Aliovalent Doping Engineered Ti1-XTaxO2 Layer for Ultra-Low Power Resistive Memory Devices

Abstract

Resistive switching (RS) behavior in metal oxides (MO) is governed by the electric field dependent back and forth migration of oxygen vacancies (Vo). Therefore, it is important to regulate the Vos in MO matrix in a systematic manner. Foreign element doping in MO is considered to be beneficial to generate controlled Vo at the vicinity of dopant elements. Based on this, an approach was made to study the RS behavior in Ta-doped TiO2 films on Pt substrates. Prior to thin film deposition, Ti1-xTaxO2 powder was synthesized chemically using Ta and Ti precursor solutions. The Ta-doped TiO2 targets were prepared for pulsed laser deposition of the films on Pt substrates using an laser wavelength of 248 nm. Enhanced RS was observed in 1.11 at. % Ta doped sample with Ron/Roff ratio of ~104 at a voltage as low as 0.25 V. The retention and endurance of the device recorded at 104 s and 105 pulses respectively are exceptionally well. The X-ray diffraction, Secondary Ion Mass Spectroscopy, X-ray absorption spectroscopy and X-ray photoelectron spectroscopy were employed, to investigate the physical and chemical properties of the film and correlated with the improved RS at particular dopant concentration. Further, the dopant concentration dependent stoichiometry was predicted using Energy Dispersive Spectroscopy during Transmission Electron Microscopy study. These observations will be discussed in detail in the light of defect induced RS phenomenon.