Achieving excellent ferroelectric and dielectric performance of HfO2/ZrO2/HfO2 thin films under low operating voltage

Although the HfO2-based ferroelectric thin films are compatible with the complementary metal-oxide-semiconductor (CMOS) technology and exhibit excellent scalability, they still suffer from low dielectric tunability, metastable ferroelectric orthorhombic phase and poor endurance. Here, we fabricated the HfO2/ZrO2/HfO2 sandwich structured thin films via atomic layer deposition process as well as the influence of voltage cycling, Hf/Zr ratios and annealing temperature on ferroelectricity and dielectric tunability of them was investigated systematically. At pristine states, the antiferroelectric-like behavior of polarization-voltage hysteresis loops become more and more obvious with the decrement of ZrO2 content in the middle layers. After waking-up, the large remnant polarization (2Pr, ∼43 μC/cm2) and high dielectric tunability (∼51 %) can be achieved under low operating voltage of 2.5 V. Noting that the 2Pr is still higher than 40 μC/cm2 and the dielectric tunability remains about 50 % after 109 cycles. In addition, the HfO2/ZrO2/HfO2 thin films also exhibited high energy storage properties with the total energy storage density of ∼62 J/cm3 and the recoverable energy storage density of ∼32 J/cm3. These results indicated that the strategy of sandwich structure design is beneficial to promoting the development of electronic devices towards miniaturization, integrated, and multifunction along with high performance and reliability.