In other embodiments, the lens apparatus comprises a magnetic dipole or virtual magnetic monopole fabricated from a variety of materials, including permanent magnets, superconducting coils, and magnetizable spheres and needles contained within an energy-conducting coil. The invention further provides apparatus, methods, and devices useful in focusing charged particle beams for lithographic processes. Similar records in OSTI.
GOV collections:. To estimate the Cc following the caution discussed in ref. These measured lens parameters are compared with another existing Lorentz type lens as shown in Supplementary Table 2. We exchanged the normal objective lens system to the newly developed magnetic field-free type objective lens system. In this system, standard double-tilt sample holders are acceptable.
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Ultramicroscopy , — Ishizuka, K. Then, what is the positional relationship between the sample and the electronic lens? There are two main sample positions. One is the "out-lens method" in which the electron beam is placed after passing through the objective lens in the case of SEM or before in the case of TEM. The other one is the "in-lens method" in which the electron beam is placed inside the objective lens in the case of SEM only.
The higher resolution is the in-lens method, which shortens the focal length, but it cannot be used if the sample is affected by a magnetic field.
In that case, the out-lens method, which is less affected by the magnetic field, will be used. In addition, the in-lens method can only target samples of a size that can be placed inside the lens. On the other hand, with the out-lens method, it is possible to target samples that are larger than the in-lens method.
Therefore, it is necessary to use the out-lens method when the sample is large or affected by the magnetic field. And you use the in-lens method when the sample is small and not affected by the magnetic field. However, a "semi-in lens snorkel method" objective lens was developed to eliminate this drawback of the in-lens as much as possible.
Since the sample is placed under the objective lens, it looks like an out-lens type, but the focal length can be shortened by devising the shape of the pole piece, so it is possible to obtain a resolution close to that of the in-lens method.
The semi-in-lens method enables high-resolution observation of even large samples. In addition, in the case of the out-lens method, there is a method of moving the detector closer to the sample for increasing the resolution.
In this case, the out lens is an obstacle to inserting the detector. Therefore, it is necessary to increase the focal length, and the advantage of bringing the detector closer is lost. The results are an unclear or out-of-focused image.
It is important to create a balance between reduction of spherical aberration and diffraction by selecting an appropriate sized aperture.
Image fomation in the electron microscope is achieved by electron scattering. Backscattered electrons are an example of elastic scattering. Inelastic scattering occurs when an electron transfers some kinetic energy of the atoms of the sample.
Examples of inelastic scattering are secondary electrons, auger electrons, and transmitted electrons. Accelerating voltage -The fixed amount of high voltage applied to the cathode cap of the transmission electron microscope. Anode -Located below the gun assembly, the anode is at ground with a small aperture for electrons to move through.
This aperture serves as the first lens encountered by the electron. Astigmation -An aberration caused by uneven electrical fields surrounding a lens. Cathode -The filament or source of the primary electron beam.
Cathode Cap- also called Wehnelt cylinder surrounds the gun assembly. The high voltage is applied here. Cold finger -A long copper rod extending along the inside of the electron column. When its reservoir is kept filled with liquid nitrogen, the rod attracts contaminants that might otherwise degrade the chamber's vacuum.
Condenser aperture -A small laser-bored hole in a flat strip of molybdenum placed near the condenser lens that helps to limit spherical aberration. Condenser lens -The first electromagnetic lens that the electron beam encounters. Focuses the electrons onto the specimen.
Chromatic aberration -Electromagnetic radiation of different energies converging at different focal planes. Crossover -The point at which the electrons converge. The smallest visual beam image on the phosphorous screen. DeBroglie's formula -The wavelength of an electron is a function of the accelerating voltage used. Elastic scattering -Electron scattering where little kinetic energy is lost, but the trajectory of the electron is substantially changed.
Electron scattering -The displacement of an electron beam by a sample, causing formation of an image. Emission current -A small amount of heat added to the electron source in order to release electrons through the column. Fresnel fringe -A diffraction pattern formed around a small hole when the beam is over-focused onto it.
Holey grid -A thin support film manufactured to have holes so that it may be used to align a TEM. Inelastic scattering -Scattering of electrons in which the electron loses kinetic energy, but changes trajectory only minimally. Objective aperture -A small laser-bored hole in a flat strip of molybdenum placed near the objective lens.
Adjustment of this aperture strip can aid in adjustment of contrast of the image. Phosphorescent screen -The screen at the bottom of the electron column, where the specimen is viewed.
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