共查询到20条相似文献,搜索用时 46 毫秒
1.
M.A. Grishin H.S. Karlsson M. Månsson U.O. Karlsson 《Applied Physics A: Materials Science & Processing》2003,76(3):299-302
The conduction band electronic structure and the electron dynamics of the clean InSb(111)2×2 surface have been studied by
laser based pump-and-probe photoemission. The results are compared to earlier studies of the InSb(110) surface. It is found
that both the energy location and the time dependence of the photoexcited structures are very similar for the two surfaces.
This indicates that the dominant part of the photoemission signal in the conduction band region is due to excitations of electrons
in the bulk region and that the surface electronic states play a minor role. The fast decay of the excited state, τ∼12 ps,
indicates that diffusion of hot electrons into the bulk is an important mechanism.
Received: 9 May 2001 / Accepted: 9 July 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +46-0824/913-1, E-mail: gm@matphys.kth.se 相似文献
2.
F.C. Fonseca G.F. Goya R.F. Jardim N.L.V. Carreño E. Longo E.R. Leite R. Muccillo 《Applied Physics A: Materials Science & Processing》2003,76(4):621-623
Ni nanoparticles embedded in an amorphous SiO2 matrix were produced by a modified sol–gel method. This method resulted in nanocomposites with a controlled size distribution
and good dispersion of the metallic particles. The particle-size distributions were found to have an average radius of ∼3 nm,
as inferred from transmission electron microscopy, X-ray-diffraction analysis, and magnetic measurements. Magnetic characterizations
revealed that samples exhibit superparamagnetic behavior above the blocking temperature TB, 20 K≤TB≤40 K, and absence of a shift along the field axis on hysteresis loops measured at T≤TB, indicating that the metallic nanoparticles are also free from an oxide layer.
Received: 7 October 2002 / Accepted: 9 October 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +55-11/3091-6984, E-mail: rjardim@if.usp.br 相似文献
3.
J.-M. Liu N. Chong H.L.W. Chan K.H. Wong C.L. Choy 《Applied Physics A: Materials Science & Processing》2003,76(1):93-96
Epitaxial (001) aluminum nitride (AlN) thin films on (111) Si substrates are prepared using pulsed-laser deposition. The epitaxial
structure of the as-prepared thin films is characterized by checking the X-ray-diffraction θ-2 θ scan and pole-figure, using
scanning electron microscopy, infrared radiation (IR) spectroscopy and Raman spectroscopy. The surface acoustic-wave resonance
at 345 MHz for a 1.5 μm thick AlN film on a (111) Si substrate is observed using an inter-digital electrode.
Received: 18 September 2001 / Accepted: 29 January 2002 / Published online: 3 June 2002
RID="*"
ID="*"Corresponding author. Fax: +86-25/359-5535, E-mail: liujm@nju.edu.cn 相似文献
4.
Investigation of size-driven phase transition in bismuth titanate nanocrystals by Raman spectroscopy 总被引:2,自引:0,他引:2
Y.L. Du M.S. Zhang Q. Chen Z. Yin 《Applied Physics A: Materials Science & Processing》2003,76(7):1099-1103
Raman spectroscopy was used to investigate the lattice dynamics and structural transformations in bismuth titanate (Bi4Ti3O12) nanocrystals prepared by a chemical coprecipitation technique. The crystal structure of the samples of different grain sizes
was determined by X-ray-diffraction analysis. The evolution of the Raman spectrum with grain size was characterized by an
intensity decrease, a broadening of the line width, a frequency shift, and the disappearance of the Raman mode. The results
revealed the appearance of a size-driven phase transition from orthorhombic to tetragonal phases at a critical size of 44 nm.
This result is quite consistent with the X-ray-diffraction measurement and differential thermal analysis. The origin was attributed
to the grain-size effect and explained by the surface-energy mechanism.
Received: 26 June 2002 / Accepted: 18 August 2002 / Published online: 15 January 2003
RID="*"
ID="*"Corresponding author. Fax: +86-25/3595535, E-mail: msz@nju.edu.cn 相似文献
5.
The authors’ endeavors over the last few years with respect to boron nitride (BN) nanotube metal filling are reviewed. Mo
clusters of 1–2 nm in size and FeNi Invar alloy (Fe ∼60 at. %; Ni ∼40 at. %) or Co nanorods of 20–70 nm in diameter were embedded
into BN nanotube channels via a newly developed two-stage process, in which multi-walled C nanotubes served as templates for
the BN multi-walled nanotube synthesis. During cluster filling, low-surface-tension and melting-point Mo oxide first filled
a C nanotube through the open tube ends, followed by fragmentation of this filling into discrete clusters via O2 outflow and C→BN conversion within tubular shells at high temperature. During nanorod filling, C nanotubes containing FeNi
or Co nanoparticles at the tube tips were first synthesized by plasma-assisted chemical vapor deposition on FeNi Invar alloy
or Co substrates, respectively, and, then, the nanomaterial was heated to the melting points of the corresponding metals in
a flow of B2O3 and N2 gases. During this second stage, simultaneous filling of nanotubes with a FeNi or Co melt through capillarity and chemical
modification of C tubular shells to form BN nanotubes occurred. The synthesized nanocomposites were analyzed by scanning and
high-resolution transmission electron microscopy, electron diffraction, electron-energy-loss spectroscopy and energy-dispersive
X-ray spectroscopy. The nanostructures are presumed to function as ‘nanocables’ having conducting metallic cores (FeNi, Co,
Mo) and insulating nanotubular shields (BN) with the additional benefit of excellent environmental stability.
Received: 10 October 2002 / Accepted: 25 October 2002 / Published online: 10 March 2003
RID="*"
ID="*"Corresponding author. Fax: +81-298/51-6280, E-mail: golberg.dmitri@nims.go.jp 相似文献
6.
A high-repetition-rate eye-safe optical parametric oscillator (OPO), using a non-critically phase-matched KTP crystal intracavity
pumped by an acousto-optically (AO) Q-switchedNd:YVO4 laser, is experimentally demonstrated. It is found that the average OPO signal power at 1573 nm can be efficiently increased
by increasing the pulse repetition rate. Moreover, the intracavity OPO process effectively shortens the pulse width so that
it is in the range 5∼8 ns for pulse repetition rates of 10 to 80 kHz. As a result of the relatively short pulse, the peak
power at 1573 nm is higher than 2 kW at a pulse repetition rate of 80 kHz.
Received: 10 July 2002 / Published online: 26 February 2003
RID="*"
ID="*"Corresponding author. Fax: +886-35/729-134, E-mail: yfchen@cc.nctu.edu.tw 相似文献
7.
We report on germania/organically modified silane (ormosil) hybrid materials produced by the sol–gel technique for photonic
applications. Acid-catalyzed solutions of γ-glycidoxypropyltrimethoxysilane mixed with germanium isopropoxide have been used
as precursors for the hybrid materials. Planar waveguide films with a thickness of about 2 μm have been prepared by a single
spin-coating process and low-temperature heat treatment from these high germanium content hybrid materials. Atomic force microscopy,
thermal gravimetric analysis, UV–visible spectroscopy, and Fourier-transform infrared spectroscopy have been used to investigate
the optical and structural properties of the films. The results have indicated that a dense, low absorption, and high transparency
(in the visible range) waveguide film could be achieved at a low temperature. A strong UV-absorption region at short wavelengths
∼200 nm, accompanied by a shoulder peaked at ∼240 nm, has been noticed due to the neutral oxygen monovacancy defects. The
propagation mode and loss properties of the planar waveguide films have also been investigated by using a prism-coupling technique.
Received: 5 November 2002 /
Revised version: 27 December 2002 / Published online: 19 March 2003
RID="*"
ID="*"Corresponding author. Fax: +65-67909081, E-mail: ewxque@ntu.edu.sg 相似文献
8.
A. Fix M. Wirth A. Meister G. Ehret M. Pesch D. Weidauer 《Applied physics. B, Lasers and optics》2002,75(2-3):153-163
A pulsed optical parametric oscillator (OPO) with intracavity sum frequency mixing was developed generating energies of up
to 16 mJ in the 281–293 nm wavelength range. Both OPO process and sum frequency mixing are pumped by the harmonics of a single,
medium-sized Nd:YAG laser. The system is characterized by a high overall efficiency (∼4% conversion from 1064 nm to the UV),
a very compact set-up and stable and reliable operation. This system was successfully employed to measure tropospheric ozone
using the differential absorption lidar (DIAL) technique and shows much promise as a lidar transmitter in airborne case studies
as well as in unattended lidar systems for long-term monitoring. An unattended ozone profiling system could already be successfully
realized.
Received: 1 April 2002 / Revised version: 30 May 2002 / Published online: 2 September 2002
RID="*"
ID="*"Corresponding author. Fax: +49-8153/28-1271, E-mail: Andreas.Fix@dlr.de 相似文献
9.
Surface nanostructuring of silicon 总被引:1,自引:0,他引:1
A.J. Pedraza J.D. Fowlkes Y.-F. Guan 《Applied Physics A: Materials Science & Processing》2003,77(2):277-284
Irradiation with polarized laser light of 248-nm wavelength induces the formation of periodic undulations ∼10-nm-highon flat
silicon substrates. The wavelength of these periodic structures is a function of the light wavelength and the angle of incidence
of the laser beam. Linear arrays of silicon nanoparticles with fairly uniform size that extended up to a millimeter were formed
if the irradiation was performed using polarized light. When non-polarized laser light with the same fluence was used to illuminate
an initially flat surface, non-aligned nanoparticle strings were obtained. However, if part of the irradiated area was microstructured,
nanoparticle linear arrays resulted in the vicinity of the microstructured region. An analysis on the evolution of these nanostructures
is presented. Nanocolumns could be grown on top of every cone of a microstructured surface upon cumulative laser irradiation
with non-polarized light, reaching a height of ∼3 μm and a diameter of 100–200 nm. The mechanisms of nanocolumn origin and
growth are analyzed.
Received: 16 December 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +1-865/974-4115, E-mail: apedraza@utk.edu 相似文献
10.
We report on the experimental study of the excitation mechanism of fluorescence in a 10000-ppm wt. Tm+3-doped ZBLAN fiber. Visible (at 453 nm and 480 nm) and near-infrared (∼800 nm) radiations were studied under excitation at
1.064 μm. The up-conversion mechanisms responsible are investigated, based on experimental data. The results show that the3
H
4 and the 1
D
2 levels are predominantly excited by ion-ion cross-relaxation processes.
Received: 19 August 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +41/31-631-3765, E-mail: Reda.El-Agmy@iap.unibe.ch 相似文献
11.
An ultra-short-pumped optical dye amplifier operating in the near-IR (720 nm) has been developed. We present an experimental
study of the input–output characteristics of this simple device in a traveling wave collinear configuration. In essence, the
combined effects of the ultrafast nature of the anisotropy induced by the exciting laser pulse along with the short transit
time across the length of the cell allow for optimal output conditions given the number of molecules in the active volume.
Two distinct amplifying regimes have been observed depending on photon density. Typical gain values of 104 of the narrow bandwidth (∼9 nm) subpicosecond output signal were measured. The 8-mm2 beam cross section enables this photon amplifier to be utilized in time-gated imaging applications.
Received: 12 December 2001 / Revised version: 13 May 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +1-819/564-5442, E-mail: Daniel.Houde@Usherbrooke.ca 相似文献
12.
S.-H. Cho H. Kumagai K. Midorikawa 《Applied Physics A: Materials Science & Processing》2003,76(5):755-761
The time-resolved dynamics of plasma self-channeling and refractive index bulk modification in silica glasses were first observed
in situ using a high-intensity femtosecond (110 fs) Ti:sapphire laser (λp=790 nm). Plasma channeling is induced in silica glass at an irradiation higher than an input intensity of 1.5×1012 W/cm2 and photoinduces either the refractive-index modification or optical crack modification. In the domain of refractive-index
modification, the lifetime of induced plasma self-channeling was 20 ps and the structural transition time for forming the
refractive-index change was 10 ps. In the domain of optical cracks, however, the lifetime of induced plasma formation was
30 ps and the structural transition time for forming the optical cracks was 40 ps. According to electron spin resonance spectroscopic
(ESP) measurement, it was found that the defect concentration of the SiE′ center increased significantly in the refractive index modification region. A maximum value of the refractive-index change
Δn was measured to be 1.6×10-2. The intensity profile of the output beam transmitted through the refractive-index modification showed that the bulk modification
produced a permanent optical waveguide.
Received: 8 April 2002 / Accepted: 12 April 2002 / Published online: 22 November 2002
RID="*"
ID="*"Corresponding author. Fax: +81-48/462-4682, E-mail: shcho@riken.go.jp 相似文献
13.
V. Brien A. Dauscher P. Weisbecker F. Machizaud 《Applied Physics A: Materials Science & Processing》2003,76(2):187-195
The preparation in thin film form of the known icosahedral phase in Ti-Ni-Zr bulk alloys has been investigated as a function
of substrate temperature. Films were deposited by pulsed laser deposition on sapphire substrates at temperatures ranging from
room temperature to 350 °C. Morphological and structural modifications have been followed by grazing-incidence and θ–2θ X-ray
diffraction, transmission electron diffraction and imaging. Chemical composition has been analyzed by electron probe microanalysis.
The in-depth variation of composition has been studied by secondary neutral mass spectroscopy. We show that pulsed laser deposition
at 275 °C makes the formation of a 1-μm-thick film of Ti-Ni-Zr quasicrystalline textured nanocrystallites possible.
Received: 7 June 2001 / Accepted: 18 February 2002 / Published online: 3 June 2002
RID="*"
ID="*"Corresponding author. Fax: +33-3/8357-6300, E-mail: brien@mines.u-nancy.fr 相似文献
14.
T. Okazaki T. Shimada K. Suenaga Y. Ohno T. Mizutani J. Lee Y. Kuk H. Shinohara 《Applied Physics A: Materials Science & Processing》2003,76(4):475-478
Electronic properties of Gd@C82 metallofullerene peapods, (Gd@C82)n@SWNTs, were investigated by electron energy-loss spectroscopy (EELS), scanning tunneling microscopy and spectroscopy (STM/STS),
and field-effect transistor (FET) transport measurements. The results indicate that the electronic structure of Gd@C82 metallofullerene peapods is completely different from that of intact single-walled nanotubes (SWNTs). For example, Gd@C82-peapod-FETs show ambipolar behavior which is not observed in the empty SWNT-FETs under our experimental conditions. Furthermore,
in semiconducting nanotubes the band gap can be varied from ∼0.5 to ∼0.1 eV using inserted Gd@C82 endohedral metallofullerenes with a spatial periodicity of 1.1 to 8.0 nm, depending on the density of the fullerenes. The
present findings suggest that metallofullerene peapods may point the way toward novel electronic devices.
Received: 6 September 2002 / Accepted: 25 October 2002 / Published online: 10 March 2003
RID="*"
ID="*"Corresponding author. Fax: +81-52/789-1169, E-mail: noris@cc.nagoya-u.ac.jp 相似文献
15.
Jin Y.Z. Zhu Y.Q. Brigatti K. Kroto H.W. Walton D.R.M. 《Applied Physics A: Materials Science & Processing》2003,77(1):113-115
Micron-scale coral-like aluminium oxide structures have been generated by heating a mixture of AlB2 and Co powders in a quartz boat at ca. 1050 °C under N2. Upon sonication in acetone, the structures break down into elongated single-crystal aluminium oxide nanorods ranging from
20 to 200 nm in diameter and up to 5 μm in length. Single Co particles are often found attached to nanorod tips. A vapour–liquid–solid
(V–L–S) mechanism appears to be responsible for the aluminium oxide nanorod growth.
Received: 21 January 2003 / Accepted: 22 January 2003 / Published online: 28 March 2003
RID="*"
ID="*"Corresponding author. E-mail: d.walton@sussex.ac.uk 相似文献
16.
V.S. Yakovlev P. Dombi G. Tempea C. Lemell J. Burgdörfer T. Udem A. Apolonski 《Applied physics. B, Lasers and optics》2003,76(3):329-332
Compressing pulses of a mode-locked extended-cavity Ti:sapphire laser using a standard single-mode fiber and tilted-front-interface
chirped mirrors yields phase-stabilized 4-fs, 3-nJ light pulses at the full, 24-MHz, repetition rate. The demonstrated source
paves the way towards exploring interactions sensitive to the carrier-envelope-offset phase, such as, for example, photoemission
from solid targets at moderate intensities (∼1012 W/cm2).
Received: 13 December 2002 / Published online: 26 February 2003
RID="*"
ID="*"Corresponding author. Fax: +43-1/58801-38799, E-mail: apolonski@tuwien.ac.at 相似文献
17.
Z.J. Li X.L. Chen L. Dai H.J. Li H.W. Liu H.J. Gao Y.P. Xu 《Applied Physics A: Materials Science & Processing》2003,76(1):115-118
A new form of GaN nanomaterial (nanotweezers) has been obtained by chemical vapor deposition on an etched cubic MgO (100)
plane. The nanotweezers consist of a bottom rod and two arms. The bottom rods have diameters of about 100–150 nm and lengths
of about 200–500 nm, on which two arms grow out. The bottoms of the arms are about 40–70 nm and the tops are about 15–30 nm
in diameter, and 0.8–1.5 μm in length. X-ray and electron diffractions indicate the nanotweezers are zinc blende gallium nitride.
We infer that the fabrication of the GaN nanotweezers is associated with small convex hillocks on the surface of the etched
cubic MgO (100) single-crystal substrates and that the nanotweezers grow by a growth mechanism that is similar to vapor-phase
heteroepitaxy.
Received: 23 April 2002 / Accepted: 25 April 2002 / Published online: 10 September 2002
RID="*"
ID="*"Corresponding author. Fax: +86-10/8264-9531, E-mail: xlchen@aphy.iphy.ac.cn 相似文献
18.
P.E. Dyer S.M. Maswadi C.D. Walton 《Applied Physics A: Materials Science & Processing》2003,76(5):817-822
We report an investigation of the ablation of NaCl crystals at the 157-nm wavelength of the F2 laser where there is very strong excitonic absorption. Probe-beam deflection and etch-rate measurements show that the interaction
is characterised by a low ablation threshold (∼80 mJ cm-2) and a capability for controllable material removal at the nanometer level. Scanning electron microscopy of the exposed surfaces
show this to be microscopically smooth but with fine cracks present. It is demonstrated that micron-scale features can be
formed in NaCl using 157-nm laser ablation, a result attributed to the strongly localised optical and thermal nature of the
interaction. The results are discussed within the framework of a thermal vaporisation model.
Received: 29 May 2002 / Accepted: 17 July 2002 / Published online: 4 November 2002
RID="*"
ID="*"Corresponding author. Fax: +44-1482/465606, E-mail: p.e.dyer@hull.ac.uk 相似文献
19.
M.A. Rana T. Osipowicz H.W. Choi M.B.H. Breese F. Watt S.J. Chua 《Applied Physics A: Materials Science & Processing》2003,77(1):103-108
Annealling experiments were performed on GaN layers, grown on sapphire, over a wide range of temperatures (500–1100 °C). Rutherford
Backscattering Spectrometry (RBS) was performed in random and 〈0001〉 channelling geometries using 2 MeV protons and helium
ions to determine the stoichiometric and structural alterations produced during annealling. We present here, for the first
time, a comprehensive and quantitative analysis of the depth distribution of both stoichiometric and structural changes in
the near-surface region (∼750 nm) with a resolution of 50 nm for stoichiometric and 20 nm for structural changes. No decomposition
was measured for temperatures up to 800 °C. Decomposition in the near-surface region increased rapidly with further increases
in temperature, resulting in a near-amorphous region (500 nm) for annealling at 1100 °C. We describe the range of annealling
conditions under which negligible stoichiometric and structural changes are observed. Our nanoscale resolution results are
useful for the fabrication and operation of conventional and nanoscale optoelectronic and high-temperature devices.
Received: 23 December 2002 / Accepted: 16 January 2003 / Published online: 28 March 2003
RID="*"
ID="*"Corresponding author. Fax: +65-6777/6126, E-mail: scip0229@nus.edu.sg 相似文献
20.
C. Dölle C. Reinhardt P. Simon B. Wellegehausen 《Applied physics. B, Lasers and optics》2002,75(6-7):629-634
. Investigations of the efficient generation of powerful coherent radiation at 82.8 nm by frequency tripling of short-pulse
KrF laser radiation are presented. Argon gas is selected as nonlinear medium due to the resonantly enhanced 3rd-order susceptibility
χ(3)(-3ω,ω,ω,ω). Pulse energies of 100 μJ at 82.8 nm have been measured for a pump pulse energy of 14 mJ. An upscaling to more
than 500 μJ is expected with available more powerful pump lasers. Features of this XUV source and possible applications are
discussed.
Received: 26 July 2002 / Published online: 15 November 2002
RID="*"
ID="*"Corresponding author. Fax: +49-511/7622211, E-mail: reinhardt@iqo.uni-hannover.de 相似文献