Nanoprobe mechanical and piezoelectric characterization of Sc sub(x)Al sub(1-x)N(0001) thin films

• Published in: Physica status solidi. A, Applications and materials science Vol. 212; no. 3; pp. 666 - 673
• Main Authors: ukauskait, Agn, Broitman, Esteban, Sandstrom, Per, Hultman, Lars, Birch, Jens
• Format: Journal Article
• Language: English
• Published: 01.03.2015
• Subjects: Aluminum nitride; Displacement; Electric potential; Microscopy; Nanostructure; Piezoelectricity; Scandium; Thin films; Voltage
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.201431634

Nanoindentation with in-situ electrical characterization is used to investigate piezoelectric scandium aluminum nitride (Sc sub(x)Al sub(1-x)N) thin films with Sc contents up to x=0.3. The films are prepared by reactive magnetron sputtering using Al sub(2)O sub(3) substrates with TiN seed layers as bottom electrodes at a substrate temperature of 400 degree C. X-ray diffraction shows c-axis oriented wurtzite Sc sub(x)Al sub(1-x)N, where the crystal quality decreases with increasing x. Piezoresponse force microscopy in mapping mode reveals a single piezoelectric polarization phase in all samples. The hardness decreases from 17GPa in AlN to 11GPa in Sc sub(0.3)Al sub(0.7)N, while reduced elastic modulus decreases from 265GPa to 224GPa, 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 diamond nanoindenter tip. The Sc sub(0.2)Al sub(0.8)N films exhibit an increase in generated voltage in comparison to AlN and a correspondingly larger displacement upon applied voltage, comparable to results obtained by double beam interferometry and piezoresponse force microscopy.