High-resolution Scanning Electron Microscopy Images Research Articles

Chemically deposited La2Zr2O7 buffer layers for YBCO-coated conductors: film growth and microstructure

An adequate buffer layer architecture is of great importance forYBa2Cu3O7−δ (YBCO)-coated conductor fabrication. We present a transmission electron microscopy (TEM) analysisof La2Zr2O7 (LZO) buffer layers on biaxially textured Ni–5 at.%W substrates for YBCO-coated conductorsprepared by chemical solution deposition (CSD). The LZO thin films were heat-treated at 900 and1050 °C respectively. Electron diffraction patterns, and bright and dark-field images were usedto determine the microstructure, texture and the nanoporosity of the films. Byx-ray diffraction the films were found to be [100] oriented and strongly biaxiallytextured. Although x-ray diffraction suggests an epitaxial growth of LZO on Ni itwas shown by TEM that this was not the case. The grain size of the films isbetween 100 and 300 nm and therefore much smaller than the Ni grain size of40 µm. Appropriate acquisition conditions for scanning electron microscopy (SEM) and TEMimaging are given to identify the nanogranularity of the films. For the film annealed at1050 °C high-resolution SEM images clearly show a polycrystalline LZO microstructure and the grain sizecan readily be determined. Electron diffraction rings are more pronounced than for the film annealedat 900 °C, indicating a higher level of polycrystallinity in the film. SEM images of the film annealed at900 °C yield no evidence of a polycrystalline microstructure; only single misoriented LZO grainsseparated by 500 nm are observed. Nanovoids 10–40 nm in size were found in the LZO bufferlayers with a high density. The voids had approximately cuboid shape, indicating ananisotropy of the surface energy in LZO. The surface planes of the voids were identified as{111} lattice planes. Despite the nanoporosity, which is a typical feature of CSD-grownbuffer layers, the LZO buffer layers act as efficient Ni diffusion barriers. Energydispersive x-ray microanalysis (EDX) in the transmission electron microscope yieldedthe composition of the films. In the LZO films no Ni-rich secondary phases weredetected and significant C contamination occurred during spectrum acquisition.

Near-infrared photoluminescence of vertically aligned InN nanorods grown on Si(111) by plasma-assisted molecular-beam epitaxy

We demonstrate that vertically aligned InN nanorods have been grown on Si(111) substrates by plasma-assisted molecular-beam epitaxy (PA-MBE) at low and high growth temperatures (LT- and HT-InN nanorods). High-resolution scanning electron microscopy images clearly show that InN nanorods grown on Si(111) are hexagonal in shape, vertically aligned, well separated and densely distributed on the substrate. The size distribution of LT-InN nanorods is quite uniform, while the HT-InN nanorods exhibit a broad, bimodal distribution. The structural analysis performed by Raman scattering indicates that PA-MBE grown InN nanorods have the wurtzite-type InN single-crystal structure with the rod axis (growth direction) along the c-axis. In addition, both types of nanorods contain high concentrations of electrons (unintentionally doped). Compared to the HT-InN nanorods and the PA-MBE-grown InN epitaxial film, the LT-grown InN nanorods have a considerable number of structural defects. Near-infrared photoluminescence (PL) from LT- (∼ 0.77 eV) and HT-InN (∼ 0.70 eV) nanorods is clearly observed at room temperature. In comparison with the LT-InN nanorods, the PL efficiency of HT-InN nanorods is better and the PL peak energy is closer to that of InN-on-Si epitaxial films (∼ 0.66 eV). We also find that the PL band at low temperatures from nanorods is significantly weaker (compared to the InN film case) and exhibits anomalous temperature effects. We propose that these PL properties are results of considerable structural disorder (especially for the LT-InN nanorods) and strong surface electron accumulation effect (for both types of nanorods).

Wet-chemical synthesis of magnesium niobate nanoparticles powders

Nanosized and highly reactive magnesium niobate ( MgNb 2 O 6 ) powders were successfully synthesized by a new wet-chemical method by means of the dissolution of Nb 2 O 5 ⋅ 5 H 2 O and in a solution of oxalic acid followed by the addition of stoichiometric amounts of magnesium carbonate. The Nb–Mg–oxalic acid solution was evaporated resulting in a dry and amorphous powder that was calcined in the temperature range from 200 to 900 °C for 2 h. The crystallization process from the amorphous state to the crystalline MgNb 2 O 6 was followed by thermal analysis. The calcined powders characterized by FT-Raman spectroscopy, X-ray diffraction (XRD) and their morphology examined by high resolution scanning electron microscopy (HR-SEM). Pure MgNb 2 O 6 , free from the second phases and obtained at 800 °C was confirmed by a combined analysis using XRD and FT-Raman. The average diameter of the particles was calculated from the HR-SEM image as 70 nm approximately. This technique allows a better mixing of the constituent elements and thus a better reactivity of the mixture to obtain pre-reaction products with high purity at lower temperatures and reducing cost. It can offer a great advantage in the PMN-PT formation with respect to the solid-state synthesis.

Three-dimensional characteristics of submandibular salivary gland of ageing rats: An HRSEM study

The characteristics of the submandibular glands of ageing Wistar rats were studied using light and high-resolution scanning electron microscopy (HRSEM) methods. For light microscopy, the samples were fixed in Bouin solution and embedded in paraffin. Sections were stained with hematoxilin-eosin and Azo-Carmin. For conventional scanning electron microscopy, the tissues were fixed in modified Karnovsky solution, and treated with NaOH solution for 3-4 days. The O-D-O method was used for HRSEM. The samples were fixed in 2% osmium tetroxide, macerated in diluted osmium and dehydrated in an increasing series of ethanol. The samples were dried in a critical point dryer, coated with gold-palladium and examined in a Hitachi high-resolution scanning electron microscope, S-900. The results showed that submandibular glands with lobules are separated by connective tissue septum. The acinar formations and the ducts, revealing the serous and mucous cells were observed. After fracture in liquid nitrogen and treatment with NaOH solution to remove the cellular components, the original disposition of the collagen bundles fibers were revealed corresponding to the round, oval or irregular acinar and ductal structures. In the cytoplasm, organelles such as mitochondria, rough endoplasmic reticulum, Golgi apparatus and serous and mucous secretory granules were observed localized in the apical portion in three-dimensional HRSEM images. The serous secretory granules presented different sizes and shapes showing the modifications which occurred in the ageing rats. The striated duct cells revealed the presence of the secretory cells and mitochondria in parallel disposition. The mitochondrial cristae were noted in three-dimensional aspects. The lumen presented numerous cytoplasmic microprojections. The lumen of excretor ducts are covered by polygonal epithelial cells containing numerous microplicae.

Mechanical properties and the evolution of matrix molecules in PTFE upon irradiation with MeV alpha particles

The morphology, chemical composition, and mechanical properties in the surface region of α-irradiated polytetrafluoroethylene (PTFE) have been examined and compared to unirradiated specimens. Samples were irradiated with 5.5 MeV 4He 2+ ions from a tandem accelerator to doses between 1 × 10 6 and 5 × 10 10 Rad. Static time-of-flight secondary ion mass spectrometry (ToF-SIMS), using a 20 keV C 60 + source, was employed to probe chemical changes as a function of α dose. Chemical images and high resolution spectra were collected and analyzed to reveal the effects of α particle radiation on the chemical structure. Residual gas analysis (RGA) was utilized to monitor the evolution of volatile species during vacuum irradiation of the samples. Scanning electron microscopy (SEM) was used to observe the morphological variation of samples with increasing α particle dose, and nanoindentation was engaged to determine the hardness and elastic modulus as a function of α dose. The data show that PTFE nominally retains its innate chemical structure and morphology at α doses <10 9 Rad. At α doses ≥10 9 Rad the polymer matrix experiences increased chemical degradation and morphological roughening which are accompanied by increased hardness and declining elasticity. At α doses >10 10 Rad the polymer matrix suffers severe chemical degradation and material loss. Chemical degradation is observed in ToF-SIMS by detection of ions that are indicative of fragmentation, unsaturation, and functionalization of molecules in the PTFE matrix. The mass spectra also expose the subtle trends of crosslinking within the α-irradiated polymer matrix. ToF-SIMS images support the assertion that chemical degradation is the result of α particle irradiation and show morphological roughening of the sample with increased α dose. High resolution SEM images more clearly illustrate the morphological roughening and the mass loss that accompanies high doses of α particles. RGA confirms the supposition that the outcome of chemical degradation in the PTFE matrix with continuing irradiation is evolution of volatile species resulting in morphological roughening and mass loss. Finally, we reveal and discuss relationships between chemical structure and mechanical properties such as hardness and elastic modulus.

Low-voltage high-resolution scanning electron microscope imaging of the uncoated and Cr-coated zeolite Beta

Fine surface features of the uncoated, as-synthesized zeolite Beta and the effect of Cr sputter coating on the appearance of these features were examined using high-resolution (lateral resolution ∼ 2.5 nm) field emission scanning electron microscopy (FE-SEM). The uncoated particles exhibited charging effects despite a reduced accelerating voltage (2 kV). Thus, only rapid scanning at “TV rates”, where an average of multiple frames is acquired, produced useful FE-SEM images. Pyramidal irregularities, resulting in the “saw teeth-like” surface features less than ∼20–30 nm in size, were observed on the uncoated particles. These images did not reveal any texture over flat areas of the surface. Deposition of thin Cr films with a nominal thickness of 1–2 nm reduced/eliminated sample charging so that a slow scanning speed could be used. The resulting images showed better topographic contrast than the images of the uncoated particles. The appearance of fine “teeth” was not affected by sputtering with thin 1–2 nm Cr films. However, the development of a grainy surface texture in the form of nodules smaller than ∼5 nm over flat areas of the surface, which appeared to grow in number density and size (to more than ∼5 nm) with the increasing nominal (up to 10 nm) Cr film thickness, could be observed. This is hypothesized to be the result of Cr particle formation. Sputtering used to deposit thin Cr films did not appear to damage crystal surfaces. Thus, thin (1–2 nm) Cr coatings improve image quality with little or no loss in surface texture resolution.

New aspects on pulsed laser deposition of aligned carbon nanotubes

We have grown carbon nanotubes (CNT) by pulsed laser deposition (PLD) at 1000 °C in Ar atmosphere. A Nd/YAG laser was used for irradiation of a graphite target containing Ni and Co rods. High-resolution scanning electron microscopy (HRSEM) and transmission electron microscopy (TEM) images showed that “closed” carbon nanotubes were grown between clusters of metallic particles, so that the individual nanotubes were arranged in parallel to each other forming a shape of “Rope-Bridge”. The nanotubes structure was analyzed by high-resolution transmission electron microscopy (HRTEM) and their type was found to be of MWNT, containing about five SWNT. Total diameter was 5–20 nm and their length was about 1 μm. High homogeneous distribution carbon nanotubes were grown and different structures were observed such as well-aligned carbon nanotubes, bamboo-like and Y-junction carbon nanotubes.

Microstructural and optical properties of self-organized GaN quantum-dot assemblies

The microstructural and optical properties of GaN quantum-dot (QD) assemblies self-organized in two-dimensional GaN epilayers grown on AlxGa1−xN layers by using plasma-assisted molecular beam epitaxy were investigated with high-resolution scanning electron microscopy (HRSEM) and cathodoluminescence (CL) measurements. The HRSEM images showed that QD assemblies were formed in separate regions of the slightly stressed GaN epilayer on the Al0.4Ga0.6N surface and that the size and the density of the self-organized QD assemblies were affected significantly by the thickness and the surface polarity of the GaN layer. The CL spectra of the GaN QD assemblies showed a blue shift of the near band gap emission, and the position of the emission peak depended on the polarity and the thickness of the GaN epilayer. Deep level luminescence spectra indicated the existence of impurity-assisted QD assembly formation.

Immobilization of Gold Nanoparticles onto Silicon Surfaces by Si−C Covalent Bonds

A series of ω-alkene-1-thiol-stabilized gold nanoparticles were prepared by a wet process and then covalently linked to a hydrogen-terminated silicon(111) surface with Si−C bonds via a thermal hydrosilylation reaction. The modified silicon surfaces were observed mainly by high-resolution scanning electron microscopy (HR-SEM). The HR-SEM images revealed that the gold nanoparticles protected with 2-propene-1-thiol (C3) were covalently bound to the hydrogen-terminated silicon surface, after which the nanoparticles self-fused; on the other hand, gold nanoparticles protected with 5-hexene-1-thiol (C6) or 10-undecene-1-thiol (C11) were linked to the hydrogen-terminated silicon surface independently. These surfaces were stable in air and can be stored for several months without detectable decomposition.

Properties of carbon onions produced by an arc discharge in water

A simple method to fabricate high-quality nanoparticles including spherical carbon onions and elongated fullerene-like nanoparticles similar to nanotubes in large quantities without the use of vacuum equipment is reported. The nanoparticles are obtained in the form of floating powder on the water surface following an arc discharge between two graphite electrodes submerged in water. High-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy images confirm the presence of spherical carbon onions with diameters ranging from 4 to 36 nm. The specific surface area of the floating powder was found to be very large, 984.3 m2/g, indicating that the material is promising for gas storage. From the surface area measurements, the mean particle diameter was calculated to be 3.7 nm. This value is close to the lower limit of the carbon onions observed in HRTEM. However, closer HRTEM observations also reveal that some carbon onions are not well crystallized. The large specific surface area can be attributed to the “surface roughness” induced by the defective nature of the carbon onion shells. To explain the formation mechanism of the carbon onions, a model of arc discharge in water with two quenching zones is proposed: (1) the presence of ion current conducive for elongated nanoparticles growth and (2) the absence of ion current for isotropic growth of carbon onions. Based on this model, we propose that the physical characteristics of the product can be controlled.

Effects of substrate defect density and annealing temperature on the nature of Pt clusters vapor deposited on the basal plane of highly oriented pyrolytic graphite

The influence of substrate defect sites on the morphology of Pt vapor deposited on the basal plane of highly oriented pyrolytic graphite (HOPG(bp)) has been investigated in situ (in ultrahigh vacuum (UHV)) by X-ray photoelectron spectroscopy (XPS), and ex situ by high-resolution scanning electron microscopy (HRSEM), and scanning tunneling microscopy (STM). Defects were introduced on selected sections of HOPG(bp) surfaces via Ar + bombardment by employing specially designed masks. The effect of such defects on the electronic and structural nature of the Pt clusters formed was examined by evaporating the metal simultaneously on both damaged and nominally pristine sections of HOPG(bp). HRSEM and STM images of Pt deposits formed at 300 K on pristine HOPG(bp) were found to display three-dimensional fractal-type aggregates. Image analysis of such Pt clusters gave a fractal dimension D L=1.7 for Pt on Pt, using area ( A)/perimeter ( P) relations, and D L=1.5 for Pt on HOPG(bp), based on the count box method. Possible origins of this difference include higher cluster edge atom diffusion rates for Pt in the first monolayer (ML) and/or small cluster mobilities as in the model investigated by Meakin [Phys. Rev. Lett. 51 (1983) 1119.]. This overall behavior was unlike that observed for Pt vapor deposited on sections of Ar +-bombarded HOPG(bp) surfaces, which yielded instead clusters roughly circular in shape, ca. 1 nm in diameter, and one to two atomic layers high. Such disparate morphologies, however, are in agreement with models proposed in the literature which predict formation of highly ramified structures for diffusion limited aggregation (DLA) on substrates with low density of defect sites and small round clusters when the defect density is increased. Also studied in this work were the effects of post-deposition thermal annealing on the nature of the deposits.

Imaging of Si nano-patterns embedded in SiO 2 using scanning electron microscopy

Detailed shapes of embedded Si nanostructures were clearly observed through a SiO 2 layer using scanning electron microscopy (SEM). We found a new imaging mechanism by which secondary electron (SE) yield from the oxide surface is greater where an embedded Si structure exists. In the range of acceleration voltages from 5 to 200 kV, we found that 30 kV provides high contrast and high resolution. Controlling the surface contrast by depositing a contaminated film using electron beam irradiation yields a clear, high-resolution SEM image of sub-10-nm Si structures embedded in a 60-nm-thick oxide. The combination of a non-destructive observation method based on SEM with a method based on AFM, which was demonstrated previously, provides detailed information on the three-dimensional shape of embedded Si nanodevices.

Characteristics of attachment and growth of Thiobacillus caldus on sulphide minerals: a chemotactic response to sulphur minerals?

To further our understanding of the ecological role of sulphur-oxidizing microorganisms in the generation of acid mine drainage (AMD), growth and attachment of the chemoautotrophic sulphur-oxidizing bacterium, Thiobacillus caldus, on the sulphide minerals pyrite, marcasite and arsenopyrite was studied. Growth curves were estimated based on total cells detected in the system (in suspension and attached to mineral surfaces). In general, higher cell numbers were detected on surfaces than in suspension. Fluorescent in situ hybridizations to cells on surfaces at mid-log growth confirmed that cells on surfaces were metabolically active. Total cell (both surface and solution phase) generation times on pyrite and marcasite (both FeS2) were calculated to be approximately equals 7 and 6 h respectively. When grown on pyrite (not marcasite), the number of T. caldus cells in the solution phase decreased, while the total number of cells (both surface and solution) increased. Additionally, marcasite supported about three times more total cells (approximately equals 3 x 10(9)) than pyrite (approximately equals 8 x 10(8)). This may be attributed to the dissolution rate of marcasite, which is twice that of pyrite. Epifluorescent and scanning electron microscopy (SEM) were used to analyse the cell orientation on surfaces. Results of Fourier transform analysis of fluorescent images confirmed that attachment to all three sulphides occurred in an oriented manner. Results from high-resolution SEM imaging showed that cell orientation coincides with dissolution pit edges and secondary sulphur minerals that develop during dissolution. Preferential colonization of surfaces relative to solution and oriented cell attachment on these sulphide surfaces suggest that T. caldus may chemotactically select the optimal site for chemoautotrophic growth on sulphur (i.e. the mineral surface).

Percolation problem in atomic transport inHg1−xCdxTe

Using high-resolution x-ray diffraction for precise measurements of structural modifications in boron-implanted ${\mathrm{Hg}}_{1\ensuremath{-}x}{\mathrm{Cd}}_{x}\mathrm{Te}$ layers, we found a percolation problem in the long-range diffusion of Cd interstitials through the Cd, Hg sublattice. The percolation threshold ${x}_{c}=0.265$ is in agreement with the calculated one, ${x}_{\mathrm{th}}=0.278,$ for dumbbell interstitials diffusion in the fcc lattice [J. Bocquet, Phys. Rev. B 50, 16 386 (1994)]. These findings were supported by high-resolution scanning electron microscopy images, taken under magnification \ifmmode\times\else\texttimes\fi{}400 000, in which very different post-implantation surface recovery (due to a flux of interstitials from an interior to the crystal surface) was observed below and above ${x=x}_{c}.$ Measurements of x-ray-diffraction profiles in samples, implanted and annealed at 150\char21{}350 \ifmmode^\circ\else\textdegree\fi{}C, allowed us to determine an energy barrier, $\ensuremath{\Delta}E=0.31\mathrm{eV},$ between Cd-Cd and Cd-Hg dumbbell configurations.

Direct Observation of Mesoporous Silica by High Resolution Scanning Electron Microscopy

The direct observation of 2D mesoporous silica by HRSEM(high resolution scanning electron microscopy) is reported here for the first time. The HRSEM images reveal that the structure consists of hexagonally packed short silicate rods (shown schematically in the Figure), which helps to explain the observed properties of mesoporous silica.

High-Resolution and Low-Voltage SEM Imaging and Chemical Microanalysis

Simple direct surface imaging of bulk samples at a resolution of 0.5 nm or better is possible in the scanning electron microscope (SEM) described here, which integrates a high-brightness field emission gun and a high-resolution condenser-objective immersion lens. The Figure shows high-resolution surface details of a carbon fiber, which could only be visualized accurately at very low voltages (<1 kV).

Improved surface morphology of NdBa 2Cu 3O 7− δ films grown by pulsed laser deposition using a large single crystal target

Smooth surface is one of the essential factors for high- T c thin film device fabrications. To obtain smooth NdBa 2Cu 3O 7− δ (NBCO) films by pulsed laser deposition (PLD), a large NBCO single crystal was used as the target instead of sintered ceramic pellet in PLD for the first time. Although NBCO films grown at optimum conditions from either a sintered or a single crystal target possessed similar excellent superconducting properties with zero resistance temperature T c0=91–94 K and current density J c>3×10 6 A/cm 2 at 77 K, they displayed a quite different surface morphology. A great improvement of surface quality was achieved by using the single crystal target. High-resolution scanning electron microscopy images showed that the droplet density on the surface of NBCO films deposited from the single crystal target was reduced by a factor of 10 4, i.e., from 10 6–10 7/cm 2 corresponding to the sintered target to 10 2–10 3/cm 2. Atomic force microscope observation revealed that the line-scan surface roughness was <40 Å over an area of 2×2 μm 2. Our results indicate that PLD using a single crystal target is a quite easy and practical technique for the growth of smooth superconducting films for device applications.

Crack formation in mesophase pitch-based carbon fibres: Part II Detailed structure of pitch-based carbon fibres with some types of open cracks

Several mesophase pitch-based carbon fibres showing radial textures in their transverse alignments were observed by high resolution scanning electron microscope (HR-SEM) to elucidate the principal factor that induces the open crack in the transverse sections of the fibre along its fibre axis. The HR-SEM images of transverse sections exhibited various features in the alignment and shapes of the domains, although they were approximately arranged in the radial direction. The alignment of the domains was often variable in the locations from the outer part to the centre. Linear domains radially oriented in the outer part of the transverse section, that induce the circumferential shrinkage at the spinning and further heat-treatment steps, were essential for the development of open cracks with the PAC-man shaped fibre. Non-radial alignment or non-linear, bent or loop domains in the outer parts prohibited the development of the crack; these are observed in the fibres with the radial skin-random core and the onion skin-radial core alignments. Fibres without cracks in their as-spun or stabilized states usually showed shallow cracks even after the graphitization because the bent and loop domains in the intermediate and centre parts prohibited cracks from propagating into the centre part because the graphitic shrinkage along the domain shapes cannot be linear.

Advantages of backscatter electron imaging scanning electron microscopy for intracellular localization of cardiac analytes by gold conjugated antibody.

Myoglobin and myosin light chain 1 (MLC1) are intracellular human cardiac marker proteins which are released as a consequence of ischemia. Human cardiomyocytes were isolated from fresh biopsies and also maintained for several passages in cell culture. The cardiomyocytes were fixed in 100% methanol at -20 degrees C, and labeled. The immunolocalization of intracellular antigen by fluorescence conjugated imaging was compared with scanning electron microscopy (SEM) backscatter electron (BSE) imaging of gold conjugated antibody. Ultra-violet light microscopy showed the intracellular distribution of both proteins to be mainly in the nuclear envelope, the cytoplasm immediately surrounding the nucleus and along portions of the cell membrane. To confirm this observed distribution of myoglobin and MLC1, labeling was repeated with antimyoglobin and anti-MLC1 monoclonal antibodies conjugated to colloidal gold particles. The advantage of colloidal gold labeling is that the intracellular antigen-antibody complexes may be more precisely located because of the significant improvement in resolution provided by BSE imaging in the SEM. BSE imaging confirmed the presence and subsarcolemma localization of myoglobin in cardiomyocytes directly isolated from fresh biopsies. The distribution of colloidal gold-conjugated antibodies did not coincide with the intracellular distribution of the two proteins in the cardiomyocytes grown in cell culture as indicated by immunofluorescence. A relatively random, intracellular gold particle distribution was confirmed by x-ray microanalysis. BSE imaging resulted in consistent auto-backscatter labeling patterns very similar to the labeling patterns obtained with immunofluorescent labeling. X-ray microanalysis confirmed that these auto-backscatter labeling patterns were formed by concentrations of intracellular phosphate. Sodium dodecyl sulfate-poly-acrylamide gel electrophoresis (SDS-PAGE) and subsequent Western blotting indicated that myoglobin and MLC1 were no longer present in detectable quantities in these cells after several passages. Polymerase chain reaction (PCR) amplification of mRNA for human myoglobin and cardiac MLC1 confirmed the absence of their transcripts. Electrophoretic analysis of proteins in cardiomyocytes grown in cell culture confirmed an increasing presence of alkaline phosphatase. Staining of this enzyme with 5-bromo-4-chloro-3-indolyl phosphate and nitroblue tetrazolium showed that alkaline phosphatase was distributed in the same intracellular pattern as the fluorescence conjugated anti-body and the phosphatase auto-backscatter. These results indicate that high-resolution backscatter SEM imaging may be used as necessary control to confirm fluorescence light microscope intracellular labeling of antigens.

Measurement of Scanning Electron Microscope resolution

The resolution performance of a scanning electron microscope (SEM) is a primary specification of the instrument. For a high-resolution SEM (HRSEM) equipped with a field emission gun (FEG), image resolutions of less than 2 nm are commonly claimed. Generally, both manufacturers and customers identify image resolution as the single most important performance criterion. It is traditionally determined with specimens such as gold islands on bulk carbon supports, where the minimum apparent separation of two islands is claimed as the resolution. This procedure is highly subjective since the spacings are not known independently. Dodson and Joy have pointed out the paradox implicit in this approach-that “the resolution of a given instrument can be verified only after a better instrument is available to characterize the structure spacing.” By analogy to the now standard approach for high-resolution transmission electron microscopes (TEMs), Dodson and Joy investigated the use of Fourier Transforms (FT) of high-resolution SEM images for measuring resolution.