Thickness Estimation of Carbon Films by Electron Microscopy of Transverse Sections and Optical Density Measurements

Moretz, R. C.; Johnson, H. M.; Parsons, Donald F.

doi:10.1063/1.1655992

Cited by 28 publications

(6 citation statements)

References 7 publications

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“…We measure the thickness by TEM observation of the curled edge of a broken film, and also by optical densitometry of the carbon film evaporated on a glass slide (Moretz et al, 1968). The two methods agree well.…”

Section: Methodsmentioning

confidence: 99%

Retrofit implementation of Zernike phase plate imaging for cryo-TEM

Marko

Leith

Hsieh

et al. 2011

Journal of Structural Biology

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In-focus phase-plate imaging is particularly beneficial for cryo-TEM because it offers a substantial overall increase in image contrast, without an electron dose penalty, and it simplifies image interpretation. We show how phase-plate cryo-TEM can be implemented with an appropriate existing TEM, and provide a basic practical introduction to use of thin-film (carbon) phase plates. We point out potential pitfalls of phase-plate operation, and discuss solutions. We provide information on evaluating a particular TEM for its suitability.

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Section: Methodsmentioning

confidence: 99%

Retrofit implementation of Zernike phase plate imaging for cryo-TEM

Marko

Leith

Hsieh

et al. 2011

Journal of Structural Biology

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“…The film thickness measurements were obtained from the optical density technique of Moretz, Johnson & Parsons (1968), developed for this purpose. Holes were drilled in the carbon films by means of a laser-microscope, made available to this laboratory by the American Optical Company.…”

Section: A T E R I a L S A N D M E T H O D Smentioning

confidence: 99%

“…The washed PSL samples were dried on to conventional formvar-carbon films (of total mass thickness approximately 2.4 pg cm-2) made from a 0.5% solution of formvar followed by a carbon layer for stability. The carbon film thickness was measured by a new densitometry technique (Moretz et al, 1968). Mass thickness calculations were based on a mass density of 1.057 g cm-3 for PSL (Pugh & Heller, 1957) and 1.98 f 0.03 g cm-3 for the evaporated carbon.…”

Section: Materials a N D M E T H O D Smentioning

confidence: 99%

Enhanced contrast in electron microscopy of unstained biological material

Johnson

Parsons

1973

Journal of Microscopy

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In-focus phase contrast electron microscopy has been investigated for the enhancement of bulk contrast (i.e. the contrast of large regions) of model biological specimens. Carbon film phase plates, of measured thickness, were introduced into the back focal plane ofthe objective lens. Image contrast was determined from Faraday-cage intensity measurements. A contrast enhancement was observed but was measured to be less than that obtained using a very small objective aperture. This was attributed to the smaller proportion of elastic scattering and the limited spatial frequency region over which the phase contrast transfer function was uniform. Electron beam interferometry established the ability of the phase plates to preserve the coherence of the beam traversing them. Carbon granularity, of specific dimensions, was significantly enhanced by the phase plate in accordance with the phase contrast transfer function and this enhanced granularity dominated the images of biological specimens. I N T R O D U C T I O NThe phase contrast technique, invented for light microscopy by Zernike (1942a, b), involved phase shifting the scattered relative to the non-scattered waves from a microscope specimen. Constructive or destructive interference was achieved when the wave components interfered in the image plane and image contrast was enhanced by rendering a specific detail brighter (negative contrast) or darker (positive contrast) than its surroundings. A phase plate in the diffraction plane (back focal plane) of the objective lens accomplished the required phase shift by providing an increased optical path (a phase delay) for one wave component relative to the other.Calculations (Bennet et al., 1946; Franqon, 1950;Barer, 1952) indicated the necessity of a 7r/2 rad phase delay of scattered waves for positive phase contrast in the case of hypothetical objects comparable to typical unstained biological specimens. Experimentally, Zernike (1942a, b) and Bennet et al. (1946, 1951) found a 57/2 rad phase plate to be the best compromise for routine biological light

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“…layers of carbon of various thickness. The thickness of these carbon layers was accurately determined according to the techniques of Moretz et al (1968). Fortuitously the density of evaporated carbon (Reed 1975) is the same as that of keratin (1.30 g em") and so we had the means of effectively determining the penetration depth for sulphur analyses of the hair surface in terms of that carbon thickness on the sulphur-containing protein substrate which at a given incident electron energy would eliminate the emission of the sulphur Ka x-rays.…”

Section: Depth Of Electron-induced X-ray Emissionmentioning

confidence: 99%

Minimum depth electron probe x‐ray microanalysis as a means for determining the sulphur content of the human hair surface

Swift

1979

Scanning

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By using incident electron energies as low as 3 keV it has been shown both theoretically and practically that the maximum depth for the excitation of sulphur Kα x‐rays from a sulphur‐containing proteinaceous solid can be restricted to 110 nm. This approach has been used to determine the concentration of sulphur in the immediate surface of human hair, and more particularly associated with the A‐layer subcomponent of the hair cuticle. The value obtained was 11.8 weight % (± 0.92, n = 10).

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Thickness Estimation of Carbon Films by Electron Microscopy of Transverse Sections and Optical Density Measurements

Cited by 28 publications

References 7 publications

Retrofit implementation of Zernike phase plate imaging for cryo-TEM

Retrofit implementation of Zernike phase plate imaging for cryo-TEM

Enhanced contrast in electron microscopy of unstained biological material

Minimum depth electron probe x‐ray microanalysis as a means for determining the sulphur content of the human hair surface

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