Forming-Free and Non-linear Resistive Switching in Bilayer \(\hbox {HfO}_{\textrm{x}}\)/\(\hbox {TaO}_{\textrm{x}}\) Memory Devices by Interface-Induced Internal Resistance

Resistive switching memory devices with tantalum oxide (\(\hbox {TaO}_{\textrm{x}}\)) and hafnium oxide (\(\hbox {HfO}_{\textrm{x}}\)) mono- and bilayers were fabricated using atomic layer deposition. The bilayer devices with Ti and TiN electrodes show non-linear switching characteristics, and can operate without requiring an initial electroforming step. The insertion of the \(\hbox {HfO}_{\textrm{x}}\) layer induces the switching behaviour on single layer \(\hbox {TaO}_{\textrm{x}}\) that shows Zener diode-like characteristics, with conductivity depending on the top electrode metal. The electronic conductivity mechanism study shows Schottky emission at low voltage regime followed by tunneling at higher applied bias, both indicating interface-dominated conduction. The switching mechanism study is supported by X-ray photoelectron spectroscopy characterization of the films that show a formation of \(\hbox {TaO}_{\textrm{x}}\hbox {N}_{\textrm{y}}\) and \(\hbox {TaN}_{\textrm{x}}\) species at the oxide-electrode interface. This interfacial layer serves as a high resistivity barrier layer enabling the homogeneous resistive switching behavior.