Nanoprobe Mechanical and Piezoelectric Characterization of Sc x Al 1-x N(0001) Thin Films [Elektronisk resurs]

• Nanoindentation with in-situ electrical characterization was used to characterize piezoelectric scandium aluminum nitride (Sc x Al 1-x N) thin films with Sc contents up to x=0.3. The films were prepared by reactive magnetron sputtering using Al 2 O3 substrates with TiN seed layer/bottom electrodes at a substrate temperature of 400 °C. X-ray diffraction shows c-axis oriented wurtzite Sc x Al 1-x N, where the crystal quality decreases with increasing x. Piezoresponse force microscopy in mapping mode shows a single piezoelectric polarization phase in all samples. The hardness and decreases from 17 GPa in AlN to 11 GPa in Sc0.3Al0.7N, while reduced elastic modulus decreases from 265 GPa to 224 GPa, respectively. Both direct and converse piezoelectric measurements are demonstrated by first applying the load and generating the voltage and later by applying the voltage and measuring film displacement using a conductive boron doped nanoindenter tip. The Sc0.2Al0.8N films exhibit an increase in generated voltage by 15% in comparison to AlN and a correspondingly larger displacement upon applied voltage, comparable to results obtained by double beam interferometry and piezoresponse force microscopy.   

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