Interference Effects in Hyperfine Induced 2s2p P-3(0), P-3(2) -> 2s(2) S-1(0) Transitions of Be-like Ions

In this paper, we explored the characteristics of the interference effects between perturbative states in hyperfine induced 2s2p P-3(0), P-3(2) -> 2s(2) S-1(0) transitions of Be-like ions. It was found that the interference effects non-monotonically change with increasing atomic number Z in these two transitions. The strongest interference effect is near Z = 9 for 2s2p P-3(0), -> 2s(2) (1)S(0)transition and near Z = 7 for the other.

Magnetic Field Design of the Dipole for Super-FRS at FAIR

The Super-FRS (Super FRagment Separator) is a part of FAIR (Facility for Antiproton and Ion Research), which will be constructed at GSI, Germany by 17 countries. The Super-FRS comprises 24 superferric dipole magnets. The 2D and 3D magnetic field simulations of the prototype magnet are described in this paper. A passive trim slot and four chamfered removable poles are used to satisfy the required field homogeneity which is better than +/-3 x 10(-4) at 1.6 T, 0.8 T and 0.16 T in a wide elliptical useable aperture of 380 mm x 140 mm. Measurement results at various field levels are shown in this paper as well. It can be seen from the comparison of calculation and measurement results that the magnetic designs of the magnet fulfils the requirements.

Weak epitaxy growth and phase behavior of planar phthalocyanines on p-sexiphenyl monolayer film

We systematically investigated the weak epitaxy growth (WEG) behavior of a series of planar phthalocyanine compounds (MPc), i.e., metal-free phthalocyanine (H2PC), nickel phthalocyanine (NiPc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), iron phthalocyanine (FePc); cobalt phthalocyanine (CoPc), grown on a p-sexiphenyl (p-6P) monolayer film by selected area electron diffraction (SAED) and atomic force microscopy (AFM). Two types of epitaxial relations, named as incommensurate epitaxy and commensurate epitaxy, were identified between phthalocyanine compounds and the substrate of the p-6P film.

Ambipolar organic heterojunction transistors with various p-type semiconductors

Ambipolar transport has been realized in organic heterojunction transistors with metal phthalocyanines, phenanthrene-based conjugated oligomers as the first semiconductors and copper-hexadecafluoro-phthalocyanine as the second semiconductor. The electron and hole mobilities of ambipolar devices with rod-like molecules were comparable to the corresponding single component devices, while the carrier mobility of ambipolar devices with disk-like molecules was much lower than the corresponding single component devices.

Weak Epitaxy Growth of Copper Hexadecafluorophthalocyanine (F16CuPc) on p-Sexiphenyl Monolayer Film

Weak epitaxy growth (WEG) behavior and mechanism of copper hexadecafluorophthalocyanine (F16CuPc) on p-sexiphenyl (p-6P) monolayer film were investigated by atomic force microscopy (AFM), selected area electron diffraction (SEAD), and wide-angle X-ray diffraction (WAXD). High-quality F16CuPc films with high order, large size, and molecular-level smoothness were obtained successfully by WEG method. It was identified that there exists incommensurate epitaxial relation between highly oriented F16CuPc and p-6P films. The geometrical channels of p-6P monolayer surface induce the nucleation and growth of F16CuPc molecules.

Fabrication and characterization of microstructured and pH sensitive interpenetrating networks hydrogel films and application in drug delivery field

Novel microstructured and pH sensitive poly(acryliac acid-co-2-hydroxyethyl methacrylate)/poly(vinyl alcohol) (P(AA-co-HEMA)/PVA) interpenetrating network (IPN) hydrogel films were prepared by radical precipitation copolymerization and sequential IPN technology. The first P(AA-co-HEMA) network was synthesized in the present of IPN aqueous solution by radical initiating, then followed by condensation reaction (Glutaraldehyde as crosslinking agent) within the resultant latex, it formed multiple IPN microstructured hydrogel film. The film samples were characterized by IR, SEM and DSC. Swelling and deswelling behaviors and mechanical property showed the novel multiple IPN nanostuctured film had rapid response and good mechanical property. The IPN films were studied as controlled drug delivery material in different pH buffer solution using cationic compound, crystal violet as a model drug.

Synthesis and luminescent properties of LaInO3: RE3+ (RE = Sm, Pr and Tb) nanocrystalline phosphors for field emission displays

LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction, field emission scanning electron microscopy, photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. XRD results reveal that the pure LaInO3 phase can also be obtained at 700 degrees C. FE-SEM images indicate that the LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors are composed of aggregated spherical particles with sizes around 80-120 nm. Under the excitation of ultraviolet light and low voltage electron beams (1-5 kV), the LaInO3: Sm3+, LaInO3: Pr3+ and LaInO3: Tb3+ phosphors show the characteristic emissions of Sm3+ ((4)G(5/2)-H-6(5/2,7/2,9/2) transitions, yellow), Pr3+ (P-3(0)-H-3(4), P-3(1)-H-3(5), D-1(2)-H-3(4) and P-3(0)-F-3(2) transitions, blue-green) and Tb3+ (D-5(4)-F-7(6.5,4.3) transitions, green) respectively. The corresponding luminescence mechanisms are discussed. These phosphors have potential applications in field emission displays.

From Tunneling to Hopping: A Comprehensive Investigation of Charge Transport Mechanism in Molecular Junctions Based on Oligo(p-phenylene ethynylene)s

The charge transport mechanism of oligo(p-phenylene ethynylene)s with lengths ranging from 0.98 to 5.11 nm was investigated using modified scanning tunneling microscopy break junction and conducting probe atomic force microscopy methods. The methods were based on observing the length dependence of molecular resistance at single molecule level and the current-voltage characteristics in a wide length distribution. An intrinsic transition from tunneling to hopping charge transport mechanism was observed near 2.75 nm. A new transitional zone was observed in the long length molecular wires compared to short ones. This was not a simple transition between direct tunneling and field emission, which may provide new insights into transport mechanism investigations. Theoretical calculations provided an essential explanation for these phenomena in terms of molecular electronic structures.

Nanocrystalline LaGaO3 : Tm3+ as an efficient blue phosphor for field emission displays with high color purity

Nanocrystalline Tm3+-doped LaGaO3 phosphors were prepared through a Pechini-type sol-gel process [M. P. Pechini, U.S. Patent No. 3,330,697 (11 July 1967)]. X-ray diffraction, field emission scanning electron microscopy, photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. Under the excitation of ultraviolet light and low voltage electron beams (0.5-3 kV), the Tm3+-doped LaGaO3 phosphors show the characteristic emissions from the LaGaO3 host lattice and the Tm3+ (D-1(2), (1)G(4)-F-3(4), and H-3(6) transitions), respectively. The blue CL of the Tm3+-doped LaGaO3 phosphors, with a dominant wavelength of 458 nm, had better Commission International I'Eclairage chromaticity coordinates (0.1552, 0.0630) and higher emission intensity than the commercial product (Y2SiO5:Ce3+).

Host-sensitized luminescence of Dy3+, Pr3+, Tb3+ in polycrystalline SrIn2O4 for field emission displays

SrIn2O4:Dy3+/Pr3+/Tb3+ white/red/green phosphors were prepared by the Pechini sol-gel process. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), diffuse reflectance, photoluminescence, cathodoluminescence spectra, and lifetimes were utilized to characterize the samples. XRD reveal that the samples begin to crystallize at 800 degrees C and pure SrIn2O4 phase can be obtained at 900 degrees C. FE-SEM images indicate that the SrIn2O4:Dy3+, SrIn2O4:Pr3+, and SrIn2O4:Tb3+ samples consist of fine and spherical grains with size around 200-400 nm. Under the excitation of ultraviolet light and low-voltage electron beams (1 - 5 kV), the SrIn2O4:Dy3+, SrIn2O4: Pr3+, and SrIn2O4: Tb3+ phosphors show the characteristic emissions of Dy3+ (F-4(9/2) - H-6(15/2) at 492 nm and 4F(9/2) - 6H(13/2) at 581 nm, near white), Pr3+ (P-3(0) - H-3(4) at 493 nm, D-1(2) - H-3(4) at 606 nm, and P-3(0) - H-3(6) at 617 nm, red) and Tb3+ (D-5(4) - F-7(6,5,4,3) transitions dominated by D-5(4) - F-7(5) at 544 nm, green), respectively. All of the luminescence resulted from an efficient energy transfer from the SrIn2O4 host lattice to the doped Dy3+, Pr3+, and Tb3+ ions, and the luminescence mechanisms have been proposed.

Host-sensitized luminescence of Dy3+, Pr3+ , Tb3+ in polycrystalline CaIn2O4 for field emission displays

Caln(2)O(4):Dy3+/Pr3+/Tb3+ blue-white/green/green phosphors were prepared by the Pechini sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), diffuse reflectance, photoluminescence (PL) and cathodoluminescencc (CL) spectra as well as lifetimes were utilized to characterize the samples. The XRD results reveal that the samples begin to crystallize at 800 degrees C 3-1 and pure CaIn2O4 phase can be obtained after annealing at 900 degrees C. The FE-SEM images indicate that the CaIn2O4:Dy3+, CaIn2O4:Pr3+ and CaIn2O4:Tb3+ samples consist of spherical grains with size around 200-400nm. Under the excitation of ultraviolet light and low electron beams (1-5kV), the CaIn2O4:Dy3+, CaIn2O4:Pr3+ and CaIn2O4:Tb3+ phosphors show the characteristic emissions of Dy3+ ((F9/2-H15/2)-F-4-H-6 and (F9/2-H13/2)-F-4-H-6 transitions, blue-white), Pr3+ ((P0-H4)-P-3-H-3, (D2-H4)-D-1-H-3 and (P1-H5)-P-3-H-3 transitions, green) and Tb3+ ((D4-F6,5,4,3)-D-5-F-7 transitions, green), respectively. All the luminescence is resulted from an efficient energy transfer from the CaIn2O4 host lattice to the doped Dy3+ ,Pr3+ and Tb3+ ions, and the corresponding luminescence mechanisms have been proposed.

High mobility vanadyl-phthalocyanine polycrystalline films for organic field-effect transistors

The organic films of vanadyl-phthalocyanine (VOPc) compounds showed weak epitaxy growth (WEG) behavior on thin ordered para-sexiphenyl (p-6P) layer with high substrate temperature. The WEG of VOPc molecules standing up on the p-6P layer leaded to high in-plane orientation and their layer-by-layer growth behavior. In consequence, high quality VOPc films were obtained, which were consisted of lamellar crystals. Organic field-effect transistors with VOPc/p-6P films as active layers realized high mobility of above 1 cm(2)/V s. This result indicated that nonplanar compounds can obtain a device performance better than planar compounds, therefore, it may provide a rule to find disklike organic semiconductor materials.

n-channel, ambipolar, and p-channel organic heterojunction transistors fabricated with various film morphologies

The relationship between the performance characteristics of organic field-effect transistors (OFETs) with 2,5-bis(4-biphenylyl)-bithiophene/copper hexadecafluorophthalocyanine (BP2T/F16CuPc) heterojunctions and the thickness of the BP2T bottom layer is investigated. Three operating modes (n-channel, ambipolar, and p-channel) are obtained by varying the thickness of the organic semiconductor layer. The changes in operating mode are attributable to the morphology of the film and the hetero-junction effect, which also leads to an evolution of the field-effect mobility with increasing film thickness. In BP2T/F16CuPc heterojunctions the mobile charge carriers accumulate at both sides of the heterojunction interface, with an accumulation layer thickness of ca. 10 nm. High field-effect mobility values can be achieved in continuous and flat films that exhibit the heterojunction effect.

Conducting probe atomic force microscopy investigation of anisotropic charge transport in solution cast PBD single crystals induced by an external field

2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxdiazole (PBD) is a good electron-transporting material and can form single crystals from solution. In this work, solution cast PBD single crystals with different crystallographic axes (b, c) perpendicular to the Au/S substrates in large area are achieved by controlling the rate of solvent evaporation in the presence and absence of external electrostatic field, respectively. The orientation of these single crystals on Au/S substrate was characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Conducting probe atomic force microscopy (CP-AFM) was used to measure the charge transport characteristics of PBD single crystals grown on Au/S substrates. Transport was measured perpendicular to the substrate between the CP-AFM tip and the Au/S substrate. The electron mobility of 3 x 10(-3) cm(2)/(V s) for PBD single crystal along crystallographic b-axis is determined. And the electron mobility of PBD single crystal along the c-axis is about 2 orders of magnitude higher than that along the b-axis due to the anisotropic charge transport at the low voltage region.

Novel highly stable semiconductors based on phenanthrene for organic field-effect transistors

Two novel phenanthrene-based conjugated oligomers were synthesized and used as p-channel semiconductors in field-effect transistors; they exhibit high mobility and excellent stability during long-time ambient storage and under UV irradiation.