JECP/PCED—a computer program for simulation of polycrystalline electron diffraction pattern and phase identification

EDP2XRD: a computer program for converting electron diffraction patterns into X-ray diffraction patterns

Mny commercial software packages for X-ray diffraction pattern analysis are capable of identifying multiple phases in bulk materials. However, X-ray diffraction patterns cannot record those phases with very small volume ratio or non-homogeneous distribution, which may mean that researchers have to use instead electron diffraction patterns from a very small region of interest. EDP2XRD, a new program for converting electron diffraction patterns into X-ray diffraction patterns, is described here. The program has been developed in order to utilize X-ray analysis software for electron diffraction patterns taken from mixed-phase nanocrystalline materials with a transmission electron microscope. It is specifically designed for material researchers who are engaged in crystallographic microstructure analysis. The difference from other popular commercial software for crystallography is that this program provides new options to convert and plot X-ray diffraction patterns for arbitrary electron diffraction rings and to process raw images to enhance conversion performance. The program contains the necessary crystallographic calculator to list planar d spacings and corresponding X-ray diffraction angles.

Patterning of crystalline organic materials by electro-hydrodynamic lithography

The control of semi-crystalline polymers in thin films and in micrometer-sized patterns is attractive for (opto-)electronic applications. Electro-hydrodynamic lithography (EHL) enables the structure formation of organic crystalline materials on the micrometer length scale while at the same time exerting control over crystal orientation. This gives rise to well-defined micro-patterned arrays of uniaxially aligned polymer crystals. This study explores the interplay of EHL structure formation with crystal alignment and studies the mechanisms that give rise to crystal orientation in EHL-generated structures.

Experimental demonstration of high quality MeV ultrafast electron diffraction

The simulation optimization and an experimental demonstration of improved performances of mega-electron-volt ultrafast electron diffraction (MeV UED) are reported in this paper. Using ultrashort high quality electron pulses from an S-band photocathode rf gun and a polycrystalline aluminum foil as the sample, we experimentally demonstrated an improved spatial resolution of MeV UED, in which the Debye-Scherrer rings of the (111) and (200) planes were clearly resolved. This result showed that MeV UED is capable to achieve an atomic level spatial resolution and a approximately 100 fs temporal resolution simultaneously, and will be a unique tool for ultrafast structural dynamics studies.

Four-dimensional ultrafast electron microscopy of phase transitions

Reported here is direct imaging (and diffraction) by using 4D ultrafast electron microscopy (UEM) with combined spatial and temporal resolutions. In the first phase of UEM, it was possible to obtain snapshot images by using timed, single-electron packets; each packet is free of space-charge effects. Here, we demonstrate the ability to obtain sequences of snapshots ("movies") with atomic-scale spatial resolution and ultrashort temporal resolution. Specifically, it is shown that ultrafast metal-insulator phase transitions can be studied with these achieved spatial and temporal resolutions. The diffraction (atomic scale) and images (nanometer scale) we obtained manifest the structural phase transition with its characteristic hysteresis, and the time scale involved (100 fs) is now studied by directly monitoring coordinates of the atoms themselves.