Alternative contacting strategy for correlated perovskite nickelates: From the overlooked perspective of the metallic work functions

While the multiple electronic phase transitions in rare-earth perovskite nickelates (ReNiO3) open up a new paradigm in developing the next-generation logical devices and sensors catering for artificial intelligence, their respective contact strategy for making electronic devices largely relies on noble metal (e.g., Pt). Herein, we demonstrate the critical roles associated with the work function (W) of the contacting metal that is critical in the device application of ReNiO3 based on both their conventional metal-to-insulator transition (MIT) and the recently discovered hydrogen-triggered Mottronic transition. Owing to the high valence Ni3+ associated with ReNiO3 that is rather oxidative and also results in bi-polar carriers from generating Ligand holes, we demonstrate that their low resistive contact is only achievable for using inert metal (e.g., the standard electrode potential beyond 0.4 V) with either high W (e.g., >5 eV) or low W (e.g., <4.7 eV). This sheds light on alternative contacting strategies for ReNiO3 using the much cheaper Cu or Ag with low W that can also achieve abrupt resistive switch across MIT, in addition to the present noble metal with high W. Furthermore, the magnitude of W was also discovered to dominate the hydrogen-triggered Mottronic transition for ReNiO3 via upward (or downward) bending the energy bands that promotes (or inhibits) the H+ inward diffusion that switches the orbital configurations between the electron itinerant Ni3+ and electron localized Ni2+. Clarifying these previously overlooked roles from the perspective of the metallic contacts further paves the way for the correlated electronic applications of ReNiO3.