Structure of graphene on the Ni(110) surface Fedorov, A. V.; Varykhalov, A. Yu; Dobrotvorskii, A. M. ...
Physics of the solid state,
09/2011, Letnik:
53, Številka:
9
Journal Article
Recenzirano
The structure of graphene on Ni(110) was studied using scanning tunneling microscopy (STM) and low-energy electron diffraction spectroscopy. STM images show a Moire structure, depending on the ...orientation of the domains making up the graphene layer. A simple model has been proposed which permits prediction of the Moire structure and interpretation of STM images based on calculation of the distances between the nearest neighbor carbon and nickel atoms. Our theoretical calculation suggests that the final orientation of graphene domains forming in the course of synthesis is defined by the angle of rotation of small clusters in the initial stages of growth.
The discovery of a square magnetic-skyrmion lattice in GdRu
2
Si
2
, with the smallest so far found skyrmion size and without a geometrically frustrated lattice, has attracted significant attention. ...In this work, we present a comprehensive study of surface and bulk electronic structures of GdRu
2
Si
2
by utilizing momentum-resolved photoemission (ARPES) measurements and first-principles calculations. We show how the electronic structure evolves during the antiferromagnetic transition when a peculiar helical order of 4f magnetic moments within the Gd layers sets in. A nice agreement of the ARPES-derived electronic structure with the calculated one has allowed us to characterize the features of the Fermi surface (FS), unveil the nested region along
k
z
at the corner of the 3D FS, and reveal their orbital compositions. Our findings suggest that the Ruderman-Kittel-Kasuya-Yosida interaction plays a decisive role in stabilizing the spiral-like order of Gd 4f moments responsible for the skyrmion physics in GdRu
2
Si
2
. Our results provide a deeper understanding of electronic and magnetic properties of this material, which is crucial for predicting and developing novel skyrmion-based systems.
A combination of momentum-resolved photoemission measurements and first-principles calculations allowed us to unveil the origin of the helical magnetic order in the GdRu
2
Si
2
skyrmion magnet.
The substrate-induced spin-orbit splitting of interface and quantum-well states formed in Au, Ag, and Cu layers on W(110) and Mo(110) surfaces has been revealed using angle- and spin-resolved ...photoelectron spectroscopy. It has been shown that the magnitude of the splitting depends noticeably on the atomic number of the substrate material and is markedly larger for layers of these metals on W(110), i.e., on the surface of a metal with a larger atomic number (
Z
W
= 74), than on the surface of Mo(110), i.e., an element with a smaller atomic number (
Z
Mo
= 42), while depending only weakly on the atomic number of the adsorbed metal. Measurements of the dispersion of the formed quantum-well states have shown that the substrate-induced spin-orbit splitting increases with increasing parallel component of the photoelectron momentum (which correlates with the Rashba model) for all thicknesses of deposited films (up to 10 ML). The magnitude of induced spin-orbit splitting of the interface states evolving in monolayer Au, Ag, and Cu coatings on W(110) and Mo(110) decreases with increasing parallel component of the excited photoelectron momentum.
► The etching is anisotropic, while the etching rate is determined by the orientation of the grain. ► The (100) face is the most resistant to chemical etching, while the etching rate of the other ...faces, including the most close-packed (110), is much larger. ► The rate of etching of iron crystals decreases over time due to the formation of the oxide layer on the surface.
Atomic force microscopy (AFM) and electron backscatter diffraction were used to study formation of the low-carbon steel surface relief upon chemical etching with nital. The combination of these techniques allowed quantitative characterization of the iron etch depth dependence on the crystallographic orientation of individual ferrite grains. The obtained results demonstrate high potential of AFM for quantitative metallography.
We present a combined experimental and theoretical study of the two-dimensional electron states at the iridium-silicide surface of the antiferromagnet GdIr2Si2 above and below the Néel temperature. ...Using angle-resolved photoemission spectroscopy (ARPES) we find a significant spin-orbit splitting of the surface states in the paramagnetic phase. By means of ab initio density-functional-theory (DFT) calculations we establish that the surface electron states that reside in the projected band gap around the M¯ point exhibit very different spin structures which are governed by the conventional and the cubic Rashba effect. The latter is reflected in a triple spin winding, i.e., the surface electron spin reveals three complete rotations upon moving once around the constant energy contours. Below the Néel temperature, our ARPES measurements show an intricate photoemission intensity picture characteristic of a complex magnetic domain structure. The orientation of the domains, however, can be clarified from a comparative analysis of the ARPES data and their DFT modeling. To characterize a single magnetic domain picture, we resort to the calculations and scrutinize the interplay of the Rashba spin-orbit coupling field with the in-plane exchange field, provided by the ferromagnetically ordered 4f moments of the near-surface Gd layer.
We present a combined experimental and theoretical study of the two-dimensional electron states at the iridium-silicide surface of the antiferromagnet GdIr2 Si2 above and below the Néel temperature. ...Using angle-resolved photoemission spectroscopy (ARPES) we find a significant spin-orbit splitting of the surface states in the paramagnetic phase. By means of ab initio density-functional-theory (DFT) calculations we establish that the surface electron states that reside in the projected band gap around the ¯¯¯¯ M point exhibit very different spin structures which are governed by the conventional and the cubic Rashba effect. The latter is reflected in a triple spin winding, i.e., the surface electron spin reveals three complete rotations upon moving once around the constant energy contours. Below the Néel temperature, our ARPES measurements show an intricate photoemission intensity picture characteristic of a complex magnetic domain structure. The orientation of the domains, however, can be clarified from a comparative analysis of the ARPES data and their DFT modeling. To characterize a single magnetic domain picture, we resort to the calculations and scrutinize the interplay of the Rashba spin-orbit coupling field with the in-plane exchange field, provided by the ferromagnetically ordered 4 f moments of the near-surface Gd layer.
The crystalline and electronic structure of nitrogen-doped graphene (N-graphene) has been studied by photoelectron spectroscopy and scanning tunneling microscopy. Synthesis of N-graphene from ...triazine molecules on Ni(111) surface results in incorporation into graphene of nitrogen atoms primarily in the pyridinic configuration. It has been found that inclusions of nitrogen enhance significantly thermal stability of graphene on nickel. An analysis of the electronic structure of N-graphene intercalated by gold atoms has revealed that the pyridinic nitrogen culminates in weak
p
-type doping, in full agreement with theoretical predictions. Subsequent thermal treatment makes possible conversion of the major part of nitrogen atoms into the substitutional configuration, which involves
n
-type doping. It has been shown that the crystalline structure of the N graphene thus obtained reveals local distortions presumably caused by inhomogeneous distribution of impurities in the layer. The results obtained have demonstrated a promising application potential of this approach for development of electronic devices based on graphene with controllable type of conduction and carrier concentration.
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