Forming-free resistive switching characteristics and improved reliability in sub-stoichiometric NbN_x films

In this study, we demonstrate forming-free and reliable resistive switching (RS) characteristics by controlling the stoichiometry of niobium nitride (NbN_x) films. Compared to a perfect stoichiometric NbN_x film, a decrease of 6% nitrogen content and an increase of 5% O₂ content are found in the sub-stoichiometric NbN_x sample (s-NbN_x), and a structural change for the s-NbN_x film is observed from X-ray diffraction results, which results in the possibility of abundant defect generation in the s-NbN_x film at virgin state. In the RS test, the s-NbN_x film normally carries out well without initial forming because of the already-formed conducting filaments; in particular, in the reliability study, the s-NbN_x film shows more stable dc cycling characteristics for 1000 cycles without any degradation and smaller variations in the operating current and voltage characteristics.