

The structural, electrical, and optical characteristics of nanometric Fe2O3−x films fabricated on ⟨100⟩ Si and SiO2 substrates by ablating an iron target with a KrF excimer laser in low pressure (0.05–1.0 Pa) O2 atmosphere are reported. The thickness of films fabricated with 4000 laser pulses is ∼80 nm for samples deposited at the lowest pressure (0.05 Pa) and decreases gradually to 50 nm at the highest used pressure (1.0 Pa). The film mean composition results close to FeO at lower pressures (0.05–0.10 Pa) and to Fe2O3 at higher pressures (0.5–1.0 Pa). From glazing incidence x-ray diffraction spectra, it was inferred that deposits are poorly crystallized, especially the ones prepared at relatively high oxygen pressures (0.5–1.0 Pa). Scanning electron microscopy inspections show that surfaces are plane and uniform, with very rare (&amp;lt;0.1 μm−2) submicron droplets. From x-ray reflectivity spectra, surface roughness results very low (0.1–0.5 nm, increasing with O2 pressure). The films present a semiconductor behavior, with electrical energy gaps increasing from 0.43 to 0.93 eV with increasing O2 pressure, while the optical energy gap varies from 1.60 eV (0.05 Pa) to 1.74 eV (1.0 Pa). Very high thermoelectromotive force coefficient values were measured (up to 1.65 mV/K). It is also shown that films present promising gas sensing properties.

Fabrication of methane gas sensor by layer-by-layer self-assembly of polyaniline/PdO ultra thin films on quartz crystal microbalance

Abstract The polyaniline/PdO composite was synthesized by chemical oxidative polymerization of aniline with PdO nanoparticles. A methane gas sensor was made by deposition polyaniline/PdO thin films on a mass-type quartz crystal microbalance (QCM) device through layer-by-layer (LbL) self-assembly method. Scanning electron microscopy inspection shows that the polyaniline/PdO multilayers are formed with a dense network of nanofibers. The frequency responses of the polyaniline/PdO based QCM sensor to methane gas were measured at room temperature and 50 °C. It exhibited that the polyaniline/PdO based QCM gas sensor has a better response at room temperature than that at 50 °C. Meanwhile, the humidity effect is also discussed.

Friction and wear variations of short carbon fiber (SCF)/PTFE/graphite (10vol.%) filled PEEK: Effects of fiber orientation and nominal contact pressure

In the present work, the effects of fiber orientation on the tribological behavior of a short carbon fiber (SCF)/PTFE/graphite (10 vol.% for each) filled PEEK composite was studied under different nominal pressures ranging from 1 MPa to 5 MPa. The fiber orientations were parallel, anti-parallel and normal relative to the sliding direction. The results indicate that the effect of fiber orientation shows strong dependence on the nominal pressure. Under most conditions, lower friction coefficients occurred when the fibers were orientated at the anti-parallel rather than the parallel and the normal directions relative to the sliding direction. At low pressures, i.e. 1–2 MPa, the fiber orientation had little effect on the wear rate. Under higher pressures, i.e. 3–5 MPa, the composite displays a higher wear resistance when the fibers are orientated at the anti-parallel rather than the parallel and the normal directions. The tribological mechanisms were discussed based on scanning electron microscopy (SEM) inspections of the worn surfaces.

Probing plasma-induced defect formation and oxidation in carbon nanotubes by Raman dispersion spectroscopy

Plasma treatment of multi-walled carbon nanotubes (MWCNTs) using an atmospheric pressure hydroxyl radical (OH) source has been monitored with micro-Raman spectroscopy. We use dispersion behavior of the intensity ratio, band position, and linewidth of the D, G, D′, and G′ bands to probe the defect formation and oxidation process in MWCNTs. A simple kinetic model is adopted to interpret the observed dispersion trends in plasma-treated MWCNTs. X-ray photoelectron spectroscopic analysis, scanning electron microscopy inspection, and Raman dispersion characterization of MWCNT surfaces suggest that the dominant effect of OH plasma on MWCNTs is reduced π-conjugated states due to creating structural defects and attachment of oxygen-containing functional groups.

Analytical model for ArF photoresist shrinkage under scanning electron microscopy inspection

Linewidth slimming is a phenomenon occurring specifically in photolithography of 193 nm wavelength (ArF) radiation. Photoresists for this wavelength appear to lose volume when exposed to electron-beam radiation, as when scanned in scanning electron microscopy for critical dimension (linewidth) measurement. This work is an attempt to understand this “shrinkage” from a polymer physics point of view. More specifically, the authors try to check the applicability of free volume theory in polymer systems by calculating some relevant physical properties, assuming that the exposure to e-beam creates an external hardened shell for the material bulk, and continued exposure will deliver heat into the polymer enclosed in a confined space. The authors’ main conclusion is that the free volume loss (annealing) shows qualitative resemblance to experiment, but this effect exclusively is not a sufficient quantitative explanation for the observed shrinkage. A possible explanation for this discrepancy is that their model is limited due to unknown material parameters, or that the annealing is coupled with other effects such as “wringing” solvent out.