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1.
A method for constructing a complete set of independent symmetry coordinates for the out-of-plane vibrations of any polycene is given. Calculated vibrational frequencies from the previously developed five-parameter approximation are reported for naphthalene, anthracene, naphthacene and pentacene. 相似文献
2.
《Current Applied Physics》2018,18(10):1095-1100
A cost-effective and efficient organic semiconductor pentacene was developed as a hole transport layer (HTL) material to replace classical PEDOT:PSS for planar perovskite solar cells (PSCs). As expected, the pentacene based device exhibits power conversion efficiency (PCE) of 15.90% (Jsc of 19.44 mA/cm2, Voc of 1.07 V, and FF of 77%), comparable to the PEDOT:PSS based device (PCE of 15.65%, Jsc of 18.78 mA/cm2, Voc of 1.07 V, and FF of 77%) under the same experimental conditions. The excellent performance of vacuum deposited pentacene is mainly attributed to the high efficient charge extraction and transfer in device due to the high-quality perovskite film grown on the top of pentacene substrate and a favorable energy-level alignment together with a desired downward band bending formed at the perovskite/pentacene interface. Our research has confirmed that pentacene could be served as a promising HTL material to achieve effective and potentially economical planar type PSCs. 相似文献
3.
We have investigated the initial stages of the growth of pentacene thin films on the Au(1 0 0) substrate using synchrotron radiation photoelectron spectroscopy (PES), near edge X-ray absorption fine structure (NEXAFS) and scanning tunnelling microscopy (STM). Results indicate a well-ordered structure with the pentacene molecules adopting a predominantly flat orientation with respect to the substrate for coverages of less than three monolayers. NEXAFS and photoemission data indicates the presence of a second molecular orientation for thicker films, with the introduction of a slight tilting away from planar bonding geometry at higher pentacene coverages. STM images of coverages less than three monolayers indicate a well-ordered pentacene structure allowing for the calculation of pentacene unit cell parameters. The pentacene molecular rows adopt a side-by-side bonding arrangement on the surface. For pentacene deposited at room temperature, step edges were observed to act as nucleation centres for film growth. Annealing of the substrate to 373 K was found to remove excess molecules and improve film quality, but did not otherwise change the bonding geometry of the pentacene with respect to the surface. 相似文献
4.
M. Pedio N. Mahne F. Borgatti S.K.M. Henze F.S. Tautz R. Hudej B. Nickel 《Applied Surface Science》2007,254(1):103-107
Thin films of pentacene (C22H14) have become widely used in the field of organic electronics. Here films of C22H14 of thickness ranging from submonolayer to multilayer were thermally deposited on Ag(1 1 1) surface. The determination of molecular geometry in pentacene films on Ag(1 1 1) studied by X-ray absorption at different stages of growth up to one monolayer is presented.XAS spectra at the C K-edge were collected as a function of the direction of the electric field at the surface. The different features of the spectra were assigned to resonances related to the various molecular unoccupied states by the comparison with the absorption coefficient of the pentacene gas phase. The transitions involving antibonding π states show a pronounced angular dependence for all the measured coverages, from submonolayer to multilayer. The spectra analysis indicates a nearly planar chemisorption of the first pentacene layer with a tilt angle of 10°. 相似文献
5.
This paper reports on the results of experimental investigations into the threshold power of the onset of nonlinearity of
magnetoacoustic vibrations in planar structures (such as a ferrite film-dielectric substrate structure) in the range of phase
matching of the higher bulk magnetostatic and acoustic modes. Under the experimental conditions, the wavelength of the higher
bulk magnetostatic modes is of the order of 1 μm and shorter. On this basis, the energy of these vibrations with respect to
the origin of the magnetostatic wave spectrum is determined by the energy of the inhomogeneous exchange interaction. The standing
magnetoacoustic waves are examined in conventional yttrium iron garnet films with free surface spins in which, under standard
conditions, only dipole magnetostatic vibrations are excited in planar resonators. Consideration is given to the threshold
power of the onset of precession instability of the dipole exchange acoustic modes which, as was shown earlier by the authors,
are excited in the range of the phase matching of the exchange and acoustic modes. A comparative analysis is performed for
the threshold powers of dipole magnetostatic, exchange acoustic, and dipole exchange acoustic modes. It is demonstrated that
the threshold power of the instability of magnetostatic modes decreases significantly when the natural frequencies of the
dipole modes coincide with those of the exchange acoustic modes.
__________
Translated from Fizika Tverdogo Tela, Vol. 44, No. 7, 2002, pp. 1285–1289.
Original Russian Text Copyright ? 2002 by Bugaev, Gorsky. 相似文献
6.
Kirchhoff’s theory of plates is used to study forced harmonic vibrations of a semi-infinite strip when the latter is in the generalized stressed state or experiences flexural deformation. The forced vibrations are excited by a load applied to the strip end. Cross-boundary conditions are imposed on the strip’s sides, which allows one to obtain a closed solution. The presence of an infinite real frequency spectrum corresponding to the edge resonances is revealed. The relation of these resonances to the Rayleigh planar and flexural waves is established. 相似文献
7.
8.
Synthesis, characterization of the pentacene and fabrication of pentacene field-effect transistors
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A comprehensive understanding of the organic semiconductor material
pentacene is meaningful for organic field-effect transistors (OFETs).
Thin films of pentacene are the most mobile molecular films known to
date. This paper reported that the pentacene sample was successfully
synthesized. The purity of pentacene is up to 95\%. The results of a
joint experimental investigation based on a combination of infrared
absorption spectra, mass spectra (MS), element analysis, x-ray
diffraction (XRD) and atom force microscopy (AFM). The authors
fabricated OFET with the synthesized pentacene. Its field effect
mobility is about 1.23\,cm$^2$/(V$\cdot$s) and on--off ratio is above
10$^{6}$. 相似文献
9.
C. Mei 《Journal of sound and vibration》2011,330(23):5530-5544
An active control approach to vibrations in multi-story planar frame structures is presented in this paper. The controller is designed from a wave vibration standpoint, in which vibrations are described as waves that propagate along uniform waveguides, and are reflected and transmitted upon structural discontinuities. Regardless of the complexity of a structure, from the wave point of view it consists of only two basic types of structural components, namely, structural elements and joints. In this paper, vibrations in a multi-story planar frame structure are controlled through controlling its structural elements and its joints. 相似文献
10.
Synthesis, characterization of the pentacene and fabrication of pentacene field-effect transistors
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A comprehensive understanding of the organic semiconductor material pentacene is meaningful for organic fieldeffect transistors (OFETs). Thin films of pentacene are the most mobile molecular films known to date. This paper reported that the pentacene sample was successfully synthesized. The purity of pentacene is up to 95%. The results of a joint experimental investigation based on a combination of infrared absorption spectra, mass spectra (MS), element analysis, x-ray diffraction (XRD) and atom force microscopy (AFM). The authors fabricated OFET with the synthesized pentacene. Its field effect mobility is about 1.23 cm^2/(V·s) and on-off ratio is above 10^6. 相似文献
11.
In-plane vibrations of an elastic rod clamped at both extremities are studied. The rod is modeled as an extensible planar Kirchhoff elastic rod under large displacements and rotations. Equilibrium configurations and vibrations around these configurations are computed analytically in the incipient post-buckling regime. Of particular interest is the variation of the first mode frequency as the load is increased through the buckling threshold. The loading type is found to have a crucial importance as the first mode frequency is shown to behave singularly in the zero thickness limit in the case of prescribed axial displacement, whereas a regular behavior is found in the case of prescribed axial load. 相似文献
12.
The P.M.R. spectra of trimethylene oxide and trimethylene sulphide dissolved in a nematic solvent have been investigated. The chemical shifts, the direct and the indirect spin-spin couplings were determined. The interpretation of the direct couplings in terms of the molecular structure shows that the ring skeleton of these molecules is not rigidly planar due to ring puckering vibrations. Mean amplitudes for the vibrations are estimated assuming fixed values for the bond distances and for the HCH bond angles. The results obtained are in good agreement with the earlier microwave studies. 相似文献
13.
Berke K Tongay S McCarthy MA Rinzler AG Appleton BR Hebard AF 《J Phys Condens Matter》2012,24(25):255802
We investigate the electronic transport properties across the pentacene/graphene interface. Current transport across the pentacene/graphene interface is found to be strikingly different from transport across pentacene/HOPG and pentacene/Cu interfaces. At low voltages, diodes using graphene as a bottom electrode display Poole–Frenkel emission, while diodes with HOPG and Cu electrodes are dominated by thermionic emission. At high voltages conduction is dominated by Poole–Frenkel emission for all three junctions. We propose that current across these interfaces can be accurately modeled by a combination of thermionic and Poole–Frenkel emission. Results presented not only suggest that graphene provides low resistive contacts to pentacene where a flat-laying orientation of pentacene and transparent metal electrodes are desired but also provides further understanding of the physics at the organic semiconductor/graphene interface. 相似文献
14.
Surface electromagnetic waves in single-layer metal-like materials (such as graphene and borophene) in planar and cylindrical geometries are studied. Expressions for the permittivity tensor, dispersion relations, and vibrational spectra are obtained under conditions when the spatial dispersion can be neglected. It is shown that vibrations of two types exist in single-layer materials: bulk-type vibrations with a field localized on the surface and surface-type vibrations in which the field exponentially decrease on both sides beyond the surface. 相似文献
15.
《Journal of Physics and Chemistry of Solids》2004,65(2-3):619-621
We have prepared the cesium doped pentacene film and have investigated the electrical properties, in order to investigate a new molecular conductive film based on pentacene. It was found that cesium is doped in the pentacene film and that electrical resistivity decreases drastically below 10 Ω cm. Moreover, in the doping process, we found the step-wise decrease of electrical resistivity. It is deduced from this result that the cesium doped pentacene forms stage structures. In addition, we have carried out the measurements of the X-ray diffraction pattern in the cesium doped pentacene film. It was found from these results that the cesium doped pentacene becomes a highly orientated intercalated conductive film. Furthermore, in the cesium doped pentacene we have observed the shift of (00l) diffraction peak to low diffraction angle. This result indicates that by doping of pentacene the c-axis lattice constant which is the length of the interval between the (001) planes becomes 1.59 nm in the stage-1 structure of the cesium doped pentacene. 相似文献
16.
17.
Fabrication of planar gratings by direct ablation using an ultrashort pulse laser in a common optical path configuration 总被引:4,自引:0,他引:4
K. Venkatakrishnan N.R. Sivakumar B. Tan 《Applied Physics A: Materials Science & Processing》2003,76(2):143-146
Planar gratings have wide applications and to date, many methods for the fabrication of gratings have been reported. Ultrashort
pulse lasers have been used for the machining of gratings primarily because they allow direct ablation and the manufacturing
of sub-wavelength structures. In this paper, we present a novel direct ablation technique for the fabrication of planar gratings
which makes use of the interference of ultrashort pulses in a common optical path configuration. This technique of grating
fabrication not only simplifies the optical setup, but also immunizes the system to extraneous and inherent vibrations, thus
enabling the manufacturing of planar gratings of good edge acuity. We have successfully fabricated planar gratings on a copper
substrate.
Received: 6 November 2001 / Accepted: 4 March 2002 / Published online: 10 September 2002
RID="*"
ID="*"Corresponding author. Fax: +65/77-904-674, E-mail: mvenkata@ntu.edu.sg 相似文献
18.
《Journal of sound and vibration》1987,115(2):233-241
Two methods for solving the eigenvalue problems of vibrations and stability of a beam on a variable Winkler elastic foundation are presented and compared. The first is based on using the exact stiffness, consistent mass, and geometric stiffness matrices for a beam on a variable Winkler elastic foundation. The second method is based on adding an element foundation stiffness matrix to the regular beam stiffness matrix, for vibrations and stability analysis. With these matrices, it is possible to find the natural frequencies and mode shapes of vibrations, and buckling load and mode shape, by using a small number of segments. It is concluded that the use of the element foundation stiffness approach yields better convergence at lower computation costs. 相似文献
19.
Sang-Il Shin 《Applied Surface Science》2008,254(21):6987-6990
We report on the fabrication of pentacene thin-film transistors (TFTs) utilizing a spun methyl siloxane-based spin-on-glass (SOG) dielectric and show that these devices can give a similar electrical performance as achieved by using pentacene TFTs with a silicon dioxide (SiO2) dielectric. To improve the electrical performance of pentacene TFTs with the SOG dielectric, we employed a hybrid dielectric of an SOG/cross-linked poly-4-vinylphenol (PVP) polymer. The PVP film was deposited onto the spun SOG dielectric prior to pentacene evaporation, resulting in an improvement of the saturation field effect mobility (μsat) from 0.01 cm2/(V s) to 0.76 cm2/(V s). The good surface morphology and the matching surface energy of the SOG dielectric that was modified with the polymer thin film allow the optimized growth of crystalline pentacene domains whose nuclei are embedded in an amorphous phase. 相似文献
20.
Thayer GE Sadowski JT Meyer zu Heringdorf F Sakurai T Tromp RM 《Physical review letters》2005,95(25):256106
We show that the orientation of pentacene molecules is controlled by the electronic structure of the surface on which they are deposited. We suggest that the near-Fermi level density of states above the surface controls the interaction of the substrate with the pentacene pi orbitals. A reduction of this density as compared to noble metals, realized in semimetallic Bi(001) and Si(111)(5 x 2)Au surfaces, results in pentacene standing up. Interestingly, pentacene grown on Bi(001) is highly ordered, yielding the first vertically oriented epitaxial pentacene thin films observed to date. 相似文献