Chen Lv - Academia.edu (original) (raw)
Papers by Chen Lv
電子情報通信学会技術研究報告 Sdm シリコン材料 デバイス, Oct 8, 2004
Extended Abstracts of the 2008 International Conference on Solid State Devices and Materials, 2008
Extended Abstracts of the 2006 International Conference on Solid State Devices and Materials, 2006
Extended Abstracts of the 2006 International Conference on Solid State Devices and Materials, 2006
Extended Abstracts of the 2004 International Conference on Solid State Devices and Materials, 2004
Extended Abstracts of the 2005 International Conference on Solid State Devices and Materials, 2005
We have successfully developed a new computer system for prediction of the electrical conductivit... more We have successfully developed a new computer system for prediction of the electrical conductivity of several realistic complex systems such as catalysts. This simulator is namely based on the combination of tight-binding quantum chemical molecular dynamics (TB-QCMD) with a kinetic Monte Carlo method (KMC). It has been applied to the prediction of the electrical conductivity of metal oxides with models for bulk and surface. Moreover, prediction of the electrical conductivity, using this simulator, was performed for materials such as Zn doped In 2 O 3 which is a p-type transparent conducting material, MgO as catalyst support, a SnO 2 (1 1 0) surface, a material used in gas sensors, and carbon materials including graphite and alkene chains. Our simulator was also successfully applied to the prediction of the electric breakdown in SiO 2 that happens under a high electric field. Finally, combining our electrical conductivity prediction simulator with the Wiedemann-Franz law enabled us to evaluate the thermal conductivity of Ti and Sn materials. The excellent results obtained in all these case studies show that our newly developed simulator is suitable to investigate the electrical conductivity of complex systems such as catalyst materials and surfaces.
電子情報通信学会技術 …, 2008
抄録 The dye-sensitize solar cell (DSSCs) attracted considerable attentions because of potentially ... more 抄録 The dye-sensitize solar cell (DSSCs) attracted considerable attentions because of potentially low cost. Organic dye sensitizers have been recognized as one of the most important parts for DSSCs to reduce the cost and improve the performance. In addition, ...
Journal of Organometallic Chemistry, 2006
This work reported the investigation of the structural distortions and charge-transfer processes ... more This work reported the investigation of the structural distortions and charge-transfer processes that occurred in the complex of cuprous(I) bis-2,9-dimethyl-1,10-phenanthroline ðCuðdmpÞ þ 2 Þ upon oxidation to copper(II), CuðdmpÞ 2þ 2 , through a excited state of CuðdmpÞ þ 2 by density functional theory. The intramolecular electronic transfer from central metal-to-ligand (MLCT) upon the irradiation of light energy is confirmed. Due to this MLCT excitation, the structure of the excited state of CuðdmpÞ þ 2 is distorted and reorganized to adapt with the change of charge in central metal. As a result, the excited state of CuðdmpÞ þ 2 is formed, which has the similar electronic and structural properties with CuðdmpÞ 2þ 2. The bulky substituents in 2-and 9-positions of the phenanthroline ligands can restrain the structural distort and decrease nonradiative decay rate. Thus, the electronic and steric effects of the ligands in the cuprous photo-sensitive complexes have important consequences in the behavior of their excited state.
Journal of Nanoscience and Nanotechnology, 2010
As the most reactive surface, the stoichiometric O-bridge terminated anatase(001) surface attract... more As the most reactive surface, the stoichiometric O-bridge terminated anatase(001) surface attracted considerable attentions in many application fields. The interfacial electron transfer in dye-sensitized anatase(001) plays a principal role in a variety of photoinduced reactions. In the present work, the UV-vis absorption spectrum of TiO2 bulk and different surface models were calculated by means of tight-binding quantum chemical molecular dynamics program "Colors-excite" for the first time. The thickness dependence on electronic and electrical properties of anatase(001) surface was achieved. The anatase(001) surface with a thickness of 1.0 nm shows excellent electronic and electrical properties. Moreover, the most suitable binding mode (dissociative adsorption) and absorption spectra of perylene with acrylic acid (PAA) on the optimum anatase(001) were investigated. A significant red-shift was observed from the UV-vis absorption spectrum of PAA/anatase(001) system. The red-shift occurring when PAA adsorbed on anatase(001) surface suggests that PAA/anatase(001) may be potential candidate for dye-sensitized solar cell. This study also proposed an effective computational tool "Colors-excite" to study of the electronic excitation properties for both molecular and periodic systems.
Japanese Journal of Applied Physics, 2009
In order to understand the behavior of electrons in complex porous structures, we have simulated ... more In order to understand the behavior of electrons in complex porous structures, we have simulated electron diffusion processes in complex porous structures that have been fabricated using a system for a three-dimensional porous structure simulator, POCO 2. For a given porosity, as the overlap ratio representing a necked porous TiO 2 structure increased, the coordination number of TiO 2 particles increased, resulting in an increase in electron flux and a decrease in trapping time. To gain better insights, we simulated the diffusion of electrons using models with different particle size distributions. This study shows that for a narrower size distribution of TiO 2 particles, a better electron diffusion process is realized. This result can be ascribed to the formation of a better TiO 2 coordination network. Consequently, through this study, we have shown that a well-formed neck between TiO 2 particles improves the electron diffusion properties of a complex porous material.
Japanese Journal of Applied Physics, 2009
We present a novel study on electromigration (EM) phenomena in Cu interconnects using a newly dev... more We present a novel study on electromigration (EM) phenomena in Cu interconnects using a newly developed multi-scale simulator that consists on a combination of a device scale simulator based on a kinetic Monte Carlo (KMC) method and an atomic scale simulator based on ultra accelerated quantum chemical molecular dynamics (UA-QCMD). We have firstly demonstrated the simulation of the lifetime of Cu interconnects using the newly developed device scale simulator setting some suitable KMC probabilities for the void movement according to the regions in which it can be divided, i.e., the crystal grain and the grain boundary. The simulated values are shown to be in good agreement with experimental values. In an attempt to connect the device scale studies to quantum chemical instances of the system-since the correlation of probability of the void movement with, for example, activation energies or diffusion coefficients is important-we have developed an atomic scale simulator based on our original UA-QCMD method. In this atomic scale simulation, the electron wind force was evaluated using our original electrical conductivity prediction simulator based on KMC method which uses the electronic states from tight-binding quantum chemical (TBQC) calculation. Using this atomic scale simulator under the conditions of 475 K of temperature and 2:5 Â 10 10 A/m 2 of current density, we were able to successfully simulate the migration of a Cu atom from a lattice site to a vacant site by evaluating the electron wind force.
Japanese Journal of Applied Physics, 2008
Japanese Journal of Applied Physics, 2008
In this study, we have developed a novel multiscale simulator for a dye-sensitized TiO 2 porous e... more In this study, we have developed a novel multiscale simulator for a dye-sensitized TiO 2 porous electrode. In the simulator, we can estimate the properties of the dye-sensitized TiO 2 porous electrode using the three-dimensional mesoscopic structure model constructed on the basis of our original porous structure simulator. The microscopic physical properties of the materials were estimated by quantum chemistry calculation using a tight-binding quantum chemical molecular dynamics program. From the calculation results, we determined the absorption coefficient and the diffusion coefficient of excited carriers used in the macroscopic simulation for photoelectrode characteristics. By using this multiscale simulator, we will be able to determine the best electrode system efficiently.
![Research paper thumbnail of Theoretical Investigation of the Photophysical Properties of Black Dye Sensitizer [(H 3 -tctpy)M(NCS) 3 ] - (M = Fe, Ru, Os) in Dye Sensitized Solar Cells](https://attachments.academia-assets.com/96246255/thumbnails/1.jpg)
](Japanese Journal of Applied Physics, 2007
The electronic properties and optical absorption spectrum of the photovoltaic sensitizer [(H 3-tc... more The electronic properties and optical absorption spectrum of the photovoltaic sensitizer [(H 3-tctpy)M(NCS) 3 ] À (M ¼ Fe, Ru and Os) in ethanol solvent are investigated using density functional theory/time-dependent density functional theory. The calculated absorption spectrum is in agreement with experiment for ruthenium complex, thus allowing an assignment of UVvisible spectral features of the dye. Red shift in the absorption spectrum is observed moving down the group from iron to osmium. The observed red shift in ruthenium and osmium complexes appears to be related to the destabilization of the occupied orbitals with t 2g-NCS Ã character. In osmium complex, the increase in the orbital splitting energy d (t 2g-e g) is found due to the destabilization of the e g orbitals. The weak d-d transitions are observed only in iron and ruthenium complexes.
Japanese Journal of Applied Physics, 2007
Robustness, versatility, high level of performance and low cost are some of the characteristics t... more Robustness, versatility, high level of performance and low cost are some of the characteristics that make capacitive sensors well suited for industrial applications. They consist only in electrodes and measurement circuits but give access to position information and/or material properties. The design of capacitive sensors is however not so obvious so that simple structures are generally used to avoid time-consuming calculations and developments. We propose an analytical method to determine the sensitivity distribution of any capacitive sensor structure. This method makes it possible to rapidly optimize structures in order to increase the sensor sensitivity to one parameter or to render it less sensitive to another. Comparisons between the sensitivity map of known sensors and those obtained with the analytical method proposed in this paper show a great accordance.
Japanese Journal of Applied Physics, 2007
Transparent conducting oxides (TCOs) continue to be in high demand because of their immediate app... more Transparent conducting oxides (TCOs) continue to be in high demand because of their immediate applications. In addition to good quality n-type TCOs, there is increasing demand for good p-type TCOs. In the present study, we reported a theoretical study on the electronic and electrical properties for p-type TCO, Zn-doped In 2 O 3 (IZO). The geometries of IZO were optimized using the density functional theory (DFT). Based on these optimized structures, the density of states, frontier molecular orbital contours, and electrical conductivity of IZO were calculated by combining the tight-binding quantum chemical molecular dynamics program, ''Colors'' and Monte Carlo method. The calculated band gap by ''Colors'' at G point is 2.87 eV, which is in good agreement with experimental value. In density of states of IZO, a shallow acceptor-type impurity level associate with Zn doping was observed above the top of the valence band. The frontier orbital analysis shows that the acceptor-type impurity level consists of O 2p and Zn 3d. On the other hand, the electrical conductivity and carrier mobility of IZO were evaluated. Comparing the electrical conductivity of IZO with that of its parent material In 2 O 3 , it was found that the electrical conductivity increased significantly when Zn-dopant was introduced to In 2 O 3. The higher electrical conductivity of IZO was considered to be attributed to impurity state and therefore the p-type conductivity.
Japanese Journal of Applied Physics, 2006
Recently, lanthanide ion doped yttrium oxide (Y 2 O 3) compounds have been attracting attention i... more Recently, lanthanide ion doped yttrium oxide (Y 2 O 3) compounds have been attracting attention in applications concerning opto-electronic materials such as laser devices and field-emission displays. Consequently, study on the excited state of lanthanide ion doped Y 2 O 3 is of major significance. In the present work, we report studies performed on the electronic excited states of undoped and Eu 3þ doped Y 2 O 3 as well as yttrium oxy-sulphide (Y 2 O 2 S) clusters using the time dependent density functional theory method to unveil the influence of europium ion in yttrium oxide compounds. The ground state electronic properties of undoped and europium ion doped clusters at different spin multiplicities were obtained using the density functional theory method. The calculated results were compared with the available experimental results. The calculated absorption spectrum of Eu doped Y 2 O 3 cluster shows quantitative agreement with experimental spectra. The absorption spectra of europium ion doped Y 2 O 3 and Y 2 O 2 S clusters have shown additional bands in the higher wavelength region due to the transitions between f-orbitals in the europium ion.
Japanese Journal of Applied Physics, 2005
We report a theoretical study on the electronic structures of indium oxide (In2O3) and indium tin... more We report a theoretical study on the electronic structures of indium oxide (In2O3) and indium tin oxide (ITO) carried out using our original tight-binding quantum chemical calculation program “Colors”, which is over 5,000 times faster than the conventional first-principles quantum chemical calculation method. The calculated band gap of In2O3 is in good agreement with the experimental results, although the value obtained by conventional first-principles calculation is less than half the experimental one. The electronic structures of In2O3 calculated by our tight-binding method are consistent with those obtained by first-principles calculations. Furthermore, the doping of tin atoms into In2O3 increased the band gap, which is also in good agreement with the experimental tendency. Hence, we confirmed that our tight-binding quantum chemical calculation method was very effective for investigation and predicting the electronic structures of In2O3 and ITO crystals with high accuracy and rel...
電子情報通信学会技術研究報告 Sdm シリコン材料 デバイス, Oct 8, 2004
Extended Abstracts of the 2008 International Conference on Solid State Devices and Materials, 2008
Extended Abstracts of the 2006 International Conference on Solid State Devices and Materials, 2006
Extended Abstracts of the 2006 International Conference on Solid State Devices and Materials, 2006
Extended Abstracts of the 2004 International Conference on Solid State Devices and Materials, 2004
Extended Abstracts of the 2005 International Conference on Solid State Devices and Materials, 2005
We have successfully developed a new computer system for prediction of the electrical conductivit... more We have successfully developed a new computer system for prediction of the electrical conductivity of several realistic complex systems such as catalysts. This simulator is namely based on the combination of tight-binding quantum chemical molecular dynamics (TB-QCMD) with a kinetic Monte Carlo method (KMC). It has been applied to the prediction of the electrical conductivity of metal oxides with models for bulk and surface. Moreover, prediction of the electrical conductivity, using this simulator, was performed for materials such as Zn doped In 2 O 3 which is a p-type transparent conducting material, MgO as catalyst support, a SnO 2 (1 1 0) surface, a material used in gas sensors, and carbon materials including graphite and alkene chains. Our simulator was also successfully applied to the prediction of the electric breakdown in SiO 2 that happens under a high electric field. Finally, combining our electrical conductivity prediction simulator with the Wiedemann-Franz law enabled us to evaluate the thermal conductivity of Ti and Sn materials. The excellent results obtained in all these case studies show that our newly developed simulator is suitable to investigate the electrical conductivity of complex systems such as catalyst materials and surfaces.
電子情報通信学会技術 …, 2008
抄録 The dye-sensitize solar cell (DSSCs) attracted considerable attentions because of potentially ... more 抄録 The dye-sensitize solar cell (DSSCs) attracted considerable attentions because of potentially low cost. Organic dye sensitizers have been recognized as one of the most important parts for DSSCs to reduce the cost and improve the performance. In addition, ...
Journal of Organometallic Chemistry, 2006
This work reported the investigation of the structural distortions and charge-transfer processes ... more This work reported the investigation of the structural distortions and charge-transfer processes that occurred in the complex of cuprous(I) bis-2,9-dimethyl-1,10-phenanthroline ðCuðdmpÞ þ 2 Þ upon oxidation to copper(II), CuðdmpÞ 2þ 2 , through a excited state of CuðdmpÞ þ 2 by density functional theory. The intramolecular electronic transfer from central metal-to-ligand (MLCT) upon the irradiation of light energy is confirmed. Due to this MLCT excitation, the structure of the excited state of CuðdmpÞ þ 2 is distorted and reorganized to adapt with the change of charge in central metal. As a result, the excited state of CuðdmpÞ þ 2 is formed, which has the similar electronic and structural properties with CuðdmpÞ 2þ 2. The bulky substituents in 2-and 9-positions of the phenanthroline ligands can restrain the structural distort and decrease nonradiative decay rate. Thus, the electronic and steric effects of the ligands in the cuprous photo-sensitive complexes have important consequences in the behavior of their excited state.
Journal of Nanoscience and Nanotechnology, 2010
As the most reactive surface, the stoichiometric O-bridge terminated anatase(001) surface attract... more As the most reactive surface, the stoichiometric O-bridge terminated anatase(001) surface attracted considerable attentions in many application fields. The interfacial electron transfer in dye-sensitized anatase(001) plays a principal role in a variety of photoinduced reactions. In the present work, the UV-vis absorption spectrum of TiO2 bulk and different surface models were calculated by means of tight-binding quantum chemical molecular dynamics program "Colors-excite" for the first time. The thickness dependence on electronic and electrical properties of anatase(001) surface was achieved. The anatase(001) surface with a thickness of 1.0 nm shows excellent electronic and electrical properties. Moreover, the most suitable binding mode (dissociative adsorption) and absorption spectra of perylene with acrylic acid (PAA) on the optimum anatase(001) were investigated. A significant red-shift was observed from the UV-vis absorption spectrum of PAA/anatase(001) system. The red-shift occurring when PAA adsorbed on anatase(001) surface suggests that PAA/anatase(001) may be potential candidate for dye-sensitized solar cell. This study also proposed an effective computational tool "Colors-excite" to study of the electronic excitation properties for both molecular and periodic systems.
Japanese Journal of Applied Physics, 2009
In order to understand the behavior of electrons in complex porous structures, we have simulated ... more In order to understand the behavior of electrons in complex porous structures, we have simulated electron diffusion processes in complex porous structures that have been fabricated using a system for a three-dimensional porous structure simulator, POCO 2. For a given porosity, as the overlap ratio representing a necked porous TiO 2 structure increased, the coordination number of TiO 2 particles increased, resulting in an increase in electron flux and a decrease in trapping time. To gain better insights, we simulated the diffusion of electrons using models with different particle size distributions. This study shows that for a narrower size distribution of TiO 2 particles, a better electron diffusion process is realized. This result can be ascribed to the formation of a better TiO 2 coordination network. Consequently, through this study, we have shown that a well-formed neck between TiO 2 particles improves the electron diffusion properties of a complex porous material.
Japanese Journal of Applied Physics, 2009
We present a novel study on electromigration (EM) phenomena in Cu interconnects using a newly dev... more We present a novel study on electromigration (EM) phenomena in Cu interconnects using a newly developed multi-scale simulator that consists on a combination of a device scale simulator based on a kinetic Monte Carlo (KMC) method and an atomic scale simulator based on ultra accelerated quantum chemical molecular dynamics (UA-QCMD). We have firstly demonstrated the simulation of the lifetime of Cu interconnects using the newly developed device scale simulator setting some suitable KMC probabilities for the void movement according to the regions in which it can be divided, i.e., the crystal grain and the grain boundary. The simulated values are shown to be in good agreement with experimental values. In an attempt to connect the device scale studies to quantum chemical instances of the system-since the correlation of probability of the void movement with, for example, activation energies or diffusion coefficients is important-we have developed an atomic scale simulator based on our original UA-QCMD method. In this atomic scale simulation, the electron wind force was evaluated using our original electrical conductivity prediction simulator based on KMC method which uses the electronic states from tight-binding quantum chemical (TBQC) calculation. Using this atomic scale simulator under the conditions of 475 K of temperature and 2:5 Â 10 10 A/m 2 of current density, we were able to successfully simulate the migration of a Cu atom from a lattice site to a vacant site by evaluating the electron wind force.
Japanese Journal of Applied Physics, 2008
Japanese Journal of Applied Physics, 2008
In this study, we have developed a novel multiscale simulator for a dye-sensitized TiO 2 porous e... more In this study, we have developed a novel multiscale simulator for a dye-sensitized TiO 2 porous electrode. In the simulator, we can estimate the properties of the dye-sensitized TiO 2 porous electrode using the three-dimensional mesoscopic structure model constructed on the basis of our original porous structure simulator. The microscopic physical properties of the materials were estimated by quantum chemistry calculation using a tight-binding quantum chemical molecular dynamics program. From the calculation results, we determined the absorption coefficient and the diffusion coefficient of excited carriers used in the macroscopic simulation for photoelectrode characteristics. By using this multiscale simulator, we will be able to determine the best electrode system efficiently.
Japanese Journal of Applied Physics, 2007
The electronic properties and optical absorption spectrum of the photovoltaic sensitizer [(H 3-tc... more The electronic properties and optical absorption spectrum of the photovoltaic sensitizer [(H 3-tctpy)M(NCS) 3 ] À (M ¼ Fe, Ru and Os) in ethanol solvent are investigated using density functional theory/time-dependent density functional theory. The calculated absorption spectrum is in agreement with experiment for ruthenium complex, thus allowing an assignment of UVvisible spectral features of the dye. Red shift in the absorption spectrum is observed moving down the group from iron to osmium. The observed red shift in ruthenium and osmium complexes appears to be related to the destabilization of the occupied orbitals with t 2g-NCS Ã character. In osmium complex, the increase in the orbital splitting energy d (t 2g-e g) is found due to the destabilization of the e g orbitals. The weak d-d transitions are observed only in iron and ruthenium complexes.
Japanese Journal of Applied Physics, 2007
Robustness, versatility, high level of performance and low cost are some of the characteristics t... more Robustness, versatility, high level of performance and low cost are some of the characteristics that make capacitive sensors well suited for industrial applications. They consist only in electrodes and measurement circuits but give access to position information and/or material properties. The design of capacitive sensors is however not so obvious so that simple structures are generally used to avoid time-consuming calculations and developments. We propose an analytical method to determine the sensitivity distribution of any capacitive sensor structure. This method makes it possible to rapidly optimize structures in order to increase the sensor sensitivity to one parameter or to render it less sensitive to another. Comparisons between the sensitivity map of known sensors and those obtained with the analytical method proposed in this paper show a great accordance.
Japanese Journal of Applied Physics, 2007
Transparent conducting oxides (TCOs) continue to be in high demand because of their immediate app... more Transparent conducting oxides (TCOs) continue to be in high demand because of their immediate applications. In addition to good quality n-type TCOs, there is increasing demand for good p-type TCOs. In the present study, we reported a theoretical study on the electronic and electrical properties for p-type TCO, Zn-doped In 2 O 3 (IZO). The geometries of IZO were optimized using the density functional theory (DFT). Based on these optimized structures, the density of states, frontier molecular orbital contours, and electrical conductivity of IZO were calculated by combining the tight-binding quantum chemical molecular dynamics program, ''Colors'' and Monte Carlo method. The calculated band gap by ''Colors'' at G point is 2.87 eV, which is in good agreement with experimental value. In density of states of IZO, a shallow acceptor-type impurity level associate with Zn doping was observed above the top of the valence band. The frontier orbital analysis shows that the acceptor-type impurity level consists of O 2p and Zn 3d. On the other hand, the electrical conductivity and carrier mobility of IZO were evaluated. Comparing the electrical conductivity of IZO with that of its parent material In 2 O 3 , it was found that the electrical conductivity increased significantly when Zn-dopant was introduced to In 2 O 3. The higher electrical conductivity of IZO was considered to be attributed to impurity state and therefore the p-type conductivity.
Japanese Journal of Applied Physics, 2006
Recently, lanthanide ion doped yttrium oxide (Y 2 O 3) compounds have been attracting attention i... more Recently, lanthanide ion doped yttrium oxide (Y 2 O 3) compounds have been attracting attention in applications concerning opto-electronic materials such as laser devices and field-emission displays. Consequently, study on the excited state of lanthanide ion doped Y 2 O 3 is of major significance. In the present work, we report studies performed on the electronic excited states of undoped and Eu 3þ doped Y 2 O 3 as well as yttrium oxy-sulphide (Y 2 O 2 S) clusters using the time dependent density functional theory method to unveil the influence of europium ion in yttrium oxide compounds. The ground state electronic properties of undoped and europium ion doped clusters at different spin multiplicities were obtained using the density functional theory method. The calculated results were compared with the available experimental results. The calculated absorption spectrum of Eu doped Y 2 O 3 cluster shows quantitative agreement with experimental spectra. The absorption spectra of europium ion doped Y 2 O 3 and Y 2 O 2 S clusters have shown additional bands in the higher wavelength region due to the transitions between f-orbitals in the europium ion.
Japanese Journal of Applied Physics, 2005
We report a theoretical study on the electronic structures of indium oxide (In2O3) and indium tin... more We report a theoretical study on the electronic structures of indium oxide (In2O3) and indium tin oxide (ITO) carried out using our original tight-binding quantum chemical calculation program “Colors”, which is over 5,000 times faster than the conventional first-principles quantum chemical calculation method. The calculated band gap of In2O3 is in good agreement with the experimental results, although the value obtained by conventional first-principles calculation is less than half the experimental one. The electronic structures of In2O3 calculated by our tight-binding method are consistent with those obtained by first-principles calculations. Furthermore, the doping of tin atoms into In2O3 increased the band gap, which is also in good agreement with the experimental tendency. Hence, we confirmed that our tight-binding quantum chemical calculation method was very effective for investigation and predicting the electronic structures of In2O3 and ITO crystals with high accuracy and rel...