Deng-Sung Lin
@nthu.edu.tw
National Tsing Hua University
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Yen-Hui Lin, Chia-Hsiu Hsu, Iksu Jang, Chia-Ju Chen, Pok-Man Chiu, Deng-Sung Lin, Chien-Te Wu, Feng-Chuan Chuang, Po-Yao Chang, and Pin-Jui Hsu
American Chemical Society (ACS)
A proximity effect facilitates the penetration of Cooper pairs that permits superconductivity in a normal metal, offering a promising approach to turn heterogeneous materials into superconductors and develop exceptional quantum phenomena. Here, we have systematically investigated proximity-induced anisotropic superconductivity in a monolayer Ni-Pb binary alloy by combining scanning tunneling microscopy/spectroscopy (STM/STS) with theoretical calculations. By means of high-temperature growth, the (33×33)R30o Ni-Pb surface alloy has been fabricated on Pb(111) and the appearance of a domain boundary as well as a structural phase transition can be deduced from a half-unit-cell lattice displacement. Given the high spatial and energy resolution, tunneling conductance (dI/dU) spectra have resolved the reduced but anisotropic superconducting gap ΔNiPb ≈ 1.0 meV, in stark contrast to the isotropic ΔPb ≈ 1.3 meV. In addition, the higher density of states at the Fermi energy (D(EF)) of the Ni-Pb surface alloy results in an enhancement of coherence peak height. According to the same Tc ≈ 7.1 K with Pb(111) from the temperature-dependent ΔNiPb and the short decay length Ld ≈ 3.55 nm from the spatially monotonic decrease of ΔNiPb, both results are supportive of a proximity-induced superconductivity. Despite a lack of a bulk counterpart, the atomically thick Ni-Pb bimetallic compound opens a pathway to engineer superconducting properties down to the two-dimensional limit, giving rise to the emergence of anisotropic superconductivity via a proximity effect.
Yen-Hui Lin, Sukhito Teh, Ta-Yu Yeh, Chin-Hsuan Chen, Deng-Sung Lin, Horng-Tay Jeng, and Pin-Jui Hsu
American Physical Society (APS)
Chia-Chi Liu, Yen Huang, Tzu-Hung Chuang, Deng-Sung Lin, and Der-Hsin Wei
AIP Publishing
Chan-Yuen Chang, Cheng-Yu Lin, and Deng-Sung Lin
IOP Publishing
A fundamental question for the adsorption of any gas molecule on surfaces is its saturation coverage, whose value can provide a comprehensive examination for the adsorption mechanisms, dynamic and kinetic processes involved in the adsorption processes. This investigation utilizes scanning tunneling microscopy to visualize the H2O adsorption processes on the Si(100) surface with a sub-monolayers (<0.05 ML) of chemically-reactive dangling bonds remaining after exposure to (1) a hydrogen atomic beam, (2) H2O, and (3) Cl2 gases at room temperature. In all three cases, each of the remaining isolated single dangling bonds (sDB) adsorb and is passivated by either of the two dissociation fragments, the H or OH radical, to form a surface Si–H and Si–OH species. A new adsorption mechanism, termed ‘dissociative and asynchronous chemisorption’, is proposed for the observation presented herein. Upon approaching a sDB site, the H2O molecule breaks apart into two fragments. One is chemisorbed to the sDB. The other attaches to the same or the neighboring passivated dimer to form a transition state of surface diffusion, which then diffuses on the mostly passivated surface and is eventually chemisorbed to another reactive site. In other words, the chemisorption reactions of the two fragments after dissociation occur at different and uncorrelated time and places. This adsorption mechanism suggests that a diffusion transition state can be an adsorption product in the first step of the dissociative adsorption processes.
Guan-Yu Chen, Chia-Hsiu Hsu, Bo-You Liu, Li-Wei Chang, Deng-Sung Lin, Feng-Chuan Chuang, and Pin-Jui Hsu
Elsevier BV
Abstract Two-dimensional (2D) Pb nanoisland has established an ideal platform for studying the quantum size effects on growth mechanism, electronic structures as well as high-temperature superconductivity. Here, we investigate the growth and quantum well electronic states of the 2D Pb nanoislands on Nb-doped SrTiO3(001) by scanning tunneling microscopy and spectroscopy. In contrast to Pb/Si(111), Pb/Cu(111) and Pb/Ag(111), there is no wetting layer of Pb formed on the Nb-doped SrTiO3(001) surface, resulting in isolated Pb nanoislands with an apparent height of 4 atomic layers as the building blocks for the island growth. According to the thickness-dependent quantum well states resolved in both occupied and unoccupied energy regions, the constant group velocity vg = 1.804 × 106 m/s and the Fermi wavevector kF = 1.575 A-1, have been extracted from a linear fit of the Pb(111) band dispersion along the Γ - L direction. In addition, the energy-dependent scattering phase shift φ(E) obtained by means of the phase accumulation model shows a metallic-like scattering interface analogous to Pb/Ag(111). These spatially decoupled 2D Pb nanoislands thus realize an opportunity to explore the intrinsic quantum confinement phenomena in nanoscale superconductors on the doped titanium-oxide-type substrate.
Guan-Yu Chen, Angus Huang, Yen-Hui Lin, Chia-Ju Chen, Deng-Sung Lin, Po-Yao Chang, Horng-Tay Jeng, Gustav Bihlmayer, and Pin-Jui Hsu
Springer Science and Business Media LLC
AbstractSpin-split Rashba bands have been exploited to efficiently control the spin degree of freedom of moving electrons, which possesses a great potential in frontier applications of designing spintronic devices and processing spin-based information. Given an intrinsic breaking of inversion symmetry and sizeable spin–orbit interaction, two-dimensional (2D) surface alloys formed by heavy metal elements exhibit a pronounced Rashba-type spin splitting of the surface states. Here, we have revealed the essential role of atomic orbital symmetry in the hexagonally warped Rashba spin-split surface state of the $$\\sqrt 3 \\times \\sqrt 3 R30^0$$ 3 × 3 R 3 0 0 BiCu2 monatomic alloy by scanning tunneling spectroscopy (STS) and density functional theory (DFT). From dI/dU spectra and calculated band structures, three hole-like Rashba-split bands hybridized from distinct orbital symmetries have been identified in the unoccupied energy region. Because of the hexagonally deformed Fermi surface, quasi-particle interference (QPI) mappings have resolved scattering channels opened from interband transitions of px,py (mj = 1/2) band. In contrast to the s,pz-derived band, the hexagonal warping is predominately accompanied by substantial out-of-plane spin polarization Sz up to 24% in the dispersion of px,py (mj = 1/2) band with an in-plane orbital symmetry.
Shin-Ching Hsieh, Chia-Hsiu Hsu, Han-De Chen, Deng-Sung Lin, Feng-Chuan Chuang, and Pin-Jui Hsu
Elsevier BV
Abstract Two-dimensional materials with sizable spin-orbit coupling are not only interesting to fundamental studies, but also useful candidates for technological applications. Here, we report on the fabrication of extended α-phase Bi atomic layer on Si(1 1 1) surface by means of thermal desorption. The atomic and electronic structures have been investigated by combining scanning tunneling microscopy (STM) experiments with density functional theory (DFT) calculations. While β-phase Bi trimer with 3 × 3 R30° surface reconstruction can be prepared by room-temperature deposition with subsequent post annealing at 700 K, the α-phase Bi monomer only appears at 800 K due to thermal desorption with the Bi desorption rate of 0.26 ML/min. From our DFT calculations, the α-phase Bi shows Rashba energies ER = 15 meV and 3 meV at high symmetry points of M ¯ and K ¯ , respectively. Since α-phase Bi monomer represents isotropic lattice symmetry with a dilute Bi density, it may serve as a potential template to tune Rashba effect by incorporating with multiple elements.
Cho-Ying Lin, Chia-Hsiu Hsu, Yu-Zhang Huang, Shih-Ching Hsieh, Han-De Chen, Li Huang, Zhi-Quan Huang, Feng-Chuan Chuang, and Deng-Sung Lin
Springer Science and Business Media LLC
Synchrotron radiation core-level photoemission spectroscopy, scanning tunneling microscopy (STM), and first-principles calculations have been utilized to explore the growth processes and the atomic structure of the resulting films during the two-step molecular beam epitaxy (MBE) of In and Bi on the Si(111) surface. Deposition of 1.0-ML Bi on the In/Si(111)-(4 × 1) surface at room temperature results in Bi-terminated BiIn-(4 × 3) structures, which are stable up to ~300 °C annealing. By contrast, deposition of In on the β-Bi/Si(111)-(√3 × √3) surface at room temperature results in three dimensional (3D) In islands. In both cases, annealing at 460 °C results in the same In-terminated In0.75Bi/Si(111)-(2 × 2) surface. Our DFT calculations confirm that the surface energy of In-terminated In0.75Bi/Si(111)-(2 × 2) system is lower than that of Bi-terminated Bi0.75In/Si(111)-(2 × 2). These findings provide means for the control of the polarity of the MBE In-Bi atomically thick films.
Peng Chen, Yun-Ting Chen, Ro-Ya Liu, Han-De Chen, Dengsung Lin, Alexei V. Fedorov, and Tai-Chang Chiang
American Chemical Society (ACS)
Chemical conversion by atomic substitution offers a powerful route toward the creation of unusual structures and functionalities. Here, we demonstrate the progressive transformation of single-layer TiTe2 into TiSe2 by reaction with a Se flux in vacuum. Angle-resolved photoemission spectroscopy and scanning tunneling microscopy reveal intriguing reaction patterns involving TiSe2 island ingrowth starting from the TiTe2 island edges, while the band structure and core level signatures of TiSe2 grow in intensity at the expense of those corresponding to TiTe2. Lattice mismatch between TiTe2 and TiSe2 results in misfit holes and lattice distortions over a distance behind a seamless fingerlike reaction front. The regions of TiSe2 and TiTe2 are distinguished by a height difference and a charge density wave (CDW) at different transition temperatures. The method of in situ chemical conversion offers opportunities for atomic-scale engineering of layered transition metal dichalcogenides that host useful properties arising from CDW, Dirac, Weyl, superconducting, spin-valley, and magnetic structures.
P. Chen, Woei Wu Pai, Y.-H. Chan, W.-L. Sun, C.-Z. Xu, D.-S. Lin, M. Y. Chou, A.-V. Fedorov, and T.-C. Chiang
Springer Science and Business Media LLC
Two-dimensional (2D) topological insulators (TIs) are promising platforms for low-dissipation spintronic devices based on the quantum-spin-Hall (QSH) effect, but experimental realization of such systems with a large band gap suitable for room-temperature applications has proven difficult. Here, we report the successful growth on bilayer graphene of a quasi-freestanding WSe2 single layer with the 1T′ structure that does not exist in the bulk form of WSe2. Using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy/spectroscopy (STM/STS), we observe a gap of 129 meV in the 1T′ layer and an in-gap edge state located near the layer boundary. The system′s 2D TI characters are confirmed by first-principles calculations. The observed gap diminishes with doping by Rb adsorption, ultimately leading to an insulator–semimetal transition. The discovery of this large-gap 2D TI with a tunable band gap opens up opportunities for developing advanced nanoscale systems and quantum devices.The current known two-dimensional topological insulators with small band gaps limit the potential for room temperature applications. Here, Chen et al. observe a sizable gap of 129 meV in a 1T'-WSe2 single layer grown on bilayer graphene with in-gap edge state near the layer boundary.
Chia-Hsiu Hsu, Zhi-Quan Huang, Cho-Ying Lin, Gennevieve M. Macam, Yu-Zhang Huang, Deng-Sung Lin, Tai Chang Chiang, Hsin Lin, Feng-Chuan Chuang, and Li Huang
American Physical Society (APS)
Using combined scanning tunneling microscopy (STM) measurements and first-principles electronic structure calculations, we extensively studied the atomic and electronic properties of a $\\sqrt{7}$-InBi overlayer on Si(111). We propose and demonstrate an effective experimental process to successfully form a large well-ordered $\\sqrt{7}$ surface by depositing Bi atoms on the In-Si(111)-$4\\ifmmode\\times\\else\\texttimes\\fi{}1$ substrate. The STM images exhibit a honeycomb pattern. After performing an exhaustive computational search, we identified the atomic structures of the surface at In and Bi coverages of 6/7 and 3/7 monolayers, respectively. We discovered a trimer model with a lower energy than the previously proposed model. The simulated STM images of trimer models confirm the presence of the honeycomb pattern in accord with our experimental STM images. Most importantly, we found that the surface is robust, preserving the topologically nontrivial phase. Our edge state calculations verify that the InBi overlayer on Si(111) is indeed a two-dimensional (2D) topological insulator (TI). Moreover, hybrid functional calculations result in band gaps up to 70 meV, which is high enough for room-temperature experiments. Our findings lay the foundation for the materials realization of 2D TIs by growing an InBi overlayer on a Si(111) substrate.
Peng Li, Zhongzheng Wu, Fan Wu, Chao Cao, Chunyu Guo, Yi Wu, Yi Liu, Zhe Sun, Cheng-Maw Cheng, Deng-Sung Lin,et al.
American Physical Society (APS)
Here we report the evolution of bulk band structure and surface states in rare earth monobismuthides with partially filled f shell. Utilizing synchrotron-based photoemission spectroscopy, we determined the three-dimensional bulk band structure and identified the bulk band inversions near the X points, which, according to the topological theory, could give rise to nontrivial band topology with odd number of gapless topological surface states. Near the surface Γ point, no clear evidence for predicted gapless topological surface state is observed due to its strong hybridization with the bulk bands. Near the M point, the two surface states, due to projections from two inequivalent bulk band inversions, interact and give rise to two peculiar sets of gapped surface states. The bulk band inversions and corresponding surface states can be tuned substantially by varying rare earth elements, in good agreement with density-functional theory calculations assuming local f electrons. Our study therefore establishes rare earth monobismuthides as an interesting class of materials possessing tunable electronic properties and magnetism, providing a promising platform to search for novel properties in potentially correlated topological materials.
D.-S. Lin
Elsevier
Group IV nonmetal elements consist of C, Si, and Ge. They can each form a 2D monolayer called graphene, silicene, and germanene on metal surfaces. Multilayer graphene can be grown with weak Van der Waals-type interlayer coupling. Naturally, it is also desirable to grow multilayer silicene and germanene and heterostructure of the two 2D materials. To this end, a good start is to study and understand the adsorption and growth mechanism of Ge and Si on the monolayer silicene on metal surfaces such as the Ag(111) surface.
Han-De Chen and Deng-Sung Lin
American Chemical Society (ACS)
Growth of Ge by molecular beam epitaxy (MBE) on top of the silicene monolayer on the Ag(111) surface results in either a dispersed adlayer or a two-dimensional (2D) ordered structure depending on the silicene phase. Scanning tunneling microscopy (STM) images show that the ordered adsorbed Ge atoms on (3 × 3)Si domains occupy a position directly on top of down atoms in the buckled silicene layer, similar to the adatom positions on the Ge(111)-c(2 × 8) surface. By contrast, no long-range ordering of Ge adatoms is observed on the domain, possibly partly because of the interference effects of the Ag substrate. Results herein suggest that the deposited Ge atoms tend to build an additional three-dimensional bulk layer on the silicene monolayer and that the growth of the 2D germanene/silicene heterostructure may not be achieved in a straightforward manner.
Han-De Chen, Ko-Hsiang Chien, Cho-Ying Lin, Tai-Chang Chiang, and Deng-Sung Lin
American Chemical Society (ACS)
Growth by molecular beam epitaxy (MBE) of Si on Ag(111) results in a two-dimensional film with (√3 × √3) surface structure at near monolayer (ML) coverage. The same (√3 × √3) pattern persists for coverages of Si up to several MLs. The atomic structure of the resulting Si film has posed an intriguing question. One possible scenario is that Ag acts as a surfactant to foster the low-temperature growth of metastable silicene multilayers, which would be an analogue of graphite and a new state of Si. Yet another possibility is the formation of diamond-structured Si. In our experiment, we use low-temperature scanning tunneling microscopy (LT-STM) to observe the chemical response of the film surface exposed to an atomic deuterium (D) beam. We find D displaces the Ag surfactant adatoms, resulting in a D-terminated (1 × 1) surface. The displaced Ag atoms migrate on the surface to form Ag(111) crystallites. The same reactions have been observed for a Si(111) bulk single-crystal surface decorated by Ag. The results c...
Guo-Wei Lee, Han-De Chen, and Deng-Sung Lin
Elsevier BV
Abstract Low-temperature scanning tunneling microscopy (LT-STM) and ab initio density functional theory (DFT) calculations have been utilized to explore the growth processes and atomic structure of silicene on the Ag(1 1 1) surface. STM images reveal an etching growth mode in the sub-monolayer range. The results confirm the existence of various overlayer structures reported previously and that the lattice parameters of several overlayer structures at sub-monolayer coverages are close to the corresponding substrate supercells. However, detailed analysis of domain boundaries and Moire-like superstructure in the STM images strongly suggest that the overlayer structures and the substrate lattices have no coincident relationships. Preliminary results of DFT calculations show that the changes in total energy upon translational displacement of the (3 × 3) Si silicene supercells with respect to the Ag(1 1 1) lattice is within a few tens of meV/Si atom.
Guo-Wei Lee, Han-De Chen, and Deng-Sung Lin
Elsevier BV
Abstract Synchrotron-radiation core-level photoemission spectroscopy has been utilized to explore the growth and annealing processes of silicon growth on the Ag(1 1 1) surface. Above 230 °C, adsorbed silicon atoms start to evaporate from the surface. No evidence of Si in-diffusion or formation of Si–Ag alloy was observed. Two components are visually discernible in the Si 2p spectra for all coverages and various growth temperatures. This observation and the analysis of the Ag 3d line shapes indicate the Si–Ag interface has similar bonding properties regardless of the reconstructions and thickness. The results are consistent with the growth scenarios that the top surface is terminated by some amounts of segregated silver atoms and has a similar structure to the Ag/Si(1 1 1)-( 3 × 3 )R30° surface.
Ying-Hsiu Lin, Horng-Tay Jeng, and Deng-Sung Lin
Elsevier BV
Abstract Dissociative adsorption of H 2 O, NH 3 , CH 3 OH and CH 3 NH 2 polar molecules on the Si(100) surface results in a 1:1 mixture of two adsorbates (H and multi-atomic fragment A = OH, NH 2 , CH 3 O, CH 3 NH, respectively) on the surface. By using density functional theory (DFT) calculations, the adsorption geometry, the total energies and the charge densities for various possible ordered structures of the mixed adsorbate layer have been found. Analyzing the systematic trends in the total energies unveils concurrently the nearest-neighbor interactions E NN and the next nearest-neighbor interactions E NNN between two polar adsorbates A. In going from small to large polar adsorbates, E NN 's exhibit an attractive-to-repulsive crossover behavior, indicating that they include competing attractive and repulsive contributions. Exploration of the charge density distributions allows the estimation of the degree of charge overlapping between immediately neighboring A's, the resulting contribution of the steric repulsions, and that of the attractive interactions to the corresponding E NN 's. The attractive contributions to nearest neighboring adsorbate–adsorbate interactions between the polar adsorbates under study are shown to result from hydrogen bonds or dipole–dipole interactions.
Tsan-Yao Chen, Hong Dao Li, Guo-Wei Lee, Po-Chun Huang, Po-Wei Yang, Yu-Ting Liu, Yen-Fa Liao, Horng-Tay Jeng, Deng-Sung Lin, and Tsang-Lang Lin
Royal Society of Chemistry (RSC)
Sub-nanometer Au clusters extract the valence charge from Pt and Ru crystallites to form a negatively charged shield that protects core–shell NCs from passivation by CO molecules.
Tsan-Yao Chen, Guo-Wei Lee, Yu-Ting Liu, Yen-Fa Liao, Chun-Chih Huang, Deng-Sung Lin, and Tsang-Lang Lin
Royal Society of Chemistry (RSC)
The heterogeneous geometric configurations confine the structure stability and the durability of the nanocrystallites (NCs) in direct methanol fuel cell.
Chan-Yuen Chang, Hong-Dao Li, Shiow-Fon Tsay, Shih-Hsin Chang, and Deng-Sung Lin
American Chemical Society (ACS)
An atomic layer of stoichiometric NaCl was formed on a covalent Si(100) surface after two successive half-reactions at room temperature. The first half-reaction due to Cl2 exposure generates a square array of Cl adatoms with a distance close to that in a NaCl(100) surface plane. By utilizing scanning tunneling microscopy (STM), core-level photoemission spectroscopy, and ab initio density functional theory (DFT) calculations, it was found that progressive deposition of Na in the second-half reaction results in surface-supported Na3Cl clusters, one-dimensional cluster chains, and (2 × 2) patches, and eventually turns the Cl-adlayer into a single-terrace, wavy NaCl layer at one monolayer Na coverage. The grown NaCl monolayer rolls over atomic steps like a carpet and covers the entire surface.The atomic and electronic structure of the topmost Si layer underneath the NaCl layer resembles that of the initial silicon surface layer with buckled dimers. Results of the comprehensive investigation together suggest t...
Shyh-Shin Ferng and Deng-Sung Lin
American Chemical Society (ACS)
Isolated, paired, and clustered dangling bonds are prepared on a Si(100) surface as well-defined chemically reactive sites for chemisorption of iodine diatomic molecules. The surrounding dangling bonds around a designed reactant configuration are passivated by hydrogen- and iodine-termination. Following exposure to I2 at room temperature, the adsorbate configurations on these reactive sites have been examined using scanning tunneling microscopy (STM). On clean Si(100), three types (type-I, type-II, and type-M) of adsorption pathways have been identified, consistent with previous findings. The results from H- and I-masked Si(100) show that at least two dangling bonds in the same row and in close proximity (<4 A) are needed to trigger chemisorption and that dissociative adsorption is the dominant mechanism. Contrary to its major role on clean Si(100), type-II adsorption is not observed when the two needed dangling bonds are surrounded by H-adatoms. These findings indicate that a seemingly simple chemisorpti...
Hsiao-Ying Hou, Hsin-Hua Wu, Jen-Yang Chung, and Deng-Sung Lin
American Chemical Society (ACS)
This work investigates the adsorption of diatomic interhalogens (XY = ICl and IBr) and hydrogen halides (HX = HBr and HCl) on Si(100) and Ge(100) surfaces by synchrotron radiation core-level photoe...
Ying-Hsiu Lin, Hong-Dao Li, Horng-Tay Jeng, and Deng-Sung Lin
American Chemical Society (ACS)
The energetics of various ordered structures of the Si(100) surface with a 1:1 mixture of two adsorbates (hydrogen–halogen) or (two halogens) are investigated using ab initio density functional theory (DFT) calculations. Through an analysis of the calculated energies of various ordered adsorbate structures, the nearest-neighbor and next-nearest-neighbor interactions between halogen adsorbates are unveiled and observed to fit well with a proposed electron-cloud overlap model. Systematic trends are revealed: The mixing energy of two adsorbates favors desegregated structures. A (2 × 2) structure has the lowest energy on the rectangular Si(100) dimerized surface for all mixed adsorbate systems resulting from the stoichiometric adsorption of diatomic interhalogen molecules and hydrogen halides. These results are in good agreement with the scanning-tunneling microcopy (STM) observations on Si(100) after the adsorption of chlorine-contained molecules HCl and ICl but not for HBr and IBr.
Jen-Yang Chung, Hong-Dao Li, Wan-Heng Chang, T. C. Leung, and Deng-Sung Lin
American Physical Society (APS)
Jen-Yang Chung,1,2 Hong-Dao Li,1,2 Wan-Heng Chang,1 T. C. Leung,3 and Deng-Sung Lin1,* 1Department of Physics, National Tsing Hua University, 101 Kuang-Fu Road Section 2, Hsinchu 30013, Taiwan 2Institute of Physics, National Chiao-Tung University, 1001 Ta-Hsueh Road, Hsinchu 30010, Taiwan 3Department of Physics, National Chung Cheng University, Chia-Yi, Taiwan 62101, Republic of China (Received 19 September 2010; revised manuscript received 17 January 2011; published 25 February 2011)