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101.
We show that at the hetero-molecular interface, the molecular band offsets can be modified by either adjusting the dopant or dopant concentration of one or both molecular layers or by changing the dipole orientation at the intermolecular interface. Photoemission studies reveal the changes in electronic structure and diode devices exhibit conduction properties that are altered in response to changes to the molecular band offsets. As a demonstration, thin film copper phthalocyanine to crystalline ferroelectric copolymer poly(vinylidene fluoride with trifluoroethylene) heterojunction diodes, without additional dopants, are compared with doped polyaniline layers on the crystalline ferroelectric copolymer poly(vinylidene fluoride with trifluoroethylene). 相似文献
102.
H. Angermann 《Applied Surface Science》2008,254(24):8067-8074
The effect of both surface morphology and wet-chemical pre-treatment on electronic surface and interface properties was investigated for mono- and polycrystalline silicon substrates with special surface structures. Surface charge, energetic distribution, and density of rechargeable states on these surfaces were determined by surface photovoltage (SPV) measurements. These results were correlated to previously reported findings on atomically flat Si(111) and Si(100) surfaces of monocrystalline wafers. In this paper, a specially optimised sequence of cleaning, wet-chemical oxidation, and oxide removal procedures is described in detail for the first time. This method was successfully applied in order to remove contaminations and damaged surface layers and to obtain atomically flat areas on substrates with evenly distributed atomic steps, polycrystalline and monocrystalline substrates with randomly distributed pyramids. A significant reduction in surface micro-roughness, interface state density, and recombination loss was achieved. Using passivation by wet-chemical oxidation or H-termination, respectively, the optimised surface state can be preserved by the time of following preparation steps and during subsequent a-Si:H plasma enhanced chemical vapour deposition (PECVD). 相似文献
103.
M. Shimizu K. Yasutake H. Ohmi A. Takeuchi H. Kakiuchi K. Yoshii Y. Mori 《Applied physics. B, Lasers and optics》2001,72(2):227-230
For laser collimation of neutral F atoms, a resonance transition cycle between the metastable and the upper excited states
(3s4
P
5/2?3p4
D
0
7/2) can be used as a two-level closed system. We have determined the lifetime of the metastable state (3s4
P
5/2) in F atoms by measuring the decay curve of the fluorescence intensity as a function of distance from the plasma source.
Combining the measured velocity of F radicals from the Doppler shift of the fluorescence peak, we have obtained the lifetime
of the F metastable state as 3.7±0.5 μs. With this short metastable lifetime of F radicals, the simple Doppler cooling method
using spontaneous light force is not practical for laser collimation of F radicals. Use of stimulated light force may be necessary
to collimate F radical beams in a short distance.
Received: 4 July 2000 / Published online: 13 September 2000 相似文献
104.
J. Diebel H. Löwe P. Samorí J.P. Rabe 《Applied Physics A: Materials Science & Processing》2001,73(3):273-279
The IR double-resonance techniques IR/R2PI (infrared/resonant 2-photon ionization), IR/PIRI (infrared-photo-induced Rydberg
ionization) and IR-photodissociation spectroscopy are valuable tools to investigate structure, vibrations, and dynamical processes
of neutral and ionic hydrogen-bonded clusters containing aromatic molecules. In this paper we report on the application of
the IR double-resonance techniques to determine the NH and OH stretching vibrations of 4-aminophenol and 4-aminophenol(H2O)1, both in the neutral (S0) and ionic (D0) ground state. All vibrational frequencies obtained for 4-aminophenol and the cluster are compared with the values obtained
from ab initio and DFT calculations. In the S0 state, a trans-linear arrangement of 4-aminophenol(H2O)1 is obtained containing an O-H·· O hydrogen bond. In the D0 state an overlay of two spectra can be observed resulting from the trans-linear structure and a second structure which contains
a N-H·· O hydrogen bond. The observation of these two structures within the ion is an interesting example of a rearrangement
reaction in the ionic state.
Received: 3 November 2000 / Accepted: 6 November 2000 / Published online: 9 February 2001 相似文献
105.
D. Vignolles A. Audouard R. B. Lyubovskii M. Nardone E. Canadell E. I. Zhilyaeva R. N. Lyubovskaya 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(4):489-495
Pressure dependence of the Shubnikov-de Haas (SdH)
oscillations spectra of the quasi-two dimensional organic metal
(ET)8[ Hg4Cl12(C6H5Br)2] have been studied up
to 1.1 GPa in pulsed magnetic fields of up to 54 T. According to
band structure calculations, its Fermi surface can be regarded as
a network of compensated orbits. The SdH spectra exhibit many
Fourier components typical of such a network, most of them being
forbidden in the framework of the semiclassical model. Their
amplitude remains large in all the pressure range studied which
likely rules out chemical potential oscillation as a dominant
contribution to their origin, in agreement with recent
calculations relevant to compensated Fermi liquids. In addition to
a strong decrease of the magnetic breakdown field and effective
masses, the latter being likely due to a reduction of the strength
of electron correlations, a sizeable increase of the scattering
rate is observed as the applied pressure increases. This latter
point, which is at variance with data of most charge transfer
salts is discussed in connection with pressure-induced features of
the temperature dependence of the zero-field interlayer
resistance. 相似文献
106.
Somesh Kr. Bhattacharya Anjali Kshirsagar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(3):355-364
Density functional calculations of structural and electronic properties
of stoichiometric and nonstoichiometric
CdTe clusters, containing up to few tens of atoms, are carried out
using projector augmented wave method.
Molecular dynamics has been performed
for Cd12Te12 and Cd15Te15
to predict the structure corresponding to global energy minimum.
Cage type structures and bulk fragments, both in zinc blende and
wurtzite structures, are used as starting geometries and
conjugate gradient method is used to locate the local energy minima for other clusters.
The aim of these calculations is to get the energetically favorable probable
structures, to be compared with the experimentally known
structures. Clusters are relaxed both in vacuum and in
the presence of surface passivating ligands and the resulting structural
rearrangement is analyzed. As expected, passivation increases the stability of an
individual cluster, as indicated by specific properties like binding energy,
vertical detachment energy, electron affinity etc.
Passivation also locks the symmetry for three-dimensional structures but the small
CdnTen (1 ≤ n ≤ 6) clusters, which are planar, attain higher
symmetry structures on passivation.
We observe `self-healing' mechanism viz., opening of optical
gap on relaxation without the aid of passivating ligand, in CdTe clusters as
observed in CdSe clusters [A. Puzder et al., Phys. Rev. Lett. 92,
217401 (2004)]. However, we note that 'self-healing' is a stoichiometry dependent
phenomenon. Te atoms are found to achieve a total coordination of 4 on passivation,
a fact useful in chemical synthesis of nanoclusters. 相似文献
107.
We present a method to discuss simultaneously the relative importance of molecular dynamic and geometric alignment induced by intense laser fields in theoretical view. This method divides the process of molecular alignment into three steps, which are tightly correlated with that of molecular multielectron dissociative ionization and Coulomb explosion. A fourth-order Runge-Kutta algorithm and a developed counting approach are used to calculate the angular distribution of molecules in the first and second steps of molecular alignment. The last step is described by a field-ionization, Coulomb explosion model. The angular distribution of molecules at the critical distance originated from geometric alignment is obtained by calculating the volume of shells associated with a series of particular angle. The final angular distributions of molecules are obtained by properly weighting the results of three steps. The numerical results of distinguishing between dynamic and geometric alignment for certain conditions are presented and discussed. Our computational results show that the alignment mechanism, which dominates the observed anisotropy of angular distributions of ionic fragments for a given condition, is determined by the dependences of the extent of dynamic and geometric alignment on laser parameters and molecular parameters. 相似文献
108.
New thiol terminated biphenyloxazole molecules are synthesized. A self assembled monolayer has been prepared on gold surface and spectral and luminescent properties of free molecules and ordered films have been studied experimentally and theoretically (DFT). The luminescence polarization degree is about 40%. New absorption and luminescence bands have been found experimentally and confirmed theoretically. The highest occupied and the lowest unoccupied molecular orbitals of adsorbed molecules strongly differ from not adsorbed thiol molecules. 相似文献
109.
Valence band photoemission spectroscopy (VB-PES) and inverse photoemission spectroscopy (IPES) were employed to determine the occupied and unoccupied density of states upon silver deposition onto layers of two phthalocyanines (H2Pc and CuPc). The two different Pc molecules give rise to very distinct behaviour already during the initial stage of silver deposition. While in the CuPc case no shift occurs in the energy levels, the H2Pc highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are shifting simultaneously by 0.3 eV, i.e., the HOMO shifts away from the Fermi level while LUMO shifts towards the Fermi level. As the silver quantity increases the HOMO levels of both Pcs are shifting towards the Fermi level. When the Fermi level is resolved in the VB spectra, the characteristic features of H2Pc and CuPc are smeared out to some extent. Shifts in HOMO and LUMO energy positions as well as changes in line shapes are discussed in terms of charge-transfer and chemical reactions at the interfaces. 相似文献
110.
O.E. Tereshchenko 《Applied Surface Science》2006,252(21):7684-7690
The InSb(0 0 1) surfaces chemically treated in HCl-isopropanol solution and annealed in vacuum were studied by means of X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and electron energy-loss spectroscopy (EELS). The HCl-isopropanol treatment removes indium and antimony oxides and leaves on the surface about 3 ML of physisorbed overlayer, containing indium chlorides and small amounts of antimony, which can be thermally desorbed at 230 °C. The residual carbon contaminations were around 0.2-0.4 ML and consisted of the hydrocarbon molecules. These hydrocarbon contaminations were removed from the surface together with the indium chlorides and antimony overlayer. With increased annealing temperature, a sequence of reconstructions were identified by LEED: (1 × 1), (1 × 3), (4 × 3), and (4 × 1)/c(8 × 2), in the order of decreasing Sb/In ratio. The structural properties of chemically prepared InSb(0 0 1) surface were found to be similar to those obtained by decapping of Sb-capped epitaxial layers. 相似文献