A nonlinear formulation of piezoelectric shells with complete electro-mechanical coupling

A nonlinear piezoelectric shell model capable of accurately expressing the direct and the converse piezoelectric effect is presented. The developed theory is meant to encompass large strains, displacements and rotations that can occur in the shell as a consequence of a complete coupling between the mechanical and the electrical fields. Based on results present in the literature according to which a linear dependence of the electric potential on the shell thickness is not adequate to represent its electrical behavior, a specific structure of the field of admissible displacements is taken into account. Warping functions characterized by an ad-hoc polynomial expansion aimed at expressing their dependence on the shell through-the-thickness coordinate are here considered to describe the shear and the extensional deformability of the shell transverse fibers. Linear constitutive relations for a transversely isotropic continuum are considered. Finally, the governing equations of motion of the shell are obtained via enforcement of the virtual work theorem

The sputtering of AlN films on top of on- and off-axis 3C-SiC (111)/Si (111) substrates at various substrate temperatures

AlN thin films have been sputtered on top of the on-axis and 4° off-axis 3C-SiC (111)/Si (111) substrates at various substrate temperatures. The grazing angle incident XRD scans show that all films have major peak at (002) plane and minor peaks at (101) and (102) planes. The AlN films are further characterized in terms of the FWHM of the rocking curve, surface morphology and deposition rate. We observed that the increasing substrate temperature improve the crystal quality of the AlN (002) films, but it has minimal impact on the surface roughness and deposition rate. We also extracted the values for the bi-axial stress, the grain size and the piezoelectric coefficient. Overall, the off-axis 3C-SiC/Si (111) substrates provide a better template for the sputtering of AlN (002) films in term of better crystal quality, lower surface roughness and lower bi-axial stress.Griffith Sciences, School of Environment and ScienceFull Tex