Microstructure and Nanometer Scale Piezoelectric Properties of c-BN Thin Films With Cu Buffer Layer by Piezoresponse Force Microscopy

Boron nitride (BN) films were deposited on different metal buffer layer (Cu, Al, Pt) using RF magnetron sputtering. Microstructure and piezoelectric properties of BN films were characterized by FTIR and piezoresponse force microscopy (PFM). After optimizing the deposition condition, the 95% cubic phase volume fraction from FTIR results indicates that BN films with the highest cubic phase is obtained under 120 V bias voltages. Based on the PFM measurements results, the images of the piezoelectric response, the butterfly curve, and the hysteresis loop of a certain grain in the films and polarization image of c-BN/Cu/SiO₂/Si structure are confirmed. Compared with Pt and Al, Cu buffer layer is more suitable for depositing c-BN films with better piezoelectric properties by conventional fabrication process.