'Secondary’ Electron Detector Design and Positioning in the Variable Pressure Scanning Electron Microscope: The Colour Option

2000 ◽  
Vol 6 (S2) ◽  
pp. 772-773
Author(s):  
Brendan J. Griffin ◽  
James R. Browne ◽  
Louise Egerton-Warburton ◽  
Dominique Drouin
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Secondary Electron ◽  
Operating Conditions ◽  
Variable Pressure ◽  
Environmental Scanning ◽  
Induced Field ◽  
Detector Configurations ◽  
Induced Signal ◽  
Scanning Electron

The simple models for low energy secondary electron (SE) detection in the variable pressure or environmental scanning electron microscope (ESEM) describe a gas-amplified cascade from sample to detector when a conventional biased detector is used. Recent images obtained using a modified specimen current imaging approach however have suggested that at least a portion of the image is an induced field effect, in agreement with some of the early work. Our recent aim has been to investigate a range of detector designs and positions within the chamber in both the old ElectroScan E-3 model ESEM and the current generation FEI XL30 ESEM TMP. The results support the earlier observations of induced signal components being present, with even ‘negative’ or inverted images being obtained under some detector configurations due to the noise cancellation techniques used (figure 1). These results are being quantified using the DQE measurement approach to allow an objective comparison of different designs and positions. This data will be presented for the commercially available detectors and for the ‘Griffin’ grid detector under a range of operating conditions.

X-Ray Microanalysis of Materials in the ESEM or VP-SEM

2001 ◽  
Vol 7 (S2) ◽  
pp. 778-779
Author(s):  
Raynald Gauvin
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Incident Beam ◽  
Operating Conditions ◽  
Variable Pressure ◽  
Environmental Scanning ◽  
Copper Strip ◽  
X Ray ◽  
Gas Molecules ◽  
Scanning Electron

When performing X-Ray microanalysis in the ESEM (Environmental Scanning Electron Microscope) or in the VP-SEM (Variable Pressure Scanning Electron Microscope), the operating conditions of the microscope must be optimized. This is to reduce the beam broadening of the incident electrons when they scatter with the gas molecules before entering into the specimen. As a result of this scattering, the incident beam is composed of two parts. The first part of the beam is the unscattered beam and the second part is the scattered beam, named the skirt. in high pressure and long working distances conditions, the diameter of the skirt may extend to several millimeters. in order to show the effect of the skirt on X-Ray generation, a copper strip was placed .5 mm away of the electron beam on a flat Al specimen. The peak to background ratio of the copper line was measured at different pressure (from 25 to 200 Pa) for Air as gas.

Novel and Advanced Applications of the Low Vacuum and Environmental Scanning Electron Microscope (SEM)

1997 ◽  
Vol 3 (S2) ◽  
pp. 385-386 ◽  
Author(s):  
Brendan J. Griffin
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Secondary Electron ◽  
Electron Gun ◽  
Environmental Scanning ◽  
Electron Detector ◽  
Environmental Sem ◽  
Practical Sense ◽  
Advanced Applications ◽  
Scanning Electron

The environmental SEM is an extremely adaptive instrument, allowing a range of materials to be examined under a wide variety of conditions. The limitations of the instrument lie mainly with the restrictions imposed by the need to maintain a moderate vacuum around the electron gun. The primary effect of this has been, in a practical sense, the limited low magnification available. Recently this has been overcome by modifications to the final pressure limiting aperture and secondary electron detector (Fig.l). The modifications are simple and users should be brave in this regard.A variety of electron detectors now exist including various secondary, backscattered and cathodoluminescence systems (Figs 2-5). These provide an excellent range of options; the ESEM must be regarded as a conventional SEM in that a range of imaging options should be installed. In some cases, e.g. cathodoluminescence, the lack of coating provides an advantage unique to the low vacuum SEMs.

Recent Advances in Gaseous Detection Modes in the ESEM

1999 ◽  
Vol 5 (S2) ◽  
pp. 268-269
Author(s):  
T. A. Hardt ◽  
W. R. Knowles
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Secondary Electron ◽  
Large Field ◽  
Environmental Scanning ◽  
Electron Detector ◽  
Field Detection ◽  
Gaseous Environment ◽  
Detection Mode ◽  
Scanning Electron

The Environmental Scanning Electron Microscope, or ESEM, is the only class of SEM that can image in a gaseous environment that will maintain a sample in a fully wet state. The use of the patented Gaseous Secondary Electron Detector, or GSED, which amplifies the secondary electron signal with the gas, has allowed the ESEM to image a multitude of samples with true secondary contrast. Recently, several new modes of imaging in a gas have been developed and will allow further expansion of the capabilities of the ESEM.To maintain pressures in the ESEM up to 20 Torr (27 mbar), the use of multiple, differentially pumped apertures, is required. This can place a restriction on the low magnification range. In the large field detection mode, all magnification restrictions are removed. Magnifications as low as lOx may be achieved. This is similar to many conventional SEMs.

scholarly journals Performance of X-ray Microanalysis in the Variable Pressure or Environmental Scanning Electron Microscope

2006 ◽  
Vol 12 (S02) ◽  
pp. 1492-1493 ◽  
Author(s):  
J-F Le Berre ◽  
K Robertson ◽  
R Gauvin ◽  
GP Demopoulos
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Environmental Scanning Electron Microscope ◽  
Variable Pressure ◽  
Environmental Scanning ◽  
X Ray ◽  
Scanning Electron

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2006

Microcharacterization of Induced Electric Fields in Poorly Conducting Specimens Irradiated in an Environmental Scanning Electron Microscope

2001 ◽  
Vol 7 (S2) ◽  
pp. 786-787
Author(s):  
Marion A. Stevens-Kalceff
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Electric Fields ◽  
High Vacuum ◽  
Charge Trapping ◽  
Environmental Scanning Electron Microscope ◽  
Variable Pressure ◽  
Environmental Scanning ◽  
Excess Charge ◽  
Scanning Electron

In a conventional scanning electron microscope, a thin, grounded conductive coating is applied to specimens that are poor electrical conductors to prevent retarding and deflection of the incident electron beam. in a variable pressure or environmental scanning electron microscope (ESEM), excess charge on the surface of uncoated poorly conducting specimens is balanced using ionized environmental gas. Ionized gas in environmental mode and grounded conductive coatings in conventional or high vacuum mode minimize charging at the specimen surface, however significant charge trapping may still occur in the implanted sub-surface regions of poorly conducting materials. A small fraction (<10-6) of the incident electrons are trapped at irradiation induced or pre-existing defects within the irradiated specimen. The trapped charge induces a highly localized electric field which can result in electro-migration and micro-segregation of charged mobile defect species within the irradiated micro-volume of specimen.

Secondary-Electron imaging by Scintillating Gaseous Detection Device

1992 ◽  
Vol 50 (2) ◽  
pp. 1302-1303 ◽  
Author(s):  
G. D. Danilatos
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Secondary Electron ◽  
Environmental Scanning Electron Microscope ◽  
Environmental Scanning ◽  
Specimen Preparation ◽  
Additional Signal ◽  
Gaseous Environment ◽  
Electron Imaging ◽  
Scanning Electron

The environmental scanning electron microscope (ESEM) incorporates the functions of the conventional SEM while it has the added capability of allowing the examination of virtually any specimen in a gaseous environment. The main modes of imaging are all represented in the ESEM, and some developments with regard to the secondary electron (SE) mode are reported herewith.The conventional E-T detector fails to operate in the gaseous conditions of ESEM, but this obstacle has been overcome with the advent of a gaseous detection device (GDD). The principle of operation of this device is based on the monitoring of the products of interaction between signals and gas. Initially, the ionization from the signal/gas interaction was used to produce images of varying contrast and, later, the gaseous scintillation, from the same interaction, was also used to produce images. First, a low bias was applied to various electrodes but later a much higher bias was used for the purpose of achieving additional signal gain. By careful shaping and positioning the respective electrode, it was shown that SE imaging is possible in the ESEM. This has been also independently demonstrated by use of a special specimen preparation.

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