Electrochemically Driven Giant Resistive Switching in Perovskite Nickelates Heterostructures

Abstract

into the corner-shared NiO 6 octahedra network (Figure 1a) modifies the NiO bond length and angle, affecting the electronic bandwidth and physical properties of RNiO 3 . Furthermore, Ni 3+ is reduced2 2x and electrons are doped into RNiO 3 via oxygen vacancies. [2,10] Previous works have shown that oxygen vacancies play an important role in perovskite heterostructures. [10][11][12][13][14][15] External electric field could induce the migration of the oxygen vacancy in the perovskite films and then change the interfacial barrier in heterostructures, leading resistive switching (RS) behavior. We expect such effect to be more prominent in nickelates-based ones due to their smaller oxygen vacancy formation energy. This motivates us to explore the possibility of electrochemically driven RS in nickelates systems. Our finding reveals giant bipolar RS behavior in Pt/RNiO 3 / Nb-SrTiO 3 heterostructures with ON/OFF ratio of about 10 5 at room temperature. The effect is tunable by varying the oxygen content or changing the rare earth element in the sample.A set of GdNiO 3−x films on Nb-SrTiO 3 substrates were grown under different deposition oxygen pressures (P(O 2 )) of 100, 20, 2, and 0.2 mTorr, respectively. The film thickness was fixed at 10 nm. The samples are labeled as D1-D4, in the order of decreasing P(O 2 ) from 100 to 0.2 mTorr. The influence of P(O 2 ) on our samples can be seen in Figure 1 (also see Figure S1 in the Supporting Information). Figure 1b displays the typical current-voltage (I-V) characteristics of the samples, and the inset is the schematic setup for the measurements. The arrows in Figure 1b represent the sequence of voltage sweeps. Sample D1 shows nonlinear I-V characteristics with negligible RS effect. In contrast, sample D4 shows obvious "counterclockwise" bipolar RS behavior. Here, we define the upper and lower branches of the I-V curves as low resistance state (LRS or ON) and high resistance state (HRS or OFF), respectively. Sample D4 switches from HRS (LRS) to LRS (HRS) when a forward (reverse) bias is applied to Pt, and this is defined as the set (reset) process. It should be pointed out that this counterclockwise I-V hysteresis in our asymmetrical devices is different from ferroelectric switchable diode behavior, [16][17][18] which is mainly controlled by the ferroelectric polarization. Since the formation energy of oxygen vacancy is low in nikelates, [9] we expect more oxygen vacancies in the GdNiO 3−x film than in the Nb-SrTiO 3 substrate. Scanning transmission electronThe rich phase diagrams and peculiar physical properties of rare earth perovskite nickelates (RNiO 3 ) have recently attracted much attention. Their electronic structures are highly sensitive to carrier density and bandwidth due to Mott physics. Here, the electrochemically driven giant resistive switching in Pt/RNiO 3 /Nb-SrTiO 3 heterostructures is reported. Systematic investigation confirms that oxygen vacancies migration modifies the interfacial barrier at the RNiO 3 /Nb-SrTiO 3 interface and causes the resistive swit...

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