DiffMap: A new free computer program to process scanned electron diffraction patterns

A free computer program, called DiffMap, is presented for off-line evaluation of both phase maps and orientation maps from a large number of diffraction patterns recorded with a nearly parallel nano-beam scanned line-by-line over a rectangular area in a scanning transmission electron microscope (STEM). The program runs in the Windows operating system on IBM PC compatible computers. The patterns, which are recorded independently from this program by a CCD or CMOS camera or by a pixelated camera are in Tif format, serve as input to DiffMap. Many STEMs can collect such a four-dimensional electron diffraction (4D-ED) data sets by proper selection of microscope parameters, even if this fact is not over-emphasized in the operating manuals. These phase and orientation maps can complement usual compositional maps collected in the same STEM with energy dispersive x-ray spectrometers (EDS) to give a complete description of the crystalline phases. Application is exemplified on the (fcc, hcp and bcc) phases in a sample with 4 major components (Co, Cr, Fe, Ni).