Investigation of domain related topography formation during chemical mechanical polishing of piezoelectric ceramic material

Abstract

Novel microelectromechanical system manufacturing can be expected if the joining areas of the concerned materials are atomically flat (roughness, <0·6 nm). In this case, the assembly should be achieved by direct bonding mechanisms. Accordingly, no additional intermediate layers or undercoatings between the active and passive material components are necessary. The surface conditioning of piezoelectric ceramics is correlated with the change of the domain morphology, particularly if very flat surfaces are processed. Ferroelastic interactions and the piezoelectric effect caused by the acting forces during the machining process come into account and change the local polarisation distribution of the treated surface area. This local modulation has a lasting effect on the resulting surface topography, which in general does not correspond to the relaxed domain structure in the surface area after machining. The preparation of the highly flattened surface of thin ceramic sheets with least roughness was conducted using chemical mechanical polishing. The removal conditions could be adjusted to be invariant to the polarisation condition of the treated surface area. The treatment resulted in an optical flat mirrorlike surface with roughness below 1 nm. The topography follows the polarisation of the ferroelectric domains underneath in a nanometre scale. Multiple investigation techniques, such as field emission scanning electron microscopy, piezoforce microscopy and scanning probe microscopy allowed for a phenomenological interpretation. With the deepened understanding of the preparation process and the related material interactions, it is now possible to treat the surface machining to be domain independent.