Impact of bottom electrode materials on the crystallographic orientation and ferroelectric performance of Al0.8Sc0.2N thin films

Abstract

Aluminum scandium nitride (Al_1−xSc_xN) has received widespread attention for its robust ferroelectric properties, whereas its cyclic failure mechanism remains elusive. In this paper, the structure and ferroelectric properties of c-axis preferred growth Al_0.8Sc_0.2N films on different electrodes were studied. Single-crystal-like epitaxy and polycrystalline Al_0.8Sc_0.2N films were obtained on (111)-Pt and polycrystalline TiN bottom electrodes, respectively. Remanent polarization (P_r) is verified to be directly related to the crystalline quality of Al_1−xSc_xN thin films, while the coercive electric field (E_c) is significantly affected by the microstructure in addition to residual stress. The E_c value was measured through dynamic hysteresis measurement (DHM) and static hysteresis measurement (SHM) across six orders of magnitude, and followed E_c ∝ f^α, indicating that the domain wall motion-dominated switching process is less sensitive to the electrode and film crystal quality. The almost unchanged shape of the ferroelectric switching current peak was observed on the Pt electrode side through a cycling test, which demonstrates the advantage of vertical domain nucleation. The significant differences in the ferroelectric current observed at different interfaces during cycling reflect the crucial role of the ferroelectric/electrode interface and trapped charges in polarization switching.