The small-angle scattering of electrons in thin films of evaporated carbon

Burge, R. E.; Misell, D L; Smart, J W

doi:10.1088/0022-3719/3/8/004

Cited by 21 publications

(18 citation statements)

References 22 publications

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“…This is a more realistic interpretation of the broad loss peak observed in the present work, and is not inconsistent with more recent views expressed by Burge, Misell and Smart (1970).…”

Section: Downloaded By [New York University] At 07:16 04 August 2015supporting

confidence: 88%

Electron energy loss studies of polymers during radiation damage

Ditchfield

Grubb

Whelan

1973

Philosophical Magazine

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“…This is a more realistic interpretation of the broad loss peak observed in the present work, and is not inconsistent with more recent views expressed by Burge, Misell and Smart (1970).…”

Section: Downloaded By [New York University] At 07:16 04 August 2015supporting

confidence: 88%

Electron energy loss studies of polymers during radiation damage

Ditchfield

Grubb

Whelan

1973

Philosophical Magazine

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“…It can be seen that although axial illumination (bright field condition) gives a large signal for the uranium atom (10.5% of the incoming beam), it is only 11% of the background. This is extremely close to the limit of detection, which is accepted to be between 5 and 10% (9). However, in the case of tilted illumination (dark field condition) the signal, although as small as 0.64% of the incoming beam, is 112% of the background, a 10-fold increase in contrast over bright field conditions and well above the detectable limit.…”

supporting

confidence: 63%

Visualization of Single Heavy Atoms by Dark Field Electron Microscopy

Henkelman¹,

Ottensmeyer²

1971

Proc. Natl. Acad. Sci. U.S.A.

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Dark field electronmicrographs of atoms of palladium, iodine, platinum, osmium, and uranium in model compounds have been obtained. Statistical analyses and a series of blind tests demonstrate the validity of the results. Moreover, optical density measurements of the images indicate that the observed relative scattering crosssections of these atoms agree well with the theoretical cross-sections calculated from a Thomas-Fermi-Dirac model of the atom.The visualization of single atoms has long been a goal of electron microscopy-a goal that the increased resolving power of modern microscopes of conventional design and the development of new kinds of microscopes are beginning to achieve. As early as 1957, Mueller (1) observed atoms in single crystal metal tips using field ion microscopy. However, the biologist interested, for instance, in analyzing the base sequence of nucleic acids by the use of heavy atom markers, requires that isolated single heavy atoms be imaged. Up to the present, the only technique capable of this has been transmission scanning electron microscopy of high resolution, in conjunction with electron energy analysis (2), although a recent report by Koller (3) indicates that it may be possible to image heavy atoms by the use of traditional brightfield transmission electron microscopy. One of the principal difficulties in the use of a conventional electron microscope for the visualization of atoms has been the lack of contrast. Even though the scattering of a single heavy atom can be shown theoretically to produce a reasonable variation in the intensity of the electron beam that produces the electronmicrograph, when the atom is supported on a substrate film, the image signal of the atom is extremely difficult to differentiate from the random fluctuations of the background caused by electron noise, supportfilm irregularities, and, to a smaller extent, photographic grain.In this paper, the use of dark field electron microscopy is proposed to overcome the contrast problem. The thin carbon film supporting the heavy atoms was produced by indirect evaporation, a method described elsewhere (Whiting and Ottensmeyer, submitted for publication). By weighing 10 films of known area and using a density of 1.9 g/cm3 for amorphous carbon, we determined the film thickness [2 ± 0.5 nm (20 ± 5 A)]. Since

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“…The formulation of doijdn on the basis of the work of Morse (1932) is treated by Lenz (1954), Burge & Smith (1962), Smith & Burge (1963) (see also Burge,255 (5) , 1970). These treatments consider only a most probable electron energy loss value, and leave out of account (apart from a first order correction discussed for solid films by Burge et al (1970)) the detailed and extensive characteristic energy loss spectrum (which in the present context strictly corre, sponds to the spectrum of a gas or vapour). The choice of a representative value for EL strongly influences the behaviour of dai,'dQ at small q.…”

Section: Coherence O F I N C I D E N T Electron B E a M ; C O H E R Ementioning

confidence: 99%