Development of a 200kV field emission TEM

1989 ◽  
Vol 47 ◽  
pp. 112-113
Author(s):  
S. Isakozawa ◽  
Y. Kashikura ◽  
Y. Sato ◽  
T. Takahashi ◽  
M. Ichihashi ◽  
...  
Keyword(s):  
Field Emission ◽  
Crystal Orientation ◽  
Electron Gun ◽  
Objective Lens ◽  
General View ◽  
Virtual Source ◽  
Lens System ◽  
Separate Paper ◽  
Small Probe ◽  
Tungsten Tip

We have completed development of a 200kV field emission TEM. Fig. 1 is a general view of the instrument showing the electron gun and illumination lens system. The electron gun is reported in a separate paper in details. The high voltage accelerator is of 6-stage with aluminum oxide insulators. It allows stable 200kV operation achieving a voltage stability of 1.5 х 10−6/min. The field emitter is a polished tungsten tip having a crystal orientation of (310). It is operated at an ambient temperature without heating. The illumination lens system has been designed and built with permalloy to suite the small virtual source and to minimize external magnetic field disturbances. The objective lens has been designed to allow a point resolution of 0.23 nm and a small probe of 1 nm diameter. The probe has an intensity of 1 х 109A/cm2 sr. or higher as measured on the specimen.

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.

Energy Filtering of Schottky Field Emission Gun Using Fringe Field Monochromator

1999 ◽  
Vol 5 (S2) ◽  
pp. 646-647
Author(s):  
H.W. Mook ◽  
A.H.V. van Veen ◽  
P. Kruit
Keyword(s):  
Field Emission ◽  
Low Voltage ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Electron Gun ◽  
Fringe Field ◽  
Objective Lens ◽  
Electronic Band ◽  
Energy Width ◽  
Energy Filtering

The energy resolution which can be attained in electron energy loss spectroscopy (EELS) is determined by the energy spread of the electron source. The energy width of a high brightness electron gun (typically 0.4 to 0.8 eV) blurs the energy spectrum. A pre-specimen energy filter or monochromator must be used to reduce the energy width of the beam below 0.1 eV to allow detailed EELS analysis of the electronic band structures in materials. The monochromator can not only improve EELS, but it is also capable of improving the spatial resolution in low voltage SEM, which is limited by the chromatic blur of the objective lens. A new type of monochromator the Fringe Field Monochromator has been designed and experiments in an ultra high vacuum setup show the monochromatisation of a Schottky Field Emission Gun.

Interference Experiments with a Field Emission Source

1970 ◽  
Vol 28 ◽  
pp. 534-535
Author(s):  
A. V. Crewe ◽  
J. Saxon
Keyword(s):  
Field Emission ◽  
Spherical Aberration ◽  
Electron Gun ◽  
Partial Coherence ◽  
Vacuum System ◽  
High Brightness ◽  
Small Spot ◽  
Tungsten Tip ◽  
Effective Source ◽  
Better Than

Field emission from a tungsten tip provides a source with very high brightness and high partial coherence. An electron gun of low spherical aberration is used to focus the electrons from the tip to a small spot about 100 Å in diameter. Since the voltages applied to the tip and gun are stable to better than 5 ppm, the temporal coherence is limited by the energy spread of the source, about 200 mv.Using the focused spot a few centimeters below the gun as an effective source, a metalized quartz fiber about 2 μ in diameter is positioned a few centimeters below the source, as shown in Fig. 1. Two cylindrica11y symmetric magnetic lenses are used to magnify the resulting Fresnel diffraction pattern. The image is produced on a fluorescent coating deposited on the vacuum side of a fiber optic window. The image is recorded directly on film placed against the window outside the vacuum system.

Development of a Field Emission Stem and its Application to Element Analysis

1976 ◽  
Vol 34 ◽  
pp. 524-525
Author(s):  
S. Nomura ◽  
H. Todokoro ◽  
T. Komoda
Keyword(s):  
Field Emission ◽  
Collection Efficiency ◽  
Scanning Transmission Electron Microscope ◽  
Electron Gun ◽  
High Signal ◽  
Element Analysis ◽  
Signal Collection ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Tungsten Tip

The Scanning Transmission Electron Microscope (STEM) has made possible specimen observation with a number of advantages such as high signal collection efficiency. In addition, STEM also permits element analysis of micro-areas, when it is used in conjunction with X-ray and/or electron spectrometers. These advantages become more effective by using a high brightness electron gun.The authors have developed a field emission STEM. The schematic diagram of the instrument is shown in Fig. 1. Electrons emitted from the tungsten tip are focused on a specimen by one electro-static and two magnetic lenses. The field emission tip is surrounded by ion pumps, and the vacuum of the gun chamber is maintained at better than 5xlO-10torr.

An Illuminating System of a 100-kV Analytical Electron Microscope with a Field-Emission Electron Gun

1990 ◽  
Vol 48 (1) ◽  
pp. 122-123
Author(s):  
A. Delong ◽  
J. Chmelík ◽  
V. Kolařík
Keyword(s):  
Electron Microscopy ◽  
Field Emission ◽  
Analytical Electron Microscopy ◽  
Electron Gun ◽  
Transmission Mode ◽  
Resolving Power ◽  
Objective Lens ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Illuminating System

Our aim was to design a microscope for application in both the classical transmission electron microscopy (CTEM) and in the analytical electron microscopy having in the scanning modes (SEM, STEM) a resolving power approaching that in the CTEM. The problem can be optimally solved by using the field emission source of electrons. The illuminating system and the objective lens have the following parameters:a) The resolving power of the objective lens in the transmission mode is as high as 3.5 Å.b) The optical aberrations of the pre—field of the objective lens and of the set of condenser lenses allow a resolution of approx. 5 Å to be achieved in the scanning mode.c) The illuminated area of the specimen observed in the transmission mode is large enough to allow operation with the objective lens switched on at a magnification 1000 x.

A Scanning Electron Microscope from Hitachi

1969 ◽  
Vol 27 ◽  
pp. 88-89
Author(s):  
Yoshirou Onuma ◽  
Tatsuo Hujiyasu ◽  
Yukio Kakinuma
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Mechanical Vibration ◽  
Electron Gun ◽  
Objective Lens ◽  
Lens System ◽  
Beam Path ◽  
External View ◽  
Electrical Fields ◽  
Scanning Electron

Hitachi, Limited has recently completed the development of a commercial scanning electron microscope, the features of which are discussed herein. Fig. 1 is an external view of the instrument.Lens SystemA three-stage reduction lens system is employed to obtain a short electron beam path. This minimizes the effects of any external electromagnetic or stray electrical fields as well as mechanical vibration or shock. Axial alignment is easily accomplished by transverse adjustment of the electron gun and lens system. Aperture plates with different hole sizes are provided in the condenser lens, deflection coil, and on the principal plane of the objective lens. The apertures are easily removed for cleaning. The electromagnetic stigmator is located outside the objective lens to facilitate removal for cleaning. Resolution of 200Å~250Å is guaranteed.

Field emission SEM with wide operating voltage range

1988 ◽  
Vol 46 ◽  
pp. 976-977
Author(s):  
S. Norioka ◽  
T. Miyokawa ◽  
S. Goto ◽  
T. Niikura ◽  
S. Sakurai
Keyword(s):  
Field Emission ◽  
General Purpose ◽  
Electron Gun ◽  
Operating Voltage ◽  
Virtual Source ◽  
Cross Sectional ◽  
Voltage Range ◽  
Voltage Change ◽  
Tip Radius ◽  
Wide Operating

A newly developed conical anode field emission electron gun (FE-GUN)has been installed on the JSM-840F Scanning Electron Microscope (SEM). The cross sectional view of the column is shown in Fig. 1. The gun is usable at a wide accelerating voltage range from 0.5 kV to 40 kV, and is suitable for general purpose SEMs. The gun can be used within the virtual source range even at an extract voltage as high as 7 kV and an accelerating voltage as low as 0.5 kV. The extract voltage can be raised up to 7 kV even when the emitter tip radius becomes larger after repeated flashing for smoothing the emitter tip surface. This allows elongation of the emitter life.With the FE-GUN, since the electron source (virtual source) moves with accelerating voltage change, an image may disappear due to the deviation of the electron probe from the optical axis when the accelerating voltage is changed.

Field Emission Analytical Electron Microscope

1976 ◽  
Vol 34 ◽  
pp. 528-529
Author(s):  
Y. Harada ◽  
Y. Kokubo ◽  
T. Goto ◽  
N. Tamura ◽  
M. Iwatsuki ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Field Emission ◽  
Objective Lens ◽  
General View ◽  
Energy Analyzer ◽  
X Ray ◽  
Transmission Electron ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Electron Microscopes

Recently, analytical electron microscopes (AEM), which provide the functions of the transmission electron microscope (TEM), scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS) have been put to practical use with a view to analyzing elements in micro areas, xo improve the performance of this type of AEM, a field emission gun was attached to our AEM instead of a conventional thermionic gun. This has allowed a sellected area smaller than several 100 Å to be easily analyzed. Moreover, an electron energy analyzer (EA) was attached to the AEM for detecting light elements which cannot be detected by the EDS.These modifications have resulted in an advanced type of an AEM, namely, a field emission analytical electron microscope (FEAEM).Fig. 1 shows a general view of our FEAEM. The feature of this FEAEM is that it is designed on the basis of a 100 kV field emission electron microscope provided with a strongly-excited objective lens having a very small aberration coefficient and with an eucentric goniometer tiltable to 60°.

The Use of Field Emission Tips in a Scanning Microscope

1968 ◽  
Vol 26 ◽  
pp. 359-359 ◽  
Author(s):  
A. V. Crewe ◽  
M. Isaacson
Keyword(s):  
Single Crystal ◽  
Field Emission ◽  
Electrical Discharge Machining ◽  
Optical Axis ◽  
Electron Gun ◽  
List Type ◽  
Type Number ◽  
Scanning Microscope ◽  
Intense Emission ◽  
Tungsten Tip

We have previously described an electron gun which uses a field emission tungsten tip as the source of electrons. In this paper we will discuss the practical aspects of the operation of such tips in an electron gun used in a scanning microscope.There are essentially three main criteria to be satisfied by these tips:The tungsten wire must be oriented so that a direction of intense emission is along the axis of the tip.The axis of the tip must coincide with the optical axis of the microscope.One must be able to obtain reasonable emission current (about 1 μ amp) at a low enough voltage (1-3 kV).It is well known that for single crystal tungsten, the planes of intense emission are perpendicular to the (310) and (111) directions (among others). Wire oriented with these directions along the axis can either be bought commercially or it can be cut by electrical discharge machining from a block of single crystal tungsten of known orientation.

Observation of Phase Contrast Images in STEM and CTEM Modes by Using 100 kV Field Emission Electron Gun

1974 ◽  
Vol 32 ◽  
pp. 390-391
Author(s):  
Y. Harada ◽  
T. Goto ◽  
H. Koike ◽  
T. Someya
Keyword(s):  
Field Emission ◽  
Phase Contrast ◽  
Image Formation ◽  
Fresnel Diffraction ◽  
Experimental Results ◽  
Electron Gun ◽  
Scanning Microscopy ◽  
Emission Electron ◽  
Lattice Images

Since phase contrasts of STEM images, that is, Fresnel diffraction fringes or lattice images, manifest themselves in field emission scanning microscopy, the mechanism for image formation in the STEM mode has been investigated and compared with that in CTEM mode, resulting in the theory of reciprocity. It reveals that contrast in STEM images exhibits the same properties as contrast in CTEM images. However, it appears that the validity of the reciprocity theory, especially on the details of phase contrast, has not yet been fully proven by the experiments. In this work, we shall investigate the phase contrast images obtained in both the STEM and CTEM modes of a field emission microscope (100kV), and evaluate the validity of the reciprocity theory by comparing the experimental results.

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