Microscopes radiation damage

Transmission electron microscopes (TEM) with their variants (scanning transmission microscopes, analytical microscopes, high-resolution microscopes, high-voltage microscopes) are now crucial tools in the study of materials crystal defects of all kinds, radiation damage, ofif-stoichiometric compounds, features of atomic order, polyphase microstructures, stages in phase transformations, orientation relationships between phases, recrystallisation, local textures, compositions of phases... there is no end to the features that are today studied by TEM. Newbury and Williams (2000) have surveyed the place of the electron microscope as the materials characterisation tool of the millennium . 

Bursill, L. A., McLaren, A. C. (1966). Transmission electron microscope study of natural radiation damage in zircon (ZrSi04). phys. stat. sol., 13, 331-43. 

When charged particles, e.g. a particles, impinge on certain types of plastic materials like polycarbonate or cellulose nitrate, they cause radiation damage tracks in the material. The tracks can be made visually detectable through chemical or electrochemical etching procedures. The visible tracks can be counted using a microscope, microfilm reader or automatic image analyzers. The number of tracks is used to calculate the total amount of radiation to which the detector material was exposed. 

The atomic structure of the films was studied by transmission electron microscopy (TEM) using a JEM lOOC electron microscope in the microdiffraction mode. The diffraction patterns were obtained at a low electron beam intensity using the CCD high-sensitive registration system to prevent the films from radiation damage by the electron beam. 

While it is plausible that dislocations also act as internal surfaces which serve as centers for the initiation of decomposition, detailed studies of the role of dislocations require further examination. Recent advances in electron-microscope techniques may permit direct observation of the role of dislocations and impurities in the mechanisms of colloid or nucleus formation. Indeed, such studies on alkali halide crystals (at liquid-helium temperatures, to avoid radiation damage by the electron beam) confirmed the special role of dislocations in sensitizing the nucleation of colloids [52]. Such techniques should be possible for at least the (more stable) alkali azides. 

The easiest method to assess the quality of two-dimensional crystals is by electron diffraction (10). Special preparation techniques may be necessary to preserve the order of two-dimensional crystals in the electron microscope. For LHC-II, washing with a dilute (0.5 %), buffered (pH 6.0) solution of tannin has proved most successful (9). Cooling the crystals to a temperature below -100 °C is essential to reduce the effect of radiation damage which is severe at room temperature. 

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