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Piezoelectric characterization of Sc0.26Al0.74N layers on Si (001) substrates

: Sinusía Lozano, M.; Pérez-Campos, A.; Reusch, Markus; Kirste, Lutz; Fuchs, Theo; Zukauskaite, Agne; Chen, Z.; Iriarte, G.F.


Materials Research Express 5 (2018), Nr.3, Art. 036407, 10 S.
ISSN: 2053-1591
Fraunhofer IAF ()
Aluminum Scandium Nitride; piezoelectric thin film; sputtering on Si (001) substrate

Scandium aluminum nitride (ScAlN) films have been synthesized by pulsed-DC reactive magnetron sputtering. The degree of c-axis orientation as well as piezoelectric characteristics of the Sc0.26Al0.74N thin films grown on Si (001) at various discharge powers and processing pressures values have been investigated. According to x-ray diffraction (XRD) measurements, the texture of the as-grown Sc0.26Al0.74N thin films becomes more prominent in the [0001]-direction at the highest target power (700W) and at the lowest processing pressure (4 mTorr). The piezoelectric response, as determined by measuring the d 33 piezoelectric constant, shows a maximum value of−12 pC/Nalso at 4 m Torr and 700 W, confirming a direct correlation between the d33 piezoelectric constant and the degree of orientation in the [0001]-direction. The atomic concentration of Sc and Al in the synthesized ScAlNthin film, determined by secondary ion mass spectroscopy (SIMS), reveals a Sc concentration lower than in the ScAl alloy target. The piezoresponse force microscopy (PFM) shows homogeneous polarity distribution with no inversion domains. The piezoelectric layers have been used to fabricate and measure surface acoustic wave (SAW) resonators on a Sc0.26Al0.74N/Si (001) bilayer system with resonance frequency of 1.4 GHz and coupling coefficient of 0.567. Such characteristic in the frequency response reveals the potential of these materials for advanced SAW devices in applications such as next generation (5G) wireless communication systems.