Wide-band detector for micro-microampere low-energy electron currents

Everhart, T. E.; Thornley, R.

doi:10.1088/0950-7671/37/7/307

Cited by 355 publications

(115 citation statements)

References 5 publications

(1 reference statement)

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“…Specimen charging is prevented by depositing a thin layer of a conducting material on to the specimen surface using high-temperature vacuum evaporation or plasma discharge techniques (Pfeffercorn, 1973;Echlin, 1974). However, whereas secondary-electron emission and resolution are improved by using a coating material of high atomic number such as gold (Everhart, 1970), such materials form energy barriers to both electron penetration and BSE emission and hence degrade any BSE image. It is therefore necessary to use a material with a low atomic number, such as carbon, but since electron channelling effects originate from very close to the specimen surface (typically < 50 nm) the thickness of carbon deposited must be carefully monitored for BSE electron channelling analysis.…”

Section: Specimen Preparation For Bse Analysismentioning

confidence: 99%

Atomic number and crystallographic contrast images with the SEM: a review of backscattered electron techniques

1987

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Backscattered electrons (BSE) are incident electrons reflected back from a target specimen and imaged with the scanning electron microscope (SEM). Three distinct BSE signals exist: atomic number or Z-contrast, in which composition determines image contrast; orientation contrast, in which specimen crystal structure determines image contrast; and electron channelling patterns (ECP), which are unique for a particular crystal orientation. The origins of these three signals are described, with particular attention being given to the necessary SEM operational and specimen preparation requirements. Z-contrast images are relatively simple to obtain and also have a familiar appearance such that their usage should become commonplace. ECP in comparison require subsequent interpretation which depends on the crystal structure and the relationship between crystal and specimen coordinate systems. A general solution to ECP interpretation is therefore presented, involving the construction of reference 'ECP-maps' over the surface of a sphere. A brief summary of the applications and potential use of the three BSE signals in the geological sciences is also given.

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Section: Specimen Preparation For Bse Analysismentioning

confidence: 99%

Atomic number and crystallographic contrast images with the SEM: a review of backscattered electron techniques

1987

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“…3). Scientists from Oatley's laboratory produced the secondary electron detector that is still so widely used today (Everhart and Thornley, 1960), as well as the first microscopes with a second column through which ions can be focussed and scanned across samples to etch away surfaces -the first focused ion-beam scanning electron microscopes. This development also produced imaging strategies that used lower energy beams while still maintaining their precision.…”

Section: Where It All Beganmentioning

confidence: 99%

Is EM dead?

Knott

Genoud

2013

Journal of Cell Science

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SummarySince electron microscopy (EM) first appeared in the 1930s, it has held centre stage as the primary tool for the exploration of biological structure. Yet, with the recent developments of light microscopy techniques that overcome the limitations imposed by the diffraction boundary, the question arises as to whether the importance of EM in on the wane. This Commentary describes some of the pioneering studies that have shaped our understanding of cell structure. These include the development of cryo-EM techniques that have given researchers the ability to capture images of native structures and at the molecular level. It also describes how a number of recent developments significantly increase the ability of EM to visualise biological systems across a range of length scales, and in 3D, ensuring that EM will remain at the forefront of biology research for the foreseeable future.

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“…Although many complex sample preparation technologies (metal coating) and instrumental operation techniques (field-emission microscopy, low-voltage microscopy, low-vacuum microscopy) were developed for overcoming this setback, the image quality could not be significantly improved. Since the early development of the SEM, it was known that some basic limitations arose from signal collection deficiency at the level of detectors (Everhart andThornley 1968, Moncrieff andBarker 1978, PGbers 1984a) as well as from the sample (Echlin 1972). The maximum instrumental resolution is theoretically dehed by the size of the electron probe, but the practically achievable topographic resolution is 10-20 times lower.…”

Section: Introductionmentioning

confidence: 99%

Collection deficiencies of scanning electron microscopy signal contrasts measured and corrected by differential hysteresis image processing

Peters

1996

Scanning

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Summary:Limitations of scanning electron microscopy (SEM) image resolution and quality were measured in digital image data and their effect on image contrasts was analyzed and corrected by differential hysteresis (DH) processing. DH processing is a mathematical procedure that utilizes hysteresis properties of intensity variations in the image for a segmentation of differential contrast patterns. These patterns display contrast properties of the data as coherent full-frame images. The contrast segmentation is revertible so that the original image can be restored from the sum of the sequentially extracted DH contrast patterns. DH imaging enhances weak contrast components so that they are more easily recognizable and displays SEM image data free of signal collection efficiency contrasts. Example image data include environmental SEM (ESEM) and SEM images of low and mediumhigh magnifications where collection deficiencies included charging of the specimen surface, obstructions from specimen topography, and uneven signal collection properties of the detector. ESEM low-vacuum image data, which appear to be of high quality, contained local areas of reduced contrasts due to residual surface charging. In such areas, signal contrasts were reduced up to 80%, which suppressed most of the weak short-range contrasts. In low-magdication SEM images, up to 93% of the local high precision contrast was lost from the various adverse effects which diminished the pixel-related contrast resolution of the microscope and resulted in images with low detail. Also, at medium magmfication, surface charging effects dramatically reduced the image quality because contrasts resulting from local electron beardspecimen interactions were reduced by as much as 71%. DH imaging restored the local contrast losses by elimination of the collected distorted fraction of signal contrasts and reconstitution of the collected maintained fraction. Restored DH images are Support Erom a Connecticut Department of Economic Development Grant 92H18 is thankfully acknowledged. Address for reprints:Klaus-Ruediger Peters, Ph.D. Biomolecular Shucture Analysis Center university of Connecticut Health Center 263 Farmington Avenue Farmington, C T 06030-201 7, USA of superior quality and enhance the imaging capability of the conventional SEM. DH contrast segmentation provides an improved basis for the measurement of various signal contrast components and detector performances. The DH analysis will ultimately facilitate a precise deduction of specimen properties from extracted contrast patterns.

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Wide-band detector for micro-microampere low-energy electron currents

Abstract: Electrons with a mean energy of a f e w electron volts

Cited by 355 publications

References 5 publications

Atomic number and crystallographic contrast images with the SEM: a review of backscattered electron techniques

Atomic number and crystallographic contrast images with the SEM: a review of backscattered electron techniques

Is EM dead?

Collection deficiencies of scanning electron microscopy signal contrasts measured and corrected by differential hysteresis image processing

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