Identification of compressive strain in thin ferroelectric Al_1–x Sc _x N films by Raman spectroscopy

Abstract

Compressive strain in thin ferroelectric Al1-xScxN films with different Sc atom concentrations (x) on sapphire substrates was identified by Raman spectroscopy measurement. Both E2H and A1(LO) spectra showed a blue shift while thinning the Al1-xScxN film thicknesses. The shift was enhanced with higher Sc atom concentration. A stress of the order of 200 MPa was applied from the substrate interface, resulting in a strain of the order of 10-4. The presence of the compressive strain at the bottom interface can be correlated to the increase in the coercive field for thinner Al1-xScxN films.