Sputtering and chemical vapour deposition of piezoelectric ZnO, AlN and K 3Li 2Nb 5O 15 films for optical waveguides and surface acoustic wave devices

Abstract

Epitaxial and c-axis-oriented ZnO thin films with surface flatness were successfully grown on various kinds of substrate by r.f. planar magnetron sputtering, ZnOH 2H 2OO 2 isothermal chemical vapour deposition (CVD) and plasma-enhanced organometallic CVD methods. c-axis-oriented AlN films were also prepared on glass and silicon substrates at substrate temperatures as low as 20–460°C by reactive r.f. planar magnetron sputtering. Furthermore, ferroelectric K 3Li 2Nb 5O 15(KLN) crystal films were grown with good epitaxy on K 2BiNb 5O 15 or sapphire substrates by sputtering. The quality of the ZnO, AlN and KLN films was evaluated from X-ray diffraction, scanning electron microscopy and reflection electron diffraction measurements. These films are excellently transparent and are of extremely good quality. The epitaxial CVD and c-axis-oriented sputtered ZnO films have guided optical wave losses as low as 0.7 dB cm −1 and 2.1 dB cm −1 respectively. All the films are piezoelectrically active and show surface acoustic wave response.