Impedance spectroscopy study of the unipolar and bipolar resistive switching states of atomic layer deposited polycrystalline ZrO₂ thin films

Abstract

The polarity of the resistive switching (RS) characteristic of metal‐oxide‐metal devices from atomic layer deposited polycrystalline ZrO2 films was studied by means of impedance spectroscopy. Pt/ZrO2/Ti/Pt cells made with 10 nm Ti and 30 nm Pt capping top electrodes, served as unipolar switching (US) devices. Bipolar switching (BS) devices were represented by Pt/ZrO2/30 nm TiN cells. Temperature measurements of the ON‐state resistances clearly show metallic and semiconducting behavior for the US and BS cells, respectively. The pristine and the ON and OFF states of the devices were analyzed by means of impedance spectroscopy. All ZrO2 based RS devices exhibited similar impedance characteristics in the pristine states. In contrast, after electroforming clear differences in the Nyquist‐plots of the US and BS devices were observed. The effect of the device structure on the RS polarity is discussed under consideration of the pillar‐shaped grainy microstructure of the ZrO2 thin films. An empirical model based on redox reactions between ZrO2 and the non‐noble metal electrode is proposed emphasizing defect formation prior at the ZrO2 grain boundaries.

Room-temperature atomic layer deposition of ZrO2 using tetrakis(ethylmethylamino)zirconium and plasma-excited humidified argon

“…11. The presence of Zr 3d 5/2 peak is confirmed at around 181.7 eV, which indicates that the zirconium atoms in ZrO 2 were fully oxidized [28].…”

Complementary Resistive Switching and Synaptic-Like Memory Behavior in an Epitaxial SrFeO2.5 Thin Film through Oriented Oxygen-Vacancy Channels

“…Interestingly, the impedance spectrum after the set1 process shows a rather vertical line, while the real impedance slightly varied from 900 to 1200 Ω with frequency sweep ranges from 1 Hz to 1 MHz, as shown in Figure f. That vertical line shape of the impedance spectra for the conductive filament has been reported in several oxide memristive devices. − Instead of looking for the fitting of an equivalent circuit model for the impedance spectrum of the set1 process, the average real impedance value ( R ) in Figure f is almost comparable to the measured resistance value after the set1 process in the direct current (DC) I – V characteristics of CRS (see Figure a). This indicates the absence of the capacitance behavior after the set1 process because of the presence of the fully connected conductive filament.…”

“…This Cole–Cole plot can be numerically fitted with an equivalent circuit consisting of three components; resistance ( R 0 ), Q bulk , and R bulk , as shown in the inset of Figure e. Here, R 0 is a contact resistance, while Q bulk is a constant phase element (CPE) representing an imperfect capacitor, , and R bulk is a bulk resistance from BM-SrFeO 2.5 . In general, the real capacitance of the system can be represented in terms of CPE as follows Here, the value of α ranges between 0 and 1; when α = 1, it represents pure capacitance ( Q = C ).…”

Interface-Driven Multifunctionality in Two-Dimensional TiO2 Nanosheet/Poly(Dimercaptothiadiazole-Triazine) Hybrid Resistive Random Access Memory Device

“…Both the semicircles are prominent at the lower voltages, which show the presence of two relaxation times for the charge carriers. The value of Q 2 corresponding to CPE changes by three orders related to bulk, which suggests that there are different relaxation times corresponding to multiple filaments or trap states in the bulk of the sample. − The significant change in the α 2 value with bias is a gauge of such imperfections. The interface-related parameters R 3 changes by two orders gradually with bias, while Q 3 and α 3 remain almost constant, indicating a different phenomenon compared to negative bias; and moreover, the two semicircles appear to be separated even at higher bias.…”