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W. Wang, Y. Fu, J. Chen, W. Xuan, J. Chen, X. Wang, P.M. Mayrhofer, P. Duan, A. Bittner, U. Schmid, J. Luo:
"AlScN thin film based surface acoustic wave devices with enhanced microfluidic performance";
Journal of Micromechanics and Microengineering, 26 (2016), 075006 - 075013.

This paper reports the characterization of scandium aluminum nitride (Al1−xScxN, x = 27%)
films and discusses surface acoustic wave (SAW) devices based on them. Both AlScN and AlN
films were deposited on silicon by sputtering and possessed columnar microstructures with
(0 0 0 2) crystal orientation. The AlScN/Si SAW devices showed improved electromechanical
coupling coefficients (K2, ~2%) compared with pure AlN films (<0.5%). The performance
of the two types of devices was also investigated and compared, using acoustofluidics as an
example. The AlScN/Si SAW devices achieved much lower threshold powers for the acoustic
streaming and pumping of liquid droplets, and the acoustic streaming and pumping velocities
were 2 × and 3 × those of the AlN/Si SAW devices, respectively. Mechanical characterization
showed that the Young´s modulus and hardness of the AlN film decreased significantly when
Sc was doped, and this was responsible for the decreased acoustic velocity and resonant
frequency, and the increased temperature coefficient of frequency, of the AlScN SAW devices.

This paper reports the characterization of scandium aluminum nitride (Al1−xScxN, x = 27%)
films and discusses surface acoustic wave (SAW) devices based on them. Both AlScN and AlN
films were deposited on silicon by sputtering and possessed columnar microstructures with
(0 0 0 2) crystal orientation. The AlScN/Si SAW devices showed improved electromechanical
coupling coefficients (K2, ~2%) compared with pure AlN films (<0.5%). The performance
of the two types of devices was also investigated and compared, using acoustofluidics as an
example. The AlScN/Si SAW devices achieved much lower threshold powers for the acoustic
streaming and pumping of liquid droplets, and the acoustic streaming and pumping velocities
were 2 × and 3 × those of the AlN/Si SAW devices, respectively. Mechanical characterization
showed that the Young´s modulus and hardness of the AlN film decreased significantly when
Sc was doped, and this was responsible for the decreased acoustic velocity and resonant
frequency, and the increased temperature coefficient of frequency, of the AlScN SAW devices.

coupling coefficiency, AlScN, surface acoustic wave, microfluidics, nanoindentation

http://dx.doi.org/10.1088/0960-1317/26/7/075006