Photoelectric characteristics of silicon P–N junction with nanopillar texture:Analysis of X-ray photoelectron spectroscopy

Silicon nanopillars are fabricated by inductively coupled plasma(ICP) dry etching with the cesium chloride(CsCl)islands as masks originally from self-assembly. Wafers with nanopillar texture or planar surface are subjected to phosphorus(P) diffusion by liquid dopant source(POCl3) at 870℃ to form P–N junctions with a depth of 300 nm. The X-ray photoelectron spectroscopy(XPS) is used to measure the Si 2p core levels of P–N junction wafer with nanopillar texture and planar surface. With a visible light excitation, the P–N junction produces a new electric potential for photoelectric characteristic, which causes the Si 2p core level to have a energy shift compared with the spectrum without the visible light.The energy shift of the Si 2p core level is-0.27 eV for the planar P–N junction and-0.18 eV for the nanopillar one. The difference in Si 2p energy shift is due to more space lattice defects and chemical bond breaks for nanopillar compared with the planar one.     

Charge transfer of 1 ML C60/Ag（100）

We have measured the synchrotron radiation photoelectron spectra of monolayer C60on Ag（100）, By calculating the intensity ratios between the LUMO bands and the two deeper bands （HOMO and HOMO- 1）, we estimate the amount of the charges transferred from Ag（100） to C60 within the range of 1 e to 1.8 e. The results dismay the expectation of surface superconductivity and afford a good reference for further studies of the monolayer C60/Ag（100） system.     

Analysis of flatband voltage shift of metallhigh-k/Si02/Si stack based on energy band alignment of entire gate stack

A theoretical model of flatband voltage （VFB） of metal/high-k/Si02/Si stack is proposed based on band alignment of entire gate stack, i.e., the VFB is obtained by simultaneously considering band alignments of metal/high-k, high-k/SiO2 and SiO2/Si interfaces, and their interactions. Then the VFB of TiN/HfO2/SiO2/Si stack is experimentally obtained and theoretically investigated by this model. The theoretical calculations are in good agreement with the experimental results. Furthermore, both positive VFB shift of TiN/HfO2/SiO2/Si stack and Fermi level pinning are successfully interpreted and attributed to the dielectric contact induced gap states at TiN/HfO2 and HfO2/SiO2 interfaces.     

Electronic and Optical Properties of Rock-Salt AIN under High Pressure via First-Principles Analysis

Electronic and optical properties of rock-salt AIN under high pressure are investigated by first -principles method based on the plane-wave basis set. Analysis of band structures suggests that the rock-salt AIN has an indirect gap of 4.53 eV, which is in good agreement with other results. By investigating the effects of pressure on the energy gap, the different movement of conduction band at X point below and above 22.5 GPa is predicted. The optical properties including dielectric function, absorption, reflectivity, and refractive index are also calculated and analyzed. It is found that the rock-salt AIN is transparent from the partially ultra-violet to the visible light area and hardly does the transparence affected by the pressure. Furthermore, the curve of optical spectrum will shift to high energy area （blue shift） with increasing pressure.     

Preparation and characterization of nanosized GdxBi0.95-xVO4：0.05Eu3＋ solid solution as red phosphor

A complete solid solutions with monophasic zircon-type structure of vanadates of formula GdxBio.95-xVO4：0.05Eu3＋ （x = 04）.95） are synthesized by combined method of co-precipitation and hydrothermal synthesis. Their microstructures and morphologies are characterized by X-ray powder diffraction and transmission electronic microscope, and the results show that each of all the samples has a monophasic zircon-type structure. The absorption spectrum of the prepared phosphor shows a blue-shift of the fundamental absorption band edge with increasing the gadolinium content. Under UV-light and visible-light excitation, all the prepared phosphors show the typical luminescence properties of Eu3＋ in the zircon-type structure. The emission intensity of GdxBi0.95-xVO4：0.05Eu3＋ （x = 0.55） is strongest in all samples under UV-light and visible-light excitations. Finally, the mechanisms of luminescence of Eu3＋ in the GdxBi0.95-xVO4：0.05Eu3＋ （x = 0-0.95） solid solutions are analyzed and discussed.     

First-principles study of orbital ordering in cubic fluoride KCrF_3

Comprehensive first-principles calculations are performed to provide insight into the intriguing physical properties of the ternary cubic fluoride KCrF3. The electronic structures exhibit a prominent dependence on the effective local Coulomb interaction parameter Ueff. The ground state of the cubic phase is a ferromagnetic （FM） half-metal with Ueff equal to 0, 2, and 4 eV, whereas the insulating A-type antiferromagnetic （A-AFM） state with concomitant homogeneous orbital ordering is more robust than the FM state for Ueff exceeding 4 eV. We propose that the origin of the orbital ordering is purely electronic when the cooperative Jahn-Teller distortions are absent in cubic KCrF3.     

Influence of the photon beam position on incident SR intensity at the SXMCD endstation

A small fluctuation of the photon beam position will affect the intensity and polarization characteristics of synchrotron radiation （SR） when it enters an endstation through the related beamline. In this paper, by changing the electron orbit equilibrium position in the vertical direction, we have measured the corresponding changes in the absorption strength of the SR with a gold mesh in different chopper aperture positions. It is found that for three aperture positions, the absorption intensity of the gold mesh shows a good Gaussian distribution as the photon beam position moves, while the ratio of the SR intensity passing through the upper and lower apertures shows a monotonous variation. This suggests a new method for estimating the circular polarization degree of SR originating from the bending magnet based on our current measurement.     

Characteristics of photonic bands generated by quadrangular multiconnected networks

In this paper, by means of the network equation and generalized dimensionless Floquet-Bloch theorem, we study the influences of the number of connected waveguide segments （NCWS） between adjacent nodes and the matching ratio of waveguide length （MRWL） on the photonic bands generated by quadrangular multiconnected networks （QMNs）, and obtain a series of formulae. It is found that multicombining networks （MCNs） and repetitive combining networks （RCNs） are equivalent to each other and they can all be simplified into the simplest fundamental combining systems. It would be useful for adjusting the number, widths, and positions of photonic bands, and would possess potential applications for the designing of all-optical devices and photonic network devices.     

Energy band structure in optical of spin-1 condensates lattices

The energy band structure of spin-1 condensates with repulsive spimindependent and either ferromagnetic or antiferromagnetic spin-dependent interactions in one-dimensional （1D） periodic optical lattices is discussed. Within the two-mode approximation, Bloch bands of spin-1 condensates are presented. The results show that the Bloch bands exhibit a complex structure as the atom density of mF = 0 hyperfine state increases： bands splitting, reversion, intersection and loop structure are excited subsequently. The complex band structure should be related to the tunneling and spin-mixing dynamics.     

Effect of post-thermal and optical properties annealing on the structural of ZnO thin films prepared from a polymer precursor

ZnO thin films were synthesised by a new method which uses polyvinyl alcohol （PVA） as the polymer precursor. The films are annealed at different temperatures and for different annealing times. The structural parameters, like grain size, lattice constants, optical band gap, and Urbach energy, depend on the annealing temperature and time. All the films possess tensile strain, which relaxes as the annealing temperature and time increase. The photoluminescence （PL） spectra contain only ultraviolet （UV） peaks at low temperature, but as the annealing temperature and time increase, we observe peaks at the blue and green regions with a variation in the intensities of these peaks with annealing temperature and time.     

Electronic Structure Analysis of USiO4

Uranium is a member of Actinides and plays important role in nuclear science and technology. Electronic and structural investigations of actinide compounds attract major interest in science. The electronic structure and chemical bonding of coffinite USiO4 are investigated by X-ray Absorption Fine Structure spectroscopy （XAFS）. U L3- edge absorption spectrum in USiO4 is compared with U L3-edge spectra in UO2 and UTe due to their different electronic and chemical structures. The study presents XANES （x-ray Absorption Near-Edge Structure） and Extended XAFS （EXAFS） calculations of USiO4 thin films. The full multiple scattering approach has been applied to the calculation of U L3 edge XANES spectra of USiO4, UO2 and UTe, based on different choices of one electron potentials according to Uranium coordinations by using the real space multiple scattering method FEFF 8.2 code.     

In situ X-ray diffraction investigation of compression behavior in Gd40Y16Al24Co20 bulk metallic glass under high pressure with synchrotron radiation

The compression behavior of the heavy RE-based BMC Gd40Y16Al24Co20 under high pressure has been investigated by in situ high pressure angle dispersive X-ray diffraction measurements using synchrotron radiation in the pressure range of 0-33.42 GPa at room temperature. By fitting the static equation of state at room temperature, we find the value of bulk modulus B is 61.27±4 GPa which is in good agreement with the experimental study by pulse-echo techniques of 58 GPa. The results show that the amorphous structure in the heavy RE-based BMG Gd40Y16Al24Co20 keeps quite stable up to 33.42 GPa although its compressibility is as large as about 33%. The coexistence of normal local structure similar to that of other BMGs and covalent bond structure similar to those of oxide glasses may be the reason for the anomalous property under high pressure of the Gd4oY16Al24Co2o BMG.     

Small-angle X-ray analysis of the effect of grain size on the thermal damage of octahydro-1, 3, 5, 7-tetranitro-1, 3, 5, 7 tetrazocine-based plastic-bounded expolsives

The microstructure evolution of plastic-bonded explosives(PBXs) after thermal stimulus plays a key role in PBX performance. In this paper, the nanoscale pores of thermal-treated octahydro-1,3,5,7-tetranitro-1,3,5,7 tetrazocine(HMX)-based PBXs with different HMX particle sizes [approximately 40(FHP) and 100 μm(LHP)] were measured using smallangle X-ray scattering(SAXS). No obvious pore variations were found in the LHP samples heated at 160℃ for 6 h,whereas the amount of pores of FHP decreased when subjected to 160℃ for 6 h. At 180℃, the average pore radii of FHP and LHP decreased from approximately 45 nm to 25 nm, and the total pore volume increased distinctively because of phase transformation. The LHP sample reached a high level of pore content after being held at 180℃ for 1 h, whereas FHP required 3 h. Both FHP and LHP had relatively high pore volumes when subjected to 200℃ for 1 and 3 h.     

High pressure X-ray diffraction study of CaMnO3 perovskite

Using a diamond anvil cell device and synchrotron radiation,the in-situ high-pressure structure of CaMnO3 has been investigated.In the pressure up to 36.5 GPa,no pressure-induced phase transition is observed.The pressure dependence on the lattice parameters of CaMnO3 is reported,and the relationship of the axial compression coefficients is βa 〉 βc 〉 βb.The isothermal bulk modulus K298=224（25） GPa is also obtained by fitting the pressure-volume data using the Murnaghan equation of state.     

Charge state effect on the K-shell ionization of iron by xenon ions near the Bohr velocity

Fe K-shell ionization cross sections induced by 2.4–6.0 MeV Xe20+are measured and compared with different binaryencounter-approximation(BEA)models.The results indicate that the BEA model corrected both by the Coulomb repulsion and by the effective nuclear charge(Zeff)agrees well with the experimental data.Comparison of Fe K-shell X-ray emission induced by 5 MeV xenon ions with different initial charge states(20+,22+,26+,30+)verifies the applicability of the effective nuclear charge(Zeff)correction for the BEA model.It is found that Zeffcorrection is reasonable to describe direct ionization induced by xenon ions with no initial M-shell vacancies.However,when the M shell is opened,the Zeffcorrected BEA model is unable to explain the inner-shell ionization,and the electron transfer by molecular-orbital promotion should be considered.     

In-situ high pressure X-ray diffraction studies of orthoferrite SmFeO_3

The high-pressure behaviors of SmFeO3 are investigated by angle-dispersive synchrotron X-ray powder diffraction under a pressure of up to 40.3 GPa at room temperature. The crystal structure of SmFeO3 remains stable at up to the highest pressure. The different pressure coefficients of the normalized axial compressibility are obtained to be βa = 0.60 × 10-3 GPa-1,βb = 0.79 × 10-3 GPa-1, βc = 1.28 × 10-3 GPa- 1, and the bulk modulus （B0） is determined to be 293（3） GPa by fitting the pressure-volume data using the Birch-Murnaghan equation of state. Furthermore, the larger compressibility of the FeO6 octahedra suggests the evolution of the orthorhombic structure towards higher symmetry configuration at high pressures.     

Small angle X-ray scattering of the colloidal crystal

The monodisperse polystyrene spheres are assembled into the colloidal crystal on the glass substrate by vertical deposition method, which is aimed at the so-called photonic crystal applications. The structural information of the bulk colloidal crystal is crucial for understanding the crystal growth mechanism and devel- oping the various applications of colloidal crystal. Small-angle X-ray scattering （SAXS） technique was used to obtain the bulk structure of the colloidal crystal at Beamline lW2A of BSRF. It is found that the SAXS pattern is sensitive to the relative orientation between the colloidal sample and the incident X-ray direction. The crystal lattice was well distinguished and determined by the SAXS data.     

Stacking stability of MoS_2 bilayer: An ab initio study

The study of the stacking stability of bilayer MoS2 is essential since a bilayer has exhibited advantages over single layer MoS2 in many aspects for nanoelectronic applications. We explored the relative stability, optimal sliding path between different stacking orders of bilayer MoS2, and （especially） the effect of inter-layer stress, by combining first-principles density functional total energy calculations and the climbing-image nudge-elastic-band （CI-NEB） method. Among five typical stacking orders, which can be categorized into two kinds （I： AA＇, AB and II： AA＇, AB＇, A＇B）, we found that stacking orders with Mo and S superposing from both layers, such as AA＇ and AB, is more stable than the others. With smaller computational efforts than potential energy profile searching, we can study the effect of inter-layer stress on the stacking stability. Under isobaric condition, the sliding barrier increases by a few eV/（uc.GPa） from AA＇ to ABt, compared to 0.1 eV/（uc.GPa） from AB to [AB]. Moreover, we found that interlayer compressive stress can help enhance the transport properties of AA＇. This study can help understand why inter-layer stress by dielectric gating materials can be an effective means to improving MoS2 on nanoelectronic applications.     

The variation of Mn-dopant distribution state with x and its effect on the magnetic coupling mechanism in Znl-xMnxO nanocrystals

Zn1-xMnxO （x = 0.0005, 0.001, 0.005, 0.01, 0.02） nanocrystals are synthesized by using a wet chemical process. The coordination environment of Mn is characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, and its X-ray absorption fine structure. It is found that the solubility of substitutional Mn in a ZnO lattice is very low, which is less than 0.4%. Mn ions first dissolve into the substitutional sites in the ZnO lattice, thereby forming Mn2＋O4 tetrahedral coordination when x ≤ 0.001, then entering into the interstitial sites and forming Mn3＋O6 octahedral coordination when x ≥ 0.005. All the samples exhibit paramagnetic behaviors at room temperature, and antiferromagnetic coupling can be observed below 100 K.     

Epitaxial growth of Ge1-xSnx films with x up to 0.14 grown on Ge （001） at low temperature

We characterize the structures of Ge1-xSnx films with x up to 0.14 grown on Ge （001） by molecular-beam epitaxy at low temperature. The results show that Ge1-xSnx films are fully strained even at high Sn composition. The in-plane lattice parameters remain exactly the same as that of the substrate. Depth sensitivity analysis of the lattice parameters indicates that the strains of the epitaxial films are all in homogeneity. The films are fully strained. Poisson ratios, the force constants for the bonds between Ge and Sn are estimated and discussed in the present paper. Raman results show Ge-Ge, Ge-Sn, Sn-Sn vibrational modes. The Sn-Sn bond aggregation may respond to the high quality of our films. The fully strained epitaxy films with high content of Sn may be useful in designing the high quality GeSn films.