Study of mechanical, piezoelectric and magnetodielectric properties of AlN/Ni-Mn-In heterostructure towards MEMS device applications

In the past few years, lead-free piezoelectric materials have been preferred in commercial device fabrication industries. Aluminum nitride (AlN) has been proved to be a potential candidate due to its lead-free nature, compatible with complementary metal-oxide-semiconductor (CMOS) technology, significant piezoelectric and magnetodielectric effect. In the present work, the AlN thin film was grown over Si (100) wafer via reactive dc magnetron sputtering. Its residual stress was measured using a wafer curvature method. The study of residual stress in thin films is essential for their use for functional device fabrication. The piezoelectric coefficient (d
33
) of AlN thin film was measured using piezoresponse force microscopy (PFM). The amplitude vs. voltage and phase vs. voltage measurements were performed. The effective piezoelectric coefficient (d
33
) was found to be $\sim4.98$ pm/V. In addition, the magnetodielectric measurement of AlN/Ni-Mn-In/Si magnetoelectric heterostructure was performed in the presence of the external magnetic field. The dielectric constant of the AlN thin film depicts a significant change with the magnetic field. It could be ascribed to the magnetic field-induced strain in the magnetostrictive Ni-Mn-In bottom electrode transferred to the piezoelectric AlN layer. Hence, such thin piezoelectric films interfacially coupled with functional materials could be employed in multifunctional magneto-electromechanical systems (MEMS) applications.