Sample preparation techniques for large-area data acquisition

Large-area transmission Kikuchi diffraction (TKD) analysis of nanostructured nickel. Inverse pole figure (IPF) color-coded orientation maps with 8 nm twin boundaries are shown. Data was collected from defect-free, ultrathin ~40 nm samples with a maximum of three grain layers. TKD analyses condition: 30 kV acceleration voltage and 1.6 nA beam current.

To achieve optimal transmission Kikuchi diffraction (TKD) results, managing the sample thickness and uniformity are critical. When too thick of a sample is used, the SEM electron beam will scatter more broadly; this causes a significant loss of resolution and reduces the effective number of electrons that traverse the full sample thickness and produce Kikuchi patterns. The result can be an attenuation (or inversion) of Kikuchi pattern contrast. Conversely, when too thin of a sample is used, the result is a lower total scattering signal, i.e., there will be insufficient number of scattered electrons to enable formation of Kikuchi patterns. In addition, if the sample does not have an area of uniform thickness, accurate and fast TKD measurements may not be possible.

Using broad ion beam milling (Model 1051 TEM Mill) or, post-FIB preparation, concentrated ion beam milling (Model 1040 NanoMill® TEM specimen preparation system), it is possible to prepare electron-transparent samples that have ideal characteristics for optimal TKD analysis – large area and uniform thickness. The Ar ion beam milling technique produces samples that are free of structural damage and amorphization.

Learn more:
• Webinar: Optimal sample preparation for large-area transmission Kikuchi diffraction analysis
• Nowakowski, P., Bonifacio, C., Ray, M., & Fischione, P. (2023). Improved sample preparation technique for transmission Kikuchi diffraction (TKD) analyses allows large-area data acquisition. Microscopy and Microanalysis, 29(S1), 134-135.
• Nowakowski, P., Wiezorek, J., Bathula, V., Mielo, S., Khanal, S., Bonifacio, C., & Fischione, P. (2018). SEM and TEM characterization of plastic deformation structures in aluminum by EBSD, TKD, and PED-based orientation imaging techniques. Microscopy and Microanalysis, 24(S1), 2182-2183.

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