The effect of bottom LaB₆ electrode and La₂O₃ interlayer on resistance switching in devices based on Li‐doped ZnO films

Abstract

Resistance switching (RS) characteristics of Al/ZnO:Li/LaB 6 and Al/ZnO:Li/La 2 O 3 /LaB 6 devices in which LaB 6 and lithium-doped ZnO (ZnO:Li) films are regarded as shallow work function metal and p-type semiconductor, respectively, are studied. The alternation from bistable unipolar memory switching (URS) to monostable threshold switching (MTS) in the Al/ZnO:Li/LaB 6 device is observed. These two switching behaviors can be activated separately depending on the polarity of applied dc voltage: with a positive polarity the URS behavior is measured, while the MTS behavior is observed with a negative polarity. With increase in the number of switching cycles, the MTS and URS behaviors irreversibly transform to bipolar resistance switching (BRS) behavior. The Al/ZnO:Li/La 2 O 3 /LaB 6 device shows only the BRS behavior, but after certain number of cycles device serves as a rectifying diode. On the basis of the I-V and C-V characteristics, it is concluded that RS properties depend on the barrier height and reactivity between LaB 6 metal and ZnO:Li oxide.

Resistive Switching in Li‐Doped ZnO Films

“…Also, the formation of LaO bonds increases the content of oxygen vacancies in the p‐type film leading to lower conductivity. It is worth noting that the BRS was not observed in symmetrical M/Li 10 ZnO/M (M = Au, Ag, Al) cells . Figure c and d show fitting results of one of the I–V curves of Au/Li 10 ZnO/LaB 6 structure.…”

“…The ferroelectric polarization effect on the RS is unlikely, since the coercive field, ± V c (0.4 and −0.3 V) is much smaller than the voltage at which resistive switching occurs. In this case, LaB 6 electrode serves as a Schottky contact, and the I–V rectifying and BRS characteristic are related to the Schottky barrier formed at the Li 10 ZnO/LaB 6 interface . Due to the fact that only superstructure with LaO bonds is easy formed on the La‐terminated (100)LaB 6 surface, one can assume that formation of LaO bonds at ZnO 10 Li/LaB 6 interface induces interface states in the band gap which may cause a large degree of the band bending at the ZnO 10 Li/LaB 6 interface resulted in low conductivity.…”

“…In this case, LaB 6 electrode serves as a Schottky contact, and the I-V rectifying and BRS characteristic are related to the Schottky barrier formed at the Li 10 ZnO/LaB 6 interface. [21] Due to the fact that only superstructure with La─O bonds is easy formed on the Laterminated (100)LaB 6 surface, [21,23] one can assume that formation of La─O bonds at ZnO 10 Li/LaB 6 interface induces interface states in the band gap which may cause a large degree of the band bending at the ZnO 10 Li/LaB 6 interface resulted in low conductivity. Also, the formation of La─O bonds increases the content of oxygen vacancies in the p-type film leading to lower conductivity.…”

“…It is worth noting that the BRS was not observed in symmetrical M/Li 10 ZnO/M (M ¼ Au, Ag, Al) cells. [21] Figure 3c and d show fitting results of one of the I-V curves of Au/Li 10 ZnO/LaB 6 structure. As shown in Figure 3c, the I-V relationship in LRS exhibits the Child (I / V 2 at V < 6 V) and Ohm (I / V 1.18 at V > 6 V) laws.…”

“…It is known that the introduction of Li ions more than 5 at.% in ZnO initiates switchable spontaneous polarization that could activate the resistive memory effect in M/ LiZnO/M cells. [20] In our previous report, [21] the URS and BRS behaviors have been obtained in the p-type 10 at.% Li-doped ZnO film deposited on LaB 6 electrode. Here, we present a bilayer resistive-switching memory Au/Li 10 ZnO/Li 1 ZnO/LaB 6 device where 1 at.% Li-doped ZnO (Li 1 ZnO) and 10 at.% Li-doped ZnO (Li 10 ZnO) films exhibit n-and p-type conductivity, respectively.…”