LEED I/V determination of the structure of a MoO3 monolayer on Au(111): Testing the performance of the CMA-ES evolutionary strategy algorithm, differential evolution, a genetic algorithm and tensor LEED based structural optimization

Abstract

The structure of a thin MoO 3 layer on Au(111) with a c(4×2) superstructure was studied with LEED I/V analysis. As proposed previously (Quek et al, Surf. Sci. 577 (2005) L71), the atomic structure of the layer is similar to that of a MoO 3 single layer as found in regular α-MoO 3 . The layer on Au(111) has a glide plane parallel to the short unit vector of the c(4×2) unit cell and the molybdenum atoms are bridge-bonded to two surface gold atoms with the structure of the gold surface being slightly distorted. The structural refinement of the structure was performed with the CMA-ES evolutionary strategy algorithm which could reach a Pendry R-factor of ∼0.044. In the second part the performance of CMA-ES is compared with that of the differential evolution method, a genetic algorithm and the Powell optimization algorithm employing I/V curves calculated with tensor LEED.

Graphene and Beyond: Recent Advances in Two-Dimensional Materials Synthesis, Properties, and Devices

“…Molybdenum oxide plays an important role in numerous applications, ranging from catalysis, gas sensors, batteries, nanoelectronics, to future twistronics. , Its high work function is also desirable for flexible organic electronics, such as utilizing a MoO 3 thin film as a hole injection layer (HIL) on graphene-based anodes. , The synthesis of mono- or few-layered MoO 3 films has been achieved by several bottom-up methods. Among them, the most common one is thermal evaporation, either in air , or in UHV, , as well as oxidation of Mo metal films. − Stoichiometric MoO 3 ultrathin film can also be made by carrying out post-growth anneal in an oxygen environment on Mo and MoO 3‑ x films. , Due to the prospective applications of MoO 3‑ x /graphene heterostructures in flexible electronics, the studies of the electronic structure of monolayer (1L) MoO 3‑ x on graphene at the nanoscale in a controlled environment (e.g., ultrahigh vacuum vs air) are essential to understand their versatile properties. Monolayered MoO 3 is defined as a single-layer of octahedrons, which corresponds to half of a unit cell of bulk α-MoO 3 (in b direction) with a thickness of 6.9 Å (Figure a).…”

Growth of well-ordered iron sulfide thin films

“…In order to try to understand the surface structure of the film, fully dynamical LEED intensity calculations were carried out as described in previous work. 56,57 Contrary to XRD, I/V-LEED is a very surface sensitive method and we hoped that it would reveal the atomic structure of the reconstructed surface. Different bulkterminated iron sulfide model structures were used as a starting point for the I/V-LEED structural optimization: iron sulfides with a hexagonal face having a lattice parameter in the range of B7 Å, i.e.…”