The self-energy of an external moving charged particle near a surface is studied within the fast-... more The self-energy of an external moving charged particle near a surface is studied within the fast-charge approximation. For a reflecting trajectory, a formula for the complex self-energy, valid for an arbitrary dielectric function of the medium and angle of incidence, is first derived by means of a semiclassical analysis in which the imaginary part is obtained from a classical evaluation of the work done by the moving charge. This work is discussed in terms of conservative and dissipative contributions. The formula for the complex self-energy is then recovered from a quantum mechanical formulation in which the passage to the semiclassical limit is readily made. The quantum approach is used later to obtain a semiclassical formula for the complex self-energy when the charged particle penetrates the medium.
Dynamical processes involving charge exchange betwen atoms and solid surfaces are studied within ... more Dynamical processes involving charge exchange betwen atoms and solid surfaces are studied within an Anderson-Newns model. We performed a perturbative treatment of the correlation term starting from a time-dependent Hartree-Fock basis, and calculated the probabilities of the final atomic charge states by using the Green-function formalism for irreversible processes. We analyzed the negative-ion fraction, assuming an Anderson symmetric case, and considering the electronic correlation effects up to a second perturbative order, for two ``extreme'' model systems: the two-level one, and a solid within the wide-band approximation.
Metal-Semiconductor interfaces continue being a challenge both to experimental and theoretical ph... more Metal-Semiconductor interfaces continue being a challenge both to experimental and theoretical physicists. The main problem to be solved remains to be which is the physical mechanism controlling the Schottky barrier formation.
Abstract It is pointed out that the theorem of factorization of the surface Green function, previ... more Abstract It is pointed out that the theorem of factorization of the surface Green function, previously proved for the eigenvalue problem of the Hamiltonian, applies generally for a surface which separates two media. This is illustrated by deriving a surface plasmon dispersion relation for a supposedly homogeneous semi-infinite electron gas.
A free-parameter linear-combination-of-atomic-orbitals method for analysing chemisorption problem... more A free-parameter linear-combination-of-atomic-orbitals method for analysing chemisorption problems is presented. Results for Li chemisorbed on Al(100) and GaAs(110) are presented. Both cases yield similar chemisorption energies, and a charge transfer from Li to the crystal that is never larger than 0.5 electrons. The Schottky-barrier formation for Li on GaAs(110) is also discussed.
Electromagnetic matching at a nonspecular dielectric surface can be described phenomenologically ... more Electromagnetic matching at a nonspecular dielectric surface can be described phenomenologically in terms of a specularity parameter $U$. This paper comments on the solution recently given by Johnson and Rimbey. It is pointed out that this solution is only partly correct. A preliminary discussion of the general form of the complete solution is briefly presented.
ABSTRACT We investigate the neutralization of low energy He+ ions in close collisions with metal ... more ABSTRACT We investigate the neutralization of low energy He+ ions in close collisions with metal surface atoms. In order to describe the neutralization process as completely as possible, we consider Auger neutralization (AN), resonant neutralization (RN) and resonant ionization (RI). Our calculation agrees well with experimental data and shows that in some metals (like Pd) AN is the dominant process, whereas in others (like Al) RN and RI contribute significantly for energies above the threshold for reionization.
The metal-semiconductor interface is analysed by means of a simple method, which includes both th... more The metal-semiconductor interface is analysed by means of a simple method, which includes both the effects of virtual surface states and the many-electron interaction. This model is used to obtain the barrier height phi Bn for the junctions of Si (111) with Al and Na; the results are in good agreement with experimental data. The trend on going from covalent to increasingly ionic semiconductors is also studied for junctions of zincblende (110) compounds for different metals. The results do not show the transition from Barden-like to Schottky-like behaviour displayed by experimental data.
By means of decimation techniques as applied in the renormalization-group method, a new method is... more By means of decimation techniques as applied in the renormalization-group method, a new method is proposed to obtain the effective interactions for two-dimensional Hamiltonians at surfaces. The method has been applied to a simplified model of a transition metal and to Si. For the transition metal we recover well-known results as regards the general properties of the surface density of
... the vector potential associated with the EM field. It has been shown elsewhere9 that the tunn... more ... the vector potential associated with the EM field. It has been shown elsewhere9 that the tunneling cur-rent between two orbitals is directly related to the hop-ping element joining both orbitals. This allows us to express HEM in ...
A self-consistent linear combination of atomic orbitals method is used to calculate the band offs... more A self-consistent linear combination of atomic orbitals method is used to calculate the band offsets for the ideal GaAs/Ge/GaAs-(100) and GaAs/Ge/AlAs-(100) interfaces, both for a few Ge monolayers and for a thick Ge intralayer. This thick limit is deduced using the results for the cation- and anion-terminated ideal GaAs/Ge- and AlAs/Ge-(100) interfaces. Charge transfer and band bending at the interface
A model is set up for the description of the chemisorption of a CO molecule on specifically Ni, P... more A model is set up for the description of the chemisorption of a CO molecule on specifically Ni, Pd and Pt surfaces. This is based on the molecular 2 pi * and 5 sigma levels lying within the metal bands, the former above the Fermi level and the latter well below. Broadening of the former into a virtual bound state which can overlap the Fermi level then leads to a situation in which it is demonstrated that one can obtain strong indirect interactions between CO molecules. The amplitude and the phase of the long-range oscillatory form B cos(2KFr+Q)/r5 for separation r between the CO molecules are thereby estimated. The results of this model are then compared with an analysis made of thermal desorption as a function of coverage for CO on Pt. Immediately the strong scattering situation predicted by the above model is revealed, with a phase shift of between pi /4 and pi /2 and a large amplitude B.
A Kohn-Sham approach is presented for analyzing the many-body properties of LCAO Hamiltonians. Th... more A Kohn-Sham approach is presented for analyzing the many-body properties of LCAO Hamiltonians. The total electronic energy of the system is shown to be a function of the different orbital occupancies. Then an exchange-correlation potential is introduced for each orbital, taking into account extra-atomic and intra-atomic many-body effects. Using this potential, the total energy can be obtained by calculating self-consistently the orbital occupancies, avoiding the use of a local representation as is done in the conventional LDA calculations. The method is applied to the calculation of the chemisorption energy and the charge transfer for the deposition of Na on Al(100), and the interaction of H with the GaAs(110) surface. Hydrogen is shown to passivate GaAs(110) surfaces for a monolayer deposition.
The self-energy of an external moving charged particle near a surface is studied within the fast-... more The self-energy of an external moving charged particle near a surface is studied within the fast-charge approximation. For a reflecting trajectory, a formula for the complex self-energy, valid for an arbitrary dielectric function of the medium and angle of incidence, is first derived by means of a semiclassical analysis in which the imaginary part is obtained from a classical evaluation of the work done by the moving charge. This work is discussed in terms of conservative and dissipative contributions. The formula for the complex self-energy is then recovered from a quantum mechanical formulation in which the passage to the semiclassical limit is readily made. The quantum approach is used later to obtain a semiclassical formula for the complex self-energy when the charged particle penetrates the medium.
Dynamical processes involving charge exchange betwen atoms and solid surfaces are studied within ... more Dynamical processes involving charge exchange betwen atoms and solid surfaces are studied within an Anderson-Newns model. We performed a perturbative treatment of the correlation term starting from a time-dependent Hartree-Fock basis, and calculated the probabilities of the final atomic charge states by using the Green-function formalism for irreversible processes. We analyzed the negative-ion fraction, assuming an Anderson symmetric case, and considering the electronic correlation effects up to a second perturbative order, for two ``extreme'' model systems: the two-level one, and a solid within the wide-band approximation.
Metal-Semiconductor interfaces continue being a challenge both to experimental and theoretical ph... more Metal-Semiconductor interfaces continue being a challenge both to experimental and theoretical physicists. The main problem to be solved remains to be which is the physical mechanism controlling the Schottky barrier formation.
Abstract It is pointed out that the theorem of factorization of the surface Green function, previ... more Abstract It is pointed out that the theorem of factorization of the surface Green function, previously proved for the eigenvalue problem of the Hamiltonian, applies generally for a surface which separates two media. This is illustrated by deriving a surface plasmon dispersion relation for a supposedly homogeneous semi-infinite electron gas.
A free-parameter linear-combination-of-atomic-orbitals method for analysing chemisorption problem... more A free-parameter linear-combination-of-atomic-orbitals method for analysing chemisorption problems is presented. Results for Li chemisorbed on Al(100) and GaAs(110) are presented. Both cases yield similar chemisorption energies, and a charge transfer from Li to the crystal that is never larger than 0.5 electrons. The Schottky-barrier formation for Li on GaAs(110) is also discussed.
Electromagnetic matching at a nonspecular dielectric surface can be described phenomenologically ... more Electromagnetic matching at a nonspecular dielectric surface can be described phenomenologically in terms of a specularity parameter $U$. This paper comments on the solution recently given by Johnson and Rimbey. It is pointed out that this solution is only partly correct. A preliminary discussion of the general form of the complete solution is briefly presented.
ABSTRACT We investigate the neutralization of low energy He+ ions in close collisions with metal ... more ABSTRACT We investigate the neutralization of low energy He+ ions in close collisions with metal surface atoms. In order to describe the neutralization process as completely as possible, we consider Auger neutralization (AN), resonant neutralization (RN) and resonant ionization (RI). Our calculation agrees well with experimental data and shows that in some metals (like Pd) AN is the dominant process, whereas in others (like Al) RN and RI contribute significantly for energies above the threshold for reionization.
The metal-semiconductor interface is analysed by means of a simple method, which includes both th... more The metal-semiconductor interface is analysed by means of a simple method, which includes both the effects of virtual surface states and the many-electron interaction. This model is used to obtain the barrier height phi Bn for the junctions of Si (111) with Al and Na; the results are in good agreement with experimental data. The trend on going from covalent to increasingly ionic semiconductors is also studied for junctions of zincblende (110) compounds for different metals. The results do not show the transition from Barden-like to Schottky-like behaviour displayed by experimental data.
By means of decimation techniques as applied in the renormalization-group method, a new method is... more By means of decimation techniques as applied in the renormalization-group method, a new method is proposed to obtain the effective interactions for two-dimensional Hamiltonians at surfaces. The method has been applied to a simplified model of a transition metal and to Si. For the transition metal we recover well-known results as regards the general properties of the surface density of
... the vector potential associated with the EM field. It has been shown elsewhere9 that the tunn... more ... the vector potential associated with the EM field. It has been shown elsewhere9 that the tunneling cur-rent between two orbitals is directly related to the hop-ping element joining both orbitals. This allows us to express HEM in ...
A self-consistent linear combination of atomic orbitals method is used to calculate the band offs... more A self-consistent linear combination of atomic orbitals method is used to calculate the band offsets for the ideal GaAs/Ge/GaAs-(100) and GaAs/Ge/AlAs-(100) interfaces, both for a few Ge monolayers and for a thick Ge intralayer. This thick limit is deduced using the results for the cation- and anion-terminated ideal GaAs/Ge- and AlAs/Ge-(100) interfaces. Charge transfer and band bending at the interface
A model is set up for the description of the chemisorption of a CO molecule on specifically Ni, P... more A model is set up for the description of the chemisorption of a CO molecule on specifically Ni, Pd and Pt surfaces. This is based on the molecular 2 pi * and 5 sigma levels lying within the metal bands, the former above the Fermi level and the latter well below. Broadening of the former into a virtual bound state which can overlap the Fermi level then leads to a situation in which it is demonstrated that one can obtain strong indirect interactions between CO molecules. The amplitude and the phase of the long-range oscillatory form B cos(2KFr+Q)/r5 for separation r between the CO molecules are thereby estimated. The results of this model are then compared with an analysis made of thermal desorption as a function of coverage for CO on Pt. Immediately the strong scattering situation predicted by the above model is revealed, with a phase shift of between pi /4 and pi /2 and a large amplitude B.
A Kohn-Sham approach is presented for analyzing the many-body properties of LCAO Hamiltonians. Th... more A Kohn-Sham approach is presented for analyzing the many-body properties of LCAO Hamiltonians. The total electronic energy of the system is shown to be a function of the different orbital occupancies. Then an exchange-correlation potential is introduced for each orbital, taking into account extra-atomic and intra-atomic many-body effects. Using this potential, the total energy can be obtained by calculating self-consistently the orbital occupancies, avoiding the use of a local representation as is done in the conventional LDA calculations. The method is applied to the calculation of the chemisorption energy and the charge transfer for the deposition of Na on Al(100), and the interaction of H with the GaAs(110) surface. Hydrogen is shown to passivate GaAs(110) surfaces for a monolayer deposition.
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