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We investigated electron emission characteristics of a hafnium carbide [HfC(100)] single-crystal tip at various temperatures toward finding a candidate of the next generation of emitters for electron microscopes. The emission mode changed from cold-field emission (CFE) to low-temperature and high-temperature thermal-field emission and, finally, to extended Schottky emission. The energy width at full width of half maximum of the emitted electrons was 0.2 eV in the CFE mode at an angular current of 20 μA/sr, and it showed good emission stability with current noise less than 3.5% in an electron gun of a scanning electron microscope (SEM). Spatial resolution of the SEM at an acceleration voltage of 0.5 kV improved 14% by using the HfC(100)-CFE tip instead of a conventional W(310)-CFE tip. High monochromaticity and stable electron emission of the HfC(100)-CFE tip are suitable for the next generation of emitters for ultrahigh-resolution field emission SEMs. [ABSTRACT FROM AUTHOR]

To address the challenges of accurate metrology of height and sidewall angle (SWA) of three-dimensional structures with critical dimension scanning electron microscopy, general modeling and algorithms based on tilted electron beam technology and the corresponding application skills are proposed, and the validity and error accuracy are evaluated as well. Three typical structures, the trapezoid, inverted trapezoid, and step, are investigated with Monte Carlo simulation. The maximum derivative method is used to extract key parameters from the secondary electron linescan. The efficiency of the proposed modeling, algorithms, and the accuracy of the calculated height and SWA are improved further with the application of wavelet transform. [ABSTRACT FROM AUTHOR]

Lateral field emission devices have been characterized before and after ultraviolet (UV) light exposure. Two types of planar device structures, diode and bowtie, were studied. These nanoscale devices have 9–15 nm tip-to-tip (bowtie) or tip-to-collector (diode) dimensions with the tips fabricated from Au/Ti. Typical currents of 2–5 nA per tip at 6 V were measured. It was observed that after UV exposure, the collected current was reduced by >28% for the case of a bowtie device; whereas the current was reduced by >39% for the case of a diode device. This reduction can be attributed to water vapor desorption on the dielectric surface between the structures, which in turn reduces surface leakage. The Fowler–Nordheim plot showed a straighter line after UV exposure. After the I-V test, the UV-exposed devices were placed on lifetime tests in a vacuum of <10−8 Torr and were biased at 5 V DC. After 2600 h, an abrupt current decrease was observed: ∼25% for the case of the bowtie and ∼28% for the case of the diode device. Scanning electron microscope images of the bowtie and diode devices showed damage to the tips. [ABSTRACT FROM AUTHOR]

This paper describes the influence of vacuum annealing on the mechanical characteristics of silicon (Si) nanowires (NWs) fabricated using focused ion beam (FIB) technologies. Two types of Si NWs having a cross-sectional one-side length or diameter ranging from 19 to 447 nm are prepared using the direct milling and Ga ion doping functions of FIB. The Si NWs prepared are annealed at 400–700 °C in high vacuum for 10 min, followed by quasi-static uniaxial tensile testing using a microelectromechanical system based tensile test system in a scanning electron microscope. All the Si NWs fracture in a brittle manner. Young's modulus of submicrometer-sized Si NWs shows both annealing and specimen size influences in the range from 120 to 170 GPa, whereas that of nano-sized Si NWs shows only annealing influence in the range from 60 to 110 GPa. Tensile strength scatters greatly, ranging from 1.0 to 7.2 GPa, which increases with increasing the NW size. A transmission electron microscope and an atomic force microscope suggest that, by annealing, recrystallization happens in the damaged layer introduced by FIB milling and the NW surface morphology changes due to its recrystallization and gallium (Ga) ion evaporation. Fracture origin is discussed through the comparison between surface roughness and crack length estimated by the Griffith theory of brittle fracture. [ABSTRACT FROM AUTHOR]

Dust-mitigating surfaces typically consist of high-aspect-ratio structures that separate particles from resting on the bulk material, thereby limiting adhesion due to short-range van der Waals forces. These surfaces can find uses in solar-panel coatings and a variety of dust-resistant optics. The current method for quantifying surface contamination is optical microscopy, but this method is inadequate for observing particles at the submicrometer scale due to the diffraction limit. Furthermore, regardless of the microscopy technique, particle identification becomes problematic as the particle contaminates approach the same length scale of the surface structures. In this work, we demonstrate a method to identify micro-/nanoparticle contaminates on nanostructured surfaces using electron microscopy and image processing. This approach allows the characterization of particles that approach the length scale of the surface structures. Image processing, including spectrum filters and edge detection, is used to remove the periodic features of the surface nanostructure to omit them from the particle counting. The detection of these small particles using electron microscopy leads to an average of 5.62 particles/100 μm2 detected compared to 0.63 particles/100 μm2 detected for the traditional confocal optical detection method. Beyond dust-mitigation nanostructures, the demonstrated particle detection technique can find applications in nanobiology, the detection of ice nucleation on a structured surface, and semiconductor mask inspections. [ABSTRACT FROM AUTHOR]

Scanning electron microscope is not only a versatile visualization and characterization tool for nanomaterials, but it is also widely used for visual feedback during assembly and manipulation of micro- and nanoparticles, novel devices based on 2D and 1D materials, and microrobots. Due to increase in the surface-to-volume ratio, adhesion forces play a significant role in micro- and nanorobotic applications. We investigate the quantitative effect of electron beam irradiation on nanoscale adhesive interactions between different end effector types and plain substrates. For this purpose, we use an interferometry-based force measurement setup integrated into the chamber of a scanning electron microscope capable of a subnano Newton force resolution. We provide quantitative results for the influence of the electron beam on the adhesion forces depending on the exposure dose, geometrical configuration in which it is applied, as well as on the material of the end effector. Simulation results, atomic force microscope adhesion measurements, and measurements with piezoresistive cantilevers serve as references. Our findings indicate that the electron beam influences the adhesive interaction not only in the case of insulating probes but also for well-grounded conducting and semiconducting probes. Its influence can range from several 10% to several 100% in comparison to the adhesion values measured with an atomic force microscope in an ambient atmosphere and no charged particle beam is applied. Moreover, it is shown that the influence of a charged particle beam is a multidimensional phenomenon that depends on several factors such as end effector and substrate material, geometry and aspect ratio of the end effector, geometrical configuration between particle beam and probe–sample arrangement, as well as exposure dose and field of view. We provide recommendations for handling and characterization of micro- and nano-objects using end effectors under the influence of charged particle beams: not to rely on adhesion values acquired in different environmental and exposure conditions, not to expect the application of conductive materials and grounding to completely avoid the effect of charged particle beams, and to be aware that charged particle beams can lower or increase the adhesion force in vacuum depending on material properties, among others. [ABSTRACT FROM AUTHOR]

The mechanical properties characterization of silicon nanowires is generally performed by tensile nanomechanical loading tests with in situ strain quantification. While the strain is characterized by electron beam (e-beam) microscopy techniques, the understanding of the sample-electron interaction is essential to guarantee artifact-free measurements. In this work, we investigated suspended strained silicon nanowires under electron beam exposure in a scanning electron microscope (SEM). The fabricated nanowires had their initial stress profile characterized by Raman spectroscopy and finite element method simulations. Then, the sample was exposed to an e-beam where we observed a gradual electrical charging of the sample, verified by the image drift, and down deflection of the suspended nanowire caused by electrostatic forces. These additional stresses induced the mechanical fracture of the nanowires in the corner region due to accumulated stress. These results ascribe electrostatic mechanical loading concerns that may generate undesirable additional stresses in nanomechanical tests performed in SEM, demonstrating the importance of proper sample preparation to avoid electrostatic charging effects. Here, we propose a simple and effective method for imposing the structures under an impinging electron beam at an equipotential, which mitigates the charging effects acting on the nanowire. [ABSTRACT FROM AUTHOR]

The photocurrent from a semiconductor photocathode with a negative-electron affinity surface can be arbitrarily controlled by the excitation laser power. Applying this characteristic to a scanning electron microscope allows the probe current to be arbitrarily controlled at any location on the sample. A photocathode with a fast time response is required to control the probe current at high speed. This study used an InGaN photocathode for pulsed electron beam generation and investigated its time response. A pulsed electron beam with 3.8 ns pulse width and 8.1 × 103 A cm−2 current density was observed, and the rise and fall times of the photocurrent were found to be 1.7 and 2.0 ns, respectively. The results show that despite the bottleneck of the time response of the laser power, the InGaN photocathode generates an electron beam that can control the probe current on a pixel-by-pixel for a 270 MHz scan speed. [ABSTRACT FROM AUTHOR]

Pulsed electron beams from a photocathode using an InGaN semiconductor have brought selectively scanning technology to scanning electron microscopes, where the electron beam irradiation intensity and area can be arbitrarily selected within the field of view in SEM images. The p-type InGaN semiconductor crystals grown in the metalorganic chemical vapor deposition equipment were used as the photocathode material for the electron beam source after the surface was activated to a negative electron affinity state in the electron gun under ultrahigh vacuum. The InGaN semiconductor photocathode produced a pulsed electron beam with a rise and fall time of 3 ns, consistent with the time structure of the irradiated pulsed laser used for the optical excitation of electrons. The InGaN photocathode-based electron gun achieved a total beam operation time of 1300 h at 15 μA beam current with a downtime rate of 4% and a current stability of 0.033% after 23 cycles of surface activation and continuous beam operation. The InGaN photocathode-based electron gun has been installed in the conventional scanning electron microscope by replacing the original field emission gun. SEM imaging was performed by selective electron beaming, in which the scanning signal of the SEM system was synchronized with the laser for photocathode excitation to irradiate arbitrary regions in the SEM image at arbitrary intensity. The accuracy of the selection of regions in the SEM image by the selective electron beam was pixel by pixel at the TV scan speed (80 ns/pix, 25 frame/s) of the SEM. [ABSTRACT FROM AUTHOR]

Quantitatively accurate, physics-based, computational modeling of etching and lithography processes is essential for modern semiconductor manufacturing. This paper presents lithography and etch models for a trilayer process in a back end of the line manufacturing vehicle. These models are calibrated and verified against top-down scanning electron microscope (SEM) and cross-sectional SEM measurements. Calibration errors are within 2 nm, while the maximum verification error is less than 3 nm. A fluorocarbon plasma etch of the spin-on-glass (SOG) layer accounts for most of the etch bias present in the process. The tapered profile in the SOG etch step is generated due to the polymerization process by fluorocarbon radicals generated in the plasma. The model predicts a strong correlation between the etch bias in the SOG etch step and the neutral-to-ion flux ratio in the plasma. The second etch step of the flow, which etches the spin-on-carbon (SOC) layer using an H2/N2 plasma, results in a negative etch bias (increase in CDs) for all measured features. The ratio of hydrogen to nitrogen radical fluxes effectively controls the etch bias in this step, with the model predicting an increase in the etch bias from negative to positive values as the H-to-N ratio decreases. The model also indicates an aspect ratio dependent etch rate in the SOG and SOC etch steps, as seen in the etch front evolution in a three-dimensional test feature. The third and final step of the process, SiO2-etch, generates an insignificant etch bias in all the test structures. Finally, the accuracy of the etch simulations is shown to be dependent on the accuracy of the incoming photoresist shapes. Models that consider only the top-down SEM measurement as input and do not account for an accurate photoresist profile, suffered significant errors in the post-etch CD predictions. [ABSTRACT FROM AUTHOR]

Integrated interferometry installed on top of dry etch equipment was developed for the in-process measurement of critical dimension (CD) in vertical NAND flash memory dry etch forming word-line steps, also known as word-line processes. The etching process sequentially consists of mask trimming and mold etching (multilayered structure of Si3N4 and SiO2). In-process real-time CD measurements can be made in a trimming step that etches the photoresist (PR) to form a vertical mask shape. The measurement principle is based on the analysis of the interference fringe signal of light reflection to a single point in the center of the wafer. To check the measurement accuracy of the interferometer, the CD measured with interferometry was compared with an in-line SEM (scanning electron microscope). The correlation coefficient between the interferometric measurements measured during the mask trimming step and the in-line SEM measured after the completed process was 86%. On the other hand, when the mask trimming and the mold etching steps including Si3N4 over etching were added, the total measurement results showed that the correlation coefficient was 95%. This is because the CD value was derived based on the phenomenon that the PR thickness change measured by interferometry in the trimming step was a linear relationship with the change in the lateral PR amount, so the lateral PR amount was weakly etched in the mold etching step after the trimming step, which eventually affected the final formed CD. This metrology method can be simply applied to dry etching equipment in real production lines. [ABSTRACT FROM AUTHOR]

The electrostatic discharge (ESD) from polymer insulators is one of the environment-related anomalies on spacecraft. Theoretically, to mitigate the ESD effects, we could modulate the secondary electron yield (SEY, σ) close to 1 in the entire energy range, suppressing surface charges. However, no single polymer insulator has been reported to achieve this seesaw-type modulation of SEY. Here, we exploringly designed and prepared MgO particles doped polytetrafluoroethylene (PTFE) composite coating to achieve this goal, which exhibits not only the reduced SEY characteristic of the microstructured PTFE coating at low energy but also the enhanced SEY characteristic of the double-layer structure of PTFE and MgO at high energy. The simulation and experiment results demonstrate that MgO particles doped PTFE coating achieves this seesaw-type modulation of SEY. The optimal MgO concentration is 20%, where the maximum SEY (σmax) changes from 2.0 to 1.1; the SEY at 10 keV (σ10k) changes from 0.6 to 0.8, and the higher energy of the SEY equal to 1 (Ep2) increases from 4.5 to 6.5 keV. The discharge test of the microstrip antennas with PTFE-MgO composite coating in a scanning electron microscope verifies the role of the seesaw-type SEY modulation in surface charge suppression. This study supplies an essential reference for suppressing surface charges on vacuum electronics based on modulation of secondary electron emission characteristics. [ABSTRACT FROM AUTHOR]

Secondary-electron yield (SEY) and surface charging of various insulating materials under irradiation of primary electrons (PEs) with energy of lower than 100 eV were investigated. Irradiation energy of the PEs with SEY of 1 (E1) for SiO2 and Si3N4 was about 20 eV and that for the resist using in extreme ultraviolet (EUV) lithography was about 40 eV. Additionally, it was found that E1 corresponds to the lower limit for obtaining scanning electron microscope images of the EUV resist pattern. The surface potential of the pattered EUV resist modulated by PE irradiation was estimated by using a retarding-field energy filter. It was found that the surface potential varies with the width and pitch of the EUV resist pattern. The variation of surface potential depends on the width and pitch due to the fact that the secondary electrons emitted from the space of the resist pattern are absorbed in the sidewalls of the resist pattern as it becomes denser. [ABSTRACT FROM AUTHOR]

Lateral field emission devices have been characterized and degradation tested for >1000 h to study stability and reliability. Two types of planar device structures, diode and bowtie, were studied. These nanoscale devices have 10–20 nm tip to tip or tip to collector dimensions with the tips fabricated from Au/Ti. Typical currents of 2–6 nA at 6 V were measured. The devices were placed on lifetime tests in a vacuum of <10−8 Torr and biased at 6 V DC for >1000 h. Seven total devices were tested with one failing at 300 h. and three of the devices showed <5% degradation in current until 1400 h when testing was stopped, and three other devices showed a sudden drop of ≈20% ranging from 700 to 900 h. Optical microscope images of one of the devices that failed catastrophically at 350 h show physical arc damage where the bond pad narrows to the emitter trace. Scanning electron microscope images of a bowtie part that completed 1400 h of operation showed no obvious erosion or damage to the tips. [ABSTRACT FROM AUTHOR]

Computational lithography is typically based on a model representing the lithographic process where a typical model consists of three components, i.e., line spread function, conversion formula (exposure-to-developing rate conversion), and noise process (exposure fluctuation). In our previous study, a practical approach to modeling the e-beam lithographic process by deriving the three components directly from SEM images was proposed. However, a 2D model of a substrate system was employed; i.e., the exposure variation along the resist-depth dimension was not considered. In this study, the possibility of improving the accuracy of modeling using a 3D model is investigated. The 3D model is iteratively determined by modeling the critical dimension estimated based on the model to those measured in SEM images. This paper describes the 3D modeling approach and new optimization procedures and discusses in detail the results from an extensive simulation for an accuracy analysis of the 3D modeling approach. [ABSTRACT FROM AUTHOR]

Deep trenches, as essential elements of silicon chips used in electronic high-power and high-frequency devices, are known as starting points for dislocation generation under the influence of internal mechanical stresses resulting mainly from the difference in the thermal expansion coefficients between silicon and silicon dioxide. Since the electrical insulation of the devices requires a sequence of mechanical, chemical, and high-temperature processes during the preparation of the deep trenches, including the formation of an amorphous SiO2 edge layer, the emergence of the internal stresses is hardly avoidable. The method of cross correlation backscattered electron diffraction in the scanning electron microscope is used here to quantitatively determine the magnitude and local distribution of internal stresses in silicon around the deep trenches after four different process steps. For this purpose, Kikuchi diffraction images are recorded of the wafer cross section areas along lines perpendicular and parallel to the deep trenches. After Fourier transformation, these images are cross correlated with the Fourier transform of the diffraction image from a stressfree reference sample site. The well-established numerical evaluation of cross correlation functions provides the complete distortion tensor for each measuring point of the line scan, from which the stress tensor can be calculated using Hooke's law. It is found that the in-plane normal stress component σ11 perpendicular to the long edges of the deep trench is larger than the other stress components. That means it essentially determines the magnitude of the von-Mises stress, which was determined as a general stress indicator for all measuring points, too. A characteristic feature is the local distribution of the stress component σ11 with maximum tensile stresses of some hundred megapascals at transition between Si and amorphous SiO2 on the long edges of the deep trench, and with even higher maximum compressive stresses immediately below the bottom of the deep trench. At a distance of about 2 μm from the edges of a single deep trench, all stress components decrease to negligibly small values so that steep stress gradients occur. The range and distribution of tensile and compressive stresses are in accordance with finite element simulations; however, the measured stresses are higher than expected for all investigated states so that dislocation formation seems to be possible. The influence of the electron acceleration voltage on the determination of the internal stresses is discussed as well. [ABSTRACT FROM AUTHOR]

Rectangular-shaped oxygen O2+ ion beam thinning for scanning transmission electron microscope (STEM) sample preparation was investigated using a projection ion beam optical system equipped with a duoplasmatron gas ion source. The ion current can be increased by increasing the area of the rectangular-shaped oxygen ion beam and thereby overcome the low brightness of the ion source. Rectangular-shaped O2+ ion beams with different amounts of projection beam edge blur were formed in the X and Y directions by using a limiting mask between the ion source and projection mask. Gallium-contamination-free STEM sample preparation (rough, medium, and fine milling) was demonstrated using a projection ion beam optical system and three types of rectangular-shaped oxygen ion beams. [ABSTRACT FROM AUTHOR]

The authors report silicon field emitter arrays (FEAs) that were fabricated using a trilevel resist process and are highly uniform. The authors explored the current sensitivity of FEAs to tip radius variation using different tip radius distributions and show that reducing the tip radius dispersion is an effective alternative to increasing the resistance of a current limiter for achieving uniform emission current. In order to reduce the tip radius dispersion, the authors use a trilevel resist process to increase the uniformity of the array of dots used as the etching mask for forming the silicon tips. SEM images show that they were able to reduce the standard deviation of the dot diameter by 60% using a trilevel resist process instead of a single layer resist process. Device characterization showed that the FEAs have a very narrow range of slopes, b FN , extracted from the Fowler–Nordheim plot, indicating that the field emitters within the FEA are highly uniform. [ABSTRACT FROM AUTHOR]

Measuring line-edge roughness in a top-down scanning electron microscope (SEM) is complicated by noise in the SEM image, which biases the measured roughness. When either the roughness is small or the noise is large, it can become very difficult to separate noise from roughness to produce an unbiased estimate of the feature roughness. Synthetic SEM images with known roughness and noise properties can be used to explore the ultimate limits of SEM-based roughness metrology, but only if the noise in the synthetic images mimics the noise behavior of real images. By carefully analyzing the properties of experimental SEM images as a function of the number of frames of averaging (which directly modulates SEM noise), a noise model is developed. This model uses a Gamma distribution for the grayscale noise and then scales the image so that no more than 0.3% of the pixels are pegged at the maximum grayscale value of 255. The resulting synthetic SEM images mimic experimental SEM images in both signal and noise and will serve as a valuable tool for studying roughness metrology. [ABSTRACT FROM AUTHOR]

Tip-based electron beam induced deposition is performed using field emission of low-energy electrons from the tip of an active (i.e., self-sensing and self-actuating) atomic force microscope cantilever inside a scanning electron microscope. By using the active cantilever for feature placement and metrology combined with fast switching between field-emission and noncontact imaging mode, high placement accuracy and time-efficient, precise 3D measurement of the deposits are enabled. First results on the effect of electron energy and exposure dose on the growth rates and dimensions of the deposits are presented, and the potential to increase spatial resolution due to the enhanced localization of the dissociation reactions induced by the low-energy electrons is discussed. [ABSTRACT FROM AUTHOR]

Increasing the process temperature in CO/NH3 plasma etching has been investigated to suppress an etch stop in high-density magnetic tunnel junction stack (MTJ stack) patterning with a Ta mask. In a previous study, the occurrence of an etch stop was observed when using a 100 nm space pattern; specifically, the etching depth was unchanged with the 100 nm space pattern when the etching time was increased, although when wider spaces were used, the etching depth increased proportionally. In this study, differences in the etch stop depth with 100 nm space patterns were examined by changing the electrode temperature from 120 to 300 °C. The etch stop depth became deeper as the electrode temperature was increased and it was found that a high-temperature CO/NH3 process was an effective way to prevent the etch stop effect. However, at 300 °C, the MTJ stack's thickness was observed to expand, which may induce a deterioration of the junction's magnetic properties. A scanning transmission electron microscope image and an energy dispersive x-ray spectroscopy image of the MTJ stack revealed that nitridation of the MTJ stack was the reason of its expansion in thickness. Moreover, pure N2 plasma irradiation of the MTJ stack clearly indicated that this thickness expansion occurred for an electrode temperature of over 265 °C. Finally, the results demonstrate that, for a CO/NH3 process with an electrode temperature of 250 °C, it is possible to etch a 52-nm-thick MTJ stack without either etch stop or film thickness expansion occurring. [ABSTRACT FROM AUTHOR]

Graphene nanopores hold great potential for applications such as molecular detection and DNA sequencing. Here, the authors present a fast and controllable way to fabricate sub-5-nm nanopores on a graphene membrane, with a process including two steps: (i) sputtering a large nanopore using a conventional, focused ion beam; and (ii) shrinking the large nanopore to under 5 nm using a scanning electron microscope. Conductance measurements confirm that the electron-beam-induced deposition of hydrocarbons not only shrinks the diameter of the nanopore but also increases its length. Furthermore, the authors report that using a salt gradient across the nanopore allows the detection of 3 nucleotide "C" and 3 nucleotide "G" homopolymer DNA strands based on differences in their physical dimensions. [ABSTRACT FROM AUTHOR]

Preferentially c-axis oriented ZnO nanorods were grown on a ZnO seed layer spin coated on a crystalline silicon substrate. A low-temperature aqueous chemical growth method using the chemical bath deposition technique was used to grow the ZnO nanorods. The samples were annealed at 700 °C in a reducing atmosphere (H2/Ar) with a relative ratio of 5%:95% for different times (20, 30, and 50 min). X-ray diffraction analysis revealed that the crystallite sizes increased with an increasing annealing time up to 30 min and then decreased for longer annealing time. Scanning electron microscope images showed a successful growth of the vertically aligned ZnO nanorods which were approximately 500 nm in length and 50 nm in diameter. The diameter of the nanorods increased with an increasing annealing time up to 30 min and then decreased when the annealing time was increased further. Photoluminescence (PL) measurements confirmed that the unannealed sample exhibited two distinct emissions, namely, the band to band emission around 378 nm and a broad orange emission centered at 600 nm which was due to the oxygen related defects. The annealed samples exhibited only a broad green emission centered at 500 nm and their intensities increased with annealing time. The highest intensity was recorded for the sample annealed for 30 min and the intensity decreased for further annealing time. The deconvoluted PL peak of the green emission indicated that three different kinds of defects were responsible for the emission at 500 nm. The decay measurements indicated that the green emission (500 nm) had an average lifetime of 11.58 μs. The quantum yield of the sample annealed for 30 min was measured using an integrating sphere at a wavelength of 325 nm, and it was found to be 43%. These ZnO nanorods can be very useful in optoelectronic applications, such as green light emitting diodes and field emission displays. [ABSTRACT FROM AUTHOR]

Micro x-ray fluorescence spectroscopy (μXRF) is a technique for local chemical analyses of materials. There are several advantages in comparison to other similar methods like energy dispersive x-ray spectroscopy in a scanning electron microscope (SEM). The main advantage is the possible abdication of an evacuated sample chamber, which offers the possibility to analyze wet and oil contaminated specimens as well as specimens with intrinsic pores in addition to conventional samples used in SEM analyses. The subject of this report is the investigation of the pyroelectric effect with regard to its application for the generation of focused x-rays and first steps to a successive usage of the generated radiation for μXRF applications. In order to answer questions concerning the energy and intensity of primary radiation and geometric parameters for a successful focusing, this paper describes several experiments and results against the background of the described aims. Different setups and measurements have been used, optimizing the experimental setups to find the basic parameters to potentially generate focal spots of the primary x-rays. Emission behavior of electrons has been visualized and characterized by using a phosphor screen positioned in front of a pyroelectric crystal. Radiation has been measured and characterized by using an energy dispersive silicon drift x-ray detector. All x-ray experiments were executed in a vacuum test rig. This allowed the optimization of the working pressure of the residual gas surrounding the crystal in an evacuated atmosphere (rarefied air). It has been shown that emitted x-ray energies are strongly influenced by the vacuum pressure. Lithiumniobate and lithiumtantalate of different geometries were used as the pyroelectric material. Different target materials and target angles have been compared to optimize the combination of the constructed x-rays source with an aperture as well as with an x-ray optic to focus the primary x-rays. A glass fiber capillary lens was used as the focusing optic. A first step to a μXRF application is shown. [ABSTRACT FROM AUTHOR]

The scanning electron microscope (SEM) is often employed in inspecting patterns transferred through a lithographic process. A typical inspection is to measure the critical dimension (CD) and line edge roughness (LER) of each feature in a transferred pattern. Such inspection may be done by utilizing image processing techniques to detect the boundaries of a feature. Since SEM images tend to include a substantial level of noise, a proper reduction of noise is essential before the subsequent process of edge detection. In a previous study, a method of designing an isotropic Gaussian filter adaptive to the noise level was developed. However, its performance for relatively small features was not so good as for large features, especially in the case of LER. The main objective of this study is to improve the design method such that the accuracy of the measured CD and LER is not deteriorated substantially as the feature size decreases. The new design method allows a Gaussian filter to be anisotropic for the better adaptability to the signal and noise, both of which show a substantial level of directional correlation. The cutoff frequency for the direction normal to features is determined to include most of the signal components, and the cutoff frequency in the other direction is set to balance the signal and noise components to be included. This procedure enables a systematic and easy design of the filter. Also, the method of estimating the noise has been modified for higher accuracy. The performance of the new design method has been thoroughly analyzed using the reference images for which feature boundaries are known. It has been shown that the anisotropic filter designed by the proposed method performs better than the isotropic filter from the viewpoint of CD, LER, and power spectral density accuracy. [ABSTRACT FROM AUTHOR]

More than 40 years after its invention, the atomic force microscopy (AFM) can be integrated with scanning electron microscope (SEM) instruments as an increasingly capable and productive characterization tool with sub-nanometer spatial resolution. The authors have designed and developed an AFM instrument capable to be integrated into any SEM or in a combination of SEM with a focused ion-beam (FIB) tool. The combination of two or more different types of techniques like SEM, energy dispersive x-ray spectroscopy, and AFM is called correlative microscopy because analytical information from the same place of the sample can be obtained and correlated. For the first time, they introduced to the SEM/FIB tool correlative nanofabrication methods like field-emission scanning probe lithography, tip-based electron beam induced deposition, and nanomachining. The combination of all these methods provides a completely new nanotechnology instrument, which should be seen as a tool for correlative nanofabrication and microscopy. Thus, it provides for the first time the capabilities of a stand-alone instrument with the capabilities of nondestructive three-dimensional tip-based metrology and nanofabrication into the combined SEM/FIB tool. In this article, the authors describe all these methods in detail and present a brief example of the results obtained. They demonstrate that the self-sensing, self-actuating cantilevers (called active cantilevers) equipped with Diamond tip are a versatile toolkit for fast imaging and emerging nanofabrication. The AFM integrated into SEM is using active cantilevers that can characterize and generate nanostructures all in situ without the need to break-vacuum or contaminate the sample. [ABSTRACT FROM AUTHOR]

The measurement of roughness of small lithographic patterns is biased by noise in the scanning electron microscopes (SEMs) used to make the measurements. Unbiasing the roughness measurement requires the measurement and subtraction of the image noise based on its unique frequency behavior. Improvement to prior white noise removal is achieved by applying a pink noise model. This pink noise removal technique was applied to roughness measurements made with different electron doses (frames of integration), different operating voltages, and different generations of SEM tools. Effective noise removal to create accurate unbiased estimates of the roughness was achieved over a wider range of SEM tool parameter settings than has been previously achieved. As a result, unbiased roughness measurements can now be used to characterize and improve stochastic variability in semiconductor lithography and patterning. [ABSTRACT FROM AUTHOR]

Standard samples with programed defects, designed to evaluate pattern inspection tools that use electron beams, were fabricated on 12-in. Si wafer. By using a structure with a conductive pattern on an insulator layer, scanning electron microscope (SEM) images with various pattern contrasts, depending on the charging effect, were obtained under different observation conditions. The impact of captured-image contrast on defect detection capability was examined using different types of inspection algorithm. It was found that the accuracy of critical dimension measurement, effectiveness of the charge suppression technique, and defect detection capability of the SEM tool, and its robustness could all be evaluated using this standard sample with a particular stacked structure. [ABSTRACT FROM AUTHOR]

In this paper, the authors introduced a novel method for the fabrication of microdevices on freestanding Si3N4 thin-film windows with a single-side mask aligner. A thin-film microdevice located on the front surface of such a freestanding window was demonstrated, where the backside of Si wafer was performed with KOH wet etching. The results showed that an alignment error could be controlled in condition less than 20 lm. By using the freestanding device, a weak change in local temperature under an e-beam in a scanning electron microscope (FEI QUANTA 600F) was detected with better sensitivity. [ABSTRACT FROM AUTHOR]

Measurements of the line edge roughness (LER) and critical dimension (CD) from scanning electron microscope (SEM) images are often required for analyzing circuit patterns transferred onto substrate systems. A common approach is to employ image processing techniques to detect feature boundaries from which the LER and CD are computed. SEM images usually contain a significant level of noise which affects the accuracy of measured LER and CD. This requires reducing the noise level by a certain type of low-pass filter before detecting feature boundaries. However, a low-pass filter also tends to destroy the boundary detail. Therefore, a careful selection of low-pass filter is necessary in order to achieve the high accuracy of LER and CD measurements. In this paper, a practical method to design a Gaussian filter for reducing the noise level in SEM images is proposed. The method utilizes the information extracted from a given SEM image in adaptively determining the sharpness and size of a Gaussian filter. The results from analyzing the effectiveness of the Gaussian filter designed by the proposed method are provided. [ABSTRACT FROM AUTHOR]

Secondary ion mass spectrometry (SIMS) plays an important role in nuclear forensics through its ability to identify isotopic ratios of particles accurately and precisely from samples obtained by inspectors [Boulyga et al., J. Anal. At. Spectrom. 30, 1469 (2015)]. As the particle mass can be on the order of subpicograms, it is important to maximize the sample utilization efficiency of U+ to make high-quality isotopic measurements. The influence of primary ion beam species and polarity on U+ sample utilization efficiency has been previously investigated by Ranebo et al. [J. Anal. At. Spectrom. 24, 277 (2009)]. However, the effect of sample substrate on uranium ion production efficiency and sputtering profile has not been investigated. This work will explore those influences on sample utilization efficiency by analyzing monodisperse uranium oxide microspheres deposited onto graphite and silicon planchets. The particles were mapped using an automated scanning electron microscope, and their coordinates were converted to the SIMS coordinate system using fiducial marks. Results indicate higher U+ sample utilization efficiencies when sputtering with O- and O2- on graphite planchets compared with O2+, whereas O2- gave higher U+ sample utilization efficiencies with silicon wafers compared to O- and O2+. Additionally, during sputtering of uranium particles on silicon wafers with O- and O2-, a sudden drop in U+ signal intensity was observed, which was not present during sputtering with O2+ or any primary ion species for particles on graphite. This drop in U+ signal intensity occurred simultaneously with an increase in UO+ and UO2+ signals, indicating a change in the local matrix around the uranium particle that is unique to silicon compared to graphite. [ABSTRACT FROM AUTHOR]

GaAs nanostructures were grown on patterned GaAs (111) B substrates with molecular beam epitaxy. Nanopatterns were achieved by patterning a thin film of silicon dioxide (SiO2) grown on the substrate surface with a self-organized porous alumina template. Growth of patterned nanostructures took place through the holes in the SiO2 film. The authors obtained two kinds of nanostructures: nanopillars and nanodots. The majority of nanopillars had two kinds of tops, i.e., hexagonal flat top and pyramidal top, as observed with a scanning electron microscope. High resolution transmission electron microscopy studies showed epitaxial relationships between the nanostructures and the substrates. Photoluminescence measurements of nanopillars showed the photoluminescence peak shifted to a higher energy compared to films grown under the same condition. [ABSTRACT FROM AUTHOR]

A multiwalled carbon nanotube (MWCNT) field emitter is developed as the electron source for a microcolumn-based field-emission scanning electron microscope (SEM). A MWCNT is first attached onto a tungsten (W) support tip using the nanomanipulator in the SEM. Then, an electrical bias is applied between the MWCNT field emitter and W tip to improve the contact between them, which lowers the threshold voltage for field emission. An emission current stability test showed that the emission current is stable. The fabricated MWCNT emitter exhibits a high emission current of 12 lA and sample current of around 2 nA, even at a low tip bias of 350V in the microcolumn. The tip bias is much lower, and the sample current is higher than the equivalent values reported for W tips. The authors acquired images of a 1000-mesh copper grid using the microcolumn-based SEM with a MWCNT field emitter as the source. Our results suggest that MWCNTs should be considered a promising candidate as an electron source for microcolumns. [ABSTRACT FROM AUTHOR]

The nanoelectronics industry demands continuous improvement in the performance of scanning electron microscopes (SEMs). Extremely low energies of less than 1 keV are required for SEM observations to allow the subsurface and nanoscale information of target specimens to be measured with minimized charge-up and beam damage depths because of the reduced interaction volumes. In this article, the authors propose a new monochromator (MC) structure and investigate its applicability to SEMs operating at such extra-low energies. The proposed MC, which uses double-offset cylindrical lenses, can perform energy filtering in its midsection and form a stigmatic and nonenergy dispersive image at the exit. The energy resolution is expected to be better than 10 meV for a pass energy of 4 keV. The MC has the additional advantage of a simple but robust structure, which is essential for industrial applications. Assuming the use of ideal and high-performance SEM optics, for which the spherical aberration coefficient and the chromatic aberration coefficient are both 1 mm, beam diameters measured in terms of the full width that contains 50% of the beam current (FW50) are calculated at the specimen position. Use of the MC improves the beam diameter dramatically to 4.4 nm, as compared to the diameter of 19.7 nm for the SEM without the MC, at a landing energy of 100 eV. The chromatic aberration contribution also becomes negligible because of the MC. The beneficial effects of the MC with regard to the beam diameter become increasingly prominent at lower landing energies ranging down to 10 eV. A SEM using this MC can generate highly monochromatic (10meV) electron probe beams with small size (5 nm) and low energy (100 eV), which indicates the additional possibility of a new surface electron microscope that uses phonon signals. Based on this theoretical investigation, the authors conclude that this MC can effectively improve the SEM's performance capabilities in the extra-low-energy region. [ABSTRACT FROM AUTHOR]

In low energy scanning electron microscope (SEM) with primary electron energy less than 1.0 keV, the dependence of SEM contrast on crystallographic orientation within a range of 1.0 nm in depth has been investigated by utilizing 4H-SiC (0001) as a standard sample having a definitive electron penetration depth marker layer at hexagonal sites. Reflecting the difference of the direction of topmost two Si-C bilayers stacking sequence (0.50 nm in depth), clear bright and dark SEM contrast has been observed by adjusting the sample tilting and rotation angles by a conventional Everhart-Thornley type in-chamber detector. It is revealed that the brighter signal emission arises when the incident primary electron beam direction is almost parallel to the topmost stacking sequence direction. This angular coincidence was verified separately by correlating low energy SEM contrast from 3C-SiC (111) of no hexagonal sites with its electron back scattered diffraction pattern for identifying stacking sequence direction. The obtained results suggest a potential of low energy electron to characterize the crystallographic orientation just beneath the surface without using any special detector. [ABSTRACT FROM AUTHOR]

A new composite oxidation method combining rapid thermal oxidation (RTO) and electrochemical oxidation (ECO) is proposed to improve electron emission characteristics of electron emitters based on thick porous silicon (PS) layers. Four groups of electron emitters with 8 µm PS layers were oxidized by RTO, ECO, composite RTO–ECO, and composite ECO–RTO, respectively. The experimental results indicated greater emission current density and efficiency of electron emitters oxidized by composite oxidation versus ECO or RTO alone. The most favorable results occurred for an electron emitter oxidized by ECO–RTO, with an emission current density of 2.2 A/m2 and efficiency of 2.9%. The higher and more uniform the oxygen content in the PS layer after oxidation, the better the electron emission characteristics that the authors noted. Thick PS layers can be oxidized completely and uniformly by composite oxidation to achieve adequate oxygen content with uniform distribution. This subsequently leads to formation of a longer acceleration tunnel, which increases effective emission area and continuously speeds up electrons. [ABSTRACT FROM AUTHOR]

The authors report on thin-film processing improvements in the fabrication of superconducting quasiparticle-trap-assisted electrothermal-feedback transition-edge sensors used in the design of cryogenic dark matter search detectors. The work was performed as part of a detector upgrade project that included optimization of a new confocal sputtering system and development of etch recipes compatible with patterning 40 nm-thick, α-β mixed-phase W films deposited on 300–600 nm-thick, patterned Al. The authors found that their standard exothermic Al wet etch recipes provided inadequate W/Al interfaces and led to poor device performance. The authors developed a modified Al wet-etch recipe that effectively mitigates geometrical step-coverage limitations while maintaining their existing device design. Data presented here include scanning electron microscope and focused ion beam images of films and device interfaces obtained with the new Al etch method. The authors also introduce a method for quantitatively measuring the energy collection efficiency through these interfaces. [ABSTRACT FROM AUTHOR]

A novel optical system for a multiple-beam scanning electron microscope (SEM) is proposed. In the case of multiple-beam SEM, multiple secondary-electron beams passing through the column are inherently blurred because of the large energy spread and broad angular distribution of secondary electrons. To avoid cross-talk between the multiple secondary-electron beams, the optical system is designed such that it is divided into two independent parts: one for primary-beam illumination and one for secondary-electron detection. As the key components for the secondary-electron detection, a scan-cancelling deflector, and accelerating electric field were applied. To demonstrate the proposed optical system, a prototype column with four beams was developed. This column enables four SEM images to be separately but simultaneously acquired with more than 99% of the generated secondary electrons. This result demonstrates that high-speed imaging with the proposed multiple-beam SEM is possible in the near future. [ABSTRACT FROM AUTHOR]

In this paper, the authors report on epitaxial thin InN layers grown on commercially available undoped GaN buffer layers and on Ga2O3 interlayers produced by Migration-Enhanced Afterglow Epitaxy (MEAglow). The InN layers reported here, also grown by the MEAglow technique, are 100–200 nm thick and have a measured absorption edge between 1.3 and 1.95 eV. Advancements in the growth process have now allowed the authors to improve the InN layers so that the growth has excellent two-dimensional morphology. Scanning electron microscope images show that terracing is strongly evident for samples grown on GaN templates. Atomic force microscopy shows a maximum height of the steps of about 2 nm. For the samples grown on Ga2O3, crystal quality is superior to InN grown on AlN buffers with similar thicknesses. X-ray diffraction ω-2θ measurements indicate a full width of half maximum (FWHM) of 342–389 arcseconds for these extremely thin layers; a good part of this x-ray diffraction FWHM is likely due to residual strain between the InN and GaN or between the InN and oxide. [ABSTRACT FROM AUTHOR]

Deposits of aggregated silver particles were grown from aqueous silver-nitrate solution by electron-beam induced deposition in a liquid cell in a scanning electron microscope. Electron energies of 2, 5, and 20keV were evaluated and found to produce distinguishably different deposits. Optimal energies exist for maximum growth rate and for minimum feature sizes. The physical structure of the deposits was found to evolve with increasing thickness as silver particles grow larger and develop more structure. Optical absorbance measurements and Raman spectroscopy on adsorbed dye suggest appropriate silver purity for using this fabrication method in nano-optics applications. [ABSTRACT FROM AUTHOR]

Electron scattering on a flat sample with a subsurface structure was simulated to investigate the signal profile and critical dimension (CD) measured by scanning electron microscope (SEM). The authors modified an electron-scattering simulator, MONSEL, which was developed by the National Institute of Standards and Technology for applications to line-width metrology using CD-SEM, to simulate a flat tungsten (W) and silicon (Si) pattern under a nanometer-order-thick amorphous carbon (a-C) film and to classify the emitted electrons from the sample according to their generation processes. The simulation result shows that the material contrast between W and Si regions for measuring backscattered electrons (BSEs) is larger than that for measuring secondary electrons (SEs), though the yield of BSEs is lower than that of SEs. The low contrast given by the SE profile is attributed to the contribution of SEs generated from the a-C film by the incident electrons, which becomes an offset component. In contrast, the offset component in the BSE profile (which is also attributed to the a-C film) is much smaller than that in the SE profile. It is therefore concluded that BSE detection is suitable for CD measurement of a subsurface pattern even under a several-nanometer-thick layer. The simulation result also shows that both CD bias (between the top width of the pattern and measured CD) and material contrast increase with increasing irradiation energy for a tapered pattern. This tradeoff relationship (i.e., where both factors increase) indicates that control of the irradiation energy is necessary to obtain an accurate CD measurement of a flat sample with a tapered subsurface pattern. Moreover, in a similar manner to the simulation result, the experimentally measured SE contrast shows a similar dependence on a-C film thickness and irradiation energy. [ABSTRACT FROM AUTHOR]

The fabrication of next-generation devices via roll-to-roll (RTR) nanoimprinting has received considerable attention due to the high throughput and resolution associated with the process. In particular, RTR nanoimprinting with ultraviolet (UV)-curable resin is expected to be useful for the fabrication of large-area devices such as nonreflective films, transparent conductive sheets, and organic solar cells. In order to improve the resolution of such devices, the roll mold must be able to produce seamless fine patterns. Generally, a roll mold for nanoimprinting is made by attaching a planar mold replicated from the master mold via a nickel electroforming technique. However, this method produces seams, which reduces the product yield. In order to resolve these issues, the authors have developed a direct writing method using electron beam (EB) lithography on a rotating cylindrical substrate. In this study, the authors examined the potential for fabricating a seamless roll mold using high-resolution inorganic EB resist and the pattern shrink effect from postexposure bake (PEB). The authors used the dip-and-pull method to form the EB resist layer on the roll mold substrate (32 mm diameter, made of brass). The cleaned roll mold was dipped in the inorganic EB resist and then pulled out at a constant speed. The resulting sample was cured at 300 °C for 1 h. Next, the sample was mounted on rotating equipment and placed in a scanning electron microscope (SEM) equipped with an EB writing system, and the roll substrate was exposed to 10 kV EB while rotating at a constant speed. The revolution speed was set to ten turns per line pattern. Subsequently, PEB was carried out at 200 °C for 10 min in air. After the sample was cooled to room temperature, the EB-exposed area of the EB resist layer was developed using buffered HF. The obtained pattern on the roll mold was examined with the same SEM used for writing. Finally, RTR nanoimprinting using the obtained roll mold was carried out using UV-photocurable resin. At that time, the sample was coated with an antisticking layer of fluorinated silane coupling agent. As a result, a seamless line pattern 190 nm wide was obtained on a polyethylene terephthalate film over a length of 10 cm. [ABSTRACT FROM AUTHOR]

The authors have demonstrated large-area suspended graphene on GaN nanopillars predefined by nanosphere lithography and inductively coupled plasma etching. The graphene was successfully suspended over large areas without ripples and corrugations. Scanning electron microscopy, atomic force microscopy and micro-Raman spectroscopy were used to characterize the properties of the suspended graphene on nanopillars. The thermal properties of the suspended and supported graphene were investigated by varying the underlying GaN nanopilllar geometries from flat-top to sharp-cone morphologies and heating the resulting structures via irradiation with laser powers of 1.53 mW, 8.03 mW, and 16.19 mW. The heat transfer was effective even when the contact area between the suspended graphene and the supporting substrate was small, due to the high thermal conductivities of graphene and GaN. The extremely high thermal conductivity of the graphene can improve the thermal management in GaN-based high power electronic and optoelectronics devices, a critical factor for their long-term reliability. [ABSTRACT FROM AUTHOR]

A next generation ion source suitable for both high resolution focused ion beam milling and imaging applications is currently being developed. The new ion source relies on a method of which positively charged ions are extracted from a miniaturized gas chamber where neutral gas atoms become ionized by direct electron impact. The use of a very small gas chamber and a very narrow electron beam (<100 nm) allows for a very small ionization volume, which, in turn, yields a small virtual source size and low energy spread. The authors estimate that using a high current density electron beam from a Schottky electron gun the reduced brightness of this source can exceed that of the Gallium Liquid Metal Ion Sources and the energy spread can be well below 1 eV at an optimal gas pressure and gas chamber spacing while producing more than 1 nA of usable ion beam current. In a proof-of-concept study, the authors have produced ions of helium, argon, xenon, and air from a prototype gas chamber using an electron probe inside a scanning electron microscope. Using micro-channel plates and a phosphor screen, ion beam patterns have been acquired demonstrating that a beam of ions can be produced from a miniaturized gas chamber. The authors have measured up to several hundreds of pico-amperes of ion current in a Faraday cup using an input electron probe current of ∼14 nA with 1 keV incident energy. The authors have also verified that the ion beam current is dependent on the incident electron beam energy, gas chamber bias voltage, and the gas pressure inside the ionization chamber. [ABSTRACT FROM AUTHOR]

An electrostatic force microscope system in a scanning electron microscope specimen chamber was developed to measure the surface potential of an insulator film on a conductive substrate irradiated by an electron beam. As the accelerating voltage varies with the constant beam current, the surface charges positively if the voltage is lower than 1 kV or higher than 3 kV but negatively if the voltage is between 1.1 and 2.7 kV. This positive-negative-positive potential alternation is explained by the relationship between the electron range and the film thickness, and verified by the Monte Carlo simulation of electron trajectories. By selecting the acceleration voltage as 30 kV to show less potential variation with time, the spatial potential distribution at the specimen surface is obtained, and a negative dip is observed around 50 μm from the edge of the irradiated area. The authors find that the depth of the dip increases with an increase in the electron dose, and the negative potential distribution spreads over 300 μm is obtained, which is almost 10 times larger than the primary electron range in the specimen. The characteristic variation in the distribution agrees with a hypothetically derived charge distribution obtained in a different experiment. [ABSTRACT FROM AUTHOR]

In this work, a well-controllable, direct-write, resistless, and crystallinity-retaining etching process for germanium using a focused electron beam with nanometer resolution has been developed. This process allows for precise, local, and efficient removal of germanium from a surface without showing any spontaneous etching effects. This focused electron beam induced etching process of germanium substrates employs pure chlorine gas as etchant. The presented process was carried out in a conventional scanning electron microscope equipped with a custom-tailored gas injection system. The etch rate of this etching process was observed to be up to 0.32 μm3 min-1 or 12 nm min-1 for an area of 1.5×1.5 μm2. The influence of various etching parameters such as electron beam current, acceleration voltage and chlorine gas flow on the etch rate as well as the shape of the etch pits have been studied systematically by atomic force microscopy analysis. It is demonstrated that etching of amorphous germanium films can be performed significantly faster (∼8 times) than etching of crystalline germanium. Finally, a comparison between silicon etching and germanium etching by chlorine is presented. [ABSTRACT FROM AUTHOR]

The authors evaluated the electron detection performance of a diamond avalanche diode (DAD) detector. In the electrode region, the gain was uniformly about 103 with little noise. Meanwhile, an avalanche multiplication occurred locally. In the avalanche region, a total gain of 5×104 was obtained. In some regions where the electric field is regarded to be intensified, the avalanche multiplication gain was estimated to be approximately 100-300, and the signal-to-noise ratio (S/N) was nearly equal to 1. The DAD can be applied to an electron detector for a scanning electron microscope due to its high gain and small dark current. However, it is necessary to improve the S/N and homogenize the gain to use the DAD detector as an electron detector. [ABSTRACT FROM AUTHOR]

Cold-field-emission current from a tungsten <310> emitter in a scanning electron microscope (SEM) gun, evacuated by an ion pump and a supplementary nonevaporative getter pump, was stabilized. It was verified that the probe current from a local (310) crystal plane exhibits different time variations in comparison to that of total current. As for the probe current under a pressure of 2×10-9 Pa, a stable plateau region-which lasted about 4 h-appeared just after flashing of the emitter. By observing emission patterns, it was verified that these different emission characteristics are originated from the anisotropy of current decay in accordance with crystal planes. With low-temperature 'mild flashings' at 700 °C, the plateau region was extended to 12 h, which is long enough for practical SEM application. The superior properties of the plateau region, namely, high current, low noise, and small current variation, will enhance the performance and usability of electron microscopes. [ABSTRACT FROM AUTHOR]

A two-dimensional fluid model is used to study an industrial Ar/Cl2 inductively coupled plasma discharge designed to etch III-V samples. The effect of rf power, gas pressure, and chlorine content on the fluxes of reactive species reaching the wafer is numerically investigated. To understand how the etch process is influenced by the discharge conditions, simulation results are confronted with GaAs and GaN etch experiments performed in the same reactor geometry. When the source power is increased, the measured etch rate increase is consistent with the Cl radical and ion fluxes increase shown in the simulation, as well as the ion energy decrease due to the constant value of the wafer-holder power. Increasing the gas pressure results in a moderate increase in the etch rate due to the lower magnitude, lower mean energy, and anisotropy of the ion flux at high pressure. When the chlorine content is increased, the total ion flux decreases while Cl and Cl2 neutral fluxes increase significantly. A good correlation is obtained between calculated fluxes and etch characteristics, analyzed with scanning electron microscope images of etch profiles. [ABSTRACT FROM AUTHOR]

Local emission characteristics of microscopic emission sites on the surface of large-area field emitters are among the most important factors influencing macroscopic emission properties. This work aimed to evaluate the local field emission characteristics using a computerized field emission projector and a technique involving multichannel recording of current–voltage characteristics. The model field emitter consisted of nanocomposite multiwall carbon nanotubes in a polymer matrix. [ABSTRACT FROM AUTHOR]