  Resistive switching devices are promising emerging non-volatile memories.
However, one of the biggest challenges for resistive switching (RS) memory
applications is the device-to-device (D2D) variability which is related to the
intrinsic stochastic formation and configuration of oxygen vacancy (VO)
conductive filaments. In order to reduce D2D variability, the control of oxygen
vacancy formation and configuration is paramount. We report in this study Zr
doping of TaOx-based RS devices prepared by pulsed laser deposition (PLD) as an
efficient mean to reduce VO formation energy and increase conductive filament
(CF) confinement, thus reducing D2D variability. Such findings were supported
by X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE) and
electronic transport analysis. Zr doped films presented increased VO
concentration, and more localized VO thanks to the interaction with Zr.
According to DC and pulse mode electrical characterization, D2D variability was
decreased by a factor of 7, resistance window was doubled and a more gradual
and monotonic long-term potentiation/depression (LTP/LTD) in pulse switching
was achieved in forming-free Zr:TaOx devices thus displaying promising
performance for artificial synapse applications.
