Analytical transmission electron microscopy in the third dimension

For researchers in metallurgy, energy storage or functional nanomaterials, where elemental distribution is crucial to performance, full characterization is more difficult by decreasing feature sizes and increasingly complex architectures. Two-dimensional imaging and analytical techniques often cannot characterize nanostructures completely. A new three-dimensional (3D) tomography technique for STEM XEDS, namely ChemiSTEM (TM) Technology [1], reveals the true microstructure of materials offering high X-ray collection efficiency via its windowless detector design, and fast XEDS mapping with tilt response at all angles. ChemiSTEM features the X-FEG and Super X, containing four symmetric detectors for 3D chemical imaging at 0 degree tilt, with significant EDX signal collected under all tilt conditions. The EDS signal of STEM XEDS image tilt series can be processed like normal z-contrast images, because of the monotonic relationship between the EDS signal and the thickness of the TEM foil. Four symmetrically arranged silicon drift detectors (SDD) provide extreme high output count rates (300 kcps) required for acquisition of EDX maps of thick samples, especially on 3 mm disk samples for 3D tomography studies. Examples of 3D chemical mapping using XEDS are given on (InGa)N Nanopyramid LEDs, Ni based super alloy material for turbine blades, dielectric transistor, and catalytic particles. In lithium ion batteries, the elemental segregation of manganese and nickel, which is responsible for the aging of electrode materials made from lithium-nickel-manganese oxide layered nanoparticles was analyzed in 3D XEDS mapping [2].