Combinatorial approach to MgHf co-doped AlN thin films for Vibrational Energy Harvesters

In this report, we studied MgHf co-doped AlN ((Mg,Hf)_xA1_1-xN) aiming for developing an AlN-based dielectric material with the large piezoelectric coefficient. To rapidly screen the wide range of composition, we applied combinatorial film growth approach. To get continuous composition gradient on a single substrate, films were deposited on Si (100) substrates by sputtering AlN and Mg-Hf targets simultaneously. Crystal structure was investigated by X-ray diffractometer equipped with a two-dimensional detector (2D-XRD). Composition was determined by Energy Dispersive Spectroscopy (EDS). These studies revealed that we successfully covered the widest ever composition range of 0 < x < 0.24 for this material. In addition, these studies found that we succeeded in realizing largest ever c-axis expansion of 2.7% at x = 0.24, which will lead to the highest enhancement in the piezoelectric coefficient. The results of this study opened the way for high-throughput development of the dielectric materials.