Morphologies and Structures of Perovskite Thin Film on Zn-face and O-face of ZnO Single Crystal

ZnO single crystal was used as the substrate to study the effect of ZnO crystal plane polarity on the morphology and structure of CH_3NH_3PbI_3（MAPbI_3） perovskite film and carrier transport properties,which is meaningful for improving ZnO-based perovskite solar cell. It is found that perovskite thin film has small grain size（about 190 nm） and high coverage rate on the O-face of ZnO single crystal,and the dominant exposed crystal plane of perovskite film is（110） plane. While the MAPbI_3 thin film has large grain size（about 1.03 μm） and low coverage rate on the Zn-face,and the（022） plane is dominantly exposed for the perovskite film. The injection of photogenerated electrons from MAPbI_3 film into the O-face of ZnO single crystal is faster and more effective than that to Zn-face. It is supposed that O-face is more suitable for ZnO single crystal based perovskite cell fabrication than Zn-face.

Northward subduction-related orogenesis of the southern Altaids:Constraints from structural and metamorphic analysis of the HP/UHP accretionary complex in Chinese southwestern Tianshan,NW China

The Chinese Tianshan belt of the southern Altaids has undergone a complicated geological evolution. Different theories have been proposed to explain its evolution and these are still hotly debated. The major subduction polarity and the way of accretion are the main problems. Southward, northward subduction and multiple subduction models have been proposed. This study focuses on the structural geology of two of the main faults in the region, the South Tianshan Fault and the Nikolaev Line. The dip direction in the Muzhaerte valley is southward and lineations all point towards the NW. Two shear sense motions have been observed within both of these fault zones, a sinistral one, and a dextral one, the latter with an age of 236-251 Ma. Structural analyses on the fault zones show that subduction has been northward rather than southward. The two shear sense directions indicate that the Yili block was first dragged along towards the east due to the cloclkwise rotation of the Tarim block. After the Tarim block stopped rotating, the Yili block still kept going eastward, inducing the dextral shear senses within the fault zones.

Temperature-frequency dependence and mechanism of dielectric properties for γ-Y_2Si_2O_7

This paper reports that single-phase γ-Y2Si2O7 is prepared via a sufficient blending and cold-pressed sintering technique from Y2O3 powder and SiO2 nanopowder. It studies the dielectric properties of γ-Y2Si2O7 as a function of the temperature and frequency. The γ-Y2Si2O7 exhibits low dielectric loss and non-Debye relaxation behaviour from 25 to 1400℃ in the range of 7.3 18 GHz. The mechanism for polarization relaxation of the as-prepared γ-Y2Si2O7 differing from that of SiO2 is explained. Such particular dielectric properties could potentially make specific attraction for extensive practical applications.

Terahertz broadband polarizer using bilayer subwavelength metal wire-grid structure on polyimide film

A tcrahcrtz （THz） broadband polarizer using bilayer subwavelength metal wire-grid structure on both sides of polyimide fihn is simulated by the finite-difference time-domain method. We amdyze tile effect of film thickness, material loss, and lateral shift between two metallic gratings on the performance of the THz polarizer. Bilayer wire-grid polarizers are fabricated by a simple way of laser induced and non-electrolytic plating with copper. The THz time-domain spectroscopy measurements show that in 0.2 1.6 THz frequency range, the extinction ratio is better than 45 dB, the average extinction ratio reaches 53 dB, and the transmittance exceeds 67%, which shows great advantage over conventional single wire-grid THz polarizer.

Polarization and structure dependent optical characteristics of the three-arm nanoantenna with C_(3v) symmetry and broken symmetry

The optical properties of a three-arm plasmonic nanoantenna with and without broken symmetry were analyzed in detail. For the symmetrical structure, the local electric field can be significantly enhanced and well confined within the feed gap, whilst the extinction spectrum illustrates polarization independence. With broken symmetry, multi-wavelength resonances are observed due to the single dipole resonance and dipole–dipole coupling effect, and wide tunability is also available through minor structural adjustment. Especially when illuminated by a circularly polarized light beam, the extinction and the electric field distribution can be effectively modulated by just varying the incident wavelength.

Subwavelength ripple formation on planar and nonplanar surfaces by femtosecond laser scanning

The self-formation of periodic subwavelength ripples by linear polarized femtosecond laser scanning planar and non-planar tungsten targets on the employed laser wavelength, scanning speed, and energy fluence are examined systematically. The results show that, for a certain laser wavelength, the scanning conditions have no obvious effect to the morphological features of grating structures in the threshold range of laser fluence. The spatial structured period of gratings can be self-consistently interpreted by recently presented physical model of surface two-plasmon resonance. The subwavelength structures on cylindrical surface would be a good method to realize unique surface functions on complex surface of micro-devices.

Prediction of semiconducting behavior in minority spin of Co_2CrZ(Z=Ga,Ge,As):LSDA

Volume optimization was performed to obtain the theoretical lattice constants by using the generalized gradient approximation （GGA）. The electronic and magnetic properties of Heusler alloys CoaCrZ （Z -- Ga, Ge, As） were investigated by using local spin density approximation （LSDA）. Amongst the systems under investigation, CoECrGe and Co2CrGa give I00% spin polarization at the Fermi level （EF）. Co2CrGe and CoECrGa are the most stable half-metallic ferromagnets （HMFs）; their EF lie exactly at the gap of 0.24 eV and 0.38 eV, respectively, in the spin-down channel. Even though CoaCrAs gives a distinct and bigger gap as compared to CoECrGa and CoECrGe, its EF is not located at the middle of the gap in the spin-down channel. We have also found that the total magnetic moments increase as the Z goes from Ga to As. The calculated density of states and band structures show the HMF character for CoECrGe and Co2CrGa.