Guided phase transition from TiO2 rutile to anatase during electroforming of memristor-like devices

The effect of X-ray nano-beam irradiation has been investigated, along with a subsequent electric discharge between the metallic electrodes of memristive-like devices fabricated on top of rutile single crystals. X-ray irradiation with a photon flux of about 6 x 10(12) photons/second impinging on an area of 74 x 60 nm(2), and with irradiation times of the order of tens of seconds per point, has been able to pattern a conducting path between the electrodes, which has guided the electric discharge process. The results from Ti K-edge XANES mapping with submicron spatial resolution show small changes in the configuration of the pre-edge peaks, suggesting the presence of anatase phase in the affected region, which is also confirmed by micro-Raman mapping. This implies the occurrence of very intense Joule heating during the electric discharge (T > 2140 K), followed by a very quick cooling process. This conversion of rutile to anatase represents a novel electrical method for the formation of localized anatase nanoparticles from rutile single crystals, which may be of help for specific applications.