Nature Of Electronic Structure Research Articles

Interface properties and electronic structures of aromatic molecules with anhydride and thio-functional groups on Ag (111) and Au (111) substrates**Project supported by the National Natural Science Foundation of China (Grant Nos. 51471185 and 51325204), the National Key Research and Development Program of China (Grant No. 2016YFJC020013), and the National Supercomputing Center in Tianjin.

First-principles calculations for several aromatic molecules with anhydride and thio groups on Ag (111) and Au (111) reveal that the self-assembly structures and the interface properties are mainly determined by the functional groups of aromatic molecules. Detailed investigations of the electronic structures show that the electrons in molecular backbone are redistributed and charge transfer occurs through the bond between the metal and the functional groups after these molecules have been deposited on a metal substrate. The interaction between Ag (111) (or Au (111)) and aromatic molecules with anhydride functional groups strengthens the π bonds in the molecular backbone, while that between Ag (111) (or Au (111)) and aromatic molecules with sulfur weakens the π bonds. However, the intrinsic electronic structures of the molecules are mostly conserved. The large-sized aromatic backbone has less influence on the nature of electronic structures than the small-sized one, either at the interface or at the molecules. These results are useful to build the good metal–molecule contact in molecule-based devices.

First principles study on the spin unrestricted electronic structure properties of transition metal doped InN nanoribbons

In the present study, first principles calculations were carried out to reveal the spin unrestricted electronic structure behavior of both pure and transition metal (TM) atom (V and Co) doped InN nanoribbons (InN-NRs). The influence of a substitutionally doped TM atom on the electronic structure nature was examined. The role of a TM dopant together with its location, governing the characteristic of spin dependent electronic property of a doped InN-NR, was addressed. The relevant properties were extracted through Hubbard correction for In-d, N-p and TM-d states. We observed that a single TM dopant diminished the spin dependent energy gap and can result in a significant induced magnetic moment in an InN-NR system. It was exposed that TM dopants can play an essential role in the spin unrestricted electronic behavior and spin polarization, which can be tuned through a V or Co atom at a certain position.

High-Resolution STEM and EELS as Tools to Study Structure and Bonding of Oxides

Due to the developments of aberration correctors, bright electron sources, stable microscopes and electron monochromators, electron microscopy has dramatically evolved in the recent years. The current microscopes provide structural, chemical and spectroscopic information with sub-angstrom resolution and with synchrotron-quality spectroscopic performance ranging from the mid-infrared to the hard X-ray regime. Using a combination of scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) with better than 0.1eV energy resolution (down to 10meV), we provide here a review of recent studies where EELS and STEM have allowed us to probe the structure, the local chemistry and the nature of the local electronic structure of a range of complex oxides. These studies show that it is possible to determine the location of particular atomic species used as dopants in a crystal [1], the local coordination and valence of atoms in crystals and at surfaces [2,3], and also the nature of the hybridization and valence in perovskites [4] and superconductors [5,6]. These applications show that EELS and STEM can be used to resolve ambiguities in structure refinements of oxides by deducing the site preference of transition metal atoms and their coordination. We also show that it is possible to extract valence information and localization of electron charge in a range of materials, thus providing essential information on termination at interfaces [7]. With these techniques, we explore defects in materials and the nature of the electronic structure at interfaces.