A simple general treatment of x-ray image formation by Fresnel diffraction is presented; the image can alternatively be considered as an in-line hologram Particular consideration is given to phase-contrast microscopy and imaging using hard x rays The theory makes use of the optical transfer function in a similar way to that used in the theory of electron microscope imaging Resolution and contrast are the criteria used to specify the visibility of an image Resolution in turn depends primarily on the spatial coherence of the illumination, with chromatic coherence of lesser importance Thus broadband microfocus sources can give useful phase-contrast images Both plane- and spherical-wave conditions are explicitly considered as limiting cases appropriate to macroscopic imaging and microscopy, respectively, while intermediate cases may also be of practical interest Some results are presented for x-ray images showing phase contrast

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Contrast and resolution in imaging with a microfocus x-ray source

A simple scanning transmission electron microscope has been built using a field‐emission electron source, a new electron gun, and one lens to produce a high‐contrast picture with 30 A resolution. The final spot size is limited by the properties of the lens, in the same manner as a conventional transmission microscope. The field‐emission tip requires a pressure below 10−9 Torr for stable operation and can have a lifetime of several months. The intensity of the source is such that high‐quality pictures can be obtained in 10 sec. Specimen contamination or damage is small, as would be expected in view of the good vacuum conditions. The theory and design of the instrument are discussed, and experimental results are shown.

A High‐Resolution Scanning Transmission Electron Microscope

A soft X ray lithographic technique capable of contactless replication of submicrometre linewidth planar-device patterns is described. Special soft X ray exposure masks have been developed for the 4-14 A wavelength region. Elastic-surface-wave-transducer patterns with 1.3 µm electrode spacings were fabricated onto such masks using electron-beam techniques, and were successfully replicated.

High-resolution pattern replication using soft X rays

The techniques of photolithography, electron lithography, X-ray lithography, ion bombardment etching, and liftoff are reviewed, and their advantages and disadvantages assessed from the point of view of fabricating surface-acoustic-wave and thin-film optical devices.

Fabrication techniques for surface-acoustic-wave and thin-film optical devices

By using intense pulsed coherent x-ray sources that are currently under development, it will be possible to obtain magnified three-dimensional images of elementary biological structures in the living state at precisely defined instants. For optimum contrast, sensitivity, and resolution, the hologram should be made with x-rays tuned to a resonance of nitrogen near 0.3 nanometer. Resolution will then be limited mainly by the hydrodynamic expansion that occurs while the necessary number of photons is being registered. Problems of technique are also briefly discussed.

Microholography of living organisms.

X‐Ray Microscopy and Microradiography

Prehistory implies the selection of a date when history begins. In solid‐state physics this is very recent, dating, perhaps, from Debye's specific‐heat theory of 1913, but most of all from the famous diffraction experiment of Friedrich, Knipping, and Von Laue in March 1912. It was this tool of perfection which laid the ground for imperfection to become of interest to physicists. The growth of solid‐state physics marks, I think, a basic change in the attitude of physicists toward matter. Virtually all the development of mechanics, marvellous though it was, was based on a treatment of matter that was essentially structureless and whose measured elastic constants and densities gave the constants to put into equations that became ever more elaborate. When physicists at last paid attention to the structure of real crystals, they soon became aware of imperfections, both theoretically and experimentally, and the great flourishing of solid‐state physics in the last three decades has been mostly based on the elucidation of the role of mechanical, ionic, and electrical imperfections in a crystal, accompanied, of course, by a continued development of understanding of bonding and dynamics of the ideal lattice.

The prehistory of solid‐state physics

The Renaissance Society of the University of Chicago is planning, as one of its regular art exhibitions, a display illustrating artistic form in the scientific research laboratory. The exhibit will be composed of specimens, apparatus, photographs, models, records, and the like (including working demonstrations), all of which are to be indigenous to the laboratory though they will be selected by a group of artists solely on the basis of intrinsic form.

Cyril Stanley Smith

Papers

X‐Ray Microscopy and Microradiography

The prehistory of solid‐state physics

Art and Form in Science