3D Au Research Articles

Single-electron tunneling study of two-dimensional gold clusters

By using scanning tunneling microscopy/spectroscopy, we have studied the current–voltage characteristics of two-dimensional (2D) Au clusters, thermally deposited on self-assembled alkanethiol monolayer. The curves display Coulomb blockade and staircase with asymmetric behavior. The measured zero conductance gap as a function of cluster size is in excellent agreement with classical model calculations, in which the 2D Au island is treated as metallic in the planar direction but nonmetallic in the normal direction.

Initial growth and morphology of thin Au films on TiO 2(110)

We have studied the growth of thin Au films (0.2 to 12 nm) and the surface morphology of individual three-dimensional (3D) Au islands on the TiO 2(110) surface by using high resolution scanning electron microscopy (HRSEM). The Au is evaporated under UHV conditions onto clean and stoichiometric TiO 2(110) with substrate temperatures ranging from 300 to 775 K. In this temperature range, Au grows initially as 3D islands on TiO 2(110). At 300 K, the Au film morphology evolves with increasing average Au thickness h, from hemispherical islands initially ( h<1.0 nm), to partially coalesced worm-like island structures ( h>1.5 nm), to percolation at h∼8 nm, and finally to a continuous and rough film at h∼12 nm. For deposition at elevated temperature (≥500 K) and for Au thickness ≥5 nm, Au islands exhibit faceted shapes. For deposition of ≥5 nm of Au at 300 K followed by annealing at 775 K, Au islands are highly faceted with hexagonal shapes. The growth behavior of 1 nm Au on an oxygen-deficient TiO 2 surface at 300 K is also reported.

Temperature induced change of surface roughness of Au(1 1 1) epitaxial films on mica

The epitaxial growth of Au(1 1 1) on mica was studied using scanning tunneling microscopy (STM). Structure and surface roughness of 100 nm thick films evaporated at substrate temperature in the range 580–890 K was examined at deposition rates of 0.2 and 0.5 nm/s. Decrease of the surface roughness at some temperature depending on the deposition rate was observed. It can be explained considering a critical island size R c at which a new layer nucleates on top of the Au(1 1 1) island. The critical size increases with temperature much faster than the size of available 3D islands formed during coalescence on mica substrate. Consequently, at lower temperatures 2D nucleation on the top of pre-deposited 3D Au islands can be observed while at higher temperatures no nucleation takes place and adatoms fill gaps between islands.

Spectromicroscopy and thermal evolution of an [formula omitted] bimetallic interface

The interaction of Ag with a (√3 × √3)R30° - Au Si(111) interface containing three-dimensional (3D) Au microparticles has been studied by means of synchrotron radiation photoelectron microspectroscopy and elemental imaging with spatial resolution of 150 nm. The evolution of the space-resolved core-level spectra from the √3-Au and 3D phases has revealed the impact of the surface morphology on the local composition and interface interactions. The correlation between the Au chemical state and the processes occurring in the two-dimensional and 3D phases after Ag deposition at 300 K and following step annealing to 870 K has been deduced from the evolution of the Ag 3d, Au 4f and Si 2p spatially resolved spectra. It has been shown that in the 3D Au particles Ag penetrates through an Au-silicide film to intermix with metallic Au below. The lack of metallic Au accounts for the slower rate of AgAu intermixing on the √3-Au areas, where formation of 3D AgAu clusters is evidenced by the appearance of a metal-Au component in the Au 4f spectra.

Observation of atomic place exchange in submonolayer heteroepitaxial Fe/Au(001) films.

Submonolayer Fe films on a Au(001) surface were found to exhibit atomic place exchanges with Au atoms during room temperature growth by using the angular profile measurement of high-resolution low-energy electron diffraction. The place exchanged atoms result in 2D Au surface islands and Fe subsurface structures. These inverted 2D islands form a structure with a roughly equal island size and spacing in \ensuremath{\sim}0.5 monolayer FeAu(001) surfaces. The observed mechanism of the atomic place exchange is consistent with recent first-principles calculations for a heteroepitaxial system.

Studies on 2D AuCu binary adsorbates on Si(111) surfaces by means of combined LEED/AES/RBS techniques

Studies on 2D AuCu binary adsorbates on Si(111) surfaces by means of combined LEED/AES/RBS techniques

REM and TEM studies of 2D AuCu alloy adsorbates on a Si(111) surface

Structures formed by co-deposition of Au and Cu on Si(111)7 × 7 surfaces were studied by transmission and reflection electron microscopy (TEM and REM). A two-dimensional alloy adsorbate structure of 3 × 3 was formed from the beginning of simultaneous deposition and by successive deposition of Au and Cu. The observed structure was different from those formed at the initial stage by deposition of individual metals. Dark field images due to reflections from the 3 × 3 structure in TEM and REM showed domain structures, which indicated p3 symmetry of the 3 × 3 structure instead of p31m.

REM and TEM studies of 2D AuCu alloy adsorbates on a Si(111) surface

REM and TEM studies of 2D AuCu alloy adsorbates on a Si(111) surface

Direct observation of 'domain like' atomic arrangement of incommensurate 2d Au3+Zn by high-voltage-high-resolution electron microscopy

A domain-like atomic arrangement is observed in the incommensurate 2d Au3+Zn with two-dimensional antiphase structure of Cu3Pd-type by high-resolution structure imaging method using 1000 kV electron microscope. Two types of domains with different structures occur by turns along (100) and (001). Inside the domains atomic arrangements are commensurate and antiphase periods are 6a and 5c, and the relative configuration of the domains produces incommensurate character.

LEED investigations of clean and Au-stabilised Si surfaces

The effect of cleaning procedure on the quality of the Si(111)-7 pattern was investigated for thermally cleaned Si surfaces by measuring the retarding-field plot, the intensities and the spectrum of back-scattered electrons. From these measurements it is deduced that oxygen is built into the surface lattice, but differently than by chemisorption. The formation of a Si-O lattice-bounded phase is proposed and illustrated by means of a model. It is demonstrated by deposition of Au that the conversion of the Si(111)-7 into the Si(111-) 5-Au or Si(111)-6-Au depends on the state of the Si-O lattice-bounded phase. It is also shown that this phase influences the nucleation rate and the shape of 3D Au clusters.