Evaluation of damages induced by Ga+ - focused ion beam in piezoelectric nanostructures
Résumé
The impact of Ga+-focused ion beam (FIB) about functional properties of continuous and nanostructured piezoelectric thin films of lead zirconate titanate (Pb(ZrxTi1-x)O3) was investigated. A suitable way to fabricate piezoelectric nanocapacitors was studied, based on the amorphous or crystallized state of the film before etching. Strong modification of structural and electrical behavior for area exposed to ion irradiation is observed when the film is etched in the crystallized state. Both the implantation of Ga+ ions and the film amorphization highlighted by Raman spectroscopy and Kelvin force microscopy analyses can explain this result. The piezoactivity detected by piezoresponse force microscopy is fully destroyed even after a post-annealing treatment. In the case of amorphous etched film, no significant degradation is observed. The latter process is used to successfully fabricate Pb(ZrxTi1-x)O3-based nanocapacitors by means of FIB method. In 50-nm-size capacitors, the local electromechanical behavior is measured at similar level that the one obtained for the un-etched film, evidencing no manifest sidewall effect or FIB-induced damages. This further evidences that amorphous FIB lithography process can reduce the etching damages, demonstrating this is an effective alternative method and very beneficial to pattern such low-dimensional structures, which is a significant result in view of the development of functional nanostructures in the field of nanoelectromechanical systems applications.