The physical and electrical characterizations of Cr-doped BiFeO3 ferroelectric thin films for nonvolatile memory applications

•We report the physical analysis of Al/Cr-doped BFO/HfO2/Si MFIS structures.•The key process parameters such as postannealing temperature and doping amount are examined.•Electrical properties such as memory window and leakage current are shown and calculated.

Metal-ferroelectric (Cr-substituted BiFeO3)-insulator (HfO2)-semiconductor (MFIS) structures have been fabricated by co-sputtering technique. The crystalline phases of Cr3+ substitution at Fe-site for BiFeO3 (BFO) films were investigated by XRD patterns at the postannealing temperatures of 500 °C, 600 °C, and 700 °C. The microstructure of Cr-substituted BiFeO3 thin film and interfacial layer between HfO2 and Si substrate were characterized by TEM. The memory window as functions of insulator film thickness and DC power for Cr was investigated. The maximum memory window is 1.7 V when the HfO2 thickness increases to 60 nm. The ferroelectric polarization increases with increasing substitution amount due to the reduction in charge injection effect. The result is consistent with the leakage current measured. As the substitution amount increases or postannealing temperature decreases, the surface roughness becomes smooth due to less crystallization of Cr-substituted BiFeO3.

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