Charge contrast imaging of material growth and defects in environmental scanning electron miscroscopy--linking electron emission and cathodoluminescence
An electron-based technique for the imaging of crystal defect distribution such as material growth histories in non- and poorly conductive materials has been identified in the variable pressure or environmental scanning electron microscope. Variations in lattice coherence at the meso-scale can be imaged in suitable materials. Termed charge contrast imaging (CCI), the technique provides images that correlate exactly with emitted light or cathodoluminescence in suitable materials. This correlation links cathodoluminescence and an electron emission. The specific operating conditions for observation of these images reflect a complex interaction between the electron beam, the positive ions generated by electron-gas interactions in the chamber, a biased detector, and the sample. The net result appears to be the suppression of all but very near surface electron emission from the sample, probably from of the order of a few nanometres. Consequently, CCI are also sensitive to very low levels of surface contaminants. Successful imaging of internal structures in a diverse range of materials indicate that the technique will become an important research tool.
Griffin
BJ
The Western Australian Centre for Microscopy, The University of Western Australia, Nedlands, Australia. bjg@cyllene.uwa.edu.au