Adsorption of indium on an InAs wetting layer deposited on the GaAs(001) surface

Abstract

In this work we perform a first-principles study of the adsorption properties of an In adatom deposited on 1.75 monolayers (ML) InAs, forming a wetting layer on GaAs(001) with the α 2 (2 × 4) or β 2 (2×4) reconstruction. The structural properties of these reconstructions have been studied: we determine the equilibrium geometry of the surfaces and their stability for various growth conditions.We have then carried out a detailed study of the potential energy surface (PES) for an In adsorbate, finding the minima and the saddle points. The main characteristics of the PES and the bonding configurations of the In adatom on the surface are analyzed by comparing with analogous studies reported in the literature, trying to extract the effects due to: (i) the compressive strain to which the InAs adlayer is subjected, (ii) the particular surface reconstruction, and (iii) the wetting layer composition. We found that, in general, stable adsorption sites are located at: (i) locations besides the As in-dimers, (ii) positions bridging two As in-dimers, (iii) between two adjacent ad-dimers (only in β 2 ), and (iv) locations bridging two As ad-dimers. We find also other shallower adsorption sites which are more reconstruction specific due to the lower symmetry of the α 2 reconstruction compared to the β 2 reconstruction.

In adsorption and diffusion on In-rich (2×4) reconstructed InGaAs surfaces on GaAs(001)

“…In this case the In adatom first bonds to both the As atoms of the dimer, then breaks the dimer bond and inserts itself into it [4,5]. These adsorption sites are characterized by a strong binding energy (even −100 meV with respect to site A 4 ) and high confining barriers ( 800 meV), while the barriers to overcome in order to enter them are comparable to the other barriers in the PES ( 300 meV).…”

“…Other important high-permanence sites are A 2 and A 4 [4]. The occupation time in the dimer-sites is about three orders of magnitude higher than that in the other sites, owing to the higher confining barriers.…”

“…These adsorption sites are characterized by a strong binding energy (even −100 meV with respect to site A 4 ) and high confining barriers ( 800 meV), while the barriers to overcome in order to enter them are comparable to the other barriers in the PES ( 300 meV). Same calculations have been performed for the β 2 (2 × 4) surface reconstruction, with similar considerations [4].…”

“…The approach presented in this paper starts from the first-principles calculation of the PES experienced by an In adatom approaching the surface [4]. The calculation has been carried out using Density Functional Theory, in the local density approximation (DFT-LDA).…”

Machine-learning-based selective sampling procedure for identifying the low-energy region in a potential energy surface: A case study on proton conduction in oxides

“…A PES is generally described as a function of 3n degrees of freedom in an n-atom system, but it is often simplified by focusing only on reduced degrees of freedom that govern the physical property of interest [7][8][9]. In this simplification, the rest of the degrees of freedom are effectively incorporated into the reduced configuration space as the minimized energy or statistical average.…”