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Description
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Within the framework of the density functional theory, the features of the electronic structure of gold monolayers are investigated. Changes in the electronic states of slabs are investigated depending on the number of monolayers and the concentration of defects. The tendencies in the formation of the total density of electronic states curve during the transformation from a monolayer to a bulk sample for gold are of a similar character. Monolayer nanostructures of gold were studied experimentally on the silicon surfaces (111) and (110) by tunneling microscopy and spectroscopy using a high-vacuum tunneling spectrometer with atomic resolution JSPM-4610 (JEOL, Japan) (2022-02-09)
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Notes
| The full-potential (L)APW + lo method was used within the Wien2k package for calculating the electronic structure of Au (111) films. We used slab calculation with distances between slabs ~ 20 Å, which should ensure that there is no interaction between them. One, two, and three monolayers of gold, which correspond to the A, AB, and ABC planes (111) of the fcc lattice, were calculated as well as bulk samples of gold. For the exchange-correlation part of the potential, we used the generalized gradient approximation (GGA) PBE as the most common GGA functional. Since the total energy of the unit cell turned out to be sensitive to the fineness of the partition of the reciprocal lattice, the integration over the Brillouin zone was performed on a relatively dense (in two directions) Monkhorst-Pack grid 12-12-1 centered at point (19 non-equivalent k-points) (Monkhorst and Pack 1976). A coarser grid 10-10-1 was used to relax the films. For all the films under study, when the wave functions were expanded in a Fourier series, the cut-off parameter Rkmax was 7. For all the films studied, the radius of the MT sphere was 1.058 Å. To calculate the relaxation of the atomic positions of the films, we used the initial coordinates of the atomic positions and the cell parameters of the corresponding metal. The density of electronic states (DOS) was calculated by the tetrahedron method (Blöchl et al. 1994). Visualizations of atomic structure were performed using VESTA (Momma and Izumi 2011). Studies of the nanorelief of gold surfaces were carried out using the tunneling microscope JSPM-4610 (Japan). Silicon plates of size 7 × 1 × 0.3 mm3 were used as a substrate. The deposition of metals on atomically clean silicon surfaces prepared by standard methods was carried out by thermal deposition. The evaporator is a spiral tungsten cuvette with a metal sample, which is located in the center of a metal cylinder with a 3-mm hole. The distance between the evaporator and the sample was about 7 cm. During deposition, a current of ~ 5.0 A was passed through the tungsten coil, which correspond to temperatures of 100° above the melting point of the metal. The deposition time was from fractions of a second to 1 min. The metal was deposited onto single-crystal surfaces without heating or cooling the sample. The vacuum in the working chamber was no worse than 10–8 Pa. All studies on a tunnel microscope were carried out in direct current mode. |