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1.
L. Kronik R. Fromherz E. Ko G. Ganteför J. R. Chelikowsky 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):33-36
We compare experimentally measured and
ab initio computed
photoelectron spectra of negatively charged deuterated silicon
clusters (
, 4m10, 0n2) produced in a plasma environment.
Based on this comparison, we discuss the kinetics and
thermodynamics of the cluster formation and the effect of
deuterium on the geometrical and electronic structure of the
clusters. 相似文献
2.
M.P. Machado P. Piquini R. Mota 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(1):91-93
The geometric structures, energetics and electronic properties of the recently discovered BN nanocones are investigated using
first-principles calculations based on the density-functional theory. We have proposed one particular structure for BN nanocones
associated with the 240° disclination, derived by the extraction of four 60° segments, presenting as characteristic four pentagons at the apex and termination in two atoms. The cones are simulated by
three clusters containing 58 B plus N atoms and additional 12 H atoms to saturate the dangling bonds at the edge. The most
stable configuration is obtained when the two terminating atoms are one B and one N. For the cases where the two terminating
atoms are of the same kind, the tip with B atoms is determined to have lower binding energy than with N atoms. The local densities
of states of these BN nanocones are investigated and sharp states are found in the regions close (below and above) to the
Fermi energy.
Received 14 October 2002 / Received in final form 6 December 2002 Published online 11 February 2003
RID="a"
ID="a"e-mail: ppiquini@smail.ufsm.br 相似文献
3.
F. Hagelberg C. Xiao B. Marsen M. Lonfat P. Scheier K. Sattler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(1):37-41
In a series of recent experiments, the HOMO-LUMO energy gaps of small Si clusters deposited on a graphite substrate have been
determined by Scanning Tunneling Microscopy (STM). The values obtained were found to be substantially smaller than the energy
gaps of corresponding passivated clusters. This work considers dimensional reduction as a possible mechanism for a sizeable
energy gap narrowing by the example of the system Si5. The impact of the graphite substrate on the deposited species is investigated in the framework of a pseudocluster model.
Received 30 November 2000 相似文献
4.
P. C.R. Rodrigues F. M.S. Silva Fernandes 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(1):115-123
Molecular dynamics simulations of the melting, freezing and nucleation are presented for unconstrained nanoclusters of KCl
with a number of ions between 512 and 10648. The maximum extent of the probed liquid supercooling is analysed to the light
of theoretical predictions and compared with experimental data. The fraction of the solid-like ions in the supercooled liquid
is used as an indicator of heterogeneities within the liquid. Induced nucleation by seeding the supercooled liquid indicates
that solid-liquid coexistence is stable, and sustained during the lifetime of the clusters, relatively to the supercooled
liquid. A phenomenological analysis on the relaxation times of the crystal growth process is made. Critical nuclei sizes computed
from the effectiveness of the seeds in the heterogeneous nucleation of the supercooled liquid, and from the residual crystallites
in clusters not totally melted, are presented as a function of the temperature. The behavior of the systems is followed through
various properties such as liquid and solid molar fractions, enthalpies of melting, heat capacities, self-diffusion coefficients
and relaxation times related to the freezing process. The consistency of the simulation results for the heterogeneous nucleation
is assessed by means of a classical nucleation model, from which an estimate of the interfacial surface tension is also worked
out and compared with experimental data. 相似文献
5.
M. Imamura T. Miyashita A. Tanaka H. Yasuda Y. Negishi T. Tsukuda 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):233-236
We have carried out optical and X-ray photoemission
studies of the dendrimer-encapsulated Au nanoclusters. The
dendrimer-encapsulated Au nanoclusters are prepared by the chemical
reduction of Au ions loaded within the dendrimer templates.
Photoluminescence spectrum of the dendrimer-encapsulated Au nanoclusters with
diameter of about 1.0 nm shows the visible luminescence centered at about
2.8 eV. In addition, we have measured the nanocluster-size dependent
photoemission spectra in the valence-band region. From line shape analysis
of Au 4f X-ray photoemission spectra, Au 4f core-level spectra of
the dendrimer-encapsulated Au nanoclusters reflect the size dependent
chemical-states. From these results, we discuss electronic structures and
chemical states of the dendrimer-encapsulated Au nanoclusters. 相似文献
6.
H. Yanagimoto K. Akamatsu K. Goto S. Deki 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):313-316
Small Copper (I) oxide, Cu2O, nanoparticles dispersed in diamine-terminated polyethyleneoxide (PEO-NH2) matrix have been successfully prepared by vacuum evaporation of copper onto the molten PEO-NH2. The obtained composite were characterized by TEM, electron diffraction, TG-DTA and FT-IR spectroscopy. The stable composite,
in which the Cu2O nanoparticles are stabilized through interaction between NH2 chain end groups of PEO molecules and Cu2O nanoparticles was obtained when the samples were heat-treated at 110
°
C. The mean size of the Cu2O nanoparticles increased from 2.5 to 3.5 nm in diameter upon increasing the amount of initial Cu deposition. The obtained
composite material having a waxy texture was soluble in many solvents without aggregation and can be handled as a simple chemical
compound for starting material in various applications.
Received 29 November 2000 相似文献
7.
C. Bréchignac Ph. Cahuzac F. Carlier C. Colliex M. de Frutos N. Kébaïli J. Le Roux A. Masson B. Yoon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):265-268
We studied shape relaxation of nano-fractal islands,
during annealing, after their growth from antimony cluster
deposition on graphite surface. Annealing at
180°C shows evidence of an increase
of the fractal branch width with time followed by branch
fragmentation, without changing the fractal dimension. The time
evolution of the width of the arm suggests the surface
self-diffusion mechanism as the main relaxation process. With
Monte Carlo simulations, we confirmed the observed behavior.
Comparison is done with our previous results on fragmentation of
nano-fractal silver islands when impurity added to the incident
cluster promotes rapid fragmentation by surface self-diffusion
enhancement [1]. 相似文献
8.
V. Kumar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):227-232
We report the recent findings of metal (M) encapsulated
clusters of silicon from computer experiments based on
ab initio total energy
calculations and a cage shrinkage and atom removal approach. Our
results show that using a guest atom, it is possible to wrap
silicon in fullerenelike (f)
structures, as sp2 bonding is not
favorable to produce empty cages unlike for carbon. Transition M
atoms have a strong bonding with the silicon cage that are
responsible for the compact structures. The size and structure
of the cage change from 14 to 20 Si atoms depending upon the
size and valence of the M atom. Fewer Si atoms lead to
relatively open structures. We find cubic,
f, Frank-Kasper (FK)
polyheral type, decahedral, icosahedral and hexagonal structures
for M@Sin with n = 12-16 and several different M
atoms. The magic behavior of 15 and 16 atom Si cages is in
agreement with experiments. The FK polyhedral cluster,
M@Si16 has an exceptionally large density
functional gap of about 2.35 eV calculated within the
generalized gradient approximation. It is likely to give rise to
visible luminescence in these clusters. The cluster-cluster
interaction is weak that makes such clusters attractive for
cluster assembled materials. Further studies to stabilize
Si20 cage with M = Zr, Ba, Sr, and Pb
show that in all cases there is a distortion of the
f cage. Similar studies on M
encapsulated germanium clusters show FK polyhedral and
decahedral isomers to be more favorable. Also perfect
icosahedral M@Ge12 and
M@Sn12 clusters have been obtained with
large gaps by doping with divalent M atoms. Recent results of
the H interaction with these clusters, hydrogenated silicon
fullerenes as well as assemblies of clusters such as nanowires
and nanotubes are briefly presented. 相似文献
9.
Q. Sun Q. Wang X.G. Gong V. Kumar Y. Kawazoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):77-81
We report results of the atomic and electronic structures of Al7C cluster using ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is
found to be the one in which carbon atom occupies an interstitial position in Al7 cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett. 316, 31 (2000)] of magic behavior of Al7C- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al7C- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al7N which has the same number of valence electrons as in Al7C- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al7N)2 to study interaction between magic clusters.
Received 28 July 2001 相似文献
10.
M. Iwamoto K. Kuroda V. Zaporojtchenko S. Hayashi F. Faupel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):365-367
Recently, production methods of metal nanoparticles have
been investigated extensively, not only for a research use in
laboratory, but also for an industrial use. However, it is
difficult to obtain metal nanoparticles in high amounts and
concentrations with simple methods. In this study, a gold
nanoparticle-polymer composite was prepared with a simple
procedure using a gold salt and a melted polymer. The composite,
which is in a wax state at room temperature, was highly soluble
in water and lower alcohols, moreover the composite was melted
at about 50
°C. 相似文献
11.
Shibin Li Yadong JiangZhiming Wu Jiang WuZhihua Ying Zhiming Wang Wei LiGregory J. Salamo 《Applied Surface Science》2011,257(20):8326-8329
Hydrogenated silicon film was fabricated by using plasma enhanced chemical vapor deposition method. The influence of crystalline volume fraction variation on the thermal conductivity was investigated. The relation between crystalline volume and film thickness was characterized by using spectroscopic ellipsometry with Bruggeman effective medium (BEMA) model. The thermal conductivity of silicon film was measured based on Fourier thermal transmitting law using sputtering platinum as electrode. The results demonstrate that the thermal conductivity of silicon film is proportional to the volume fraction of crystalline silicon, and there is crystalline and thermal conductive gradient between surface and bottom in the microcrystalline film. 相似文献
12.
H. B. Liu Y. L. Li H. Y. Luo H. J. Fang H. M. Li S. Q. Xiao Z. Q. Shi S. X. Xiao D. B. Zhu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):405-408
We demonstrate a new, simple, inexpensive process and
systemic control over CdS nanowires using sulfur powders and
organic diamines without any catalysts, surfactants, and
templates under atmospheric benchtop conditions. By changing the
kinds of amines and reaction temperatures can result in control
of the shape and size of the nanocrystals, which are moderately
monodispered with unique forms. 相似文献
13.
T. Orii M. Hirasawa T. Seto N. Aya S. Onari 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):119-122
The temperature dependence of photoluminescence (PL) from
mono-dispersed Si nanoparticles was studied from 4 to 300 K. Si
nanoparticles produced by pulsed laser ablation in He background
gas were sorted into the 6 nm size range by a differential
mobility analyzer (DMA). The spread of the size distribution was
narrowed to a geometrical standard deviation
g = 1.05. On decreasing the temperature
from 300 to 4 K, the intensity of the PL spectra increased
gradually, peaked at about 60 K, and then decreased rapidly. The
temperature dependences of the intensity and the full width at
half maximum (FWHM) on the PL spectra are discussed in terms of
radiative and nonradiative decay rates. 相似文献
14.
A. Tanaka R. Saito T. Kamikake M. Imamura H. Yasuda 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):229-232
We have performed the optical and photoelectron
spectroscopic studies of alkyl-passivated Si nanoparticles synthesized by a
solution route. The alkyl-passivated Si nanoparticle with mean diameter less
than about 2 nm exhibits a strong ultraviolet-blue photoluminescence.
Furthermore, we have directly investigated their electronic structures in
the vicinity of Fermi level by means of valence-band photoemission
measurements using synchrotron radiation. From these results, the detailed
optical properties and electronic structures of alkyl-passivated Si
nanoparticles are discussed. 相似文献
15.
S.J. Lee S.W. Han H.J. Choi K. Kim 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):293-296
We have investigated the structure and phase behavior of nonmolecularly layered silver stearate by means of temperature-dependent
diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Upon heating the sample, remarkable spectral changes
took place. The first phase transition took place that might be associated with a premelting event characterized by the formation
of gauche conformers at 390-420 K. A second phase transition took place in which silver nanoparticles with a size of ∼4 nm
were formed by thermal decomposition of silver stearate at 520-550 K. These silver nanoparticles, derivatized by stearate,
were readily spread as a monolayer at air/water interface, and could be packed in 3-D assemblies by the Langmuir-Blodgett
method.
Received 29 November 2000 相似文献
16.
T. S. Li C. H. Lee M. F. Lin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(1):45-50
The transport properties of finite length double-walled carbon nanotubes subject to the influences of
a transverse electric field and a magnetic field with varying polar angles
are investigated theoretically. The electrical conductance, thermal conductance and Peltier coefficient
dependences on the external fields and symmetric configuration are studied in linear response regime.
Prominent peak structures of the electrical conductance are predicted when varying the electric field strength.
The features of the
conductance peaks are found to be strongly dependent on the external fields and
the intertube interactions.
The heights of the electrical and thermal conductance peaks display the quantized behavior,
while those of the Peltier coefficient do not. The conductance peaks are found to be broadened
by the finite temperature. 相似文献
17.
W.T. Wallace R.L. Whetten 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):123-126
Smaller gold-cluster anions, typified by Au
7
-
, adsorb multiple CO molecules in a high-pressure, room-temperature flow-reactor, tending toward previously unknown saturation
compositions, Au7(CO)
4
-
. The weakness of the gold-carbonyl adsorption bond is evidenced indirectly by the high CO partial pressure required and more
directly by the high probability of fragmentation in the field-free flight region of the reflectron-type time-of-flight mass
spectrometer. The analysis of this metastability reveals that the actual distribution fN,M of products Au7(CO)
M
-
in the reactor may be highly non-statistical, e.g. with only even-M species present.
Received 17 April 2001 相似文献
18.
P. Scheier K. Sattler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):347-349
Monolayer and bi-layer silicon nanoparticle (SiNP) films
with wide band gaps (up to 4 eV) have been produced in UHV with
narrow size distributions of particles with 2-4 nm diameters and
were studied using scanning tunneling microscopy (STM) and
spectroscopy (STS). The films then were manipulated by applying
different values for the tunneling resistance. Nanoparticle
fusion and fission processes allow to shape the particles in the
films in various ways and to write in white and black on the
film template. 相似文献
19.
H.I. Hidmi D.H.E. Gross H.R. Jaqaman 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):87-92
The fragmentation of multiply charged atomic sodium clusters of mass 200 is investigated using the Micro-canonical Metropolis
Monte Carlo (MMMC) statistical technique for excitation energies up to 200 eV and for cluster charges up to +9e. In this work we present caloric curves and charged and uncharged fragment mass distributions for clusters with charges 0,
2, and 4. The caloric curves show a dip at the critical point implying a negative specific heat, as expected for finite systems,
while the fragment mass distributions corroborate the picture of a phase transition from one dominant liquid-like cluster
to complete vaporization.
Received 7 November 2001 / Received in final form 4 April 2002 Published online 28 June 2002 相似文献
20.
M. Han J.F. Zhou F. Q. Song C. R. Yin M. D. Liu J. G. Wan G. H. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):269-272
Free beam of silicon oxide nanoclusters is produced by a
gas aggregation source from SiO precursor. Due to the
disproportionation reaction during the condensation of SiO vapor
the generated clusters are Si-riched. The clusters are
collimated to be a fine beam and deposited on the substrate at
room temperature. The microstructures of the cluster-based
nanofilm are characterized by TEM. It is shown that with
appropriate impacting parameters, Si-riched oxide nanofilms
assembled from uniformly distributed isolated clusters can be
obtained. And the clusters can self-organize into partially
densely ordered packing within local domains. XPS spectra are
taken to analyze the chemical components of the nanofilms.
Photoluminescence from the Si-riched oxide nanofilms has also
been observed. 相似文献