Effect of hydrogenation on the electronic structure of the P/Si(001)-(1×2) surface (original) (raw)

Ab initio study of hydrogen adsorption on the Si(111)-(7X7) surface

Physical review. B, Condensed matter

First-principles total-energy pseudopotential calculations are performed to investigate the adsorption interaction of a H atom with dangling bonds on the Si(111)-(7X7)surface. The binding energies for adsorption of H at the adatom, rest atom, and corner hole sites are calculated to be 2.9, 3.2, and 3.5 eV, respectively. Spectral analysis of the electronic states shows that nonlocal changes of chemical reactivity are induced by charge transfer upon H adsorption. It is found that H adsorption on the adatoms or rest atoms induces a charge transfer onto the Si-H bond and a shift in energy of the remaining dangling-bond states. Adsorption on the corner hole, however, does not involve any charge transfer. The relationship between charge transfer and binding energies is discussed.

Geometrical reconstructions and electronic relaxations of silicon surfaces. I. An electron density topological study of H-covered and clean Si(111)(1×1) surfaces

The Journal of Chemical Physics, 2000

The relaxations of the first three interlayer distances in the H-covered Si͑111͒͑1ϫ1͒ surface were calculated using a fully periodic Hartree-Fock approach and a finely tuned slab model. All computed relaxations fall well within the error bounds of the experiment, provided the relevant geometrical parameters and the basis set of the first layer Si atoms ͑Si1͒ are both optimized. The quantum theory of atoms in molecules is applied on the wave functions of Si bulk and of H-covered or clean Si͑111͒͑1ϫ1͒ slabs so as to shed light on how the electronic perturbation caused by H adsorption and surface formation propagates and dampens through the first Si atoms layers. In the H-covered surface, the large charge transfer from Si1 to H induces a noticeable asymmetry in and strengthening of the surface Si1-Si2 back bonds, whereas in the clean slab the same bonds are found to be weakened compared to the bulk in agreement with the well-known tendency of this system to evolve in favor of other reconstructions. The negatively charged hydrogen layer in the Si͑111͒͑1ϫ1͒-H slab is almost entirely counterbalanced by the first two silicon layers with the Si1 atoms bearing more than 94 percent of the compensating positive charge. The hydrogen and Si1 atoms in the H-covered surface polarize in such a way as to oppose the electric field created by charge transfer into the surface double layer. The effect of H-coverage is to reverse the outwards polarization of Si1 atoms present in the clean system and to enhance its magnitude. Due to the surface electric field, the atomic energies in both slabs are not found to converge towards bulk values even for the atoms of the innermost layers, although the other calculated local and integrated properties exhibit an almost perfect convergence beyond the first two or three atomic layers. In the H-covered slab, the Si1 atoms have their interatomic surface completely isolated from the outside through their interaction with H atoms, while Si2 are found to be the only surface silicon atoms in agreement with the experimental observation that passivant substitution or oxidation are mediated by Si2 and never occur directly at Si1 atoms.

Hydrogen covered Si(111) surfaces

Surface Science, 1992

The recently discovered method for the production of an ideally H-terminated, stable and easdy transferable S~(111)1 × 1 surface renews the interest for this prototypical system. Through a density functional description of the eleetrontc structure based on pseudopotent'al and LMTO mcthod~, we dJ~cu~ m deT~d ~pectro~cop~cal reformation, bond geometry, strechmg trequency and the energetlcs of this surface. Further attent,on is devoted to the chemisorptton of atomic hydrogen on the St(! 11)2 x 1 surface and to the removal of the reconstruction, which leads to a less perfect 1 x 1 surface. 0039-6028/92/$05130

Electronic structure of the Si(001)2 × 1:H surface and pathway for H2 desorption

Surface Science, 1995

Electronic structures for the hydrogen-passivated Si(001)2 X 1 surface are calculated using a first-principles method with planar basis functions constructed from two-dimensional (2D) plane waves and one-dimensional (1D) Gaussian functions. Hydrogen passivation causes the surface bands in the fundamental energy gap of a clean Si(001)2 X 1 surface to move deeply into the Si valence bands. A pathway was found for the desorption of H e molecules from the Si(001)2 x 1 surface in which the activation energy barrier is negligible and the desorption energy is approximately 60 kcal/mol, in agreement with experimental findings. The effect on desorption of the hydrogen-induced relaxation of the dimer bonds between surface Si atoms (from 2.44 to 2.23 A) was found to be quite small.

Electronic properties of then-doped hydrogenated silicon (100) surface and dehydrogenated structures at 5 K

Physical Review B, 2009

We present a comparative study of the electronic properties of the clean Si͑100͒ and the hydrogenated Si͑100͒:H surfaces performed with a low-temperature ͑5 K͒ scanning tunneling microscope. Various surface structures such as single silicon dangling bonds and bare silicon dimers created by local desorption of hydrogen atoms from the Si͑100͒:H surface are also investigated. The experimental scanning tunneling spectroscopy ͑STS͒ curves acquired locally on each of these structures are compared with STS measurements performed on the Si͑100͒ and Si͑100͒:H surfaces. First principle density-functional theory calculations of the projected local density of states, taking into account the influence of the dopant atoms ͑As͒, enable to assign the observed STS spectra.

Surface States of Hydrogen-terminated Si(111) by Metastable Atom Electron Spectroscopy and Angle-resolved Ultraviolet Photoelectron Spectroscopy

Japanese Journal of Applied Physics, 2000

The surface electronic states of hydrogen-terminated Si(111) [H-Si(111)-(1 × 1)] were studied by metastable atom electron spectroscopy (MAES) and angle-resolved ultraviolet photoelectron spectroscopy (ARUPS), coupled with an intensity analysis used for organic systems. The surface states of H-Si(111)-(1 × 1) originated from Si-H bonds were selectively observed by MAES which can excite electrons distributed at the outermost surface. Furthermore, the prominent ARUPS peak with very small dispersion at around 10 eV binding energy from the vacuum level was confirmed to originate from a nondispersive Si-H σ state by quantitative analysis of the photoelectron angular distribution using a simple computation model used for organic thin films.

Electronic structure and its dependence on local order for H/Si(111)-(1×1) surfaces

Physical Review Letters, 1993

The valence and core level spectra of chemically prepared, ideally H-terminated Si(111) surfaces are characterized by remarkably sharp features. The valence band levels and their dispersion are well described by first-principles calculations using a quasiparticle self-energy approach within the GR'approximation. From the Si2~spectra, an upper limit of 35 l0 meV is derived for the core hole lifetime broadening, a value substantially lower than previously measured.

Hydrogenation of Si(113) surfaces by photoelectrochemical treatment

Physical Review B, 1995

Si(113) surfaces have been prepared photoelectrochemically in an aqueous solution of NH4F. Using high-resolution electron-energy-loss spectroscopy and low-energy electron diffraction, it is shown that Si(113)1X 1-H, i.e. , a bulk-truncated and H-terminated Si(113) surface, can be prepared. It is concluded that the truncation plane is such that all SiH bonds lie in the (110)plane. The HSiH (dihydride) groups are located in the surface and the SiH (monohydride) groups in the second layer. Using a number of wet processing steps which include a final etching in the aqueous NH4F solution, atomically smooth, bulk-truncated, and H-terminated Si(111)1X 1-H surfaces can be prepared both, chemically' and electrochemically. ' So far, one has not succeeded in preparing atomically Aat, bulk-truncated, and H-terminated Si(001) surfaces. " ' The Si(113) surface consists of an equal number of threefoldand twofold-coordinated atoms. In comparison to Si(001), the density of twofoldcoordinated atoms is reduced by a factor of approximately two on Si(113). Stable, nonfaceted Si(113) surfaces can

Atomic and electronic structure of the Si(001)2×1–K surface

Surface Science, 2004

The plane-wave pseudopotential density functional theory method has been used to study the Si(0 0 1)2 · 1-K adsorption system for 0.5 and 1.0 monolayer coverage. The minimum energy atomic configuration for 0.5 monolayer coverage was found to correspond to the potassium atom in each 2 · 1 surface unit cell occupying the valley bridge site. A double-layer model was determined to be the optimised geometry of the Si(0 0 1)2 · 1-K chemisorption system for 1.0 monolayer coverage. The geometry of this double-layer model was found to be in good agreement with the current experimental data. A detailed analysis of the electronic structure of this double-layer model has also been performed. The overall dispersion of the occupied and unoccupied surface state bands has been shown to be in excellent agreement with the angle-resolved and inverse photoemission data. The nature and dispersion of the surface states of the doublelayer model in the vicinity of the energy gap provide evidence of strong interactions, both between the two inequivalent potassium atoms in each 2 · 1 surface unit cell, and between these adatoms and the underlying substrate.

Ab initio cluster calculations of the chemisorption of hydrogen on the Si(111)√3 × √3R30°-B surface

Surface Science, 1997

First principles all-electron Hartree-Fock and density functional theory cluster calculations have been performed to investigate the chemisorption of atomic hydrogen on the Si(1 l 1 )'v/3 x ~JR30°-B surface. Both the equilibrium geometries corresponding to n hydrogen atoms (1 _< n _< 5) chemisorbing on the B-S5 and B-T 4 reconstructed structures, and the desorption energies for a silicon or boron adatom bonded to x hydrogen atoms (0 _< x _< 3), have been obtained. As successively more hydrogen is chemisorbed, a silicon or boron adatom is found to move from its original threefold site to an adjacent bridge site, and then to a neighbouring on-top site. It is also found that boron will most likely occupy a subsurface substitutional S 5 site at low hydrogen coverages (_<0.67 ML), but appear as an adatom at an on-top site directly above one of the first-layer silicon atoms for hydrogen exposures higher than 0.67 ML. This boron segregation at high hydrogen exposures prevents the formation of Sill2 and Sill3 complexes and leads to the prediction that only Sill and BH2 will be observed on an Si(111):B hydrogenated surface. It also provides an explanation for the lack of Si surface etching at high hydrogen exposure. All of these results are in good agreement with the available experimental data on hydrogenated B/Si( 111 ) surfaces. © 1997 Elsevier Science B.V.