Pb(111)film is a special system that exhibits strong quantum size effects in many electronic properties.The collective excitations,i.e.,plasmons,in Pb(111)films are also expected to show signatures of the quantum size...Pb(111)film is a special system that exhibits strong quantum size effects in many electronic properties.The collective excitations,i.e.,plasmons,in Pb(111)films are also expected to show signatures of the quantum size effect.Here,using high-resolution electron energy loss spectroscopy,we measured the plasmons on the surface of Pb(111)films with different film thicknesses and analyzed the plasmon dispersions.One surface plasmon branch exhibits prominent damping in the small momentum range,which can be attributed to the interaction between the top and bottom interfaces of the Pb(111)films.With the film thickness increasing,the critical momentum characterizing the damping in Pb(111)films decays not only much slower in Pb(111)films than in other metal films,and even in films with the thickness up to 40 monolayers the damping still exists.The slow decay of the surface plasmon damping,manifesting the strong quantum size effect in Pb(111)films,might be related to the strong nesting of the Fermi surface along the(111)direction.展开更多
We carry out first-principles calculations of Ru（0001） films up to 30 monolayers （MLs） to study the quantum size effect （Q, SE） of Ru films for two cases： the freestanding Ru films and Ru films on Pt（111） sub...We carry out first-principles calculations of Ru（0001） films up to 30 monolayers （MLs） to study the quantum size effect （Q, SE） of Ru films for two cases： the freestanding Ru films and Ru films on Pt（111） substrates. Our studies show that the properties of these films （surface energy, work-function, charge density decay length in a vacuum and chemical reactivity） exhibit pronounced oscillatory behavior as a function of the film thickness, with an oscillation period of about four MLs for both cases due to the relationship of the match between the Fermi wave vector and the film thickness. Due to the localization of d-electron of Ru films, these quantum oscillations almost disappear when the thickness of the film is more than -20 ML for the free standing Ru films, while for the Ru films on Pt substrates the oscillations disappear quickly when the thickness of the film is beyond -13 ML. Our results reveal that the stability and reactivity of the Ru films could be tailored through Q, SE and the Ru bilayer grown on Pt substrates observed in the experiment is also related to the effect.展开更多
The interface-optical-propagating （IO-PR） mixing phonon modes of a quasi-zero-dimensional （QOD） wurtzite cylindrical quantum dot （QD） structure are derived and studied by employing the macroscopic dielectric con...The interface-optical-propagating （IO-PR） mixing phonon modes of a quasi-zero-dimensional （QOD） wurtzite cylindrical quantum dot （QD） structure are derived and studied by employing the macroscopic dielectric continuum model. The analytical phonon states of IO-PR mixing modes are given. It is found that there are two types of IO-PR mixing phonon modes, i.e. p-IO//z-PR mixing modes and the z-IO//p-PR mixing modes existing in QOD wurtzite QDs. And each IO-PR mixing modes also have symmetrical and antisymmetrieal forms. Via a standard procedure of field quantization, the Frohlich Hamiltonians of electron-（IO-PR） mixing phonons interaction are obtained. Numerical calculations on a wurtzite GaN cylindrical QD are performed. The results reveal that both the radial-direction size and the axial-direction size as well as the dielectric matrix have great influence on the dispersive frequencies of the IO-PR mixing phonon modes. The limiting features of dispersive curves of these phonon modes are discussed in depth. The phonon modes ＂reducing＂ behavior of wurtzite quantum confined systems has been observed obviously in the structures. Moreover, the degenerating behaviors of the IO-PR mixing phonon modes in wurtzite QOD QDs to the IO modes and PR modes in wurtzite Q2D QW and QID QWR systems are analyzed deeply from both of the viewpoints of physics and mathematics.展开更多
The energies and the magnetization of an electron in a piece of metal in the structure of Metal/Insulator/Metal/Insulator… (M/I/M/I…), in a magnetic field, at high temperature, and in range of quantum size thickness...The energies and the magnetization of an electron in a piece of metal in the structure of Metal/Insulator/Metal/Insulator… (M/I/M/I…), in a magnetic field, at high temperature, and in range of quantum size thickness of the piece of metal layer have been obtained. The results show that when the thickness of the metal layer becomes smaller, the orbital magnetism of the charged particles which collide with the wall of the metal layer is to vary from diamagnetism to paramagnetism. The smaller the thickness of the metal layer becomes, the more particles will collide with the boundary of the metal layer, and then the paramagnetism becomes stronger. Finally, when the thickness of the metal layer becomes very small (<100 nm), all of the orbital diamagnetism will reverse to paramagnetism, and then the paramagnetization will be almost a maximum constant.展开更多
Exciton energies as a function of radii of quantum dots in the range of 5–35 ? are calculated based on effective mass approximation model with the B-spline technique and compared with experimental and other theoretic...Exciton energies as a function of radii of quantum dots in the range of 5–35 ? are calculated based on effective mass approximation model with the B-spline technique and compared with experimental and other theoretical data for the CdS dots. This method leads to accurate and fast convergent exciton energy, which are in good agreement with experimental data in the whole confinement regime. The effect of penetration of wave function from the inside to the outside of the dots and the effect of dielectric constants are taken into account. The magnitudes of dynamical parameters are discussed. It is found that the different materials surrounding the CdS quantum dot affect not only the potential energy and Coulomb interaction energy of the system, but also the effective masses. The comparison shows that the effective mass approximation model can describe very well the quantum size effects observed experimentally on the exciton ground state energy.展开更多
The amorphous silicon nanoparticles （Si NPs） embedded in silicon nitride （SiNx） films prepared by helicon wave plasma-enhanced chemical vapor deposition （HWP-CVD） technique are studied. From Raman scattering inv...The amorphous silicon nanoparticles （Si NPs） embedded in silicon nitride （SiNx） films prepared by helicon wave plasma-enhanced chemical vapor deposition （HWP-CVD） technique are studied. From Raman scattering investigation, we determine that the deposited film has the structure of silicon nanocrystals embedded in silicon nitride （nc-Si/SiNx） thin film at a certain hydrogen dilution amount. The analysis of optical absorption spectra implies that the Si NPs is affected by quantum size effects and has the nature of an indirect-band-gap semiconductor. Further, considering the effects of the mean Si NP size and their dispersion on oscillator strength, and quantum-confinement, we obtain an analytical expression for the spectral absorbance of ensemble samples. Gaussian as well as lognormal size-distributions of the Si NPs are considered for optical absorption coefficient calculations. The influence of the particle size-distribution on the optical absorption spectra was systematically studied. We present the fitting of the optical absorption experimental data with our model and discuss the results.展开更多
Taking into account the quantum size effects and considering three types of scattering from bulk impurities,rough surface and rough interfaces, we use quantum-statistical Green's function approach and Kubo theory ...Taking into account the quantum size effects and considering three types of scattering from bulk impurities,rough surface and rough interfaces, we use quantum-statistical Green's function approach and Kubo theory to calculate the electronic conductivity and the giant magnetoresistance in magnetic multilayered cylindrical systems. It is found that in the limit of weakly scattering from impurities surface and interfaces, the total conductivity is given by a sum of conductivities of all the subbands and two spin-channels. For each subband and each spin-channel the scattering rate due to the impurities, surface and interfaces is added up.展开更多
Using first-principles calculations, we systematically study the dissociations of 02 molecules on different ultrathin Pb（lll） films. According to our previous work revealing the molecular adsorption precursor states...Using first-principles calculations, we systematically study the dissociations of 02 molecules on different ultrathin Pb（lll） films. According to our previous work revealing the molecular adsorption precursor states for O2, we further explore why there are two nearly degenerate adsorption states on Pb（lll） ultrathin films, but no precursor adsorption states existing at all on Mg（0001） and Al（lll） surfaces. The reason is concluded to be the different surface electronic structures. For the O2 dissociation, we consider both the reaction channels from gas-like and molecularly adsorbed O2 molecules. We find that the energy barrier for O2 dissociation from the molecular adsorption precursor states is always smaller than that from O2 gas. The most energetically favorable dissociation process is found to be the same on different Pb（lll） fihns, and the energy barriers are found to be influenced by the quantum size effects of Pb（lll） films.展开更多
The nanometer cobalt blue pigments were prepared by microemulsion method. Using dynamic light scattering(DLS) test method, the influences of water content on the size of liquid drop of microemulsion and the liquid dro...The nanometer cobalt blue pigments were prepared by microemulsion method. Using dynamic light scattering(DLS) test method, the influences of water content on the size of liquid drop of microemulsion and the liquid drop of microemulsion on the final diameter of nanometer particle were studied in the course of preparation. Accordingly, the method to control the diameter of nanometer particle by changing water content was established. The nanometer cobalt blue particles were confirmed by XRD and TEM. Color parameters of pigments were determined. The quantum size effect of the pigments was discussed.展开更多
Optoelectronic nanocomposites are a new class of materials, which exhibit very interesting and particular properties and attract a growing attention due to their potential applications in information storage and optoe...Optoelectronic nanocomposites are a new class of materials, which exhibit very interesting and particular properties and attract a growing attention due to their potential applications in information storage and optoelectronic devices. Zinc oxide, ZnO, is one of the most interesting binary semiconductor （3.37 eV） with very important optical properties, which can be used in the fields such as short wavelength lasers, blue light emitting diodes, UV detectors, gas sensors, etc. This paper reviews the very recent progress in the prepa- ration of silica-based ZnO nanocomposites. After an introduction reviewing the theoretical background, the article will begin with a survey of the optical properties and the quantum size effect （QSE） of ZnO/SiO2 nanocomposites prepared by the inclusion of ZnO nanoclusters inside silica mesoporous materials. The second part will focus on one of the most interesting properties of ZnO/SiO2 nanocomposites, which is the random lasing effect after one- and two-photon excitation. The final part will deal with the introduction of ZnO nanoparticles inside microporous zeolites and the observation of QSE. For comparison, the photoluminescence （PL） and QSE properties of ZnS nanoparticles occluded in mesoporous media are also described. New potential applications will be discussed since short-wavelength devices are required by industry to design, for instance, new information storage supports and biolabelling devices.展开更多
The phonon thermal contribution to the melting temperature of nano-particles is inspected. The discrete summation of phonon states and its corresponding integration form as an approximation for a nano-particle or for ...The phonon thermal contribution to the melting temperature of nano-particles is inspected. The discrete summation of phonon states and its corresponding integration form as an approximation for a nano-particle or for a bulk system have been analyzed. The discrete phonon energy levels of pure size effect and the wave-vector shifts of boundary conditions are investigated in detail. Unlike in macroscopic thermodynamics, the integration volume of zero-mode of phonon for a nano-particle is not zero, and it plays an important role in pure size effect and boundary condition effect. We find that a nano-particle will have a rising melting temperature due to purely finite size effect; a lower melting temperature bound exists for a nano-particle in various environments, and the melting temperature of a nano-particle with free boundary condition reaches this lower bound. We suggest an easy procedure to estimation the melting temperature, in which the zero-mode contribution will be excluded, and only several bulk quantities will be used as input. We would like to emphasize that the quantum effect of discrete energy levels in nano-particles, which is not present in early thermodynamic studies on finite size corrections to melting temperature in small systems, should be included in future researches.展开更多
CONSPECTUS:Metal nanoclusters represent a unique class of nanomaterials with monodisperse sizes,atomically precise structures,and rich physicochemical properties,and they find wide applications in optics,catalysis,and...CONSPECTUS:Metal nanoclusters represent a unique class of nanomaterials with monodisperse sizes,atomically precise structures,and rich physicochemical properties,and they find wide applications in optics,catalysis,and biomedicine.The strong quantum size effects and discrete electronic energy levels endow metal nanoclusters with structuredependent properties,where any perturbation of their compositions or structures induces significant variations in their properties.This makes the research of metal nanoclusters particularly exciting but also challenging,as small changes in their atomic composition or arrangement can result in substantial differences in their behavior.展开更多
Periodic disposed quantum dot arrays are very useful for the large scale integration of single electron devices. Gold quantum dot arrays were self-assembled inside pore channels of ordered amino-functionalized mesopor...Periodic disposed quantum dot arrays are very useful for the large scale integration of single electron devices. Gold quantum dot arrays were self-assembled inside pore channels of ordered amino-functionalized mesoporous silica thin films, employing the neutralization reaction between chloroauric acid and amino groups. The diameters of quantum dots are controlled via changing the aperture of pore channels from 2.3 to 8.3 nm, which are characterized by HRTEM, SEM and FT-IR. UV-vis absorption spectra of gold nanoparticle/mesoporous silica composite thin films exhibit a blue shift and intensity drop of the absorption peak as the aperture of mesopores decreases, which represents the energy level change of quantum dot arrays due to the quantum size effect.展开更多
基金the National Natural Science Foundation of China(Grant Nos.11874404 and 11634016)the National Key Research and Development Program of China(Grant Nos.2016YFA0302400,2016YFA0202300,and 2017YFA0303600)+1 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB33000000)supported by the Youth Innovation Promotion Association of Chinese Academy of Sciences。
文摘Pb(111)film is a special system that exhibits strong quantum size effects in many electronic properties.The collective excitations,i.e.,plasmons,in Pb(111)films are also expected to show signatures of the quantum size effect.Here,using high-resolution electron energy loss spectroscopy,we measured the plasmons on the surface of Pb(111)films with different film thicknesses and analyzed the plasmon dispersions.One surface plasmon branch exhibits prominent damping in the small momentum range,which can be attributed to the interaction between the top and bottom interfaces of the Pb(111)films.With the film thickness increasing,the critical momentum characterizing the damping in Pb(111)films decays not only much slower in Pb(111)films than in other metal films,and even in films with the thickness up to 40 monolayers the damping still exists.The slow decay of the surface plasmon damping,manifesting the strong quantum size effect in Pb(111)films,might be related to the strong nesting of the Fermi surface along the(111)direction.
文摘We carry out first-principles calculations of Ru（0001） films up to 30 monolayers （MLs） to study the quantum size effect （Q, SE） of Ru films for two cases： the freestanding Ru films and Ru films on Pt（111） substrates. Our studies show that the properties of these films （surface energy, work-function, charge density decay length in a vacuum and chemical reactivity） exhibit pronounced oscillatory behavior as a function of the film thickness, with an oscillation period of about four MLs for both cases due to the relationship of the match between the Fermi wave vector and the film thickness. Due to the localization of d-electron of Ru films, these quantum oscillations almost disappear when the thickness of the film is more than -20 ML for the free standing Ru films, while for the Ru films on Pt substrates the oscillations disappear quickly when the thickness of the film is beyond -13 ML. Our results reveal that the stability and reactivity of the Ru films could be tailored through Q, SE and the Ru bilayer grown on Pt substrates observed in the experiment is also related to the effect.
基金Supported by National Natural Science Foundation of China under Grant Nos. 60711120203, 60890193STPAA of Guangzhou City under Grant No. 2060
文摘The interface-optical-propagating （IO-PR） mixing phonon modes of a quasi-zero-dimensional （QOD） wurtzite cylindrical quantum dot （QD） structure are derived and studied by employing the macroscopic dielectric continuum model. The analytical phonon states of IO-PR mixing modes are given. It is found that there are two types of IO-PR mixing phonon modes, i.e. p-IO//z-PR mixing modes and the z-IO//p-PR mixing modes existing in QOD wurtzite QDs. And each IO-PR mixing modes also have symmetrical and antisymmetrieal forms. Via a standard procedure of field quantization, the Frohlich Hamiltonians of electron-（IO-PR） mixing phonons interaction are obtained. Numerical calculations on a wurtzite GaN cylindrical QD are performed. The results reveal that both the radial-direction size and the axial-direction size as well as the dielectric matrix have great influence on the dispersive frequencies of the IO-PR mixing phonon modes. The limiting features of dispersive curves of these phonon modes are discussed in depth. The phonon modes ＂reducing＂ behavior of wurtzite quantum confined systems has been observed obviously in the structures. Moreover, the degenerating behaviors of the IO-PR mixing phonon modes in wurtzite QOD QDs to the IO modes and PR modes in wurtzite Q2D QW and QID QWR systems are analyzed deeply from both of the viewpoints of physics and mathematics.
基金Supported by the National Natural Science Foundation of China(5 96 0 2 0 0 4)
文摘The energies and the magnetization of an electron in a piece of metal in the structure of Metal/Insulator/Metal/Insulator… (M/I/M/I…), in a magnetic field, at high temperature, and in range of quantum size thickness of the piece of metal layer have been obtained. The results show that when the thickness of the metal layer becomes smaller, the orbital magnetism of the charged particles which collide with the wall of the metal layer is to vary from diamagnetism to paramagnetism. The smaller the thickness of the metal layer becomes, the more particles will collide with the boundary of the metal layer, and then the paramagnetism becomes stronger. Finally, when the thickness of the metal layer becomes very small (<100 nm), all of the orbital diamagnetism will reverse to paramagnetism, and then the paramagnetization will be almost a maximum constant.
文摘Exciton energies as a function of radii of quantum dots in the range of 5–35 ? are calculated based on effective mass approximation model with the B-spline technique and compared with experimental and other theoretical data for the CdS dots. This method leads to accurate and fast convergent exciton energy, which are in good agreement with experimental data in the whole confinement regime. The effect of penetration of wave function from the inside to the outside of the dots and the effect of dielectric constants are taken into account. The magnitudes of dynamical parameters are discussed. It is found that the different materials surrounding the CdS quantum dot affect not only the potential energy and Coulomb interaction energy of the system, but also the effective masses. The comparison shows that the effective mass approximation model can describe very well the quantum size effects observed experimentally on the exciton ground state energy.
基金Supported by the National Natural Science Foundation of China under Grant No.60940020the Natural Foundation of Hebei Province under Grant No.E2008000619
文摘The amorphous silicon nanoparticles （Si NPs） embedded in silicon nitride （SiNx） films prepared by helicon wave plasma-enhanced chemical vapor deposition （HWP-CVD） technique are studied. From Raman scattering investigation, we determine that the deposited film has the structure of silicon nanocrystals embedded in silicon nitride （nc-Si/SiNx） thin film at a certain hydrogen dilution amount. The analysis of optical absorption spectra implies that the Si NPs is affected by quantum size effects and has the nature of an indirect-band-gap semiconductor. Further, considering the effects of the mean Si NP size and their dispersion on oscillator strength, and quantum-confinement, we obtain an analytical expression for the spectral absorbance of ensemble samples. Gaussian as well as lognormal size-distributions of the Si NPs are considered for optical absorption coefficient calculations. The influence of the particle size-distribution on the optical absorption spectra was systematically studied. We present the fitting of the optical absorption experimental data with our model and discuss the results.
文摘Taking into account the quantum size effects and considering three types of scattering from bulk impurities,rough surface and rough interfaces, we use quantum-statistical Green's function approach and Kubo theory to calculate the electronic conductivity and the giant magnetoresistance in magnetic multilayered cylindrical systems. It is found that in the limit of weakly scattering from impurities surface and interfaces, the total conductivity is given by a sum of conductivities of all the subbands and two spin-channels. For each subband and each spin-channel the scattering rate due to the impurities, surface and interfaces is added up.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.90921003,10904004 and 60776063)the Fundamental Research Funds for the Central Universities,China(Grant No.JD1109)
文摘Using first-principles calculations, we systematically study the dissociations of 02 molecules on different ultrathin Pb（lll） films. According to our previous work revealing the molecular adsorption precursor states for O2, we further explore why there are two nearly degenerate adsorption states on Pb（lll） ultrathin films, but no precursor adsorption states existing at all on Mg（0001） and Al（lll） surfaces. The reason is concluded to be the different surface electronic structures. For the O2 dissociation, we consider both the reaction channels from gas-like and molecularly adsorbed O2 molecules. We find that the energy barrier for O2 dissociation from the molecular adsorption precursor states is always smaller than that from O2 gas. The most energetically favorable dissociation process is found to be the same on different Pb（lll） fihns, and the energy barriers are found to be influenced by the quantum size effects of Pb（lll） films.
文摘The nanometer cobalt blue pigments were prepared by microemulsion method. Using dynamic light scattering(DLS) test method, the influences of water content on the size of liquid drop of microemulsion and the liquid drop of microemulsion on the final diameter of nanometer particle were studied in the course of preparation. Accordingly, the method to control the diameter of nanometer particle by changing water content was established. The nanometer cobalt blue particles were confirmed by XRD and TEM. Color parameters of pigments were determined. The quantum size effect of the pigments was discussed.
基金the FNRS(Fonds National de la Recherche Scientifique,Belgium)for a FRIA doctoral fellowship and then a"Chargéde Recherches"fellowshipThis work was realised in the frame of the Belgian Federal Government PAI-IUAP program(INANOMAT P6/17)The financial support from the University of Namur(FUNDP),"Aide institutionnelle aux collaborations internationales"is also acknowledged.
文摘Optoelectronic nanocomposites are a new class of materials, which exhibit very interesting and particular properties and attract a growing attention due to their potential applications in information storage and optoelectronic devices. Zinc oxide, ZnO, is one of the most interesting binary semiconductor （3.37 eV） with very important optical properties, which can be used in the fields such as short wavelength lasers, blue light emitting diodes, UV detectors, gas sensors, etc. This paper reviews the very recent progress in the prepa- ration of silica-based ZnO nanocomposites. After an introduction reviewing the theoretical background, the article will begin with a survey of the optical properties and the quantum size effect （QSE） of ZnO/SiO2 nanocomposites prepared by the inclusion of ZnO nanoclusters inside silica mesoporous materials. The second part will focus on one of the most interesting properties of ZnO/SiO2 nanocomposites, which is the random lasing effect after one- and two-photon excitation. The final part will deal with the introduction of ZnO nanoparticles inside microporous zeolites and the observation of QSE. For comparison, the photoluminescence （PL） and QSE properties of ZnS nanoparticles occluded in mesoporous media are also described. New potential applications will be discussed since short-wavelength devices are required by industry to design, for instance, new information storage supports and biolabelling devices.
基金Supported by National Natural Science Foundation of China under Grant No.1121403
文摘The phonon thermal contribution to the melting temperature of nano-particles is inspected. The discrete summation of phonon states and its corresponding integration form as an approximation for a nano-particle or for a bulk system have been analyzed. The discrete phonon energy levels of pure size effect and the wave-vector shifts of boundary conditions are investigated in detail. Unlike in macroscopic thermodynamics, the integration volume of zero-mode of phonon for a nano-particle is not zero, and it plays an important role in pure size effect and boundary condition effect. We find that a nano-particle will have a rising melting temperature due to purely finite size effect; a lower melting temperature bound exists for a nano-particle in various environments, and the melting temperature of a nano-particle with free boundary condition reaches this lower bound. We suggest an easy procedure to estimation the melting temperature, in which the zero-mode contribution will be excluded, and only several bulk quantities will be used as input. We would like to emphasize that the quantum effect of discrete energy levels in nano-particles, which is not present in early thermodynamic studies on finite size corrections to melting temperature in small systems, should be included in future researches.
基金support of the NSFC(22371003,22101001,and 22471001)the Ministry of Education,Natural Science Foundation of Anhui Province(2408085Y006)+1 种基金the University Synergy Innovation Program of Anhui Province(GXXT-2020-053)the Scientific Research Program。
文摘CONSPECTUS:Metal nanoclusters represent a unique class of nanomaterials with monodisperse sizes,atomically precise structures,and rich physicochemical properties,and they find wide applications in optics,catalysis,and biomedicine.The strong quantum size effects and discrete electronic energy levels endow metal nanoclusters with structuredependent properties,where any perturbation of their compositions or structures induces significant variations in their properties.This makes the research of metal nanoclusters particularly exciting but also challenging,as small changes in their atomic composition or arrangement can result in substantial differences in their behavior.
基金supported by the National High Technology Research and Development Program of China(No.2009AA01Z114)the Advanced Research Foundation of National University of Defense Technology(No.JC08-02-08)the Innovation Program of National University of Defense Technology for Excellent Postgraduate
文摘Periodic disposed quantum dot arrays are very useful for the large scale integration of single electron devices. Gold quantum dot arrays were self-assembled inside pore channels of ordered amino-functionalized mesoporous silica thin films, employing the neutralization reaction between chloroauric acid and amino groups. The diameters of quantum dots are controlled via changing the aperture of pore channels from 2.3 to 8.3 nm, which are characterized by HRTEM, SEM and FT-IR. UV-vis absorption spectra of gold nanoparticle/mesoporous silica composite thin films exhibit a blue shift and intensity drop of the absorption peak as the aperture of mesopores decreases, which represents the energy level change of quantum dot arrays due to the quantum size effect.
