Characterization of ferroelectric switching in 43 nm Y-36 lithium niobate films

Lithium niobate (LN) is a promising ferroelectric material used for emerging memories and radio frequency (RF) micromechanical resonators. The ferroelectric behavior of the bulk properties of LN has been well studied, and investigations on thin films have shown promising performance. However, the macroscopic ferroelectric properties of LN films that are sub-100 nm thick, which are desired to truly harness the advantages and scalability of the material, have not been explored. Here, we report the ferroelectric properties of 43 nm ultra-thin films of Y-36 LN sandwiched between two metal electrodes. Y-36 is a particularly promising cut for RF microacoustics, but can also be employed for integrated memories and photonics. Switching occurred with an average positive coercive field (+Ec) of 0.92 MV cm−1 and an average −Ec of 0.39 MV cm−1, resulting in the ability to switch the film polarization with < 2 V. The 43 nm film maintains a large positive remanent polarization (+PR) of 58 μC·cm−2 and a -PR of 55 μC·cm−2. The thin film shows excellent endurance, maintaining a stable PR value after 1 billion polarization switching cycles. Retention characteristics also show stable PR value after 100 s. Additionally, findings indicate a power series relationship of Ec∝ Fβ with β value at 0.253 and 0.053 for +Ec and −Ec, respectively. Overall, the characterization of these ultra-thin films of LN showcase its potential for miniaturization and application to tunable RF acoustics or emerging memories.