Spectroscopy of radiation defects in rutile TiO2

Abstract

TiO2 is a prototypical memristive material, very promising for applications in ReRAMs, a new kind of nonvolatile memories. The electromigration of oxygen vacancies in TiO2 is commonly accepted as a key mechanism of the memristive phenomena. However, spectroscopic studies of defects involved in the electromigration are rare. In this work we created defects in rutile TiO2 single crystals by irradiationwith 50 keV Ar+ ions to fluences up to 2×1017 ion cm-2 at 1000K and investigated them by means of Raman scattering, photoluminescence, impedance spectroscopy and electron paramagnetic resonance. With the latter, Ti interstitials have been detected. Against expectations, spectra of isolated vacancies have not been observed. Instead, a rich variety of defects appeared, indicating a very complex character of the defect creation and transformation processes in rutile. An interaction of the Fe3+ and Cr3+ impurities with radiation-induced defects has been concluded. The activation process observed in our IS measurements is identified as the thermal ionization of defect-related donors. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.