Biological imaging with a new type of soft x-ray microscope

Abstract

Imaging of biological specimens using a new type of soft x-ray microscope is described. The instrument is significantly simpler in design than existing x-ray microscopes. The technique used is a variation of the photoelectron-conversion contact method. The instrument is very similar to the field emission microscope in geometry but uses special cone-like hollow emitters instead of solid emitters. Specimens to be examined are placed inside the hollow emitter tips. Soft x rays are beamed down the axis of the hollow cone from the open end, through the specimen, and onto the hemispherical emitter tip membrane. An x-ray contact image is thereby produced on the emitter tip, corresponding to the x-ray absorption of the specimen. Photoelectrons are liberated into the vacuum, outside the emitter tip, in a pattern corresponding to the contact image of the specimen. A high voltage placed on the emitter accelerates the photoelectrons radially to a detector. The result is a magnified, high-resolution, real-time image. Experiments produced images of various dried fungi, bacterial, and mammalian cells with a resolution down to ≊1000 Å.