Thermal field emission for low-voltage SEM

1984 ◽  
Vol 42 ◽  
pp. 450-453
Author(s):  
J. Orloff
Keyword(s):  
Field Emission ◽  
Current Density ◽  
Beam Energy ◽  
Low Voltage ◽  
High Energy ◽  
Beam Diameter ◽  
High Energy Electrons ◽  
Passivation Layers ◽  
Circuit Components ◽  
Voltage Contrast

Low voltage SEM is an increasingly important technique for examining specimens which can be damaged by high energy electrons or which are insulators. It is particularly useful for the study of semiconductor devices and a number of specialized methods have been developed. These include voltage contrast SEM, e-beam induced conductivity, stroboscopic SEM, inspection and line width measurement. Low energy is necessary because many circuit components, especially MOS devices are easily damaged. Moreover, insulating components of circuits, including passivation layers, dictate beam energies ≲ 1 keV in order to avoid electrical charging.The current density and brightness of a thermionic cathode are proportional to the voltage of the cathode with respect to the specimen; consequently the current which can be focused into a given beam diameter decreases with beam energy. In contrast, the current density and brightness of a field emission cathode depend on the electric field at the emitter surface, so that by the appropriate choice of gun geometry, high brightness can be attained at low beam energy.

Low-Voltage Scanning Electron Microscope (LVSEM) with a Single-Polepiece Lens

1990 ◽  
Vol 48 (1) ◽  
pp. 398-399
Author(s):  
I. Müllerová ◽  
M. Lenc
Keyword(s):  
Field Emission ◽  
Electrostatic Field ◽  
Beam Energy ◽  
Semiconductor Detector ◽  
Low Voltage ◽  
Primary Beam ◽  
Resolution Limit ◽  
Magnetic Lens ◽  
Angular Density ◽  
Cathode Lens

The advantages of the LV SEM are well known. Recently a lot of interesting results from this field were presented which were obtained thanks to development of field emission guns and to the enourmous progress in the computation techniques in electron optics.One of the simplest arrangements of the LVSEM is shown in Figure 1. The Tesla SEM BS 350 with a field emission gun and the TF-W/100-Zr cathode was used for our experiment. The gun provides 10−10 A current in the diffraction limited spot (for the angular density 0.20mA sr−1). If a potential Usp is applied to the specimen the energy E of the electrons that strike the specimen is Ep-eUsp (Ep-primary beam energy, e-elementary charge). The produced secondary (SE) and backscattered (BSE) electrons are accelerated towards the semiconductor detector by the electrostatic field and their energy spectrum extends from eUsp to Ep. The final energy of the SE and BSE can then be sufficient for achieving a reasonable amplification of the semiconductor detector which is directly proportional to the energy of the electrons that strike the detector. We calculated optical properties for a combination of the electrostatic and magnetic lenses of the basic geometry shown in Figure 1 and for an arrangement with the single polepiece lens shown in Figure 2. We particularly investigated coefficients of the chromatic (Cc) and spherical (Cs) aberrations as functions of the ratio of the primary beam energy to the energy of the electrons that strike the specimen Ep/E for some optimum position of the specimen, electropstatic and magnetic field. Our results are shown in Table 1. The coefficients Cs and Cc do not change with the energy Epor E if the ratio Ep/E is maitained the same and aberrations are lower for larger ratios Ep/E, so that the influence of the contribution of the electrostatic lens aberrations is negligible for our geometry. For example, if we require a resolution limit r=2nm and an energy of the electrons that strike the specimen E=300eV, it is possible to calculate that the coefficient of the aberrations must be Cs<0.21mm and Cc<0.14mm for an energy width AE=0.2eV, so that we need the ratio Ep/E≥150 for the arrangement shown in Figure 1 (i.e.Ep≥45keV) and Ep/E≥33 for the arrangement shown in Figure 2 (i.e.Ep≥10keV).The advantages of the combination of the magnetic lens with the electrostatic cathode lens for the high resolution very low energy electron microscopy are well known . We assume that for the LVSEM only a medium electrostatic field strength is admitted at the specimen surface. Nevertheless, our experimental arrangements should certainly be optimized in the future.

scholarly journals Decomposition of gas phase benzene under different conditions in atmospheric strong ionization non–thermal plasma

2020 ◽  
Vol 2 (2) ◽  
pp. 22-29
Author(s):  
Prince Junior Asilevi ◽  
Chengwu Yi ◽  
Jue Li ◽  
Huijuan Wang ◽  
Muhammad Imran Nawaz
Keyword(s):  
Removal Efficiency ◽  
Current Density ◽  
High Energy ◽  
Ring Cleavage ◽  
Oh Radicals ◽  
Test Results ◽  
High Energy Electrons ◽  
Study Results ◽  
Key Species ◽  
Specific Input Energy

Atmospheric volatile organic compounds (VOCs) from industry and automobiles are posing a serious threat to the environment and human health, and hence efficient control methods are indispensable. This paper presents a laboratory-scale study on the decomposition mechanism for benzene using strong ionization dielectric barrier discharge (DBD) at atmospheric pressure. The specific input energy (SIE), current density, and concentration were studied. The results show that the removal efficiency of benzene increased from 12% to 69% with the increase of SIE from 0.5 to 3.8 kJ/L. The decline in current density by 66.48% and 43.7% for an initial benzene concentration of 300 ppm, was due to increased oxygen content (from 2.4% to 20.9%) and relative humidity (from 18.9% to 90%), respectively, thus electron concentration and consequentially enhancing the removal efficiency over 93%. Further, the beta parameter of the VOC decomposition law decreased from 3.1 kJ/L at 300 ppm to 1.6 kJ/L at 100 ppm. This shows that •O and •OH radicals are key species for the decomposition of benzene and electron dissociation reactions principally control the process. The highest ozone concentration was detected at 5.5 mg/L when no benzene is present, while the main NOx species (NO and NO2) increased with increasing SIE. The Maxwell–Boltzmann electron energy distribution function was solved using the strong ionization discharge reactor (~10 eV), showing that approximately 84.8 % of high-energy electrons possess enough energy to cause the benzene ring cleavage and free radical production. Finally, GCMS and FTIR test results suggested that the byproducts mainly consisted of phenol and substitutions of phenol. The study results show that the strong ionization DBD reactor efficiently removes benzene from polluted air.

scholarly journals At the downstream of the RF cavity of the electron storage ring there is emission of abnormal ultra-high energy electrons with energy up to 105 times of the beam energy

2021 ◽  
Author(s):  
Dapeng Qian
Keyword(s):  
Storage Ring ◽  
Beam Energy ◽  
High Energy ◽  
New Physics ◽  
Ultra High Energy ◽  
Electron Storage ◽  
Rf Cavity ◽  
High Energy Electrons ◽  
Relationship Of ◽  
Heisenberg's Uncertainty Principle

Abstract After considering Heisenberg's uncertainty principle, the mass-speed relationship of special relativity i.e. the Einstein-Lorentz mass formula can be extended to a more complete equation, which predicts that abnormal ultra-high energy electrons will be generated with a small probability when the electron beam passes through an accelerating electric field. The author used the accumulating detection method of a large number of events to test at the electron storage ring of BEPCII, of which results show that under the beam energy of 2GeV there is emission of abnormal ultra-high energy electrons with the highest energy reaching 400TeV at downstream of the RF cavity. For this reason, it is recommended that particle physicists conduct more experiments to fully verify this previously unknown phenomenon and further discover new physics.

Direct Refrigeration by Electron Field Emission From Diamond Microtips

2000 ◽  
Author(s):  
T. S. Fisher ◽  
D. G. Walker
Keyword(s):  
Energy Conversion ◽  
Field Emission ◽  
Current Density ◽  
High Capacity ◽  
Wide Band ◽  
Electrical Current ◽  
Emission Current Density ◽  
High Energy ◽  
Electron Field Emission ◽  
Electron Field

Abstract This paper describes a concept for creating high-capacity, direct electrical-to-thermal energy conversion for compact cooling based on electron field emission. Electron field emission involves the transport of electrons that tunnel through a potential barrier. The thermodynamics of field emission have remained relatively unexplored. However, emission from wide-band-gap semiconductors, such as diamond, is known to produce an energy filtering effects such that high-energy electrons possess higher probabilities of emission. Lower energy electrons replace the emitted electrons, and thus, this process can produce a refrigeration effect. The refrigeration capacity is proportional to the emission current density, which is very high for diamond emitters. This high electrical current density implies that high thermal current densities are possible. The present work provides a thermodynamic analysis and energy conversion predictions based on experimental current-voltage data from diamond tip emitters. Energy fluxes in excess of 100 W/cm2 are predicted by the theory for room-temperature operation.

scholarly journals Signs of ultra-high-energy electrons emission with energy up to 105 times of beam energy are detected at downstream of the RF cavity of storage ring

2021 ◽  
Author(s):  
Dapeng Qian
Keyword(s):  
Storage Ring ◽  
Beam Energy ◽  
High Speed ◽  
High Energy ◽  
New Physics ◽  
Ultra High Energy ◽  
Rf Cavity ◽  
High Energy Electrons ◽  
Low Mass ◽  
New Equation

Abstract In a new version of special relativity that absorbed the uncertainty principle, the Einstein-Lorentz mass formula proved to be a special case of a more universal equation. The new equation indicates that there is a “high speed but low mass” weak effect in particle motion, which will cause the generation of abnormal ultra-high energy electrons with a small probability when an electron beam passes through an accelerating electric field. The author used the method of long-times accumulation detection to test it on the BEPCII, which results show that there is indeed emission of abnormal electrons with energy up to 105 times of the beam energy at the downstream of the RF cavity of the electron storage ring. Therefor, it is suggested to use the detector with an online real-time display function, such as the “Shashlyk calorimeter”, to detect the single event of ultra-high energy electron, so to fully verify this previously unknown phenomenon and further discover new physics.

Development of a conical anode Fe-gun for low voltage SEM

1988 ◽  
Vol 46 ◽  
pp. 978-979
Author(s):  
T. Miyokawa ◽  
S. Norioka ◽  
S. Goto
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Low Voltage ◽  
Irradiation Damage ◽  
Cold Cathode ◽  
Virtual Source ◽  
Source Position ◽  
Electrostatic Lens ◽  
Electrostatic Lenses ◽  
Wide Range

Field emission SEMs (FE-SEMs) are becoming popular due to their high resolution needs. In the field of semiconductor product, it is demanded to use the low accelerating voltage FE-SEM to avoid the electron irradiation damage and the electron charging up on samples. However the accelerating voltage of usual SEM with FE-gun is limited until 1 kV, which is not enough small for the present demands, because the virtual source goes far from the tip in lower accelerating voltages. This virtual source position depends on the shape of the electrostatic lens. So, we investigated several types of electrostatic lenses to be applicable to the lower accelerating voltage. In the result, it is found a field emission gun with a conical anode is effectively applied for a wide range of low accelerating voltages.A field emission gun usually consists of a field emission tip (cold cathode) and the Butler type electrostatic lens.

Edge Penetration Effects in the Low-Loss Electron Image in the SEM

1988 ◽  
Vol 46 ◽  
pp. 202-203
Author(s):  
Oliver C. Wells
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Beam Energy ◽  
Secondary Electron ◽  
Sharp Edge ◽  
Beam Diameter ◽  
Low Loss ◽  
Additional Information ◽  
Electron Image ◽  
Scanning Electron

The low-loss electron (LLE) image in the scanning electron microscope (SEM) is useful for the study of uncoated photoresist and some other poorly conducting specimens because it is less sensitive to specimen charging than is the secondary electron (SE) image. A second advantage can arise from a significant reduction in the width of the “penetration fringe” close to a sharp edge. Although both of these problems can also be solved by operating with a beam energy of about 1 keV, the LLE image has the advantage that it permits the use of a higher beam energy and therefore (for a given SEM) a smaller beam diameter. It is an additional attraction of the LLE image that it can be obtained simultaneously with the SE image, and this gives additional information in many cases. This paper shows the reduction in penetration effects given by the use of the LLE image.

Comparison of freeze-fractured yeast replicas using conventional TEM and low-voltage field-emission SEM

1989 ◽  
Vol 47 ◽  
pp. 74-75
Author(s):  
William P. Wergin ◽  
Eric F. Erbe ◽  
Terrence W. Reilly
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Field Emission ◽  
Low Voltage ◽  
Objective Lens ◽  
Specimen Preparation ◽  
Lens System ◽  
Air Drying ◽  
Preparation Techniques ◽  
Scanning Electron

Although the first commercial scanning electron microscope (SEM) was introduced in 1965, the limited resolution and the lack of preparation techniques initially confined biological observations to relatively low magnification images showing anatomical surface features of samples that withstood the artifacts associated with air drying. As the design of instrumentation improved and the techniques for specimen preparation developed, the SEM allowed biologists to gain additional insights not only on the external features of samples but on the internal structure of tissues as well. By 1985, the resolution of the conventional SEM had reached 3 - 5 nm; however most biological samples still required a conductive coating of 20 - 30 nm that prevented investigators from approaching the level of information that was available with various TEM techniques. Recently, a new SEM design combined a condenser-objective lens system with a field emission electron source.

Ultra high resolution SEM at high voltage images individual fab fragments applied as molecular label to cell surface receptors

1989 ◽  
Vol 47 ◽  
pp. 70-71
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
High Resolution ◽  
High Energy ◽  
Metal Coating ◽  
Beam Diameter ◽  
Surface Receptors ◽  
Surface Mobility ◽  
Metal Atoms ◽  
Shadowing Effect ◽  
Imaging Mode ◽  
Deposition Techniques

Topographic ultra high resolution can now routinely be established on bulk samples in cold field emission scanning electron microscopy with a second generation of microscopes (FSEM) designed to provide 0.5 nm probe diameters. If such small probes are used for high magnification imaging, topographic contrast is so high that remarkably fine details can be imaged on 2DMSO/osmium-impregnated specimens at ribosome surfaces even without a metal coating. On TCH/osmium-impregnated specimens topographic resolution can be increased further if the SE-I imaging mode is applied. This requires that beam diameter and metal coating thickness be made smaller than the SE range of ~1 nm and background signal contributions be reduced. Subnanometer small probes can be obtained (only) at high accelerating voltages. Subnanometer thin continuous metal films can be produced under the following conditions: self-shadowing effect between metal atoms must be reduced through appropriate deposition techniques and surface mobility of metal atoms must be diminished through high energy sputtering and/or specimen cooling.

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