The surface magnetism of one monolayer Mn atoms on GaAs(001)surface is studied by the self-consistent tight-binding linear muffin-tin orbital method.It is found that the magnetic ordered phases(ferromagnetic and antif...The surface magnetism of one monolayer Mn atoms on GaAs(001)surface is studied by the self-consistent tight-binding linear muffin-tin orbital method.It is found that the magnetic ordered phases(ferromagnetic and antiferromagnetic)are more favorable than the paramagnetic one,the density of states peak far below the Fermi level observed in synchrotron radiation photoemission study has been identified as due to the contribution of Mn 3d majority states.展开更多
Chaos game representation （CGR） is proposed as a scale-independent representation for DNA sequences and provides information about the statistical distribution of oligonucleotides in a DNA sequence. CGR images of DN...Chaos game representation （CGR） is proposed as a scale-independent representation for DNA sequences and provides information about the statistical distribution of oligonucleotides in a DNA sequence. CGR images of DNA sequences represent some kinds of fractal patterns, but the common multifractal analysis based on the box counting method cannot deal with CGR images perfectly. Here, the wavelet transform modulus maxima （WTMM） method is applied to the multifractal analysis of CGR images. The results show that the scale-invariance range of CGR edge images can be extended to three orders of magnitude, and complete singularity spectra can be calculated. Spectrum parameters such as the singularity spectrum span are extracted to describe the statistical character of DNA sequences. Compared with the singularity spectrum span, exon sequences with a minimal spectrum span have the most uniform fractal structure. Also, the singularity spectrum parameters are related to oligonueleotide length, sequence component and species, thereby providing a method of studying the length polymorphism of repeat oligonucleotides.展开更多
Under high pressure, the long believed single-phase material CaB6 was latterly discovered to have a new phase tI56. Based on the density-functional theory, the pressure effects on the structural and elastic properties...Under high pressure, the long believed single-phase material CaB6 was latterly discovered to have a new phase tI56. Based on the density-functional theory, the pressure effects on the structural and elastic properties of CaB6 are obtained. The calculated bulk, shear, and Young’s moduli of the recently synthesized high pressure phase tI56-CaB6 are larger than those of the low pressure phase. Moreover, the high pressure phase of CaB6 has ductile behaviors, and its ductility increases with the increase of pressure. On the contrary, the calculated results indicate that the low pressure phase of CaB6 is brittle. The calculated Debye temperature indicates that the thermal conductivity of CaB6 is not very good. Furthermore, based on the Christoffel equation, the slowness surface of the acoustic waves is obtained.展开更多
The irradiation effects of femtosecond pulses on Ag-embedded composite glasses fabricated by ion-exchange are investigated using z-scan measurement. Both changes of the refractive index caused by the laser irradiation...The irradiation effects of femtosecond pulses on Ag-embedded composite glasses fabricated by ion-exchange are investigated using z-scan measurement. Both changes of the refractive index caused by the laser irradiation effect and the third-order optical nonlinearity are observed in the experiment. Taking the change of the linear and nonlinear refractive index into consideration, the fitting results are in agreement with the experimental results.展开更多
This paper reports that the doped bi-layer organic light-emitting devices are fabricated by doping in different regions of the light-emitting layer, the admittance and luminance spectra to characterize the capacitance...This paper reports that the doped bi-layer organic light-emitting devices are fabricated by doping in different regions of the light-emitting layer, the admittance and luminance spectra to characterize the capacitance and luminance of the device are measured. Negative capacitance （NC） appeared at low frequencies when the doped devices are biased with high voltages. The measured phase difference between AC voltage applied across the device and AC current flowing through the device show that the device is inductive when NC appears.展开更多
We exploit theoretically a class of rectangular cylindrical devices for noise shielding by using acoustic metamateriais. The function of noise shielding is justified by both the far-field and near-field full-wave simu...We exploit theoretically a class of rectangular cylindrical devices for noise shielding by using acoustic metamateriais. The function of noise shielding is justified by both the far-field and near-field full-wave simulations based on the finite element method. The enlargement of equivalent acoustic scattering cross sections is revealed to be the physical mechanism for this function. This work makes it possible to design a window with both noise shielding and air flow.展开更多
By using compositionally graded SiGe films as virtual substrates, tensile strained Si films with the strain of 1.5% and the threading dislocation density less than 1.0 × 10^5 cm-2 are successfully grown in micron...By using compositionally graded SiGe films as virtual substrates, tensile strained Si films with the strain of 1.5% and the threading dislocation density less than 1.0 × 10^5 cm-2 are successfully grown in micron size windows by molecular beam epitaxy （MBE）. The thickness of the virtual substrates was only 33Onto. On the surface of the s-Si films no cross-hatched lines resulting from misfit dislocations could be observed. We attribute these results to the edge-induced strain relaxation of the epitaxial films in windows, and the patterned virtual substrates with compositionally graded SiGe films.展开更多
Electrical properties of individual self-assembled GeSi quantum dots grown on Si substrates are investigated by using conductive atomic force microscopy at room temperature. By controlling the bias voltage sweep in a ...Electrical properties of individual self-assembled GeSi quantum dots grown on Si substrates are investigated by using conductive atomic force microscopy at room temperature. By controlling the bias voltage sweep in a certain fast sweep rate range, a novel current peak is observed in the current-voltage characteristics of the quantum dots. The current peaks are detectable only during the backward voltage sweep immediately after a forward sweep. The current peak position and intensity are found to depend strongly on the voltage sweep conditions. This kind of current-voltage characteristic under fast sweep is very different from the ordinary steady state current behaviour of quantum dots measured previously. trapping in the potential well formed bottom Si substrate. The origin of this phenomenon by the quantum dot sandwiched can be attributed to the transient hole between the native oxide layer and the展开更多
By utilizing the electrorheological effect, three-dimensional colloidal crystals can be produced, whose lattice structure can be changed from the body-centered-tetragonal lattice to other lattices under the applicatio...By utilizing the electrorheological effect, three-dimensional colloidal crystals can be produced, whose lattice structure can be changed from the body-centered-tetragonal lattice to other lattices under the application of electric fields. This paper calculates photonic band structures of such crystals with lattice structure transformation, and demonstrates the existence of complete band gaps for some intermediate lattices. Thus, it becomes possible to use the electrorheological effect to achieve photonic crystals with desired photonic gap properties resulting from tunable structures.展开更多
By using a first-principles approach, we investigate the pathway of electric displacement fields in shaped graded dielectric materials existing in the form of cloaks with various shapes. We reveal a type of apparently...By using a first-principles approach, we investigate the pathway of electric displacement fields in shaped graded dielectric materials existing in the form of cloaks with various shapes. We reveal a type of apparently negative electric polarization （ANEP）, which is due to a symmetric oscillation of the paired electric permittivities, satisfying a sum rule. The ANEP does not occur for a spherical cloak, but appears up to maximum as a/b （the ratio between the long and short principal axis of the spheroidal cloak） is about 5/2, and eventually disappears as a/b becomes large enough corresponding to a rod-like shape. Further, the cloaking efficiency is calculated for different geometrical shapes and demonstrated to closely relate to the ANEP. The possibility of experiments is discussed. This work has relevance to dielectric shielding based on shaped graded dielectric materials.展开更多
Amorphous Er2O3 films are deposited on Si （001） substrates by using reactive evaporation. This paper reports the evolution of the structure, morphology and electrical characteristics with annealing temperatures in a...Amorphous Er2O3 films are deposited on Si （001） substrates by using reactive evaporation. This paper reports the evolution of the structure, morphology and electrical characteristics with annealing temperatures in an oxygen ambience. X-ray diffraction and high resolution transimission electron microscopy measurement show that the films remain amorphous even after annealing at 700 ℃. The capacitance in the accumulation region of Er2O3 films annealed at 450 ℃ is higher than that of as-deposited films and films annealed at other temperatures. An Er2O3/ErOx/SiOx/Si structure model is proposed to explain the results. The annealed films also exhibit a low leakage current density （around 1.38 × 10^-4 A/cm^2 at a bias of -1 V） due to the evolution of morphology and composition of the films after they are annealed.展开更多
We study shot noise in tunneling current through a double quantum dot connected to two electric leads. We derive two master equations in the occupation-state basis and the eigenstate basis to describe the electron dyn...We study shot noise in tunneling current through a double quantum dot connected to two electric leads. We derive two master equations in the occupation-state basis and the eigenstate basis to describe the electron dynamics. The approach based on the occupation-state basis, despite being widely used in many previous studies, is valid only when the interdot coupling strength is much smaller than the energy difference between the two dots. In contrast, the calculations using the eigenstate basis are valid for an arbitrary interdot coupling. Using realistic model parameters, we demonstrate that the predicted currents and shot-noise properties from the two approaches are significantly different when the interdot coupling is not small. Furthermore, properties of the shot noise predicted using the eigenstate basis successfully reproduce qualitative features found in a recent experiment.展开更多
The epitaxial growth of Er2O3 films has been achieved on Si(001) substrates by MBE at the growth temperature of 700 ℃ in an oxygen pressure of 7×10-6 Torr. Synchrotron radiation photoemission spectroscopy was us...The epitaxial growth of Er2O3 films has been achieved on Si(001) substrates by MBE at the growth temperature of 700 ℃ in an oxygen pressure of 7×10-6 Torr. Synchrotron radiation photoemission spectroscopy was used to study the initial growth of Er2O3 films on Si in O2 pressures of 7×10-6 Torr. An interface layer was observed at the initial growth of Er2O3 film on Si even at room temperature, which is supposed to be attributed to the effect of the Er atom catalytic oxidation effect. With the film growth process continued, oxygen deficient Er oxide will capture oxygen from the interface layer which is formed inevitably at the initial growth of Er2O3 film and thus reduce and even remove the interface layer if the condition of O2 pressure is a little insufficient at a high substrate temperature.展开更多
We have investigated the steady-state cavity-field properties of a single-mode two-photon microreader when the atoms in a cascade three-level configuration are initially prepared in a mixture of the upper and intermed...We have investigated the steady-state cavity-field properties of a single-mode two-photon microreader when the atoms in a cascade three-level configuration are initially prepared in a mixture of the upper and intermediate states. The mean photon number, trapping state and sub-Poissonian effect are discussed with upper （intermediate）-state population changing from 1（0） to 0（1）. These properties are very different from those in a pure two- or one-photon transition process, due to the competition among different transition processes. In particular, the trapping states of nonzero photons are discovered in this system under some conditions, which is contrary to the previous findings.展开更多
The electronic structure of the new superconductor SmO1-xFxFeAs （x = 0.15） is studied by angle-integrated photoemission spectroscopy. Our data show a sharp feature very close to the Fermi energy, and a relative fiat...The electronic structure of the new superconductor SmO1-xFxFeAs （x = 0.15） is studied by angle-integrated photoemission spectroscopy. Our data show a sharp feature very close to the Fermi energy, and a relative fiat distribution of the density of states between 0.5eV and 3eV binding energy, which agrees well with the band structure calculations considering an antiferromagnetic ground state. No noticeable gap opening is observed at 12 K below the superconducting transition temperature, indicating the existence of large ungapped regions in the Brillouin zone.展开更多
Measurements of magnetization precession are performed for L2_(1) and B2−ordered Co_(2)FeAl_(0.5)Si_(0.5) full Heusler alloy films using the time−resolved magneto-optical Kerr effect technique in the out-of-plan confi...Measurements of magnetization precession are performed for L2_(1) and B2−ordered Co_(2)FeAl_(0.5)Si_(0.5) full Heusler alloy films using the time−resolved magneto-optical Kerr effect technique in the out-of-plan configuration.Dependence of the precession frequency on the external magnetic field can be fitted by the Landau–Lifshitz–Gilbert equation.The chirp parameters are close to each other for the L2_(1) and B2 structures,and decrease with the external magnetic field increasing.The relaxation rate of the B2−ordered film is smaller than that of the L2_(1) one.展开更多
Stoichiometric and amorphous Er2O3 films were deposited on Si(001) substrates by radio frequency magnetron technique. Spectroscopic ellipsometry measurement showed that the refractive index of the Er2O3 film in wavele...Stoichiometric and amorphous Er2O3 films were deposited on Si(001) substrates by radio frequency magnetron technique. Spectroscopic ellipsometry measurement showed that the refractive index of the Er2O3 film in wavelength region of 400–1000 nm was between 1.6–1.7. The reflectivity of the Er2O3 films decreased greatly with respect to that from the uncoated Si substrates. The absorption coefficient of the Er2O3 film indicated that it had an energy gap larger than 4.5 eV. The obtained characteristics indicated...展开更多
The wurtzite MnO has been obtained lately and is expected to have large potentiai in varies applications. Since elastic properties are the bases of various applications, we calculate these properties of wurtzite MnO b...The wurtzite MnO has been obtained lately and is expected to have large potentiai in varies applications. Since elastic properties are the bases of various applications, we calculate these properties of wurtzite MnO based on the density-functionai theory and compare it with other two phases of MnO （rocksalt and zinc-blende MnO）. The Young＇s modulus of wurtzite and zinc-blende MnO are 65.6 GPa and 73.4 GPa, respectively, which are much lower than those of rocksaJt MnO （177.6 GPa）. More importantly, both the Poisson ratio and the bulk modulus to shear modulus ratio indicate that wurtzite MnO should have much better ductile properties than rocksalt MnO. The calculated piezoelectric constants of wurtzite MnO are comparable to those of ZnO, This suggests wurtzite MnO is a good piezoelectric material. Furthermore, the slowness surfaces of acoustic waves of them are given from Christoffel equation.展开更多
The optical properties of porous silicon（PS） samples fabricated by pulse etching in a temperature range from-40 to 50-C have been investigated using reflectance spectroscopy,photoluminescence spectroscopy,and scanni...The optical properties of porous silicon（PS） samples fabricated by pulse etching in a temperature range from-40 to 50-C have been investigated using reflectance spectroscopy,photoluminescence spectroscopy,and scanning electron microscopy（SEM）.The dependence of the optical parameters,such as the refractive index n and the optical thickness（nd） of PS samples,on the etching temperature has been analyzed in detail.As the etching temperature decreases,n decreases,indicating a higher porosity,and the physical thickness of PS samples also decreases.Meanwhile,the reflectance spectra exhibit a more intense interference band and the interfaces are smoother.In addition,the intensity of the PL emission spectra is dramatically increased.展开更多
基金Supported by the National Climbing Program of China(Grant No.95-YU-41)the National Natural Science Foundation of China under Grant Nos.19625410 and 19734002+2 种基金the Fok Ying-dong Education Foundation for Young FacultiesShanghai Commission of Science and Technologythe Science Foundation of He'nan Province(984051800).
文摘The surface magnetism of one monolayer Mn atoms on GaAs(001)surface is studied by the self-consistent tight-binding linear muffin-tin orbital method.It is found that the magnetic ordered phases(ferromagnetic and antiferromagnetic)are more favorable than the paramagnetic one,the density of states peak far below the Fermi level observed in synchrotron radiation photoemission study has been identified as due to the contribution of Mn 3d majority states.
基金Project supported by the Science and Technology Commission of Shanghai Municipality (Grant No. 05DZ19747)the National Basic Research Program of China (Grant No. 2006CB504509)
文摘Chaos game representation （CGR） is proposed as a scale-independent representation for DNA sequences and provides information about the statistical distribution of oligonucleotides in a DNA sequence. CGR images of DNA sequences represent some kinds of fractal patterns, but the common multifractal analysis based on the box counting method cannot deal with CGR images perfectly. Here, the wavelet transform modulus maxima （WTMM） method is applied to the multifractal analysis of CGR images. The results show that the scale-invariance range of CGR edge images can be extended to three orders of magnitude, and complete singularity spectra can be calculated. Spectrum parameters such as the singularity spectrum span are extracted to describe the statistical character of DNA sequences. Compared with the singularity spectrum span, exon sequences with a minimal spectrum span have the most uniform fractal structure. Also, the singularity spectrum parameters are related to oligonueleotide length, sequence component and species, thereby providing a method of studying the length polymorphism of repeat oligonucleotides.
文摘Under high pressure, the long believed single-phase material CaB6 was latterly discovered to have a new phase tI56. Based on the density-functional theory, the pressure effects on the structural and elastic properties of CaB6 are obtained. The calculated bulk, shear, and Young’s moduli of the recently synthesized high pressure phase tI56-CaB6 are larger than those of the low pressure phase. Moreover, the high pressure phase of CaB6 has ductile behaviors, and its ductility increases with the increase of pressure. On the contrary, the calculated results indicate that the low pressure phase of CaB6 is brittle. The calculated Debye temperature indicates that the thermal conductivity of CaB6 is not very good. Furthermore, based on the Christoffel equation, the slowness surface of the acoustic waves is obtained.
基金Supported by the National Natural Science Foundation of China under Nos 10674031, 50672069 and 60878018, and China Postdoctoral Science Foundation （20090451006）, the Program for New Century Excellent Talents in University （NCET）, the Program of Excellent Team and Development Program for Outstanding Young Teachers in Harbin Institute of Technology （HITQNJS.2009.003） in Harbin Institute of Technology.
文摘The irradiation effects of femtosecond pulses on Ag-embedded composite glasses fabricated by ion-exchange are investigated using z-scan measurement. Both changes of the refractive index caused by the laser irradiation effect and the third-order optical nonlinearity are observed in the experiment. Taking the change of the linear and nonlinear refractive index into consideration, the fitting results are in agreement with the experimental results.
基金supported by the Natural Science Foundation of the Shanghai Committee of Science and Technology,China (GrantNo. 08JC1402300)
文摘This paper reports that the doped bi-layer organic light-emitting devices are fabricated by doping in different regions of the light-emitting layer, the admittance and luminance spectra to characterize the capacitance and luminance of the device are measured. Negative capacitance （NC） appeared at low frequencies when the doped devices are biased with high voltages. The measured phase difference between AC voltage applied across the device and AC current flowing through the device show that the device is inductive when NC appears.
基金Support by the National Natural Science Foundation of China under Grant Nos. 10604014 and 10874025by Chinese National Key Basic Research Special Fund under Grant No. 2006CB921706
文摘We exploit theoretically a class of rectangular cylindrical devices for noise shielding by using acoustic metamateriais. The function of noise shielding is justified by both the far-field and near-field full-wave simulations based on the finite element method. The enlargement of equivalent acoustic scattering cross sections is revealed to be the physical mechanism for this function. This work makes it possible to design a window with both noise shielding and air flow.
基金Supported by the Natural Science Foundation of China under Grant No 60376012, and the National Advanced Materials Committee of China under Grant No 2002AA313020.
文摘By using compositionally graded SiGe films as virtual substrates, tensile strained Si films with the strain of 1.5% and the threading dislocation density less than 1.0 × 10^5 cm-2 are successfully grown in micron size windows by molecular beam epitaxy （MBE）. The thickness of the virtual substrates was only 33Onto. On the surface of the s-Si films no cross-hatched lines resulting from misfit dislocations could be observed. We attribute these results to the edge-induced strain relaxation of the epitaxial films in windows, and the patterned virtual substrates with compositionally graded SiGe films.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60425411 and 10874030, the National Basic Research Programme of China under Grant No 2006CB921505, and Shanghai Science and Technology Commission.
文摘Electrical properties of individual self-assembled GeSi quantum dots grown on Si substrates are investigated by using conductive atomic force microscopy at room temperature. By controlling the bias voltage sweep in a certain fast sweep rate range, a novel current peak is observed in the current-voltage characteristics of the quantum dots. The current peaks are detectable only during the backward voltage sweep immediately after a forward sweep. The current peak position and intensity are found to depend strongly on the voltage sweep conditions. This kind of current-voltage characteristic under fast sweep is very different from the ordinary steady state current behaviour of quantum dots measured previously. trapping in the potential well formed bottom Si substrate. The origin of this phenomenon by the quantum dot sandwiched can be attributed to the transient hole between the native oxide layer and the
基金supported by the National Key Basic Research Special Fund (Grant No. 2006CB921706)the National Natural Science Foundation of China (Grant Nos. 10604014 and 10874025)
文摘By utilizing the electrorheological effect, three-dimensional colloidal crystals can be produced, whose lattice structure can be changed from the body-centered-tetragonal lattice to other lattices under the application of electric fields. This paper calculates photonic band structures of such crystals with lattice structure transformation, and demonstrates the existence of complete band gaps for some intermediate lattices. Thus, it becomes possible to use the electrorheological effect to achieve photonic crystals with desired photonic gap properties resulting from tunable structures.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 10604014 and 10874025the Shanghai Education Committee and the Shanghai Education Development Foundation ("Shu Guang" Project under Grant No. 05SG01)+1 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, ChinaChinese National Key Basic Research Special Fund under Grant No. 2006CB921706
文摘By using a first-principles approach, we investigate the pathway of electric displacement fields in shaped graded dielectric materials existing in the form of cloaks with various shapes. We reveal a type of apparently negative electric polarization （ANEP）, which is due to a symmetric oscillation of the paired electric permittivities, satisfying a sum rule. The ANEP does not occur for a spherical cloak, but appears up to maximum as a/b （the ratio between the long and short principal axis of the spheroidal cloak） is about 5/2, and eventually disappears as a/b becomes large enough corresponding to a rod-like shape. Further, the cloaking efficiency is calculated for different geometrical shapes and demonstrated to closely relate to the ANEP. The possibility of experiments is discussed. This work has relevance to dielectric shielding based on shaped graded dielectric materials.
基金supported by the China Postdoctoral Science Foundation and Shaoxing Science and Technology Commission (Grant No2007A21015)supported by the Project of Shanghai Nanotechnology (Grant No 0852NM02400)the National Natural Science Foundation of China (Grant No 60806031)
文摘Amorphous Er2O3 films are deposited on Si （001） substrates by using reactive evaporation. This paper reports the evolution of the structure, morphology and electrical characteristics with annealing temperatures in an oxygen ambience. X-ray diffraction and high resolution transimission electron microscopy measurement show that the films remain amorphous even after annealing at 700 ℃. The capacitance in the accumulation region of Er2O3 films annealed at 450 ℃ is higher than that of as-deposited films and films annealed at other temperatures. An Er2O3/ErOx/SiOx/Si structure model is proposed to explain the results. The annealed films also exhibit a low leakage current density （around 1.38 × 10^-4 A/cm^2 at a bias of -1 V） due to the evolution of morphology and composition of the films after they are annealed.
基金Project supported by the National Basic Research Program of China (Grant Nos. 2009CB929300 and 2006CB921205)the National Natural Science Foundation of China (Grant Nos. 10534060 and 0625416)the Research Grant Council of Hong Kong SAR project (Grant No. 500908)
文摘We study shot noise in tunneling current through a double quantum dot connected to two electric leads. We derive two master equations in the occupation-state basis and the eigenstate basis to describe the electron dynamics. The approach based on the occupation-state basis, despite being widely used in many previous studies, is valid only when the interdot coupling strength is much smaller than the energy difference between the two dots. In contrast, the calculations using the eigenstate basis are valid for an arbitrary interdot coupling. Using realistic model parameters, we demonstrate that the predicted currents and shot-noise properties from the two approaches are significantly different when the interdot coupling is not small. Furthermore, properties of the shot noise predicted using the eigenstate basis successfully reproduce qualitative features found in a recent experiment.
文摘The epitaxial growth of Er2O3 films has been achieved on Si(001) substrates by MBE at the growth temperature of 700 ℃ in an oxygen pressure of 7×10-6 Torr. Synchrotron radiation photoemission spectroscopy was used to study the initial growth of Er2O3 films on Si in O2 pressures of 7×10-6 Torr. An interface layer was observed at the initial growth of Er2O3 film on Si even at room temperature, which is supposed to be attributed to the effect of the Er atom catalytic oxidation effect. With the film growth process continued, oxygen deficient Er oxide will capture oxygen from the interface layer which is formed inevitably at the initial growth of Er2O3 film and thus reduce and even remove the interface layer if the condition of O2 pressure is a little insufficient at a high substrate temperature.
基金Project supported by the National Natural Science Foundation of China, the National Key Basic Research Special Foundation of China, the Major Program of the National Natural Science Foundation of China （Grant No 10234040）, and the Shanghai Foundation for Development of Science and Technology （Grant No 02DJ14066）.
文摘We have investigated the steady-state cavity-field properties of a single-mode two-photon microreader when the atoms in a cascade three-level configuration are initially prepared in a mixture of the upper and intermediate states. The mean photon number, trapping state and sub-Poissonian effect are discussed with upper （intermediate）-state population changing from 1（0） to 0（1）. These properties are very different from those in a pure two- or one-photon transition process, due to the competition among different transition processes. In particular, the trapping states of nonzero photons are discovered in this system under some conditions, which is contrary to the previous findings.
基金Supported by the National Natural Science Foundation of China, the National Fundamental Research Program of China under Grant Nos 2006CB601002 2006CB921300 and 2006CB922005, and STCSM of China.
文摘The electronic structure of the new superconductor SmO1-xFxFeAs （x = 0.15） is studied by angle-integrated photoemission spectroscopy. Our data show a sharp feature very close to the Fermi energy, and a relative fiat distribution of the density of states between 0.5eV and 3eV binding energy, which agrees well with the band structure calculations considering an antiferromagnetic ground state. No noticeable gap opening is observed at 12 K below the superconducting transition temperature, indicating the existence of large ungapped regions in the Brillouin zone.
基金by the National Natural Science Foundation of China under Grant Nos 10874247,50871030 and 10974032the National Basic Research Program of China under Grant No 2009CB929201.
文摘Measurements of magnetization precession are performed for L2_(1) and B2−ordered Co_(2)FeAl_(0.5)Si_(0.5) full Heusler alloy films using the time−resolved magneto-optical Kerr effect technique in the out-of-plan configuration.Dependence of the precession frequency on the external magnetic field can be fitted by the Landau–Lifshitz–Gilbert equation.The chirp parameters are close to each other for the L2_(1) and B2 structures,and decrease with the external magnetic field increasing.The relaxation rate of the B2−ordered film is smaller than that of the L2_(1) one.
基金Project supported by the Special Project of Shanghai Nano-Technology (0852nm02400)the National Natural Science Foundation of China (10804072, 11004130, 60806031)the Key Fundamental Project of Shanghai (08JC1410400)
文摘Stoichiometric and amorphous Er2O3 films were deposited on Si(001) substrates by radio frequency magnetron technique. Spectroscopic ellipsometry measurement showed that the refractive index of the Er2O3 film in wavelength region of 400–1000 nm was between 1.6–1.7. The reflectivity of the Er2O3 films decreased greatly with respect to that from the uncoated Si substrates. The absorption coefficient of the Er2O3 film indicated that it had an energy gap larger than 4.5 eV. The obtained characteristics indicated...
文摘The wurtzite MnO has been obtained lately and is expected to have large potentiai in varies applications. Since elastic properties are the bases of various applications, we calculate these properties of wurtzite MnO based on the density-functionai theory and compare it with other two phases of MnO （rocksalt and zinc-blende MnO）. The Young＇s modulus of wurtzite and zinc-blende MnO are 65.6 GPa and 73.4 GPa, respectively, which are much lower than those of rocksaJt MnO （177.6 GPa）. More importantly, both the Poisson ratio and the bulk modulus to shear modulus ratio indicate that wurtzite MnO should have much better ductile properties than rocksalt MnO. The calculated piezoelectric constants of wurtzite MnO are comparable to those of ZnO, This suggests wurtzite MnO is a good piezoelectric material. Furthermore, the slowness surfaces of acoustic waves of them are given from Christoffel equation.
基金supported by the National Natural Science Foundation of China and the Hunan Provincial Natural Science Foundation of China(No. 04JJ40031)
文摘The optical properties of porous silicon（PS） samples fabricated by pulse etching in a temperature range from-40 to 50-C have been investigated using reflectance spectroscopy,photoluminescence spectroscopy,and scanning electron microscopy（SEM）.The dependence of the optical parameters,such as the refractive index n and the optical thickness（nd） of PS samples,on the etching temperature has been analyzed in detail.As the etching temperature decreases,n decreases,indicating a higher porosity,and the physical thickness of PS samples also decreases.Meanwhile,the reflectance spectra exhibit a more intense interference band and the interfaces are smoother.In addition,the intensity of the PL emission spectra is dramatically increased.
