Han Woong Yeom

Yonsei University

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Han Woong Yeom has a total of 102 co-authors. Here are the top co-authors by number of shared publications:

J. R. Ahn
Center for Atomic Wires and Layers and Institute of Physics and Applied Physics, Yonsei University, Seoul 120-746, Korea
8 shared publications
J. W. Kim
Institute of Physics and Applied Physics and Center for Atomic Wires and Layers, Yonsei University, Seoul, 120-749, Korea
7 shared publications
H. Koh
Center for Atomic Wires and Layers, Yonsei University, Seoul 120-749, Korea
6 shared publications
Y. K. Kim
Institute of Physics and Applied Physics and Center for Atomic Wires and Layers, Yonsei University, Seoul 120-749, Korea
6 shared publications
H. S. Lee
Institute of Physics and Applied Physics and Center for Atomic Wires and Layers, Yonsei University, Seoul, 120-749, Korea
5 shared publications
W. H. Choi
Institute of Physics and Applied Physics and Center for Atomic Wires and Layers, Yonsei University, Seoul 120-746, Korea
5 shared publications

Latest Publications

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Cited by 3
- 4 March 2008
- Published by AIP Publishing in The Journal of Chemical Physics
Unidirectional Pt silicide nanowires grown on vicinal Si(100)
by Do Kyung Lim, Sung-Soo Bae, Junghun Choi, Dohyun Lee, Da Eun Sung, Sehun Kim, J. K. Kim, H. W. Yeom, Hangil Lee
We investigated the structure and electronic properties of unidirectional ${Pt}_{2} Si$ nanowires (NWs) grown on a Si(100)-2° off surface. We found that ${Pt}_{2} Si$ NWs were formed along the step edges of the Si(100)-2° off surface with $c (4 \times 6)$ reconstructions that occurred on the terraces of Si(100) using scanning tunneling microscopy and the structure of formed NWs was found to be ${Pt}_{2} Si$ by core-level photoemission spectroscopy. Moreover, we confirmed that the electronic band structures of the NWs along the NW direction are different from those perpendicular to the NWs and the surface state induced by the ${Pt}_{2} Si$ NWs was observed with a small density of state using the angle-resolved photoemission spectra.
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- 4 March 2008
- Published by AIP Publishing in The Journal of Chemical Physics
Unidirectional Pt silicide nanowires grown on vicinal Si(100)
by Do Kyung Lim, Sung-Soo Bae, Junghun Choi, Dohyun Lee, Da Eun Sung, Sehun Kim, J. K. Kim, H. W. Yeom, Hangil Lee
We investigated the structure and electronic properties of unidirectional ${Pt}_{2} Si$ nanowires (NWs) grown on a Si(100)-2° off surface. We found that ${Pt}_{2} Si$ NWs were formed along the step edges of the Si(100)-2° off surface with $c (4 \times 6)$ reconstructions that occurred on the terraces of Si(100) using scanning tunneling microscopy and the structure of formed NWs was found to be ${Pt}_{2} Si$ by core-level photoemission spectroscopy. Moreover, we confirmed that the electronic band structures of the NWs along the NW direction are different from those perpendicular to the NWs and the surface state induced by the ${Pt}_{2} Si$ NWs was observed with a small density of state using the angle-resolved photoemission spectra.
Cited by 3
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Cited by 22
- 18 January 2007
- Published by American Physical Society (APS) in Physical Review B
Absence of dynamic fluctuation in metallic In chains on Si(111): Core-level and valence-band photoemission study
by J. R. Ahn, J. H. Byun, J. K. Kim, H. W. Yeom
We have studied in detail the evolution of the metal-insulator transition with temperature for the $(4 \times 1) − In$ chain structure on Si(111) using core-level and valence-band photoemission spectroscopy. Photoemission spectra unambiguously reveal that the high- and low-temperature phases are distinct with well-separated and characteristic spectral features. No sign of extra broadening or change of the spectral features was observed above the well-defined critical temperature. This result clearly rules out the existence of any dynamic fluctuation for the high-temperature metallic phase in contradiction with a recent theory [Phys. Rev. Lett. 96, 136101 (2006)].
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- 18 January 2007
- Published by American Physical Society (APS) in Physical Review B
Absence of dynamic fluctuation in metallic In chains on Si(111): Core-level and valence-band photoemission study
by J. R. Ahn, J. H. Byun, J. K. Kim, H. W. Yeom
We have studied in detail the evolution of the metal-insulator transition with temperature for the $(4 \times 1) − In$ chain structure on Si(111) using core-level and valence-band photoemission spectroscopy. Photoemission spectra unambiguously reveal that the high- and low-temperature phases are distinct with well-separated and characteristic spectral features. No sign of extra broadening or change of the spectral features was observed above the well-defined critical temperature. This result clearly rules out the existence of any dynamic fluctuation for the high-temperature metallic phase in contradiction with a recent theory [Phys. Rev. Lett. 96, 136101 (2006)].
Cited by 22
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Cited by 17
- 22 March 2006
- Published by American Physical Society (APS) in Physical Review B
Temperature-dependent adsorption and dissociation behaviors of $N H_{3}$ on $Si (111) 7 \times 7$ : A high-resolution core-level photoemission study
by I. K. Cho, Y. K. Kim, H. W. Yeom
Adsorption of $N H_{3}$ on the $Si (111) 7 \times 7$ surface below room temperature has been investigated by high-resolution core-level photoemission. The N $1 s$ spectra reveal intriguing details of temperature-dependent adsorption and dissociation behaviors by clearly resolving out $N H_{3}$ , $N H_{2}$ , and NH species. The initial adsorption occurs through the dissociation into not only $N H_{2}$ but also NH with a substantial fraction even down to $70 K$ , which is in clear contrast with that on $Si (001) 2 \times 1$ . The saturation of this initial adsorption is shown to be related to the depletion of restatom sites from the Si $2 p$ spectra. In addition to the initial dissociation, $N H_{3}$ molecular adsorption occurs below $120 K$ . At that low temperature, the total coverage of the dissociated species increases substantially, well beyond the saturation coverage above $120 K$ , as the coverage of the molecular adsorbates increases. From these results, it is concluded that the adsorption of $N H_{3}$ on $Si (111) 7 \times 7$ proceeds through two largely different processes; (i) an initial active dissociation into both $N H_{2}$ and NH involving Si restatoms and (ii) a low-temperature high-coverage dissociation involving an $N H_{3}$ precursor state.
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- 22 March 2006
- Published by American Physical Society (APS) in Physical Review B
Temperature-dependent adsorption and dissociation behaviors of $N H_{3}$ on $Si (111) 7 \times 7$ : A high-resolution core-level photoemission study
by I. K. Cho, Y. K. Kim, H. W. Yeom
Adsorption of $N H_{3}$ on the $Si (111) 7 \times 7$ surface below room temperature has been investigated by high-resolution core-level photoemission. The N $1 s$ spectra reveal intriguing details of temperature-dependent adsorption and dissociation behaviors by clearly resolving out $N H_{3}$ , $N H_{2}$ , and NH species. The initial adsorption occurs through the dissociation into not only $N H_{2}$ but also NH with a substantial fraction even down to $70 K$ , which is in clear contrast with that on $Si (001) 2 \times 1$ . The saturation of this initial adsorption is shown to be related to the depletion of restatom sites from the Si $2 p$ spectra. In addition to the initial dissociation, $N H_{3}$ molecular adsorption occurs below $120 K$ . At that low temperature, the total coverage of the dissociated species increases substantially, well beyond the saturation coverage above $120 K$ , as the coverage of the molecular adsorbates increases. From these results, it is concluded that the adsorption of $N H_{3}$ on $Si (111) 7 \times 7$ proceeds through two largely different processes; (i) an initial active dissociation into both $N H_{2}$ and NH involving Si restatoms and (ii) a low-temperature high-coverage dissociation involving an $N H_{3}$ precursor state.
Cited by 17
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Cited by 4
- 2 February 2006
- Published by American Physical Society (APS) in Physical Review B
Long-period surface structure stabilized by Fermi surface nesting:Cu(001)−(20×20)R26.6°−In
by T. Nakagawa, H. W. Yeom, E. Rotenberg, B. Krenzer, S. D. Kevan, H. Okuyama, M. Nishijima, T. Aruga
We have studied the atomic and electronic structure of the $Cu (001) − (\sqrt{20} \times \sqrt{20}) R 26.6 ° − In$ surface, which undergoes a reversible transition to a $p (2 \times 2)$ phase at high temperature. Low temperature scanning-tunneling microscopy indicates a $p (2 \times 2)$ structure modulated at the $(\sqrt{20} \times \sqrt{20})$ periodicity. Angle-resolved photoelectron spectroscopy shows a surface resonance exhibiting gap opening and backfolding along a $(\sqrt{20} \times \sqrt{20})$ zone boundary. We suggest that the $(\sqrt{20} \times \sqrt{20})$ structure is stabilized due to the Fermi surface nesting accompanying a surface charge density wave.
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- 2 February 2006
- Published by American Physical Society (APS) in Physical Review B
Long-period surface structure stabilized by Fermi surface nesting:Cu(001)−(20×20)R26.6°−In
by T. Nakagawa, H. W. Yeom, E. Rotenberg, B. Krenzer, S. D. Kevan, H. Okuyama, M. Nishijima, T. Aruga
We have studied the atomic and electronic structure of the $Cu (001) − (\sqrt{20} \times \sqrt{20}) R 26.6 ° − In$ surface, which undergoes a reversible transition to a $p (2 \times 2)$ phase at high temperature. Low temperature scanning-tunneling microscopy indicates a $p (2 \times 2)$ structure modulated at the $(\sqrt{20} \times \sqrt{20})$ periodicity. Angle-resolved photoelectron spectroscopy shows a surface resonance exhibiting gap opening and backfolding along a $(\sqrt{20} \times \sqrt{20})$ zone boundary. We suggest that the $(\sqrt{20} \times \sqrt{20})$ structure is stabilized due to the Fermi surface nesting accompanying a surface charge density wave.
Cited by 4
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Cited by 60
- 11 November 2005
- Published by American Physical Society (APS) in Physical Review Letters
Robust One-Dimensional Metallic Band Structure of Silicide Nanowires
by H. W. Yeom, Y. K. Kim, E. Y. Lee, K.-D. Ryang, P. G. Kang
Angle-resolved photoemission (ARP) is employed to investigate the electronic structure of an extremely anisotropic form of nanocrystals— ${GdSi}_{2 - x}$ nanowires on Si(100). Using a stepped Si(100) surface, a well-ordered and uniformly oriented array of nanowires is formed along the step edges as confirmed by diffraction and microscopy. The ARP measurement discloses two distinct electronic bands near the Fermi level, which disperse one dimensionally along the nanowires. These bands are metallic with the electron filling of $1 / 4$ and $2 / 5$ , respectively, and with the effective mass close to that of a free electron along the wires. The metallicity is robust down to 20 K, in contrast to metallic surface atomic chain systems, paving a way to further studies on one-dimensional physics of metallic nanowires.
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- 11 November 2005
- Published by American Physical Society (APS) in Physical Review Letters
Robust One-Dimensional Metallic Band Structure of Silicide Nanowires
by H. W. Yeom, Y. K. Kim, E. Y. Lee, K.-D. Ryang, P. G. Kang
Angle-resolved photoemission (ARP) is employed to investigate the electronic structure of an extremely anisotropic form of nanocrystals— ${GdSi}_{2 - x}$ nanowires on Si(100). Using a stepped Si(100) surface, a well-ordered and uniformly oriented array of nanowires is formed along the step edges as confirmed by diffraction and microscopy. The ARP measurement discloses two distinct electronic bands near the Fermi level, which disperse one dimensionally along the nanowires. These bands are metallic with the electron filling of $1 / 4$ and $2 / 5$ , respectively, and with the effective mass close to that of a free electron along the wires. The metallicity is robust down to 20 K, in contrast to metallic surface atomic chain systems, paving a way to further studies on one-dimensional physics of metallic nanowires.
Cited by 60
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Cited by 160
- 31 October 2005
- Published by American Physical Society (APS) in Physical Review Letters
Coexistence of Two Different Peierls Distortions within an Atomic Scale Wire: Si(553)-Au
by J. R. Ahn, P. G. Kang, K. D. Ryang, H. W. Yeom
The ground state property of a Au-induced atomic wire array on a stepped Si(553) surface with interesting 1D metallic bands was investigated. Electron diffraction and scanning tunneling microscopy reveal an intriguing coexistence of triple- and double-period lattice distortions at low temperature. Angle-resolved photoemission observes both the nearly $1 / 3$ - and $1 / 2$ -filled bands to gradually open energy gaps upon cooling. We explain these unusual findings as due to the occurrence of Peierls distortions of triple and double periods on the two different atomic-scale chain elements, respectively, within a single unit wire. The two Peierls distortions are suggested to have different transition temperatures and little lateral correlation between each other.
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- 31 October 2005
- Published by American Physical Society (APS) in Physical Review Letters
Coexistence of Two Different Peierls Distortions within an Atomic Scale Wire: Si(553)-Au
by J. R. Ahn, P. G. Kang, K. D. Ryang, H. W. Yeom
The ground state property of a Au-induced atomic wire array on a stepped Si(553) surface with interesting 1D metallic bands was investigated. Electron diffraction and scanning tunneling microscopy reveal an intriguing coexistence of triple- and double-period lattice distortions at low temperature. Angle-resolved photoemission observes both the nearly $1 / 3$ - and $1 / 2$ -filled bands to gradually open energy gaps upon cooling. We explain these unusual findings as due to the occurrence of Peierls distortions of triple and double periods on the two different atomic-scale chain elements, respectively, within a single unit wire. The two Peierls distortions are suggested to have different transition temperatures and little lateral correlation between each other.
Cited by 160
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Cited by 25
- 15 September 2005
- Published by American Physical Society (APS) in Physical Review B
Electronic states of two-dimensional adatom gas and nanocluster array: Na on $Si (111) 7 \times 7$
by J. R. Ahn, K. Yoo, J. T. Seo, J. H. Byun, H. W. Yeom
Electronic structure evolution of Na adsorbates on $Si (111) 7 \times 7$ has been investigated by angle-resolved photoemission spectroscopy, which was recently reported to transit from a two-dimensional adatom gas state to a nanocluster array as Na coverage increases [Wu et al., Phys. Rev. Lett. 91, 126101 (2003)]. The distinct electronic states being characteristic to the adatom gas and the nanoclusters are clearly resolved. Both phases are semiconducting and the nanocluster-induced state has a higher binding energy than that due to the mobile adatoms. The adatom-induced state shifts systematically to a higher binding energy as the density of the adatoms increases in the gas phase. This is apparently incompatible with the localized bond formation between an adatom and Si atom(s). The effective delocalization of the bond charge through the dynamic motion of adatoms is proposed.
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- 15 September 2005
- Published by American Physical Society (APS) in Physical Review B
Electronic states of two-dimensional adatom gas and nanocluster array: Na on $Si (111) 7 \times 7$
by J. R. Ahn, K. Yoo, J. T. Seo, J. H. Byun, H. W. Yeom
Electronic structure evolution of Na adsorbates on $Si (111) 7 \times 7$ has been investigated by angle-resolved photoemission spectroscopy, which was recently reported to transit from a two-dimensional adatom gas state to a nanocluster array as Na coverage increases [Wu et al., Phys. Rev. Lett. 91, 126101 (2003)]. The distinct electronic states being characteristic to the adatom gas and the nanoclusters are clearly resolved. Both phases are semiconducting and the nanocluster-induced state has a higher binding energy than that due to the mobile adatoms. The adatom-induced state shifts systematically to a higher binding energy as the density of the adatoms increases in the gas phase. This is apparently incompatible with the localized bond formation between an adatom and Si atom(s). The effective delocalization of the bond charge through the dynamic motion of adatoms is proposed.
Cited by 25
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Cited by 50
- 13 July 2005
- Published by American Physical Society (APS) in Physical Review B
Real-space investigation of the metal-insulator transition of $Si (557) − Au$
by H. W. Yeom, J. R. Ahn, H. S. Yoon, I.-W. Lyo, Hojin Jeong, Sukmin Jeong
The Si(557) surface with Au adsorbates consists of a well ordered array of atomic chains, which exhibit interesting one-dimensional (1D) metallic band structure with two nearly half-filled 1D bands. This system was recently found to undergo a metal-insulator transition below room temperature [Phys. Rev. Lett. 91, 196403 (2003)]. The structural and electronic changes upon the phase transition have been investigated in detail using scanning tunneling microscopy and spectroscopy (STM/STS) with the guide of first-principles calculations. While the detailed bias-dependent STM images at room temperature are well simulated based on the present structure model, the characteristics of low-temperature images are not successfully reproduced. This casts doubts on the structure model of the low-temperature phase based on the step-edge buckling. The spatially resolved density of states (DOS) in STS measurements indicates clearly that only the step-edge Si chains are metallic, which exhibit strong reductions of DOS near Fermi level upon the metal-insulator transition together with the periodic lattice distortion. The band-gap opening on this metallic chain is shown to be symmetric in filled and empty states with a consistent gap size with the previous photoemission result. This result denies the recently proposed mechanism of the phase transition based on the dynamic fluctuation of the step-edge buckling. The effect of vacancy defects on the local lattice structures is also discussed for both the room- and low-temperature phases.
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- 13 July 2005
- Published by American Physical Society (APS) in Physical Review B
Real-space investigation of the metal-insulator transition of $Si (557) − Au$
by H. W. Yeom, J. R. Ahn, H. S. Yoon, I.-W. Lyo, Hojin Jeong, Sukmin Jeong
The Si(557) surface with Au adsorbates consists of a well ordered array of atomic chains, which exhibit interesting one-dimensional (1D) metallic band structure with two nearly half-filled 1D bands. This system was recently found to undergo a metal-insulator transition below room temperature [Phys. Rev. Lett. 91, 196403 (2003)]. The structural and electronic changes upon the phase transition have been investigated in detail using scanning tunneling microscopy and spectroscopy (STM/STS) with the guide of first-principles calculations. While the detailed bias-dependent STM images at room temperature are well simulated based on the present structure model, the characteristics of low-temperature images are not successfully reproduced. This casts doubts on the structure model of the low-temperature phase based on the step-edge buckling. The spatially resolved density of states (DOS) in STS measurements indicates clearly that only the step-edge Si chains are metallic, which exhibit strong reductions of DOS near Fermi level upon the metal-insulator transition together with the periodic lattice distortion. The band-gap opening on this metallic chain is shown to be symmetric in filled and empty states with a consistent gap size with the previous photoemission result. This result denies the recently proposed mechanism of the phase transition based on the dynamic fluctuation of the step-edge buckling. The effect of vacancy defects on the local lattice structures is also discussed for both the room- and low-temperature phases.
Cited by 50
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Cited by 34
- 17 March 2005
- Published by American Physical Society (APS) in Physical Review B
Coverage-dependent adsorption behavior of benzene on Si(100): A high-resolution photoemission study
by Y. K. Kim, M. H. Lee, H. W. Yeom
The adsorption of benzene molecules on Si(100) is investigated by high-resolution core-level photoelectron spectroscopy using synchrotron radiation as well as ultraviolet photoelectron spectroscopy (UPS) for valence bands. The C $1 s$ photoelectron spectra of benzene adsorbates are found to consist of two different components, which represent carbon atoms with or without a direct $Si - C$ bond. The population ratio of these two components exhibits a drastic change upon increasing the molecular coverage. This is explained by the coverage-dependent change of the adsorbate structure, which is corroborated by the noticeable variation of the molecular orbitals in the valence bands as observed by UPS. From these results, it is deduced that the population of the di- $σ$ structure increases significantly at a high coverage over the tetra- $σ$ structure which is energetically favored at a low coverage. This indicates the importance of the interaction between the adsorbate molecules at a high coverage.
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- 17 March 2005
- Published by American Physical Society (APS) in Physical Review B
Coverage-dependent adsorption behavior of benzene on Si(100): A high-resolution photoemission study
by Y. K. Kim, M. H. Lee, H. W. Yeom
The adsorption of benzene molecules on Si(100) is investigated by high-resolution core-level photoelectron spectroscopy using synchrotron radiation as well as ultraviolet photoelectron spectroscopy (UPS) for valence bands. The C $1 s$ photoelectron spectra of benzene adsorbates are found to consist of two different components, which represent carbon atoms with or without a direct $Si - C$ bond. The population ratio of these two components exhibits a drastic change upon increasing the molecular coverage. This is explained by the coverage-dependent change of the adsorbate structure, which is corroborated by the noticeable variation of the molecular orbitals in the valence bands as observed by UPS. From these results, it is deduced that the population of the di- $σ$ structure increases significantly at a high coverage over the tetra- $σ$ structure which is energetically favored at a low coverage. This indicates the importance of the interaction between the adsorbate molecules at a high coverage.
Cited by 34
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Cited by 47
- 27 October 2004
- Published by American Physical Society (APS) in Physical Review B
Nitrogen bonding structure in ultrathin silicon oxynitride films on Si(100) prepared by plasma nitridation
by Yu Kwon Kim, Hyun Seok Lee, H. W. Yeom, Doo-Yeol Ryoo, Sang-Bum Huh, Jeong-Gun Lee
High-resolution core-level photoemission using synchrotron radiation is applied to the ultrathin SiON films on Si(100) nitrided by $N_{2}$ plasma, which gives a systematic view of the various transient or stable N chemical states. $N 1 s$ spectra disclose at least two characteristic nitrogen bonding states in addition to the well-established and thermally stable $N  {Si}_{3}$ species. While the stable $N  {Si}_{3}$ species are located near the interface, the extra high-binding energy states are distributed mainly in the surface region. Among these high-binding species, assigned reliably to the $N  O$ and $N  O_{2}$ bonding states, only the $N  O$ species is quasi-stable up to $900 ° C$ , surviving the post-annealing treatment. These oxidized N species convert to the stable $N  {Si}_{3}$ mostly within the $Si O_{2}$ film. This result indicates that the $N  O$ and $N  O_{2}$ species formed by energetic plasma process is kinetically trapped within the shallow part of the film. It is inferred that the quasi-stable $N  O$ species would play an important role in characterizing the physical and electrical properties of the plasma oxynitrides.
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- 27 October 2004
- Published by American Physical Society (APS) in Physical Review B
Nitrogen bonding structure in ultrathin silicon oxynitride films on Si(100) prepared by plasma nitridation
by Yu Kwon Kim, Hyun Seok Lee, H. W. Yeom, Doo-Yeol Ryoo, Sang-Bum Huh, Jeong-Gun Lee
High-resolution core-level photoemission using synchrotron radiation is applied to the ultrathin SiON films on Si(100) nitrided by $N_{2}$ plasma, which gives a systematic view of the various transient or stable N chemical states. $N 1 s$ spectra disclose at least two characteristic nitrogen bonding states in addition to the well-established and thermally stable $N  {Si}_{3}$ species. While the stable $N  {Si}_{3}$ species are located near the interface, the extra high-binding energy states are distributed mainly in the surface region. Among these high-binding species, assigned reliably to the $N  O$ and $N  O_{2}$ bonding states, only the $N  O$ species is quasi-stable up to $900 ° C$ , surviving the post-annealing treatment. These oxidized N species convert to the stable $N  {Si}_{3}$ mostly within the $Si O_{2}$ film. This result indicates that the $N  O$ and $N  O_{2}$ species formed by energetic plasma process is kinetically trapped within the shallow part of the film. It is inferred that the quasi-stable $N  O$ species would play an important role in characterizing the physical and electrical properties of the plasma oxynitrides.
Cited by 47

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