Ion-beam effect on functional properties of La2Ti2O7 piezoelectric thin films and nanoislands

Low-dimensional material can display unique physical phenomena allowing an interesting way for the development of new technologies. In addition, owing the environmental requirements about electronic devices (ferroelectric memories, M/NEMS...), new lead-free piezoelectrics need to be created. In this context, lanthanum dititanate oxide (La2Ti2O7) thin films have been synthesized then nanostructured by focused ion beam (FIB) technique. The impact of Ga+ ion beam about functional properties of continuous and nanostructured crystallized La2Ti2O7 films has been investigated on the nanoscale by scanning probe microscopy. Modifications of both surface and electrical behavior for area exposed to ion irradiation were revealed. Nevertheless, local piezoactivity is still detected confirming the robust nature of this compound to ion-beam exposures. Besides, crystallized La2Ti2O7 film with Pt electrode on top was successfully patterned by FIB process to get 500 down to 300 nm islands in lateral size. Nanoscale electromechanical response was measured inside these nanostructures by piezoresponse force microscopy. In this case, the local piezosignal is measured at similar level that the one obtained for the unetched film evidencing no manifest sidewall effect, and this without usual post-annealing treatment for recovering functional properties. These findings highlight the La2Ti2O7 oxide is a potential candidate for the fabrication of such lead-free low-dimensional nanostructures.