EPMA OF THE COMPOSITION OF OPAL-BASED NANOSTRUCTURED MATERIALS

Electron probe microanalysis (EPMA) was used to study the composition of nanostructured materials based on insulating porous 'hosts' (namely synthetic SiO2 opal) infilled with different 'guest' materials. In th e bare opal a reduction of the k-ratio compared with that of bulk amor phous silica was observed. In the case of partially or completely infi lled opals this discrepancy was found to be less pronounced. The effec t was explained in terms of the space charge induced under the inciden t electron beam. Obviously, this effect is of importance for all micro porous materials if the size scale of their voids matches the ionisati on length of the electron beam. We have shown that with the right choi ce of the accelerating voltage and probe size the EPMA-determined comp osition can be consistent with the data from wet chemical analysis.