Optimizing Morphology and Structure with Multi-Signal FIB/SEM Tomography
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Optimizing Morphology and Structure with Multi-Signal FIB/SEM Tomography Lucille A. Giannuzzi L.A. Giannuzzi and Associates, Fort Myers, FL 33913, U.S.A ABSTRACT Focused ion beam (FIB) milling coupled with scanning electron microscopy (SEM) on the same platform enables 3D microstructural analysis of structures using FIB for serial sectioning and SEM for imaging. Since FIB milling is a destructive technique, the acquisition of multiple signals from each slice is desirable. The feasibility of collecting both an inlens backscattered electron (BSE) signal and an inlens secondary electron (SE) simultaneously from a single scan of the electron beam from each FIB slice is demonstrated. The simultaneous acquisition of two different SE signals from two different detectors (inlens vs. Everhart-Thornley (ET) detector) is also possible. Obtaining multiple signals from each FIB slice with one scan increases the acquisition throughput. In addition, optimization of microstructural and morphological information from the target is achieved using multi-signals. Examples of multisignal FIB/SEM tomography from a dental implant will be provided where both material contrast from the bone/ceramic coating/Ti substrate phases and porosity in the ceramic coating will be characterized. INTRODUCTION FIB/SEM tomography has become a routine method for analyzing 3D morphology and structure in samples from both the physical and biological sciences [1]. The FIB may be used to site specifically mill hundreds of slices, each with a predefined width, z. The SEM is then used to image each FIB milled face which defines the x and y dimensions. The FIB/SEM process is alternated sequentially over the entire volume of interest. The total acquisition time can be on the order of hours to days depending on the number of slices and volume analyzed. Ideally, operating parameters should be chosen such that the image spatial resolution defined by pixel dimensions in x and y is similar to the slice dimension, z, resulting in a square (or nearly square) 3D voxel. Each slice may require a tilt correction (e.g., in the y direction) depending on the angle of incidence of the SEM image acquisition. The stack of slices is aligned and the 3D volume may be rendered, segmented, and quantified. In this paper we present multi-signal 3D FIB/SEM results from a failed TiUnite dental implant sample which has incorporated bone growth (e.g., osseonintegration) on the surface and within the surface pores of the ceramic coating. This biomaterials system has been analyzed previously using FIB and electron microscopy methods [2,3]. The implant itself consists of a ceramic coating on a Ti substrate [2-6]. The porous ceramic coating consists of nanocrystalline anatase (TiO2) and amorphous TiOx. The ceramic coating consists of surface pores as well as internal pores. A high density of nanoporosity is observed at the coating/Ti interface. Bone was observed to grow into and partially conform to the pore morphology. Observation of the crystalline bone collagen structure is possible using dir
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