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Field Emission Scanning Electron Microscopy (FE-SEM) and Energy Dispersive X-Ray (EDX) Spectroscopy

The materials characterization laboratory is equipped with a Hitachi S-4700 Field Emission Scanning Electron Microscope (FE-SEM) as shown in Figure 1. The FE-SEM combines the versatility of PC control with a novel electron optical column to give exceptional performance. Resolution of 1.5 nm at 15 kV is guaranteed at 12 mm working distance. The FE-SEM also offers excellent low kV performance with resolution of 2.5 nm at 2 kV, at a working distance of 3 mm. Pre-programmed operating modes allow the user to switch from high resolution conditions to microanalysis conditions at the click of the mouse with no change of objective aperture. Dual SE detectors allow versatile imaging. The FE-SEM is equipped with fully digital imaging, image processing, and archiving system.

Figure 1: The Hitachi S-4700 Field Emission Scanning Electron Microscope (FE-SEM).

The FE-SEM is equipped with EDAX Energy Dispersive X-Ray (EDX) spectroscopy system with 30º take-off angle for quantitative analysis, digital imaging, and X-ray mapping. The EDAX SAPPHIRE SEM detector has a 20,000 : 1 peak-to-background ratio, and 128 eV resolution maintained at high throughputs. EDAX Phoenix microanalysis system contains the EDAM III data acquisition module, which allows for flexibility and enhanced performance through Digital Signal Processing for spectral and image acquisition and data reduction.

At CAMMP, FE-SEM is used to generate images of exceptional quality and detail (Figures 2-5). EDAX's simple, single window interface easily accommodates any task. A complete analysis is accomplished with the push of a button, and any number of parameters can be easily adjusted to tweak an analysis. Standard file formats merge easily with word processor and spreadsheet applications, allowing generation of electronic or hardcopy reports in a very short time.

Figure 2: FE-SEM image showing rectangular growth terraces on the {110} faces of small ~2-3 µm zeolite A crystal with a truncated cuboctahedron morphology. Crystal was coated with a thin Cr film prior to imaging. Height of growth terraces on the {100} faces of zeolite A were measured by AFM to be ~1.2 nm (Bazzana et al., Studies in Surface Science and Catalysis, 2002, 142:117-124).

Figure 3: FE-SEM image showing triangular growth terraces on the (111) face of ~1-2 µm zeolite X crystal with octahedral morphology. Crystal was coated with a thin Cr film prior to imaging. Height of growth terraces was measured by AFM to be ~1.5 nm (Bazzana et al., Studies in Surface Science and Catalysis, 2002, 142:117-124).

Figure 4: FE-SEM image showing growth spirals on the (100) face of monolithic ETS-4 crystal with a rectangular prism morphology and dimensions ~1x15x2 µm. Crystal was coated with a thin Cr film prior to imaging. Step height was measured by AFM to be ~1.2 nm (Yilmaz et al., Microporous and Mesoporous Materials, 2004, 71: 167-175).

Figure 5: (a) FE-SEM image of square-shaped islands and growth terraces on the truncated surface of ETS-10 crystal with a truncated square bipyramidal morphology shown in FE-SEM image (b). Heights of growth terraces were measured by AFM to be ~1.2-1.7 nm. The slight deviation from the square shape in (a) is due to distortion caused by inclination of the imaged surface to the horizontal. Crystal was coated with a thin Cr film prior to imaging (Ji et al., Microporous and Mesoporous Materials, 2005, 81:1-10).