Grain-wise piezoelectric response of polycrystalline aluminum nitride thin films: an empirical investigation using piezo force microscopy

Abstract

Abstract Local mapping of piezoelectric response across grains with different crystal-planes is essential to enhance the level of understanding about piezoelectric behaviour of wurtzite hexagonal (WH) AlN thin films. For this, polycrystalline WH-AlN thin films were deposited by pulsed-DC magnetron sputtering using a mixture of argon (Ar) and nitrogen (N2) with varying N2-content as 5%, 10% and 20% in the form of AlN/Ti/Si(100) heterostructure. Piezo force microscopy (PFM) was used to establish a correlation between piezo-response (PR) phase contrast, polarity and crystal-planes constituting the film surface. A phenomenological model is also presented to correlate the distribution of interface sheet charges with polar (0002), semi-polar (10 1) and non-polar (10 0)-planes present on the film surface. This interdependence eventually controls the phase between piezoelectric oscillations and modulation voltage which is ultimately translated into a grain-wise contrast obtained on PR-phase image.