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1.
We present a two-part systematic density functional theory (DFT) study of the electronic structure of selected transition
metal phthalocyanines. We use a semi-local generalized gradient approximation (GGA) functional, as well as several hybrid
exchange-correlation functionals, and compare the results to experimental photoemission data. Here, we study the intermediate
spin systems MnPc and FePc. We show that DFT calculations of these systems are extremely sensitive to the choice of functional
and basis set with respect to the obtained electronic configuration and to symmetry breaking. Interestingly, all simulated
spectra are in good agreement with experiment despite the differences in the underlying electronic configurations. 相似文献
2.
We present a two-part systematic density functional theory study of the electronic structure of selected transition metal
phthalocyanines. We use a semi-local generalized gradient approximation (GGA) functional, as well as several hybrid exchange-correlation
functionals, and compare the results to experimental photoemission data. Here, we study the low-spin systems NiPc and CoPc.
We show that hybrid functionals provide computed photoemission spectra in excellent agreement with experimental data, whereas
the GGA functional fails qualitatively. This failure is primarily because of under-binding of localized orbitals due to self-interaction
errors. 相似文献
3.
Hiroyuki Yoshida Yuji Watazu Naoki Sato Toshihiro Okamoto Shigehiro Yamaguchi 《Applied Physics A: Materials Science & Processing》2009,95(1):185-191
Ultraviolet photoemission spectroscopic measurements of bis (benzo)pentathienoacene were carried out in gas and solid phase.
For the measurements of solid phase, vacuum deposited films in both amorphous and crystalline phase were prepared on different
substrates of HOPG and polycrystalline Au, respectively. The adiabatic ionization energies were determined to be 6.84, 5.32, and 5.08 eV, for gas, amorphous, and crystalline phases, respectively. The spectral lineshapes were interpreted with the aid of the
density functional calculations for both isolated molecule and single-crystal structure. The calculated electronic structures
were further analyzed in terms of the energy band dispersion and the transport properties of charge carriers. 相似文献
4.
Yanming Sun Yunqi Liu Ying Wang Chongan Di Weiping Wu Gui Yu 《Applied Physics A: Materials Science & Processing》2009,95(3):777-780
Organic thin-film transistors based on polycrystalline copper phthalocyanine (CuPc) were fabricated by using poly(vinyl alcohol)
as gate dielectric. After treatment of the gate dielectric using an octadecyltrichlorosilane self-assembled monolayer, a mobility
of up to 0.11 cm2/V s was achieved, which is comparable to that of single-crystal CuPc devices (0.1–1 cm2/V s). The surface morphology was analyzed and the possible reasons for the enhanced mobility are discussed. 相似文献
5.
M.?Fiebig C.?Erlen M.?G?llner P.?Lugli B.?Nickel 《Applied Physics A: Materials Science & Processing》2009,95(1):113-117
A confocal setup with a spatial resolution in the submicron regime is employed for investigating the response of pentacene
transistors to local illumination. The transistors show enhanced and inhomogeneous photoresponse in the proximity of the hole-injecting
contact. These inhomogeneities represent contact areas of varying injection efficiency. Thus, this technique allows imaging
of contact efficiencies with submicron resolution over large areas up to hundreds of microns. Drift–diffusion simulations
including a photogeneration/recombination process have been performed to model the photoresponse. The simulations illustrate
that the potential drop along the channel is dramatically reduced in the illuminated area due to photoconductance (i.e. photoinjection
of excitons and subsequent dissociation). Also, the injection barrier for holes is reduced if the illumination is close to
the hole-injecting electrode. The rapid decay of the photoresponse with increasing distance to the positively biased electrode
is caused by the limited electron mean free path in our devices. 相似文献
6.
Zhong-Min Ren Fang Lu Yuan-Cheng Du Zhi-Feng Ying Fu-Ming Li 《Applied Physics A: Materials Science & Processing》1995,61(6):643-644
Ultrathin silicon-nitride films have been synthesized on silicon substrates by low-energy nitrogen-ionbeam bombardment. The thicknesses of the obtained films are found to increase slightly with the duration of bombardment. Capacitance-voltage and current-voltage characteristics of silicon-nitride films prepared at different bombarding times show that the density of damages, charges in the films and interface states, the capacitance of the obtained ultrathin silicon-nitride films, the flat-band capacitance and the flat-band voltage increase with the duration of the bombarding process. The results of these analyses suggest a short bombarding processing for such a silicon-nitridation technique proposed here. 相似文献
7.
A. I. Belogorokhov S. I. Bozhko A. N. Chaika A. M. Ionov S. A. Trophimov V. D. Rumiantseva D. Vyalikh 《Applied Physics A: Materials Science & Processing》2009,94(3):473-476
The main goal of this paper is to investigate the electronic structure of valence band and core levels as well as surface
topography of pristine tetraphenylporphyrin and Pt-based compounds Pt-TPP(p-COOH3)4, Pt-TPP(m-OCH3)4, PtCl2-TPP(m-OCH3)4 thin films. The electronic structure of various Pt-based metalloporphyrins which were investigated in dependence on their
chemical structure and spectra were measured by high-resolution X-ray photoelectron spectroscopy (XPS) of valence band and
Pt4f, Pt4d, C1s, O1s, N1s core levels. Results of atomic force microscopy (AFM) studies of topography and self-assembling
processes in thin films of porphyrines are presented and discussed. 相似文献
8.
Tomoaki Sawabe Koshi Okamura Tomoki Sueyoshi Takashi Miyamoto Kazuhiro Kudo Nobuo Ueno Masakazu Nakamura 《Applied Physics A: Materials Science & Processing》2009,95(1):225-232
Vertical electrical conduction in Au/(polycrystal-line pentacene)/Al diode structures and the influence of the kinetic energy
of incident Au atoms on the conduction property have been comprehensively studied using current–voltage–temperature (I–V–T) measurements, ultraviolet photoelectron spectroscopy (UPS), atomic-force-microscope (AFM) current imaging, etc. In the I–V characteristics, a symmetrical ohmic current component appeared when a low voltage was applied, and a super-linear one appeared
when a high positive voltage was applied to Au. The component in the high-forward-voltage region was concluded to be a thermionic
emission of holes from Au with a 0.23-eV injection barrier, which is the normal hole conduction through the highest occupied
molecular orbital of pentacene. On the other hand, the ohmic component was concluded to be a metal-like electron transport
through high-density gap states at grain boundaries which were induced by the Au penetration into pentacene. UPS and I–V–T measurements clearly indicated the generation of the gap states and the enhancement of their density by the reduction of
Au kinetic energy. For vertical-type devices with polycrystalline organic films, the ohmic conduction through the grain boundary
will increase the leakage current. On the contrary, it possibly enhances the carrier injection in lateral-type transistors
in the case of top-contact configuration. 相似文献
9.
10.
A. Vollmer X. L. Feng X. Wang L. J. Zhi K. Müllen N. Koch J. P. Rabe 《Applied Physics A: Materials Science & Processing》2009,94(1):1-4
We demonstrate that graphene-based transparent and conductive thin films (GTCFs), fabricated by thermal reduction of graphite
oxide, have very similar electronic and structural properties as highly oriented pyrolytic graphite (HOPG). Electron spectroscopy
results suggest that the GTCFs are also semi-metallic and that the individual graphene sheets of the film are predominantly
oriented parallel to the substrate plane. These films may therefore be considered as a technologically relevant analogue to
HOPG electrodes, which cannot be easily processed into thin films. 相似文献
11.
Haichao Huang Haibo Wang Jidong Zhang Donghang Yan 《Applied Physics A: Materials Science & Processing》2009,95(1):125-130
P-type copper phthalocyanine (CuPc) and n-type hexadecafluorophthalocyanina-tocopper (F16CuPc) polycrystalline films were investigated by Kelvin probe force microscopy (KPFM). Topographic and corresponding surface
potential images are obtained simultaneously. Surface potential images are related with the local work function of crystalline
facets and potential barriers at the grain boundaries (GBs) in organic semiconductors. Based on the spatial distribution of
surface potential at GBs, donor- and acceptor-like trapping states in the grain boundaries (GBs) of p-CuPc and n-F16CuPc films are confirmed respectively. In view of spatial energy spectrum in micro-scale provided by KPFM, it is going to
be a powerful tool to characterize the local electronic properties of organic semiconductors. 相似文献
12.
M. Tsukamoto N. Abe Y. Soga M. Yoshida H. Nakano M. Fujita J. Akedo 《Applied Physics A: Materials Science & Processing》2008,93(1):193-196
Titanium dioxide (TiO2) films were irradiated with a femtosecond laser beam to alter their electrical resistances. The TiO2 film was produced by aerosol beam deposition. The wavelength, pulse duration, and repetition rate of the femtosecond laser
scanned across the sample surface were 800 nm, 100 fs, and 1 kHz, respectively. By attenuating the laser fluence on the TiO2 film, a range was found in which the electrical resistance of the TiO2 film was varied even though the morphology of the film surface was not changed. 相似文献
13.
Pramod Bhatt E. Carlegrim A. Kanciurzewska M. P. de Jong M. Fahlman 《Applied Physics A: Materials Science & Processing》2009,95(1):131-138
Thin film iron-tetracyanoethylene Fe(TCNE)
x
, x∼2, as determined by photoelectron spectroscopy, was grown in situ under ultra-high vacuum conditions using a recently developed
physical vapor deposition-based technique for fabrication of oxygen- and precursor-free organic-based molecular magnets. Photoelectron
spectroscopy results show no spurious trace elements in the films, and the iron is of Fe2+ valency. The highest occupied molecular orbital of Fe(TCNE)
x
is located at ∼1.7 eV vs. Fermi level and is derived mainly from the TCNE− singly occupied molecular orbital according to photoelectron spectroscopy and resonant photoelectron spectroscopy results.
The Fe(3d)-derived states appear at higher binding energy, ∼4.5 eV, which is in contrast to V(TCNE)2 where the highest occupied molecular orbital is mainly derived from V(3d) states. Fitting ligand field multiplet and charge
transfer multiplet calculations to the Fe L-edge near edge X-ray absorption fine structure spectrum yields a high-spin Fe2+ (3d6) configuration with a crystal field parameter 10Dq∼0.6 eV for the Fe(TCNE)
x
system. We propose that the significantly weaker Fe-TCNE ligand interaction as compared to the room temperature magnet V(TCNE)2 (10Dq∼2.3 eV) is a strongly contributing factor to the substantially lower magnetic ordering temperature (T
C
) seen for Fe(TCNE)
x
-type magnets. 相似文献
14.
Daniel Kolacyak Heiko Peisert Thomas Chassé 《Applied Physics A: Materials Science & Processing》2009,95(1):173-178
Core hole screening effects at organic/metal interfaces were studied by core level X-ray photoemission spectroscopy (XPS),
X-ray excited Auger electron spectroscopy (XAES), and valence band ultraviolet photoemission spectroscopy (UPS). The comparison
of energetic shifts in XPS and XAES enables the estimation of electronic relaxation energy (screening ability). Magnesium
phthalocyanine (MgPc) and zinc phthalocyanine (ZnPc) evaporated on single crystalline Au(100) were used as model molecules.
Two different features in the Mg KLL spectra can be clearly separated for (sub-)monolayer coverages, while only minor changes
of the shape of Mg 1s are observed. Applying a dielectric continuum model, the major screening mechanism cannot be described
sufficiently by polarization screening due to mirror charges, significant contributions by charge transfer screening have
to be considered. In contrast, small screening effects in the bulk material can be explained by surface polarization. 相似文献
15.
Kaname Kanai Kouki Akaike Kiichirou Koyasu Kentaro Sakai Toshio Nishi Yasunori Kamizuru Tatsuhiko Nishi Yukio Ouchi Kazuhiko Seki 《Applied Physics A: Materials Science & Processing》2009,95(1):309-313
The unoccupied π
* states of the solid film of electron accepting organic molecules, 7,7,8,8-tetracyanoquinodimethane (TCNQ), fluorinated TCNQ
derivatives, 11,11,12,12-tetracyanonaphtho-2,6-quinodimethane (TNAP), C60, and 6,6-phenyl-C61-butyric acid methyl ester (PCBM) have been studied by inverse photoemission spectroscopy. The assignment of the π
* affinity levels of these typical electron accepting molecules provides the basic information for the organic electronics
and the new electronic functional molecular design. The comparison with density functional theory calculations enables understanding
how the electron affinity evolves in terms of molecular orbitals. The correlation between the film morphology and the irradiation
damage on the TCNQ derivative samples by electron impact during the inverse photoemission measurements is also discussed. 相似文献
16.
Dana M. Alloway Neal R. Armstrong 《Applied Physics A: Materials Science & Processing》2009,95(1):209-218
We present here the characterization of organic/organic′ heterojunctions created from either of two perylene dyes, perylenetetracarboxylicdianhydride
(PTCDA) or the bisimide derivative perylenetetracarboxylicdianhydride-N,N′-bis (butyl)imide (C4-PTCDI), and two chloro-metallated
donor phthalocyanines (ClAlPc or ClInPc). The perylene dyes were selected to create thin films with the core of the perylene
dye parallel to the substrate plane (PTCDA) or nearly vertical to the substrate plane, with layer planes defined by the butyl
substituents (C4-PTCDI). We compare the frontier orbital offsets revealed by UV-photoelectron spectroscopy, and quenching
of luminescence of the perylene dyes, as a function of Pc coverage. The ionization potentials (IPs) of the Pc layers, the
degree to which interface dipoles are formed at the Pc/perylene dye interface, and the degree of quenching of the perylene
luminescence are affected by the structure of the Pc/perylene interface. Pc/PTCDA heterojunctions show significant interface
dipoles and higher IPs for the first-deposited Pc layers compared to Pc/C4-PTCDI heterojunctions, which show negligible interface
dipoles and lower overall IP values for initial Pc layers. Luminescence of the selectively excited perylene layers is quenched
by the addition of even submonolayer coverages of Pc. This quenching process occurs as a result of both energy transfer (perylene
to Pc) and charge transfer (Pc to perylene). Luminescence from monomeric and aggregated ClAlPc and ClInPc monolayers is seen
on C4-PTCDI films, whereas only luminescence from the aggregated forms of these Pcs is seen on PTCDA films. These studies
reveal aspects of organic heterojunction energetics which may have important implications for organic solar cell design. 相似文献
17.
G. Chaidogiannos F. Petraki N. Glezos S. Kennou S. Ne?p?rek 《Applied Physics A: Materials Science & Processing》2009,96(3):763-767
The class of sodium salts of sulphonated metal phthalocyanines (MePCS
x
, S = SO3Na, x=1–4) was investigated as a p-type channel component in organic field-effect transistors (OFETs). The solubility of these
materials appears to be enhanced compared to their non-sulphonated counterparts (MePCs). We fabricated transistors based on
MePCS
x
varying the central metal atom (Me = Ni, Co, Zn, Al) and we evaluated the dependence of transistor performance on the nature
of the central atom and the degree of sulphonation. The best results were obtained in the case of Ni and low sulphur content.
In this case the mobility value is μ=1.08 cm2 V−1 s−1 and the on/off current ratio ∼103. The degree of sulphonation affects the electric field inside the active film in a way analogous to the case of polyelectrolyte-gated
OFETs. The Na+ counter ions present in the channel contribute to the device characteristics but their concentration should be controlled
in order to optimize device performance. 相似文献
18.
N. D. Scarisoreanu G. Dinescu R. Birjega M. Dinescu D. Pantelica G. Velisa N. Scintee A. C. Galca 《Applied Physics A: Materials Science & Processing》2008,93(3):795-800
SBN thin films were grown on MgO and Silicon substrates by PLD and RF-PLD (radiofrequency assisted PLD) starting from single
crystal Sr0.6Ba0.4Nb2O6 and ceramic Sr0.5Ba0.5Nb2O6 stoichiometric targets. Morphological and structural analyses were performed on the SBN layers by AFM and XRD and optical
properties were measured by spectroellipsometry. The films composition was determined by Rutherford Backscattering Spectrometry.
The best set of experimental conditions for obtaining crystalline, c-axis preferential texture and with dominant 31° in-plane orientation relative to the MgO (100) axis is identified. 相似文献
19.
E. Abad J. Ortega Y. J. Dappe F. Flores 《Applied Physics A: Materials Science & Processing》2009,95(1):119-124
A local orbital DFT-approach combined with a “scissor”-operator is used to obtain the Charge Neutrality Level and the screening
parameter in the benzene/Au(111) and C60/Au(111) interfaces. The “pillow” dipole and interface Fermi level are also calculated. The total dipole induced across the
interface is compared with the experimental evidences: while the agreement for C60/Au(111) is excellent, for benzene/Au(111), some discrepancies appear that are discussed in the light of other models. 相似文献
20.
A. Sikora A. Berkesse O. Bourgeois J.-L. Garden C. Guerret-Piécourt A.-S. Loir F. Garrelie C. Donnet 《Applied Physics A: Materials Science & Processing》2009,94(1):105-109
We report on electrical measurements and structural characterization performed on boron-doped diamond-like carbon thin films
deposited by femtosecond pulsed laser deposition. The resistance has been measured between 77 and 300 K using four probe technique
on platinum contacts for different boron doping. Different behaviours of the resistance versus temperature have been evidenced
between pure DLC and boron-doped DLC. The a-C:B thin film resistances exhibit Mott variable range hopping signature with temperature.
Potential applications of DLC thin films to highly sensitive resistive thermometry is going to be discussed. 相似文献