Theoretical study of hydrogen adsorption on the GaN(0001) surface

Bermudez, V. M.

doi:10.1016/j.susc.2004.06.209

Cited by 43 publications

(47 citation statements)

References 84 publications

(201 reference statements)

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“…8 The investigations confirmed the earlier results indicating that ammonia may be adsorbed dissociatively, leading to the creation of NH 2 radicals located in a bridge position and H adatom in the "on-top" position. [17][18][19][20] Alternatively, also as reported, ammonia may be adsorbed molecularly in the "'on-top" position. 21 The results concerning the adsorption energy may be understood using the recently formulated theory of the charge transfer at the surface contribution to the adsorption energy.…”

Section: Nh 3 Adsorption At Empty Sitementioning

confidence: 59%

“…12,13 These results were confirmed by the DFT determination of the stable structures of polar and nonpolar GaN(0001) surfaces by Ito et al 14 The reaction of ammonia with a bare and H-covered GaN(0001) surface was investigated by several groups by ab initio modeling. [15][16][17][18][19][20] Fritsch et al simulated several configurations of GaN(0001) surface, showing that ammonia adsorption is dissociative to H and a NH 2 radical and transformation of the GaN(0001) flat surface into a p(2 × 2) vacancy reconstruction. The NH 2 radical was bound to gallium and the H atom to gallium and nitrogen broken bonds.…”

Section: Introductionmentioning

confidence: 99%

“…17,18 However, in these calculations the surface remained flat with both products adsorbed on top of Ga surface atoms. Similarly, the dissociative adsorption of ammonia at a clean GaN(0001) surface, with the NH 2 radical adsorbed in the asymmetric bridge position, was obtained by Bermudez. 18, 19 Kempisty et al modeled the adsorption of ammonia on a highly H-covered GaN(0001) surface showing that ammonia is adsorbed molecularly in a barrierless process with the adsorption energy equal to 2.5 eV. 21 Recently, intensive investigations of ammonia adsorption were conducted by the same authors.…”

Section: Introductionmentioning

confidence: 99%

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Adsorption of ammonia at GaN(0001) surface in the mixed ammonia/hydrogen ambient - a summary of ab initio data

Kempisty

Krukowski

2014

AIP Advances

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Adsorption of ammonia at NH 3 /NH 2 /H covered GaN(0001) surface was analyzed using results of ab initio calculations. The whole configuration space of partially NH 3 /NH 2 /H covered GaN(0001) surface was divided into zones differently pinned Fermi level: at Ga broken bond state for dominantly bare surface (region I), at VBM for NH 2 and H covered (region II), and at CBM for NH 3 covered surface (region III). The extensive ab intio calculations show validity of electron counting rule (ECR) for all mixed coverage, for bordering these three regions. The adsorption was analyzed using newly identified dependence of the adsorption energy on the charge transfer at the surface. For region I and II ammonia adsorb dissociatively, disintegrating into H adatom and HN 2 radical for large fraction of vacant sites while for high coverage the ammonia adsorption is molecular. The dissociative adsorption energy strongly depends on the Fermi level at the surface (pinned) and in the bulk (unpinned) while the molecular adsorption energy is determined by bonding to surface only, in accordance to the recently published theory. The molecular adsorption is determined by the energy of covalent bonding to the surface. Ammonia adsorption in region III (Fermi level pinned at CBM) leads to unstable configuration both molecular and dissociative which is explained by the fact that Ga-broken bond sites are doubly occupied by electrons. The adsorbing ammonia brings 8 electrons to the surface, necessitating transfer of the electrons from Ga-broken bond state to Fermi level, energetically costly process.Adsorption of ammonia at H-covered site leads to creation of NH 2 radical at the surface and escape of H 2 molecule. The process energy is close to 0.12 eV, thus not large, but the inverse process is not possible due to escape of the hydrogen molecule.

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Section: Nh 3 Adsorption At Empty Sitementioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Adsorption of ammonia at GaN(0001) surface in the mixed ammonia/hydrogen ambient - a summary of ab initio data

Kempisty

Krukowski

2014

AIP Advances

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“…The DFT studies of the adsorption of hydrogen on GaN (0001) surface show some discrepancies which may be attributed to different methods used in the calculations [12][13][14]. Elsner et al [12] found that the 0.75 ML H coverage GaN (0001) surface has the lowest, the 0.5 ML coverage slightly higher, while full covered, (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…H-Ga site to site structure) the highest energy. Bermudez [13] calculated the properties of 0.75 H ML (hydrogen monolayer) surface and compared it with the ultraviolet photoemission spectroscopic (UPS) data. He found that the 0.75 H ML structure is not consistent with the UPS data.…”

Section: Introductionmentioning

confidence: 99%

Modelling the growth of nitrides in ammonia‐rich environment

Krukowski¹,

Kempisty

Strąk

et al. 2007

Cryst. Res. Technol.

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Key words gallium nitride, hydrogen vapor phase epitaxy, metal organic vapor phase epitaxy, density functional theory. PACS 61.50.Ah, 81.10.Aj Surface properties and the principal processes at the growth of gallium nitride on GaN (0001) face in ammonia-based are modeled using DFT (density functional theory -SIESTA code) ab initio calculations and 2-d diffusion analysis. The GaN growth methods are: ammonia-source MBE, MOVPE, and also HVPE. The adiabatic trajectories, calculated for hydrogen-rich and hydrogen-free state of the GaN(0001) surface, include the adsorption of NH 3 , GaCl and HCl molecules and the desorption of Ga atoms. The adsorption of ammonia and GaCl has no energy barrier. Thus, in contrast to the results concerning Plasma-Assisted Molecular Beam Epitaxy (PA MBE), proving that the GaN(0001) surface remains in metal-rich state, these results indicate that, in the ammonia-rich environment, typical for HVPE and MOVP growth, the GaN(0001) surface remains in the nitrogen-rich state. In the case of HCl adsorption, the energy barrier depends on the surface coverage, and could reach 2.0 eV. The direct desorption of single Ga atom has the energy barrier, close to 7 eV. This indicates that Ga surface diffusion (growth controlling process) length is very large, leading to strong interaction of the step kinetics and the diffusion on the terraces. This interaction leads to double-step intertwined structures both in the case of dislocation-mediated spiral growth and in the step flow growth mode. These morphologies, proposed by the geometric arguments, are observed in the atomic force microscopy (AFM) scans of the GaN(0001) surface. Additionally we have compared the interaction energy of two hydrogen atoms obtained in the DFT SIESTA and the high precision Gaussian in coupled cluster singles, double and perturbation triples CCSD(T) approximation. Both approaches yielded virtually identical interaction energy confirming the validity of DFT analysis of ammonia-rich growth of GaN.

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Review: GaN growth by ammonia based methods – density functional theory study

Krukowski¹,

Kempisty²,

Strąk³

2009

Cryst. Res. Technol.

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Key words gallium nitride, hydrogen vapor phase epitaxy, metal organic vapor phase epitaxy, density functional theory. PACS 61.50.Ah, 81.10.AjRecent results in Density Functional Theory (DFT) simulations of ammonia-based growth of gallium nitride on GaN (0001) are reviewed. These simulations are important to the following GaN growth methods that use ammonia as active nitrogen source: ammonothermal, MOVPE, HVPE and also ammonia-source MBE. In the simulations of GaN growth, the two main approaches were discussed: (1) equilibrium, based on chemical potentials of the components, and (2) dynamic, based on consideration of atomistic processes on the surface. These two approaches are unified by the kinetic procedure of determination of the chemical potential levels for nitrogen and hydrogen as a function of partial pressure of ammonia. Here the DFT modeling of GaN(0001) surface employing the technique of the simulation of subsurface electric field is described and employed. The results of DFT modeling include the ammonia and molecular hydrogen adsorption on GaN(0001) surface that allows to determine some basic features of ammonia-based growth of GaN. Dedicated to Prof. Wolfgang Neumann on the occasion of his 65th birthday

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Theoretical study of hydrogen adsorption on the GaN(0001) surface

Cited by 43 publications

References 84 publications

Adsorption of ammonia at GaN(0001) surface in the mixed ammonia/hydrogen ambient - a summary of ab initio data

Adsorption of ammonia at GaN(0001) surface in the mixed ammonia/hydrogen ambient - a summary of ab initio data

Modelling the growth of nitrides in ammonia‐rich environment

Review: GaN growth by ammonia based methods – density functional theory study

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