Microscopy/Imaging

These techniques use the light-source beam to obtain pictures with fine spatial resolution of the samples under study and are used in diverse research areas such as cell biology, lithography, infrared microscopy, radiology, and x-ray tomography.

The wavelengths of soft x-ray photons (1–15 nm) are very well matched to the creation of “nanoscopes” capable of probing the interior structure of biological cells and inorganic mesoscopic systems.Topics addressed by soft x-ray imaging techniques include cell biology, nanomagnetism, environmental science, and polymers. The tunability of synchrotron radiation is absolutely essential for the creation of contrast mechanisms. Cell biology CAT scans are performed in the “water window” (300–500 eV). Nanomagnetism studies require the energy range characteristic of iron, cobalt, and nickel (600–900 eV).

Mid- and far-infrared (energies below 1 eV) microprobes using synchrotron radiation are being used to address problems such as chemistry in biological tissues, chemical identification and molecular conformation, environmental biodegradation, mineral phases in geological and astronomical specimens, and electronic properties of novel materials. Infrared synchrotron radiation is focused through, or reflected from, a small spot on the specimen and then analyzed using a spectrometer. Tuning to characteristic vibrational frequencies serves as a sensitive fingerprint for molecular species. Images of the various species are built up by raster scanning the specimen through the small illuminated spot.

Lithography, a technique used in the art world for many centuries, has been adopted and adapted with phenomenal success by the high-tech industry. In microchip manufacturing, a silicon wafer is coated with a thin layer of photosensitive material called a resist. An image of a mask containing the desired pattern is projected onto the resist. The exposed (or unexposed) parts of the resist are etched away and, with further processing, the desired circuit is built up. The same basic process can be used in the manufacture of small mechanical components. Work at synchrotron light sources focuses primarily on the exposures of the resists.