The Performance of a Thermal Field Emission Gun

1975 ◽  
Vol 33 ◽  
pp. 146-147
Author(s):  
Dennis M. Maher ◽  
David C. Joy
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Field Emission ◽  
Thermal Field ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Magnetic Alignment ◽  
Stable Operation ◽  
Alignment System ◽  
Scanning Electron

Although the "cold" field emission gun has been used successfully for both transmission and scanning electron microscopy it requires ultra-high vacuum which is not obtained easily when such a gun is interfaced to a conventional microscope system. Recently, the "thermal" field emission gun (TFEG) in which the emitting tip is held at around 1700°K has been proposed as an alternative electron source for such applications. Under this condition the tip is cleaned continuously, and surface asperities are smoothed, therefore stable operation is possible in a high vacuum. In this paper we report on the build-up characteristics, current stability and brightness of a TFEG which has been interfaced to a JEOL JEM 100B microscope equipped with a scanning attachment. The gun consists of a (111) tungsten emitter set on a rhenium filament, three anodes and a two stage magnetic alignment system. The gun chamber is ion pumped to a pressure in the range 6xl0-8 to 2xl0-9 torr.

Growth of Molybdenum Trioxide Nanoribbons on Oriented Ag and Au Nanostructures: A Scanning Electron Microscopy (SEM) Study

2019 ◽  
Vol 25 (6) ◽  
pp. 1449-1456 ◽  
Author(s):  
Paramita Maiti ◽  
Arijit Mitra ◽  
R. R. Juluri ◽  
Ashutosh Rath ◽  
Parlapalli V Satyam
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Molybdenum Trioxide ◽  
High Vacuum ◽  
Composite Films ◽  
Ultra High Vacuum ◽  
Native Oxide ◽  
Native Oxide Layer ◽  
Sem Study ◽  
Scanning Electron

AbstractWe report the growth of molybdenum trioxide (MoO3) nanoribbons (NRs) on epitaxial Ag and oriented Au nanostructures (NSs) using an ultra-high vacuum (UHV)-molecular beam epitaxy (MBE) technique at different substrate temperatures. An approximately 2 nm silver (Ag) film has been deposited at different growth temperatures (using UHV-MBE) on cleaned Si(100), Si(110), and Si(111) substrates. For faceted Au NSs, an approximately 50 nm Au film has been deposited (using high-vacuum thermal evaporation) on a Si(100) substrate with a native oxide layer at the interface and the sample was annealed in low vacuum (≈10−2) and at high temperature (≈975°C). Scanning electron microscopy measurements were performed to determine the morphology of MoO3/Ag and MoO3/Au composite films. From energy dispersive X-ray spectroscopy elemental mapping and line scans it is found that faceted Au NSs are more favorable for the growth of MoO3 NRs than epitaxial Ag microstructures.

Sublimation and Phase Transitions on Si(111) Surface Observed by Ultra High Vacuum Scanning Electron Microscopy

1998 ◽  
Vol 05 (03n04) ◽  
pp. 685-691 ◽  
Author(s):  
Yoshikazu Homma
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transition Temperature ◽  
High Vacuum ◽  
Ultrahigh Vacuum ◽  
Ultra High Vacuum ◽  
Atomic Step ◽  
Current Direction ◽  
Step Flow ◽  
Scanning Electron

We studied the atomic step behavior on Si(111) during sublimation using ultrahigh vacuum scanning electron microscopy. A (111) plane with step spacings as large as several tens of micrometers could be obtained at the bottom of a crater by heating a vicinal Si(111) substrate with craters at around 1200°C in an ultrahigh vacuum. The step spacing on the plane was determined by nucleation of macrovacancies at the center of the plane while steps moved in a step flow manner, and was related to the adatom diffusion length. Above 1200°C, we found a transition-like increase in the step spacing. The electric current direction that induced step bunching changed at around the transition temperature. We attributed these phenomena to incomplete surface melting on the Si(111) surface. We also investigated the influence of heating current on the 7 × 7 phase transition using the wide Si(111) plane and found that the size of the 7 × 7 phase just below the transition temperature depended on the current direction.

scholarly journals A modified ‘NanoSuit®’ preserves wet samples in high vacuum: direct observations on cells and tissues in field-emission scanning electron microscopy

2017 ◽  
Vol 4 (3) ◽  
pp. 160887 ◽  
Author(s):  
Yasuharu Takaku ◽  
Hiroshi Suzuki ◽  
Hideya Kawasaki ◽  
Isao Ohta ◽  
Daisuke Ishii ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Field Emission ◽  
Structural Changes ◽  
Cultured Cells ◽  
High Vacuum ◽  
Insect Larvae ◽  
Direct Observations ◽  
High Vacuum Environment ◽  
Scanning Electron

Although field-emission scanning electron microscopy (FE-SEM) has proven very useful in biomedical research, the high vacuum required (10 −3 to 10 −7  Pa) precludes direct observations of living cells and tissues at high resolution and often produces unwanted structural changes. We have previously described a method that allows the investigator to keep a variety of insect larvae alive in the high vacuum environment of the electron microscope by encasing the organisms in a thin, vacuum-proof suit, the ‘NanoSuit®'. However, it was impossible to protect wet tissues freshly excised from intact organisms or cultured cells. Here we describe an improved ‘NanoSuit' technique to overcome this limitation. We protected the specimens with a surface shield enhancer (SSE) solution that consists of glycerine and electrolytes and found that the fine structure of the SSE-treated specimens is superior to that of conventionally prepared specimens. The SSE-based NanoSuit affords a much stronger barrier to gas and/or liquid loss than the previous NanoSuit did and, since it allows more detailed images, it could significantly help to elucidate the ‘real' organization of cells and their functions.

An Experimental System Combining Medium Energy Electron Diffraction and Scanning Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 136-137
Author(s):  
J.M. Cowley ◽  
F.A. Koch ◽  
J.L. Albain
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Diffraction ◽  
High Vacuum ◽  
Experimental System ◽  
Ultra High Vacuum ◽  
Vacuum System ◽  
Medium Energy ◽  
Pumping System ◽  
Scanning Electron

The theoretical and experimental advantages of using medium energy electrons (1-10 keV) instead of LEED and RHEED methods for quantitative surface studies were discussed by Moon and Cowley. A highly versatile ultra high vacuum system that exploits some of these advantages was constructed in our laboratory. The purpose of this paper is to describe design details of the instrument and to present initial data obtained.An overall view of the jinstrument is shown in Fig. 1. A commercially available field emission gun was attached to a Varian 240 LEED chamber. The pumping system is oil free and consists of cryosorbtion and Vaclon pumps.

Sign in / Sign up

Export Citation Format

Share Document