A method for predicting thickness of the unoriented layer in ZnO film using piezoelectricity distribution in depth direction

作者：Takayanagi S^*; Yanagitani T; Matsukawa M

来源：Journal of Physics D: Applied Physics , 2013, 46(31): 315305.

DOI：10.1088/0022-3727/46/31/315305

The crystalline orientation of thin films gradually improves as the growth proceeds. Especially in the non-epitaxial growth, its initial layer is often unoriented. Because the unoriented layer degrades the performance of the device, the degree of crystalline orientation in depth direction is a very important issue. We propose a non-destructive method for predicting the thickness of the unoriented layer, making use of piezoelectricity distribution of films. An electromechanical resonator consisting of the single highly oriented layer excites a fundamental mode, but does not excite a second-overtone mode. The unoriented layer, on the other hand, exhibits little piezoelectric effect. A bilayer resonator consisting of the highly oriented layer on the unoriented layer excites a second-overtone mode because of the deference of piezoelectricity in these layers. In this study, the electromechanical resonance characteristics of Cu/ZnO(0 0 0 1)/Ti(0 0 0 1)/SiO2, Cu/ZnO(0 0 0 1)/AZO(0 0 0 1)/Ti(0 0 0 1)/ SiO2 and Cu/ZnO(1 1 (2) over bar 0)/Al/SiO2 were experimentally observed. These results were compared with the theoretical estimations by a mechanical transmission line model to determine the thicknesses of the piezoelectrically inactive layers in the (0 0 0 1) or (1 1 (2) over bar 0) oriented ZnO films. The inactive layer thickness in the (1 1 (2) over bar 0) oriented ZnO film was in good agreement with the unoriented layer thickness observed by the cross-sectional transmission electron microscopy and electron diffraction.

• 出版日期2013-8-7