Phase transformation of ZnMoO4 by localized thermal spike

We show that ZnMoO4 remains in stable phase under thermal annealing up to 1000 degrees C, whereas it decomposes to ZnO and MoO3 under transient thermal spike induced by 100MeV Ag irradiation. The transformation is evidenced by X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Thin films of ZnMoO4 were synthesized by thermal evaporation and subsequent annealing in oxygen ambient at 600 degrees C for 4 h. XRD results show that as the irradiation fluence increases, the peak related to ZnMoO4 decreases gradually and eventually disappear, whereas peaks related to ZnO grow steadily up to fluence of 3 x 10(12) ions/cm(2) and thereafter remain stable till highest fluence. This indicates that polycrystalline ZnMoO4 film has transformed to polycrystalline ZnO thin film. The Raman lines related to ZnMoO4 are observed to have disappeared with increasing irradiation fluence. XPS results show modification in bonding and depletion of Mo from near surface region after the ion irradiation. Cross-sectional transmission electron microscopy result shows the formation of ion track of diameter 12-16 nm. These results demonstrate that ion beam methods provide the means to control phase splitting of ZnMoO4 to ZnO and MoO3 within nanometric dimension along the ion track. The observation of phase splitting and Mo loss are explained in the framework of ion beam induced thermal spike formalism. VC 2014 AIP Publishing LLC.