Cem Kaderoglu - Academia.edu (original) (raw)
Papers by Cem Kaderoglu
Surface Science, 2009
Ab initio calculations, based on pseudopotentials and density functional theory (DFT), have been ... more Ab initio calculations, based on pseudopotentials and density functional theory (DFT), have been performed to investigate the effect of hydrogenation on the electronic properties of P/Si(0 0 1)-(1 Â 2) surface. In parallel with this, the electronic band structure of the hydrogenated and non-hydrogenated P/Si(0 0 1)-(1 Â 2) surface have been calculated for half-and full-monolayer P. For the mixed SiP dimer structure, we have identified two occupied and one unoccupied surface state, which correspond to 0.5 ML coverage of P. When this surface is terminated with H, we see that two occupied states completely disappeared and that one unoccupied state is shifted towards the conduction band. A similar calculations for the 1 ML coverage of P have been also carried out. It is seen that the unoccupied state C 1 appeared in the P/Si(0 0 1)-(1 Â 2) surface is passivated when this surface is terminated with the H atoms. To explain the nature of the surface states, we have also plotted the total and partial charge densities at the K point of the Surface Brillouin Zone (SBZ).
Surface Science, 2008
The atomic and electronic properties of the adsorption of furan (C 4 H 4 O) molecule on the Si(1 ... more The atomic and electronic properties of the adsorption of furan (C 4 H 4 O) molecule on the Si(1 0 0)-(2 Â 2) surface have been studied using ab initio calculations based on pseudopotential and density functional theory. We have considered two possible chemisorption mechanisms: (i) [4 + 2] and (ii) [2 + 2] cycloaddition reactions. We have found that the [4 + 2] interaction mechanism was energetically more favorable than the [2 + 2] mechanism, by about 0.2 eV/molecule. The average angle between the C@C double bond and Si(1 0 0) surface normal was found to be 22°, which is somewhat smaller than the experimental value of 28°, but somewhat bigger than other theoretical value of 19°. The electronic band structure, chemical bonds, and theoretical scanning tunneling microscopy images have also been calculated. We have determined a total of six surface states (one unoccupied and five occupied) in the fundamental band gap. Our results are seen to be in good agreement with the recent near edge X-ray absorption fine structure and high resolution photoemission spectroscopy data.
The European Physical Journal Applied Physics, 2011
ABSTRACT The atomic and electronic properties of the substitutional phosphorus (P) on the Si(1 1 ... more ABSTRACT The atomic and electronic properties of the substitutional phosphorus (P) on the Si(1 1 1)-(2 × 1) surface have been studied by using the ab initio density functional theory (DFT) based on pseudopotential approach. We have considered four different possible binding sites for P adatom in the π-bonded chain labeled sites 1-4 respectively in Figure 1. We have found that the site 1 position in the π-bonded chain was energetically more favorable than the other binding sites, by about 0.1 eV/adatom. We have also calculated the corresponding surface electronic band structure and found one surface state, labeled C, in the fundamental band gap of Si(1 1 1)-(2 × 1) surface. Our calculations show that the P/Si(1 1 1)-(2 × 1) surface has a metallic character in the nature. In order to explain the nature of this surface state in the bonding geometry, we have depicted the total and partial charge density contours plots at the point of the surface Brillouin zone (SBZ).
The European Physical Journal B, 2010
The atomic and electronic properties of the adsorption of tert-butanol [(CH3)3OH] molecule on the... more The atomic and electronic properties of the adsorption of tert-butanol [(CH3)3OH] molecule on the Si(001)-(2 × 1) surface have been studied by using the ab-initio density functional theory (DFT) based on pseudopotential approach. We have found that tert-butanol bonded the Si(001) surface by oxygen atom, cleaving a O-H bond and producing a Si-H bond and tert-butoxy surface species. We have also investigated the influence of chemisorption of tert-butanol on the electronic structure of the clean Si(001)-(2×1) surface. Two occupied surface states situated entirely below the bulk valence band maximum have been identified, which means that the clean Si(001)-(2 × 1)surface was passivated by the chemisorption of tert-butanol. In order to explain the nature of the surface components we have also plotted the total and partial charge densities at theK point of the surface Brillouin zone (SBZ).
Surface Science, 2012
The chemisorption of the allylamine molecule, which contains two functional groups (ethenyl and h... more The chemisorption of the allylamine molecule, which contains two functional groups (ethenyl and hydroxyl), on a Si(001) − (2 × 1) surface was studied using density functional theory (ab-initio DFT) based on the pseudopotential approach. In particular, we focused on the determination of the most stable position of the C_C double bond in the ethenyl group and observation of the passivation effect of allylamine on the electronic structure of the clean Si(001) − (2 × 1) phase. For this purpose, all of the possible interaction mechanisms occurring at the interface were considered: (i) dissociative bonding where the C_C bond is parallel to the silicon surface, (ii) dissociative bonding where the C_C bond is perpendicular to the silicon surface, and (iii) the [2 + 2] C_C cycloaddition reaction. From our total energy calculations, it was found that the bifunctional allylamine molecule attached to the Si(001) − (2 × 1) surface through the amino functional group, by breaking the N-H bond and forming a Si-H bond and Si-NHCH2CHCH2 surface fragments. During this process, the ethenyl functional group remains intact, and so can be potentially used as an extra reactive site for additional chemical interactions. In addition to these findings, the nudged elastic band method (NEB) calculations related with the reaction paths showed that the parallel position of the C_C bond with respect to the surface of the substrate is more favorable. In order to see the influence of the chemisorbed allylamine molecule on the surface states of the clean Si(001)-(2 × 1), we also plotted the density of states (DOS), in which it is seen that the clean Si(001)-(2 × 1) surface was passivated by the adsorption of allylamine.
Surface Science, 2009
Ab initio calculations, based on pseudopotentials and density functional theory (DFT), have been ... more Ab initio calculations, based on pseudopotentials and density functional theory (DFT), have been performed to investigate the effect of hydrogenation on the electronic properties of P/Si(0 0 1)-(1 Â 2) surface. In parallel with this, the electronic band structure of the hydrogenated and non-hydrogenated P/Si(0 0 1)-(1 Â 2) surface have been calculated for half-and full-monolayer P. For the mixed SiP dimer structure, we have identified two occupied and one unoccupied surface state, which correspond to 0.5 ML coverage of P. When this surface is terminated with H, we see that two occupied states completely disappeared and that one unoccupied state is shifted towards the conduction band. A similar calculations for the 1 ML coverage of P have been also carried out. It is seen that the unoccupied state C 1 appeared in the P/Si(0 0 1)-(1 Â 2) surface is passivated when this surface is terminated with the H atoms. To explain the nature of the surface states, we have also plotted the total and partial charge densities at the K point of the Surface Brillouin Zone (SBZ).
Surface Science, 2008
The atomic and electronic properties of the adsorption of furan (C 4 H 4 O) molecule on the Si(1 ... more The atomic and electronic properties of the adsorption of furan (C 4 H 4 O) molecule on the Si(1 0 0)-(2 Â 2) surface have been studied using ab initio calculations based on pseudopotential and density functional theory. We have considered two possible chemisorption mechanisms: (i) [4 + 2] and (ii) [2 + 2] cycloaddition reactions. We have found that the [4 + 2] interaction mechanism was energetically more favorable than the [2 + 2] mechanism, by about 0.2 eV/molecule. The average angle between the C@C double bond and Si(1 0 0) surface normal was found to be 22°, which is somewhat smaller than the experimental value of 28°, but somewhat bigger than other theoretical value of 19°. The electronic band structure, chemical bonds, and theoretical scanning tunneling microscopy images have also been calculated. We have determined a total of six surface states (one unoccupied and five occupied) in the fundamental band gap. Our results are seen to be in good agreement with the recent near edge X-ray absorption fine structure and high resolution photoemission spectroscopy data.
The European Physical Journal Applied Physics, 2011
ABSTRACT The atomic and electronic properties of the substitutional phosphorus (P) on the Si(1 1 ... more ABSTRACT The atomic and electronic properties of the substitutional phosphorus (P) on the Si(1 1 1)-(2 × 1) surface have been studied by using the ab initio density functional theory (DFT) based on pseudopotential approach. We have considered four different possible binding sites for P adatom in the π-bonded chain labeled sites 1-4 respectively in Figure 1. We have found that the site 1 position in the π-bonded chain was energetically more favorable than the other binding sites, by about 0.1 eV/adatom. We have also calculated the corresponding surface electronic band structure and found one surface state, labeled C, in the fundamental band gap of Si(1 1 1)-(2 × 1) surface. Our calculations show that the P/Si(1 1 1)-(2 × 1) surface has a metallic character in the nature. In order to explain the nature of this surface state in the bonding geometry, we have depicted the total and partial charge density contours plots at the point of the surface Brillouin zone (SBZ).
The European Physical Journal B, 2010
The atomic and electronic properties of the adsorption of tert-butanol [(CH3)3OH] molecule on the... more The atomic and electronic properties of the adsorption of tert-butanol [(CH3)3OH] molecule on the Si(001)-(2 × 1) surface have been studied by using the ab-initio density functional theory (DFT) based on pseudopotential approach. We have found that tert-butanol bonded the Si(001) surface by oxygen atom, cleaving a O-H bond and producing a Si-H bond and tert-butoxy surface species. We have also investigated the influence of chemisorption of tert-butanol on the electronic structure of the clean Si(001)-(2×1) surface. Two occupied surface states situated entirely below the bulk valence band maximum have been identified, which means that the clean Si(001)-(2 × 1)surface was passivated by the chemisorption of tert-butanol. In order to explain the nature of the surface components we have also plotted the total and partial charge densities at theK point of the surface Brillouin zone (SBZ).
Surface Science, 2012
The chemisorption of the allylamine molecule, which contains two functional groups (ethenyl and h... more The chemisorption of the allylamine molecule, which contains two functional groups (ethenyl and hydroxyl), on a Si(001) − (2 × 1) surface was studied using density functional theory (ab-initio DFT) based on the pseudopotential approach. In particular, we focused on the determination of the most stable position of the C_C double bond in the ethenyl group and observation of the passivation effect of allylamine on the electronic structure of the clean Si(001) − (2 × 1) phase. For this purpose, all of the possible interaction mechanisms occurring at the interface were considered: (i) dissociative bonding where the C_C bond is parallel to the silicon surface, (ii) dissociative bonding where the C_C bond is perpendicular to the silicon surface, and (iii) the [2 + 2] C_C cycloaddition reaction. From our total energy calculations, it was found that the bifunctional allylamine molecule attached to the Si(001) − (2 × 1) surface through the amino functional group, by breaking the N-H bond and forming a Si-H bond and Si-NHCH2CHCH2 surface fragments. During this process, the ethenyl functional group remains intact, and so can be potentially used as an extra reactive site for additional chemical interactions. In addition to these findings, the nudged elastic band method (NEB) calculations related with the reaction paths showed that the parallel position of the C_C bond with respect to the surface of the substrate is more favorable. In order to see the influence of the chemisorbed allylamine molecule on the surface states of the clean Si(001)-(2 × 1), we also plotted the density of states (DOS), in which it is seen that the clean Si(001)-(2 × 1) surface was passivated by the adsorption of allylamine.