TEM study of irradiation effects on tin oxide nanopowder

The effects of swift heavy ions in bulk materials have now long been studied and some models - such as the thermal spike - have been developed in order to explain the observed phenomena. Nevertheless, some questions remain debatable, among which the following ones: i) What is the spatial extension of the huge energy deposited by the swift heavy ions on the target electrons? ii) Can we evidence a pressure effect in some materials due to the lattice temperature increase? In most cases, we are able to predict whether a bulk material may be sensitive or not to the electronic energy loss S-e of the incident ion. According to the thermal spike, a given material could be all the more sensitive to S-e as the energy density deposited on the electrons is high, Therefore, an interesting way to increase this energy density is to confine the electrons in small target grains (i,e. submicrometric grains), This work reports the first experimental results obtained on irradiated tin oxide (SnO2) nanopowders. The same grains have been observed by TEM and HREM before and after lead ion irradiation at several fluences (from 0.3 to 7.5 x 10(12) Pb cm(-2)), A modification gradually appears as the fluence increases up to a critical fluence above which the grains split into nanodomains. A possible explanation is given through the thermal properties of SnO2.