A new method for the observation of Type II magnetic contrast

1990 ◽  
Vol 48 (4) ◽  
pp. 764-765
Author(s):  
R.P. Ferrier ◽  
S. McVitie
Keyword(s):  
Domain Walls ◽  
Incident Beam ◽  
Objective Lens ◽  
Type Ii ◽  
Backscattering Coefficient ◽  
Magnetic Contrast ◽  
Standard Geometry ◽  
Backscattered Electron ◽  
Imaging Performance ◽  
Good Probe

Type II magnetic contrast was first observed by Philibert and Tixier and relies on the change in the effective backscattering coefficient due to interaction of the scattered electrons within the specimen and the local magnetic induction (for a review see Tsuno). Depending on the tilt of the specimen and the position of the backscattered electron detector(s), contrast due to the presence of either or both domains and domain walls can be obtained; in the case of the latter, the standard geometry is for the specimen to be normal to the incident beam and the detectors are positioned above it and close to the optic axis. This is the geometry adopted in our studies, which used a JEOL 2000FX with a special split objective lens polepiece; this permitted the specimen to be in magnetic field-free space, the separate lens gaps above and below allowing good probe forming capabilities combined with excellent Lorentz imaging performance. A schematic diagram is shown in Fig. 1.

The depth sensitivity of Type II magnetic contrast

1991 ◽  
Vol 49 ◽  
pp. 766-767
Author(s):  
R.P. Ferrier ◽  
S. McVitie
Keyword(s):  
Domain Wall ◽  
Type Ii ◽  
Backscattering Coefficient ◽  
Effective Electron ◽  
Domain Wall Dynamics ◽  
Magnetic Contrast ◽  
Recording Heads ◽  
Depth Sensitivity ◽  
Lock In ◽  
Relative Geometry

Type II magnetic contrast arises from the change in the effective electron backscattering coefficient due to interaction of the scattered electrons and the magnetic induction present within a ferromagnetic sample; both domain and "domain wall" contrast are observable depending on the relative geometry of the beam, the specimen and the detector (for a review see Tsuno). A major problem with Type II contrast is that it is very weak and can be swamped easily by even relatively low topographic or atomic number contrast. For studies of the domain wall dynamics in thin film recording heads Wells and Savoy overcame this problem by driving the head with an a.c. voltage and detecting, via a lock-in amplifier, the synchronous part of the backscattered signal.

Remarks on the application of backscattered electron imaging (BEI) to the scanning electron microscopy (SEM) of biological structures

1983 ◽  
Vol 41 ◽  
pp. 484-487
Author(s):  
Etienne de Harven
Keyword(s):  
High Resolution ◽  
Incident Beam ◽  
Spot Size ◽  
Primary Electron ◽  
Critical Point Drying ◽  
Cell Shapes ◽  
High Resolution Images ◽  
Backscattered Electron ◽  
Electron Imaging ◽  
Scanning Electron

Biological ultrastructures have been extensively studied with the scanning electron microscope (SEM) for the past 12 years mainly because this instrument offers accurate and reproducible high resolution images of cell shapes, provided the cells are dried in ways which will spare them the damage which would be caused by air drying. This can be achieved by several techniques among which the critical point drying technique of T. Anderson has been, by far, the most reproducibly successful. Many biologists, however, have been interpreting SEM micrographs in terms of an exclusive secondary electron imaging (SEI) process in which the resolution is primarily limited by the spot size of the primary incident beam. in fact, this is not the case since it appears that high resolution, even on uncoated samples, is probably compromised by the emission of secondary electrons of much more complex origin.When an incident primary electron beam interacts with the surface of most biological samples, a large percentage of the electrons penetrate below the surface of the exposed cells.

Temperature Dependence of Magnetic Domains and Wall Structures

1972 ◽  
Vol 30 ◽  
pp. 496-497
Author(s):  
Sonoko Tsukahara ◽  
Tadami Taoka ◽  
Hisao Nishizawa
Keyword(s):  
Temperature Dependence ◽  
Domain Walls ◽  
Magnetic Domain ◽  
Iron Film ◽  
Objective Lens ◽  
Lorentz Microscopy ◽  
Domain Structures ◽  
Wall Structures ◽  
Crystal Films ◽  
Metallurgical Structure

The high voltage Lorentz microscopy was successfully used to observe changes with temperature; of domain structures and metallurgical structures in an iron film set on the hot stage combined with a goniometer. The microscope used was the JEM-1000 EM which was operated with the objective lens current cut off to eliminate the magnetic field in the specimen position. Single crystal films with an (001) plane were prepared by the epitaxial growth of evaporated iron on a cleaved (001) plane of a rocksalt substrate. They had a uniform thickness from 1000 to 7000 Å.The figure shows the temperature dependence of magnetic domain structure with its corresponding deflection pattern and metallurgical structure observed in a 4500 Å iron film. In general, with increase of temperature, the straight domain walls decrease in their width (at 400°C), curve in an iregular shape (600°C) and then vanish (790°C). The ripple structures with cross-tie walls are observed below the Curie temperature.

Voltage-center COMA-free alignment for high-resolution Electron Microscopy

1994 ◽  
Vol 52 ◽  
pp. 410-411
Author(s):  
K. Ishizuka ◽  
K. Shirota
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Incident Beam ◽  
Chromatic Aberration ◽  
High Resolution Electron Microscopy ◽  
Beam Deflection ◽  
Objective Lens ◽  
Main Magnetic Field ◽  
Beam Direction ◽  
Resolution Electron

In a conventional alignment for high-resolution electron microscopy, the specimen point imaged at the viewing-screen center is made dispersion-free against a voltage fluctuation by adjusting the incident beam direction using the beam deflector. For high-resolution works the voltage-center alignment is important, since this alignment reduces the chromatic aberration. On the other hand, the coma-free alignment is also indispensable for high-resolution electron microscopy. This is because even a small misalignment of the incident beam direction induces wave aberrations and affects the appearance of high resolution electron micrographs. Some alignment procedures which cancel out the coma by changing the incident beam direction have been proposed. Most recently, the effect of a three-fold astigmatism on the coma-free alignment has been revealed, and new algorithms of coma-free alignment have been proposed.However, the voltage-center and the coma-free alignments as well as the current-center alignment in general do not coincide to each other because of beam deflection due to a leakage field within the objective lens, even if the main magnetic-field of the objective lens is rotationally symmetric. Since all the proposed procedures for the coma-free alignment also use the same beam deflector above the objective lens that is used for the voltage-center alignment, the coma-free alignment is only attained at the sacrifice of the voltage-center alignment.

Ultra-high resolution SEMI-in-lens type FE-SEM, JSM-6320F, with strong magnetic-field lens with built-in secondary-electron detector

1994 ◽  
Vol 52 ◽  
pp. 484-485
Author(s):  
T. Miyokawa ◽  
H. Kazumori ◽  
S. Nakagawa ◽  
C. Nielsen
Keyword(s):  
High Resolution ◽  
Secondary Electron ◽  
Spherical Aberration ◽  
Incident Beam ◽  
Chromatic Aberration ◽  
Magnetic Flux Density ◽  
Objective Lens ◽  
Electron Detector ◽  
High Resolution Images ◽  
Working Distance

We have developed a strongly excited objective lens with a built-in secondary electron detector to provide ultra-high resolution images with high quality at low to medium accelerating voltages. The JSM-6320F is a scanning electron microscope (FE-SEM) equipped with this lens and an incident beam divergence angle control lens (ACL).The objective lens is so strongly excited as to have peak axial Magnetic flux density near the specimen surface (Fig. 1). Since the speciien is located below the objective lens, a large speciien can be accomodated. The working distance (WD) with respect to the accelerating voltage is limited due to the magnetic saturation of the lens (Fig.2). The aberrations of this lens are much smaller than those of a conventional one. The spherical aberration coefficient (Cs) is approximately 1/20 and the chromatic aberration coefficient (Cc) is 1/10. for accelerating voltages below 5kV. At the medium range of accelerating voltages (5∼15kV). Cs is 1/10 and Cc is 1/7. Typical values are Cs-1.lmm. Cc=l. 5mm at WD=2mm. and Cs=3.lmm. Cc=2.9 mm at WD=5mm. This makes the lens ideal for taking ultra-high resolution images at low to medium accelerating voltages.

Observation of GaAs/AlAs Superlattice Structures in both Secondary and Backscattcred Electron Imaging Modes with an Ultrahigh Resolution Scanning Electron Microscope

1990 ◽  
Vol 48 (1) ◽  
pp. 404-405
Author(s):  
K. Ogura ◽  
A. Ono ◽  
S. Franchi ◽  
P.G. Merli ◽  
A. Migliori
Keyword(s):  
Gaas Layer ◽  
Objective Lens ◽  
Superlattice Structure ◽  
Backscattered Electron ◽  
Instrumental Resolution ◽  
Electron Microscopes ◽  
Superlattice Structures ◽  
Electron Imaging ◽  
Scanning Electron Microscopes ◽  
Scanning Electron

In the last few years the development of Scanning Electron Microscopes (SEM), equipped with a Field Emission Gun (FEG) and using in-lens specimen position, has allowed a significant improvement of the instrumental resolution . This is a result of the fine and bright probe provided by the FEG and by the reduced aberration coefficients of the strongly excited objective lens. The smaller specimen size required by in-lens instruments (about 1 cm, in comparison to 15 or 20 cm of a conventional SEM) doesn’t represent a serious limitation in the evaluation of semiconductor process techniques, where the demand of high resolution is continuosly increasing. In this field one of the more interesting applications, already described (1), is the observation of superlattice structures.In this note we report a comparison between secondary electron (SE) and backscattered electron (BSE) images of a GaAs / AlAs superlattice structure, whose cross section is reported in fig. 1. The structure consist of a 3 nm GaAs layer and 10 pairs of 7 nm GaAs / 15 nm AlAs layers grown on GaAs substrate. Fig. 2, 3 and 4 are SE images of this structure made with a JEOL JSM 890 SEM operating at an accelerating voltage of 3, 15 and 25 kV respectively. Fig. 5 is a 25 kV BSE image of the same specimen. It can be noticed that the 3nm layer is always visible and that the 3 kV SE image, in spite of the poorer resolution, shows the same contrast of the BSE image. In the SE mode, an increase of the accelerating voltage produces a contrast inversion. On the contrary, when observed with BSE, the layers of GaAs are always brighter than the AlAs ones , independently of the beam energy.

Design of Projection Lithography Objective Lens with Sub-Ten Micrometer Line-Width and its MTF Experimental Measurements

2014 ◽  
Vol 901 ◽  
pp. 111-115
Author(s):  
Liang Lei ◽  
Xin Liu ◽  
Lang Lin Li ◽  
Jin Yun Zhou
Keyword(s):  
Wave Length ◽  
Optical Design ◽  
Field Of View ◽  
Objective Lens ◽  
Modulation Transfer ◽  
Projection Lithography ◽  
Fold Reduction ◽  
Result Show ◽  
Design Software ◽  
Imaging Performance

Double fold reduction projection lithography objective lens with bi-telecentric configuration, consists of 6 lenses and the number aperture , is designed based on the optical design software Zemax. It uses the 405nm laser diode (LD) as light source. The spatial resolving capacity approaches to 5um. In a field of view of , its wave-front aberration is less than a quarter of wave-length and the distortion ratio is not more than. The imaging performance, in particular, the accurate modulation transfer function (MTF) value of the projection objective lens being fabricated by experiments is determined in this paper. Through analyzing the noise disturbance law in MTF tests, the result show that the projection objective lens has sub ten micrometer resolving ability.

Observation of Ferrimagnetic Domain Walls in CoFe2O4 With A High Voltage T.E.M.

1973 ◽  
Vol 31 ◽  
pp. 26-27
Author(s):  
L. C. De Jonghe
Keyword(s):  
Domain Wall ◽  
Ceramic Material ◽  
High Voltage ◽  
Domain Walls ◽  
Magnetic Ordering ◽  
Objective Lens ◽  
Spinel Type ◽  
Equal Energy ◽  
Cobalt Ferrites ◽  
Regular Position

Cobalt ferrites are ferrimagnetic oxides of the spinel type, exhibiting magnetic ordering along <100>. Ferrimagnetic domain walls have been observed in this ceramic material with the specimens in the regular position. Even though the field of the objective lens is quite high ∼7 k gauss) domain walls may be observed if the specimens are symmetrically oriented with respect to the field direction of the objective lens, so that adjacent domains have approximately equal energy. Ill are such orientations for cobalt ferrites. Under these conditions, only ╥/2 domain walls are expected. Such ╥/2 ferrimagnetic domain walls are shown in Fig. 1. Since magnetostriction accompanies magnetic ordering, the domain wall boundaries are also coherent twin boundaries which can be imaged with the specimen in focus.

Lorentz Electron Microscopy of Magnetic Domains in Eptaxial Iron Films

1974 ◽  
Vol 32 ◽  
pp. 476-477
Author(s):  
K. R. Lawless ◽  
G. R. Proto
Keyword(s):  
Electron Microscopy ◽  
Single Crystal ◽  
Rock Salt ◽  
Domain Walls ◽  
Weak Field ◽  
Objective Lens ◽  
Magnetic Domains ◽  
Iron Films ◽  
Normal Operating ◽  
Iron Wire

This paper describes the results of a study of domain walls in single crystal iron films by Lorentz electron microscopy. The films were prepared by evaporating 99.99% iron wire onto an air cleaved (100) rock salt substrate heated to 400°C. The films were stripped from the rock salt, mounted on Cu folding grids and annealed at a temperature between 700°C and 900°C. The study was performed in a Siemens Elmiskop 1 A operated in the weak field objective lens mode with the specimen raised 5.4 mm. above its normal operating position.

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