Keywords: XAFS, EXAFS, X-ray absorption fine structure, structure, disorder, bond length, nanoparticles, quantum confinement, ZnO, nanorods, Kondo effect, CeAl, CePt, nanostructures, oxygen contamination
X-ray absorption fine structure and nanostructures
The X-ray absorption fine structure (XAFS) is a powerful tool to investigate local atomic structures in matter. The XAFS can select a specific type of atom as a probe atom and measure the structural environments near the probe atom. The XAFS can therefore describe the bond lengths, bond-length distributions and the species of the atoms located around the probe atom. XAFS measurements can be made with a transmission or fluorescence mode. The XAFS technique does not depend on the density of material, nor on the types of the specimens, such as, powder, thin film, or even liquid. However, the XAFS signals decay quickly and loose their coherence with increased distance from a probe atom, and are useful only within a distance of ~5–6Å from the probe atom. Although the XAFS technique is a unique and powerful probe to measure the short-range orderings of atoms, the quantitative information of the structural properties can be obtained as the XAFS data are carefully analysed. We studied the structural properties of non-Fermi liquid nanoparticle CeAl2 and CePt2 and quantum confinement ZnO nanorods using normal XAFS and orientation-dependent XAFS, respectively. We observed a substantial amount of disorders/distortion existing in the both the CeAl2 and CePt2 nanoparticles, and bond length distortion in the vertically well-aligned ZnO nanorods. The XAFS exhibits oxygen contamination in both the nanocrystals of CeAl2 and CePt2. The orientation-dependent XAFS reveals that oxygen is the terminating atom on the lateral surface of ZnO nanorods.