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Structural study of growth, orientation and defects characteristics in the functional microelectromechanical system material aluminium nitride

: Hrkac, V.; Kobler, A.; Marauska, S.; Petraru, A.; Schürmann, U.; Chakravadhanula, V.S.K.; Duppel, V.; Kohlstedt, H.; Wagner, B.; Lotsch, B.V.; Kübel, C.; Kienle, L.


Journal of applied physics 117 (2015), No.1, Art. 014301
ISSN: 0021-8979
ISSN: 1089-7550
Deutsche Forschungsgemeinschaft DFG
SFB 855;
Journal Article
Fraunhofer ISIT ()

The real structure and morphology of piezoelectric aluminum nitride (AlN) thin films as essential components of magnetoelectric sensors are investigated via advanced transmission electron microscopy methods. State of the art electron diffraction techniques, including precession electron diffraction and automated crystal orientation mapping (ACOM), indicate a columnar growth of the AlN grains optimized for piezoelectric application with a {0 0 0 1} texture. Comparing ACOM with piezoresponse force microscopy measurements, a visual correlation of the structure and the piezoelectric properties is enabled. With a quantitative analysis of the ACOM measurements, a statistical evaluation of grain rotations is performed, indicating the presence of coincidence site lattices with Sigma 7, Sigma 13a, Sigma 13b, Sigma 25. Using a geometric phase analysis on high resolution micrographs, the occurrence of strain is detected almost exclusively at the grain boundaries. Moreover, high resolution imaging was applied for solving the atomic structure at stacking mismatch boundaries with a displacement vector of 1/2 < 1 0 - 1 1 >. All real structural features can be interpreted via simulations based on crystallographic computing in terms of a supercell approach.