Self-similar fractals are of importance in both science and engineering. Metal-organic Sierpin′ ski triangles are particularly attractive for applications in gas separation, catalysis and sensing. Such fractals are c...Self-similar fractals are of importance in both science and engineering. Metal-organic Sierpin′ ski triangles are particularly attractive for applications in gas separation, catalysis and sensing. Such fractals are constructed in this study by using 1208 V-shaped 4,400-dicyano-1,10：30,100-terphenyl molecules and Fe atoms on Au（1 1 1）, and studied in detail by low-temperature scanning tunneling microscopy. Density functional theory calculations are employed to rationalize the invisible Fe atoms in STM images. Monte Carlo simulations are performed to understand the formation mechanism of the surface-supported fractal crystals.展开更多
Geometries of molecule-molecule interfaces strongly influence the current passing from one molecule to another. The contact conductance of molecule-molecule junctions which consist of fullerene and tin phthalocyanine ...Geometries of molecule-molecule interfaces strongly influence the current passing from one molecule to another. The contact conductance of molecule-molecule junctions which consist of fullerene and tin phthalocyanine molecules is investigated with a low-temperature scanning tunneling microscope. Two types of molecules are deposited onto Cu(111). Fullerene molecules are transferred to tips through controlled contact of STM tips on molecules. The molecule-molecule junctions are formed by approaching fullereneterminated tips to tin phthalocyanine molecules on Cu(111). Our experimental method can be extended to study the intermolecular charge transport of a range of molecular junctions.展开更多
Electronic transport properties of magnetically disordered R(-3)c phase Fe1.5Ti0.5O3-δ thin films epitaxially grown on Al2O3(0001) substrates have been studied. The measured magnetization in configurations with the m...Electronic transport properties of magnetically disordered R(-3)c phase Fe1.5Ti0.5O3-δ thin films epitaxially grown on Al2O3(0001) substrates have been studied. The measured magnetization in configurations with the magnetic field perpendicular and parallel to the film plane shows weak values of 0.1μB/formula compared to the theoretical value of 2μB/formula and a strong anisotropy with no saturation in perpendicular configuration. These properties are associated with the ato- mic scale disorder of Ti/Fe ions along c-axis. At zero-magnetic field and within the temperature range of 80 K to 400 K, the conduction mechanism appears to be Efros-Shklovskii variable range hopping with a carrier localization length of ξ0= 0.86nm. Magneto-resistance (MR) is positive in perpendicular configuration, while it is negative in parallel configuration, with significant values of MR = 27%- 37% at room temperature at 9 Tesla. Electron localization lengths were deduced from experiment for different external magnetic fields. The origin of magneto-resistance observed in experiment, is discussed.展开更多
In this study,a commercial magnesium alloy AZ31(Mg-3Al-1Zn-0.3Mn)sheet through a short manufacturing process was found to be ductile and highly formable in bending.Despite possessing a strong basal texture,the short-p...In this study,a commercial magnesium alloy AZ31(Mg-3Al-1Zn-0.3Mn)sheet through a short manufacturing process was found to be ductile and highly formable in bending.Despite possessing a strong basal texture,the short-processed sheet without any annealing can be bent at a small radius,only 0.2 times its thickness in the 90°bending test.Additionally,it could withstand direct deformation by repeated folding-flattening.The in-situ microstructural characterization reveals that extension twin bands with strain localization appear in the bending area.During subsequent flattening,these twin bands underwent detwinning,reducing local strain concentrations and enabling further bending deformation.Such outstanding bend formability originated from the significant-type dislocation loops slipping on the prismatic crystal planes within dynamic-recrystallized grains.These grains underwent a uniform refinement to several microns in the short manufacturing process and exhibited low residual strain.The active prismatic dislocation slip within refined grains was due to its much lower relative activation stress to basal slip(CRSSprism/CRSSbasal of only∼1.6)owing to the effective grain boundary hardening.Furthermore,the prismatic dislocation activity was further enhanced when bypassing Al-Mn nano-particles during motion,leaving debris and loops that facilitated easy multiplication.展开更多
Light emission of europium(Eu^(3+))ions placed in the vicinity of optically resonant nanoantennas is usually controlled by tailoring the local density of photon states(LDOS).We show that the polarization and shape of ...Light emission of europium(Eu^(3+))ions placed in the vicinity of optically resonant nanoantennas is usually controlled by tailoring the local density of photon states(LDOS).We show that the polarization and shape of the excitation beam can also be used to manipulate light emission,as azimuthally or radially polarized cylindrical vector beam offers to spatially shape the electric and magnetic fields,in addition to the effect of silicon nanorings(Si-NRs)used as nanoantennas.The photoluminescence(PL)mappings of the Eu^(3+)transitions and the Si phonon mappings are strongly dependent of both the excitation beam and the Si-NR dimensions.The experimental results of Raman scattering and photoluminescence are confirmed by numerical simulations of the near-field intensity in the Si nanoantenna and in the Eu^(3+)-doped film,respectively.The branching ratios obtained from the experimental PL maps also reveal a redistribution of the electric and magnetic emission channels.Our results show that it could be possible to spatially control both electric and magnetic dipolar emission of Eu^(3+)ions by switching the laser beam polarization,hence the near field at the excitation wavelength,and the electric and magnetic LDOS at the emission wavelength.This paves the way for optimized geometries taking advantage of both excitation and emission processes.展开更多
Molecular Landers are a class of compounds containing an aromatic board as well as bulky side groups which upon adsorption of the molecule on a surface may lift the molecular board away from the substrate.Different mo...Molecular Landers are a class of compounds containing an aromatic board as well as bulky side groups which upon adsorption of the molecule on a surface may lift the molecular board away from the substrate.Different molecular Landers have extensively been studied as model systems for nanomachines and the formation of molecular wires,as well as for their function as“molecular moulds”,i.e.,acting as templates by accommodating metal atoms underneath their aromatic board.Here,we investigate the adsorption of a novel Lander molecule 1,4-bis(4-(2,4-diaminotriazine)phenyl)-2,3,5,6-tetrakis(4-tert-butylphenyl)benzene(DAT,C_(64)H_(68)N_(10))on Cu(110)and Au(111)surfaces under ultrahigh vacuum(UHV)conditions.By means of scanning tunneling microscopy(STM)imaging and manipulation,we characterize the morphology and binding geometries of DAT molecules at terraces and step edges.On the Cu(110)surface,various contact configurations of individual DAT Landers were formed at the step edges in a controlled manner,steered by STM manipulation,including lateral translation,rotation,and pushing molecules to an upper terrace.The diffusion barrier of single DAT molecules on Au(111)is considerably smaller than on Cu(110).The DAT Lander is specially designed with diamino-triazine side groups making it suitable for future studies of molecular self-assembly by hydrogen-bonding interactions.The results presented here are an important guide to the choice of substrate for future studies using this compound.展开更多
The proliferation of mobile devices in society accessing data via the ＂cloud＂ is imposing a dramatic increase in the amount of information to be stored on hard disk drives （HDD） used in servers. Forecasts are that...The proliferation of mobile devices in society accessing data via the ＂cloud＂ is imposing a dramatic increase in the amount of information to be stored on hard disk drives （HDD） used in servers. Forecasts are that areal densities will need to increase by as much as 35% compound per annum and by 2,020 cloud storage capacity will be around 7 zettabytes corresponding to areal densities of 2 Tb/in^2. This requires increased performance from the magnetic pole of the electromag- netic writer in the read/write head in the HDD. Current state-of-art writing is undertaken by morphologically complex magnetic pole of sub 100 nm dimensions, in an environment of engineered magnetic shields and it needs to deliver strong directional magnetic field to areas on the recording media around 50 nm × 13 nm. This points to the need for a method to perform direct quantitative measurements of the magnetic field generated by the write pole at the nanometer scale. Here we report on the complete in situ quantitative mapping of the magnetic field generated by a functioning write pole in operation using electron holography. The results point the way towards a new nanoscale magnetic field source to further develop in situ transmission electron microscopy.展开更多
We present an interplay of high-resolution scanning tunneling microscopy imaging and the corresponding theoretical calculations based on elastic scattering quantum chemistry techniques of the adsorption of a gold-func...We present an interplay of high-resolution scanning tunneling microscopy imaging and the corresponding theoretical calculations based on elastic scattering quantum chemistry techniques of the adsorption of a gold-functionalized rosette assembly and its building blocks on a Au(111)surface with the goal of exploring how to fabricate functional 3-D molecular nanostructures on surfaces.The supramolecular rosette assembly stabilized by multiple hydrogen bonds has been sublimed onto the Au(111)surface under ultra-high vacuum conditions;the resulting surface nanostructures are distinctly different from those formed by the individual molecular building blocks of the rosette assembly,suggesting that the assembly itself can be transferred intact to the surface by in situ thermal sublimation.This unanticipated result will open up new perspectives for growth of complex 3-D supramolecular nanostructures at the vacuum-solid interface.展开更多
基金supported by National Natural Science Foundation of China(Nos.21373020,21403008,61321001,21433011,21522301,21133001,21333001,913000002)Ministry of Science and Technology(Nos.2014CB 239302,2013CB 933404,2011CB808702)the Research Fund for the Doctoral Program of Higher Education(No.20130001110029)
文摘Self-similar fractals are of importance in both science and engineering. Metal-organic Sierpin′ ski triangles are particularly attractive for applications in gas separation, catalysis and sensing. Such fractals are constructed in this study by using 1208 V-shaped 4,400-dicyano-1,10：30,100-terphenyl molecules and Fe atoms on Au（1 1 1）, and studied in detail by low-temperature scanning tunneling microscopy. Density functional theory calculations are employed to rationalize the invisible Fe atoms in STM images. Monte Carlo simulations are performed to understand the formation mechanism of the surface-supported fractal crystals.
基金supported by the Ministry of Science and Technology (Nos.2018YFA0306003,2017YFA0205003)National Natural Science Foundation of China (Nos.21972002,21902003)supported by High-performance Computing Platform of Peking University。
文摘Geometries of molecule-molecule interfaces strongly influence the current passing from one molecule to another. The contact conductance of molecule-molecule junctions which consist of fullerene and tin phthalocyanine molecules is investigated with a low-temperature scanning tunneling microscope. Two types of molecules are deposited onto Cu(111). Fullerene molecules are transferred to tips through controlled contact of STM tips on molecules. The molecule-molecule junctions are formed by approaching fullereneterminated tips to tin phthalocyanine molecules on Cu(111). Our experimental method can be extended to study the intermolecular charge transport of a range of molecular junctions.
文摘Electronic transport properties of magnetically disordered R(-3)c phase Fe1.5Ti0.5O3-δ thin films epitaxially grown on Al2O3(0001) substrates have been studied. The measured magnetization in configurations with the magnetic field perpendicular and parallel to the film plane shows weak values of 0.1μB/formula compared to the theoretical value of 2μB/formula and a strong anisotropy with no saturation in perpendicular configuration. These properties are associated with the ato- mic scale disorder of Ti/Fe ions along c-axis. At zero-magnetic field and within the temperature range of 80 K to 400 K, the conduction mechanism appears to be Efros-Shklovskii variable range hopping with a carrier localization length of ξ0= 0.86nm. Magneto-resistance (MR) is positive in perpendicular configuration, while it is negative in parallel configuration, with significant values of MR = 27%- 37% at room temperature at 9 Tesla. Electron localization lengths were deduced from experiment for different external magnetic fields. The origin of magneto-resistance observed in experiment, is discussed.
基金the financial supported by the Science and Technology Innovation Program of Hunan Province (2020RC4013 and 2021JC0005)“Technology Innovation 2025” Major Special Project of Ningbo City+1 种基金the Joint Funds of the National Natural Science Foundation of China (U22A20187)the Future Fellowship of the Australian National University.
文摘In this study,a commercial magnesium alloy AZ31(Mg-3Al-1Zn-0.3Mn)sheet through a short manufacturing process was found to be ductile and highly formable in bending.Despite possessing a strong basal texture,the short-processed sheet without any annealing can be bent at a small radius,only 0.2 times its thickness in the 90°bending test.Additionally,it could withstand direct deformation by repeated folding-flattening.The in-situ microstructural characterization reveals that extension twin bands with strain localization appear in the bending area.During subsequent flattening,these twin bands underwent detwinning,reducing local strain concentrations and enabling further bending deformation.Such outstanding bend formability originated from the significant-type dislocation loops slipping on the prismatic crystal planes within dynamic-recrystallized grains.These grains underwent a uniform refinement to several microns in the short manufacturing process and exhibited low residual strain.The active prismatic dislocation slip within refined grains was due to its much lower relative activation stress to basal slip(CRSSprism/CRSSbasal of only∼1.6)owing to the effective grain boundary hardening.Furthermore,the prismatic dislocation activity was further enhanced when bypassing Al-Mn nano-particles during motion,leaving debris and loops that facilitated easy multiplication.
基金We acknowledge funding from Agence Nationale de la Recherche under project HiLight(ANR-19-CE24-0020-01)support by the Toulouse computing facility HPC CALMIP(grants p12167 and p19042)the LAAS-CNRS micro and nanotechnologies platform,a member of the French RENATECH network.ICB is partner of the French Investissements d’Avenir program EUR-EIPHI(17-EURE-0002).
文摘Light emission of europium(Eu^(3+))ions placed in the vicinity of optically resonant nanoantennas is usually controlled by tailoring the local density of photon states(LDOS).We show that the polarization and shape of the excitation beam can also be used to manipulate light emission,as azimuthally or radially polarized cylindrical vector beam offers to spatially shape the electric and magnetic fields,in addition to the effect of silicon nanorings(Si-NRs)used as nanoantennas.The photoluminescence(PL)mappings of the Eu^(3+)transitions and the Si phonon mappings are strongly dependent of both the excitation beam and the Si-NR dimensions.The experimental results of Raman scattering and photoluminescence are confirmed by numerical simulations of the near-field intensity in the Si nanoantenna and in the Eu^(3+)-doped film,respectively.The branching ratios obtained from the experimental PL maps also reveal a redistribution of the electric and magnetic emission channels.Our results show that it could be possible to spatially control both electric and magnetic dipolar emission of Eu^(3+)ions by switching the laser beam polarization,hence the near field at the excitation wavelength,and the electric and magnetic LDOS at the emission wavelength.This paves the way for optimized geometries taking advantage of both excitation and emission processes.
基金We acknowledge financial support from the IST Pico-Inside and NMP Frontiers European projects as well as grants from the Danish Ministry of Science,Technology and Innovation and from the Danish Research Councils.M.H and Y.B.J thank the CMIFM via the Volubilis France-Morocco exchange program.
文摘Molecular Landers are a class of compounds containing an aromatic board as well as bulky side groups which upon adsorption of the molecule on a surface may lift the molecular board away from the substrate.Different molecular Landers have extensively been studied as model systems for nanomachines and the formation of molecular wires,as well as for their function as“molecular moulds”,i.e.,acting as templates by accommodating metal atoms underneath their aromatic board.Here,we investigate the adsorption of a novel Lander molecule 1,4-bis(4-(2,4-diaminotriazine)phenyl)-2,3,5,6-tetrakis(4-tert-butylphenyl)benzene(DAT,C_(64)H_(68)N_(10))on Cu(110)and Au(111)surfaces under ultrahigh vacuum(UHV)conditions.By means of scanning tunneling microscopy(STM)imaging and manipulation,we characterize the morphology and binding geometries of DAT molecules at terraces and step edges.On the Cu(110)surface,various contact configurations of individual DAT Landers were formed at the step edges in a controlled manner,steered by STM manipulation,including lateral translation,rotation,and pushing molecules to an upper terrace.The diffusion barrier of single DAT molecules on Au(111)is considerably smaller than on Cu(110).The DAT Lander is specially designed with diamino-triazine side groups making it suitable for future studies of molecular self-assembly by hydrogen-bonding interactions.The results presented here are an important guide to the choice of substrate for future studies using this compound.
文摘The proliferation of mobile devices in society accessing data via the ＂cloud＂ is imposing a dramatic increase in the amount of information to be stored on hard disk drives （HDD） used in servers. Forecasts are that areal densities will need to increase by as much as 35% compound per annum and by 2,020 cloud storage capacity will be around 7 zettabytes corresponding to areal densities of 2 Tb/in^2. This requires increased performance from the magnetic pole of the electromag- netic writer in the read/write head in the HDD. Current state-of-art writing is undertaken by morphologically complex magnetic pole of sub 100 nm dimensions, in an environment of engineered magnetic shields and it needs to deliver strong directional magnetic field to areas on the recording media around 50 nm × 13 nm. This points to the need for a method to perform direct quantitative measurements of the magnetic field generated by the write pole at the nanometer scale. Here we report on the complete in situ quantitative mapping of the magnetic field generated by a functioning write pole in operation using electron holography. The results point the way towards a new nanoscale magnetic field source to further develop in situ transmission electron microscopy.
基金the Danish Ministry for Science,Technology and Innovation through the iNANO Center,the Danish Research Councils,a Marie Curie-Intra-European Fellowship for H.G.(MEIF-CT-2004-010038)the SONS Eurocores program FUN-SMARTS,and the NMP Frontiers European project(NMP4-CT-2004-500328).
文摘We present an interplay of high-resolution scanning tunneling microscopy imaging and the corresponding theoretical calculations based on elastic scattering quantum chemistry techniques of the adsorption of a gold-functionalized rosette assembly and its building blocks on a Au(111)surface with the goal of exploring how to fabricate functional 3-D molecular nanostructures on surfaces.The supramolecular rosette assembly stabilized by multiple hydrogen bonds has been sublimed onto the Au(111)surface under ultra-high vacuum conditions;the resulting surface nanostructures are distinctly different from those formed by the individual molecular building blocks of the rosette assembly,suggesting that the assembly itself can be transferred intact to the surface by in situ thermal sublimation.This unanticipated result will open up new perspectives for growth of complex 3-D supramolecular nanostructures at the vacuum-solid interface.
