Electron‐Doping Mottronics in Strongly Correlated Perovskite

Abstract

Hydrogen (proton) induced switchable multiphase transformations in d-band electron-correlated materials recently opened a new field for exploring merging multifunctional proton-gated electronic devices, [1] synaptic plasticity, [2,3] sensors, [4] and novel energy conversion devices. [5] Compared to other dopant elements, hydrogen is small in radius and has high ionic mobility. [1,[4][5][6] Therefore, the proton distribution is highly adjustable via external electric fields, and the respective tuning of the physical properties of materials is feasible. This is, in particular, the case for the hydrogen-induced sharp transitions in electron orbital configurations and the magnetoelectric/spintronic states for d-band electron-correlated materials, such as SmNiO 3 , [1][2][3][4][5] SrCoO 3−δ , [6] and VO 2 . [7] As a typical example, the hydrogenation of the perovskite-structured SmNiO 3 d-band electron-correlated system results in an abrupt electronic transition of the e g orbital from the electron-itinerant Ni 3+ t e 2g 6 g 1 state to the electron-localized Ni 2+ t e 2g 6 g 2 The discovery of hydrogen-induced electron localization and highly insulating states in d-band electron correlated perovskites has opened a new paradigm for exploring novel electronic phases of condensed matters and applications in emerging field-controlled electronic devices (e.g., Mottronics). Although a significant understanding of doping-tuned transport properties of single crystalline correlated materials exists, it has remained unclear how dopingcontrolled transport properties behave in the presence of planar defects. The discovery of an unexpected high-concentration doping effect in defective regions is reported for correlated nickelates. It enables electronic conductance by tuning the Fermi-level in Mott-Hubbard band and shaping the lower Hubbard band state into a partially filled configuration. Interface engineering and grain boundary designs are performed for H x SmNiO 3 /SrRuO 3 heterostructures, and a Mottronic device is achieved. The interfacial aggregation of hydrogen is controlled and quantified to establish its correlation with the electrical transport properties. The chemical bonding between the incorporated hydrogen with defective SmNiO 3 is further analyzed by the positron annihilation spectroscopy. The present work unveils new materials physics in correlated materials and suggests novel doping strategies for developing Mottronic and iontronic devices via hydrogen-doping-controlled orbital occupancy in perovskite heterostructures.

Electrochromic Properties of Perovskite NdNiO3 Thin Films for Smart Windows

“…Rare earth nickelates with a perovskite structure (ABO 3 ) are of broad research interest due to their highly sensitive electronic phase diagram with respect to orbital electron occupancy. − As a representative, NdNiO 3 (NNO) shows metallic conduction behavior and is neutral gray at room temperature with single electron occupancy in the e g orbital of Ni 3d bands (e g 1 ). − Upon cation intercalation accompanied by an extra electron filling, the Ni state in the pristine NNO experiences crossover to the Ni 2+ state that is highly localized (e g 2 ). , The strong carrier localization opens up an optical gap and makes the material transmissive. The ion–electron intercalation therefore leads to completely opposing effects compared with WO 3 , as shown schematically in Figure .…”

What Can Electric Noise Spectroscopy Tell Us on the Physics of Perovskites?

“…Perovskite magnetic materials have been studied for almost 50 years. These systems offer a degree of chemical flexibility which allows the relation between the oxides structure, and electronic and magnetic properties that can be controlled in various ways, such as: Doping [61][62][63], magnetic field [64][65][66], electric field [67,68], temperature [69][70][71], pressure, and photoexcitation [72][73][74][75]. Research on these compounds has revealed the relevant phe-nomenon of magnetoresistance [76][77][78][79], and has led to the formulation of important physical concepts such as double exchange [1] and the Jahn-Teller polaron [80].…”

Deep Proton Insertion Assisted by Oxygen Vacancies for Long‐Term Memory in VO2 Synaptic Transistor

“…However, the switching speed of an insertion transistor is fundamentally limited by the slow rates at which ions are inserted into and extracted from the VO 2 lattice. [ 1,3,6 ] To overcome the slow switching by H + insertion, in the previous study, the rate of proton‐induced phase transformation was controlled by inducing planar defects that determine alignment [ 16 ] and density, [ 17 ] but these strategies could only be achieved within a narrow range of a control parameter (e.g., use of a specific substrate). Moreover, externally inserted H + dynamics under electric field enable to be modulated by the amount of intrinsically‐formed oxygen ionic defects (e.g., oxygen vacancies), which have a higher activation barrier for migration than H + do, [ 18 ] but the influence of oxygen defects in the lattices on the rate of H + insertion/extraction by electric field has yet to be explored.…”