Plasma deposition of piezoelectric ZnO layers by rf sputtering, SolGel and pulsed laser deposition

As “lab‐on‐a‐chip‐devices” suited for analyses of least amounts of liquids are emerging from prototype status, cost‐effective materials for mass production of these devices are sought. For handling and mixing components, surface acoustic waves generated by piezoelectric elements are routinely employed; however, the LiNbO 3 single crystals used in such units are a significant cost factor. As an alternative, zinc oxide layers deposited onto the glass substrates hold the promise of cheaper production and easier integration into the assembly. In the present study, experiments regarding the deposition of such layers using different plasma processes are presented. Film synthesis was performed using rf magnetron sputtering, pulsed laser deposition and plasma based ion bombardment of Sol‐Gel films on crystalline and amorphous substrates. The impacts of significant deposition parameters are discussed. At optimum deposition parameters, excellent columnar growth in the preferred c‐axis orientation could be observed. The suitability of such films for the desired application is substanciated through first mixing experiments using optically lithographed interdigital transducers (IDTs). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)