Si adatom binding and diffusion on the Si(100) surface: Comparison of ab initio, semiempirical and empirical potential results (original) (raw)
Related papers
Chem Phys, 1995
The binding energies and configurations for single Si adatoms on the Si͑100͒ surface are investigated theoretically. Detailed comparisons between previously published and new calculations using classical potentials, semiempirical formulations, and density functional theory ͑DFT͒ are made. The DFT calculations used both the plane-wave-pseudopotential approach in a periodic slab geometry and the Gaussian-orbital based all-electron approach employing cluster geometries. In the local-density approximation excellent agreement between the cluster and slab results was obtained. Inclusion of gradient corrections to the exchange-correlation energy significantly improves absolute binding energies and changes relative energies by as much as 0.3-0.5 eV depending on the particular exchange-correlation functional used. Binding energies and relative energies obtained using the classical potentials disagree with the gradient corrected DFT energies at about the 0.6-0.9 eV level, and most find qualitatively different local minima from those found in the DFT calculations. The semiempirical approaches give results intermediate in quality between those of the classical potentials and the ab initio calculations. Analysis of the energies and binding site geometries provides insight into the shortcomings of some of the classical potentials.
Large-scale ab initio study of the binding and diffusion of a Ge adatom on the Si(100) surface
Physical review. B, Condensed matter, 1994
We identify the binding sites for adsorption of a single Ge atom on the Si(100}surface using ab initio total-energy calculations. The theoretical diffusion barriers are in excellent agreement with experimental estimates. Using a large supercell we resolve the controversy regarding the binding geometry and migration path for the adatom, and investigate its inhuence on the buckling of Si dimers. We Snd that the adatom induces a buckling defect that is frequently observed using scanning tunneling microscopy, indicating that the study of a single adatom may be experimentally accessible.
Journal of Physical Chemistry C, 2009
When group III metals are deposited onto the Si(100)-2 × 1 reconstructed surface they are observed to selfassemble into chains of atoms that are one atom high by one atom wide. To better understand this onedimensional island growth, ab initio electronic structure calculations on the structures of Al atoms on silicon clusters have been performed. Natural orbital occupation numbers show that these systems display significant diradical character, suggesting that a multireference method is needed. A multiconfiguration self-consistent field (MCSCF) calculation with a 6-31G(d) basis set and effective core potentials was used to optimize geometries. The surface integrated molecular orbital molecular mechanics embedded cluster method was used to take the surface chemistry into account, as well as the structure of an extended surface region. Potential energy surfaces for binding of Al adatoms and Al−Al dimers on the surface were determined, and the former was used to obtain a preliminary assessment of the surface diffusion of adatoms. Hessians were calculated to characterize stationary points, and improved treatment of dynamic electron correlation was accomplished using multireference second order perturbation theory (MRMP2) single-point energy calculations. Results from the MRMP2//MCSCF embedded cluster calculations are compared with those from QM-only cluster calculations, embedded cluster unrestricted density functional theory calculations, and previous Car−Parrinello DFT studies.
The Journal of Physical Chemistry C, 2009
When group III metals are deposited onto the Si(100)-2 × 1 reconstructed surface they are observed to selfassemble into chains of atoms that are one atom high by one atom wide. To better understand this onedimensional island growth, ab initio electronic structure calculations on the structures of Al atoms on silicon clusters have been performed. Natural orbital occupation numbers show that these systems display significant diradical character, suggesting that a multireference method is needed. A multiconfiguration self-consistent field (MCSCF) calculation with a 6-31G(d) basis set and effective core potentials was used to optimize geometries. The surface integrated molecular orbital molecular mechanics embedded cluster method was used to take the surface chemistry into account, as well as the structure of an extended surface region. Potential energy surfaces for binding of Al adatoms and Al−Al dimers on the surface were determined, and the former was used to obtain a preliminary assessment of the surface diffusion of adatoms. Hessians were calculated to characterize stationary points, and improved treatment of dynamic electron correlation was accomplished using multireference second order perturbation theory (MRMP2) single-point energy calculations. Results from the MRMP2//MCSCF embedded cluster calculations are compared with those from QM-only cluster calculations, embedded cluster unrestricted density functional theory calculations, and previous Car−Parrinello DFT studies.
Ab initio total energy study of adsorption and diffusion on the Si(100) surface
Thin Solid Films, 1996
A revkw is given of the pseudopotential total energy method and of its applications to the study of adsorption and diffusion processes of single adatoms on the Si( 100) surface. The subjects covered include the description of the computer code CASTEP/CETEP used for the simulations, results on the equilibrium structure and reconstructions of the clean Si( 100) surface, the potential energy surface for a single Ge adatom c'n the Si( 100) surface, investigation of the possibility of the exchange mechanism for the Ge diffusion on this surface, the influence of the adatom on the buckling of Si dimers, and the structure of the Sa rebonded step.
Binding and diffusion of a Si adatom around the type A step on Si(001) c(4×2)
Applied Physics Letters, 1995
The results of a simulation are described, using a density functional method, of the diffusion of adatoms on a flat Si͑001͒c͑4ϫ2͒ surface and around one type of surface step ͑the S A step͒. These indicate that there is a moderate additional energy barrier ͑0.2Ϯ0.1 eV͒ to cross the S A step as compared to the energy for diffusion on a flat surface. The dimer-top lattice site on the lower terrace adjacent to the step edge is stabilized ͑by 0.15Ϯ0.1 eV͒ with respect to the flat surface result although the most stable binding sites near the step are unaffected. This behavior can be understood based on the disruption of dimer tilt near the step. The results suggest that adatoms are more likely to stop on lattice sites at the S A step edge than on lattice sites on the open surface. This may affect the relative dimer formation rate near the step with respect to the behavior on the flat surface even in the absence of a clear change in binding energy. The effect of the S A step terrace edge on adatom behavior is very short ranged and weak. This is consistent with the relatively small strain field and lack of change in dangling bond density associated with the step edge.
The reconstruction of the Si(110) surface and its interaction with Si adatoms
Physical Review B, 1997
The reconstruction of the Si͑110͒ surface and the chemisorption of the Si atom on this surface are investigated using a tight-binding molecular-dynamics scheme incorporating Green's-function methods. The present method belongs to a more general class of the embedding methods that have the advantage of allowing an efficient embedding of a finite subspace in an infinite or semi-infinite substrate. Our results support the rotational model for surface reconstruction of the nϫ1(nу1) type. The reconstruction of the Si͑110͒ surface was found to be removed, in general, upon chemisorption with Si adatoms and selectively in the presence of surface vacancies. ͓S0163-1829͑97͒05228-4͔ PHYSICAL REVIEW B
Surface Science, 2006
Density functional theory (DFT) calculations have been used to characterize the bonding geometry in Si nanostructures, such as trimers (Si 3 ), tetramers (Si 4 ) and hexamers (Si 6 ) formed on a Si(1 1 1) surface. Trimers and tetramers were simulated by placing three respectively four Si adatoms in high symmetry adsorption sites on the Si(1 1 1) surface. For Si 6 clusters, a combination of these adsorption sites were used. We found that only trimer and tetramer formed by adsorbing Si adatoms in ontop position can be considered as clusters because of bonding interaction among their constituents. For hexamers, bonds are also formed between Si adatoms suggesting their existence as stable entity.
AB Initio Study of the Ge Adsorption and Diffusion on Si (100) Surface
MRS Proceedings, 1993
We identify the binding sites for adsorption of a single Ge atom on the Si(100) surface using ab initio total energy calculations. The calculated diffusion barriers are in excellent agreement with experimental estimates. Using a large supercell we resolve the controversy regarding the binding geometry and migration path for the adatom, and investigate the influence of the adatom on the buckling of Si dimers. The adatom induces a buckling defect that is frequently observed using scanning tunneling microscopy (STM); therefore the study of single adatoms may be experimentally accessible.