Abstract
The role of interfacial defect chemistry in time dependent breakdown and associated charge transport mechanisms was investigated for Pb0.99(Zr0.52Ti0.48)0.98Nb0.02O3 (PNZT) films. Electrical degradation was strongly dependent on the sign of the electric field; a significant increase in the median time to failure from 4.8 ± 0.7 to 7.6 ± 0.4 h was observed when the top electrode was biased negatively compared to the bottom electrode. The improvement in the electrical reliability of Pt/PNZT/Pt films is attributed to (1) a VO•• distribution across the film due to PbO nonstoichiometry and (2) Ti/Zr segregation in PNZT films. Compositional mapping indicates that PbO loss is more severe near the bottom electrode, leading to a VO•• gradient across the film thickness. Upon degradation, VO•• migration toward the bottom Pt electrode is enhanced. The concentration of VO•• accumulated near the bottom Pt interface (6.2 × 1018/cm3) after degradation under an electric field of 350 kV/cm for 12 h was two times higher than that near the top Pt/PNZT interface (3.8 × 1018/cm3). The VO•• accumulation near the bottom Pt/PNZT interface causes severe band bending and a decrease in potential barrier height, which in turn accelerates the electron injection, followed by electron trapping by Ti4+. This causes a dramatic increase in the leakage current upon degradation. In contrast to the bottom Pt/PNZT interface, only a small decrease in potential barrier height for electron injection was observed at the top Pt/PNZT interface following degradation. It is also possible that a Zr-rich layer near the top interface reduces electron trapping by Ti4+.
Highlights
Lead zirconate titanate (PZT) films are used extensively in MEMS devices such as energy harvesters,1 inkjet printers,2 actuators,3 medical transducers,4 and resonators5 due to their high piezoelectric properties
This study aims to provide experimental evidence to demonstrate how the pristine state interfacial defect chemistry affects the transport mechanism upon electrical degradation in Nb doped PZT films
Scitation.org/journal/apm from 4.8 ± 0.7 to 7.6 ± 0.4 h. These results clearly indicate that the electrical reliability characteristics of Nb doped PZT films are superior when the top Pt electrode is biased negatively, for the PZT and Pt deposition conditions utilized
Summary
Lead zirconate titanate (PZT) films are used extensively in MEMS devices such as energy harvesters, inkjet printers, actuators, medical transducers, and resonators due to their high piezoelectric properties. It is probable that the wide range of models is a function of the fact that the electrical behavior depends explicitly on the stoichiometry and the defect chemistry, as well as the interface characteristics of PZT thin films and electrodes. One consequence of this is that films prepared under different conditions are likely to behave differently
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