Low-dimensional systems investigated by x-ray absorption spectroscopy: a selection of 2D, 1D and 0D cases

Abstract

During the last three decades low dimensional systems attracted increasing interest both from the fundamental and the technological point of view due to their unique physical and chemical properties. X-ray Absorption Spectroscopy (XAS) is a powerful tool for the characterization of such kind of systems, owing to its chemical selectivity and high sensitivity in interatomic distances determination. Moreover this technique can simultaneously provide information on electronic and local structural properties of the nanomaterials, significantly contributing to clarify the relation between their atomic structure and their peculiar physical properties. This review provides a general introduction to XAS, discussing the basic theory of the technique, the most used detection modes, the related experimental setups and some complementary relevant characterization techniques (DAFS, EXELFS, PDF, XES, HERFD XAS, XRS). Subsequently a selection of significant applications of XAS spectroscopy to 2D, 1D and 0D systems will be presented. The selected low dimensional systems include IV and III-V semiconductor films, quantum wells, quantum wires and quantum dots; carbon based nanomaterials (epitaxial graphene and carbon nanotubes); metal oxide films, nanowires, nanorods and nanocrystals; metal nanoparticles. Finally, the future perspectives for the application of XAS to nanostructures are discussed.

MoS2 supported on P25 titania: A model system for the activation of a HDS catalyst

“…Because of its element selectivity [76], XAFS is one of the most suitable techniques to follow the evolution of the Mo coordination sphere in nanostructured supported phases [77].…”

XAS and XES Techniques Shed Light on the Dark Side of Ziegler–Natta Catalysts: Active‐Site Generation

“…[14][15][16][17][18] The specific goal is to gain insights into the electronic properties and the local structure around the Ti active sites (in terms of number and type of ligands, and of coordination distances), and to provide direct evidence (if possible) of the presence of Ti-alkyl bond. To this end, we combined two synchrotron-based techniques that have the advantage to be element-selective: i) Ti K-edge X-ray Absorption Spectroscopy (XAS) [19,20] and ii) valence-to-core Xray Emission Spectroscopy (vtc-XES). [21,22] The XAS and XES experiments were performed at the BM26A [23] and ID26 beamlines at the ESRF facility (Grenoble, France), respectively.…”

Temperature dependence of the local structure and lattice dynamics of wurtzite-type ZnO

“…Zinc oxide (ZnO) is a wide band-gap (E g = 3.37 eV [1]) semiconductor, which has many promising technological applications [2,3,4,5] and, therefore, is an extremely popular research field during the last years [6,7,8].…”

“…For example, the local environment around Fe [31], Co [32,33], Ni [34,35] and Cu [28,36,37] in ZnO has been investigated, based on the analysis of the dopant metal K-edge X-ray absorption spectra. An excellent review on the applications of x-ray absorption spectroscopy for the investigation of nanostructured ZnO can be found in [1]. Finally, the study of the O K-edge in single-crystal ZnO has been also carried out in [38].…”