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Abstract-2 -It has long been known that x-ray holography offered the possibility of three-dimensional microscopy with resolution higher than the light microscope and with special forms of contrast based on x-ray edges. In principle, the

Calculations are presented which indicate an extensive suboptical region in the microscopy of biological materials in their natural state which is accessible to ultrasoft x-ray transmission microscopy. Throughout most of the region, radiation dosage levels to the specimen are lower than in electron microscopy.

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Improved image quality in soft x-ray contact microscopy can be obtained by examining the resist with transmission rather than scanning electron microscopy. Application of the new technique to air-dried preparations of human blood platelets reveals structures not visible in the same cells with transmission electron microscopy or when the resist is examined by scanning electron microscopy. As seen by the new technique, platelet pseudopods contain a central structure connected to a network in the platelet and dense bodies exhibit a lamellar structure.

X-ray micrographs of biological objects have been obtained with a resolution better than 1000 angstroms by using poly(methyl methacrylate) x-ray resist and carbon Kalpha or synchrotron radiation. Synchrotron radiation allows short exposure times; storage rings especially designed as radiation sources and improved x-ray resists would make exposure times under 1 second possible.

A 100-nanosecond pulse of long-wavelength x-rays was used to produce high-resolution stop-motion images of living human platelets. Although some aspects of the structure conform to those seen in dehydrated specimens, novel features are apparent. The technique should permit detailed stop-motion examination of the interaction of platelets with their surrounding medium as well as exploration of the phagocytic and secretory activities of a wide variety of other cells.

Synchrotron radiation from the German electron synchrotron DESY in Hamburg has been used for x-ray lithography. Replications of different master patterns (for magnetic bubble devices, Fresnel zone plates, etc.) were made using various wavelengths and exposures. High-quality lines down to 500 Å wide have been reproduced using very soft x rays. The sensitivities of x-ray resists have been evaluated over a wide range of exposures. Various critical factors (heating, radiation damage, etc.) involved with x-ray lithography using synchrotron radiation have been studied. General considerations of storage ring sources designed as radiation sources for x-ray lithography are discussed, together with a comparison with x-ray tube sources. The general conclusion is that x-ray lithography using synchrotron radiation offers considerable promise as a process for forming high-quality-submicron images with exposure times as short as a few seconds.