Microstructure and piezoelectric properties of reactively sputtered highly C-axis ScxAl1-xN thin films on diamond-like carbon/Si substrate

• Published in: Surface & coatings technology Vol. 308; pp. 101 - 107
• Main Authors: Liauh, Woan Jwu, Wu, Sean, Huang, Jow-Lay, Lii, Ding-Fwu, Lin, Zhi-Xun, Yeh, Wen-Kuan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 25.12.2016
• Subjects: Aluminum; Atom probe analysis; Co-sputtering; Diamond-like carbon films; DLC; Piezoelectricity; ScAlN films; Scandium; Silicon substrates; Thin films; X-ray diffraction; Co-sputtering; Piezoelectricity; ScAlN films; DLC
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2016.06.097

We report deposition of pure AlN and ScxAl1-xN thin films with different Sc concentration on DLC/Si substrate by RF and DC reactive magnetron co-sputtering method by using Al and Sc as targets. The X-ray diffraction (XRD) results showed that the films have high c-axis-orientation. Electron probe microanalyzer (EPMA) analysis reveals the presence of scandium atoms reduce the space occupied by aluminum atoms, leading to lattice distortion during the phase transition. The SEM cross-section results showed that the ScxAl1-xN films are highly aligned along c-axis and have columnar like morphology. The top view of SEM results indicated that the new phase formation above Sc 30.33%, however no new peak appeared in the XRD pattern. The piezoelectric coefficient (d33) of ScxAl1-xN thin films are measured and the highest value (11.54 pC/N) is achieved at x=30.33% increasing 14 times, as that with AlN/DLC/Si, 0.73 pC/N. ScxAl1-xN films on DLC/Si substrate have a great potential to be applied on high frequency SAW devices in the future. •This work successfully deposited highly c-axis orientated ScxAl1-xN films on DLC/Si substrate by a co-sputtering technique.•The morphologies of ScxAl1-xN thin films can be controlled by adding various Sc content and affect its piezoelectricity.•The d33 of Sc0.303Al0.697N achieved highest value (11.54 pC/N), which was increasing 14 times higher than AlN (0.73 pC/N).