Temperature-dependent phase evolution of copper-oxide thin-films on Au(111)

Abstract

The formation of ultrathin copper oxide layers on an Au(111) surface is explored with scanning tunneling microscopy and density functional theory. Depending on the thermal treatment of as-grown Cu-O samples, a variety of thin-film morphologies is observed. Whereas 1D oxide stripes with Au[112[combining macron]] and Au[11[combining macron]0] orientation emerge at 450 and 550 K annealing, respectively, a planar (2 × 2) Cu-O network with specific domain structure develops at higher temperature. The latter is ascribed to a CuO honeycomb lattice with oxygen ions alternatingly located in surface and interface positions. Strain minimization and a thermodynamic preference for Cu-rich edges lead to the formation of structurally well-defined boundaries, delimiting either triangular, elongated or stripe-like CuO domains. The low-temperature phases compirse complex arrangements of hexagonal and square Cu-O units, similar to those found in CuO(111) and (100) surfaces, respectively. The transitions between different thin-film phases are driven by Cu dissolution in the gold crystal and O evaporation and therefore accompanied by a thinning of the oxide layer with increasing temperature.

Negative differential conductance in the electron-transport through copper-rich cuprous oxide thin films

“…The oxide film is permeated by dislocation lines, compensating for the misfit strain with the gold support. Depending on thickness and thermal treatment of the Cu 2 O layer, the domain boundaries adopt triangular, zig-zag and straight configurations [23]. The films prepared here are composed of triangular domains with 5 nm edge length.…”

“…Rising the temperature to 700 K finally destroys the oxide film and renders the pristine Au(111) surface visible in the STM. The oxide decomposition is driven by Cu dissolution into the Au support, associated with oxygen desorption from the surface [23]. The peculiar electronic structure of ML Cu islands on Cu 2 O/Au(111) is addressed in the following paragraph.…”

Properties of M2O3/Au(111) Honeycomb Monolayers (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni)

“…The same honeycomb structure has also been found in the copper oxide Cu 3 O 2 ML, which forms on Au(111). 19 We have recently shown that the low dimensionality of freestanding M 2 O 3 monolayers, associated with their peculiar, perfectly flat atomic structure, is responsible for their specific electronic characteristicschange in the degree of covalency and in the gap width, orbital reconstruction, and new spin ordering compared to their bulk counterpartsand that the same is true for MLs of mixed MM′O 3 composition. 20 Since M 2 O 3 monolayers cannot be exfoliated, the question arises as to how the specific properties displayed by freestanding MLs are preserved in an experimentally achievable context, that is, when the MLs are deposited/grown on a substrate.…”

Atomic and electronic structure of an epitaxial Nb2O3 honeycomb monolayer on Au(111)

“…However, this is unlikely to be the case for honeycomb M 2 O 3 structures synthesized on metals due to a stronger oxide/substrate interaction. Simulations of such systems include V 2 O 3 on Pd(111) [22,23], Ti 2 O 3 [5] and FeWO 3 [19] on Pt(111), and M 2 O 3 (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni) [16,23,24] or Cu 3 O 2 [25] on Au(111). The honeycomb structure is a fully coordinated network consisting of hexagonal rings which can be used as a template for the adsorption of metal atoms, and a novel ternary oxide of Ba x Ti 2 O 3 was grown using this method [14].…”