We studied an electron-induced metal-insulator transition in a two-terminal device based on oxide NdNiO3. In our device, the NdNiO3 is electrostatically doped by the voltage applied between the terminals, resulting in an asymmetric conductivity with respect to the bias polarity. The asymmetry is temperature-dependent and is most significant near the metal-insulator transition. The I-V characteristics exhibit a strong dependence both on the thermal history and the history of the applied voltage bias. Our two-terminal device represents a simple and efficient route for studies of the effect of electron doping on the metal-insulator transition.The ability to electronically control the resistance of materials is the fundamental mechanism underlying the operation of modern semiconductor devices. In addition, a number of advanced materials and structures that exhibit controllable resistance switching phenomena are currently being explored as a basis for the future devices that will combine robust processibility, scalability, energy efficiency, and high speed. In strongly correlated oxide materials exhibiting a metal-insulator transition (MIT), phase transitions between states with different transport and magnetic properties [1-3] provide a fundamental mechanism for the operation of electronic devices with advanced functionalities. Such devices can be controlled by electric field,[4-6] optical excitation, [7] or a combination of thermal and electronic effects. [8,9] The electric field can not only modulate the charge density, but also shift the phase transition temperature, thus enhancing the direct effects of the electric field on the conductivity. The effects of electrical gating on the MIT have been demonstrated in La 0.8 Ca 0.2 MnO 3 films backgated through the substrate, and in NdNiO 3 (NNO) films gated through ionic liquids. [11][12][13][14][15] The electric fieldinduced variations of MIT temperature T MI resulted in a strong variation of the phase-dependent charge density.[17] These experiments provided a significant fundamental insight into the interplay between the charge carrier density and phase transitions in correlated oxides.Studies of electric field effects have so far focused on three-terminal field-effect transistor (FET) structures incorporating a gate electrode separated from the oxide film by an electrically insulating gate dielectric. However, these studies have been constrained by the difficulty of incorporating complex oxides into the standard threeterminal FET structure with a separate gate electrode. Here, we demonstrate a simple unipolar two-terminal device, a field-effect diode (FED), that enables studies of field effects in correlated oxides. The device is more straightforward than a FET both in terms of the fabrication and measurements. In our device geometry, the * Sergei.Urazhdin@emory.edu electric field is determined by the voltage applied between the two terminals. Thus, by measuring the dependence of the device conductivity on the applied voltage, one can determine the effects of the el...