Probing overheatings under microprobe irradiation via Zn vaporisation

A thin layer of ZnO0.3deposited on a SiO2glass substrate was irradiated with a 2 MeV α microbeam. The disappearance of ZnO0.3in the neighbourhood of the beam was registered in situ. We quantitatively account for this behaviour in the framework of a very simple vaporisation model based both upon the local temperature increase resulting from the microbeam itself and upon the variation of the Zn vapour pressure with the local temperature. Other possible explanations are briefly discussed.