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1.
L. Kipp 《Applied Physics A: Materials Science & Processing》2002,75(1):59-67
Photoelectron spectroscopy with synchrotron radiation employing high energy and angular resolutions is a very efficient tool
for experimental investigations of the electronic structure of solids and their surfaces. In addition to standard band-mapping
applications, photoemission intensity and line-shape analyses provide valuable information about wave functions, bonds and
interactions of a many-electron system. In this report we choose covalent semiconductor surfaces as well as metallic clean
and nanostructured surfaces of layered materials to serve as model systems for assessing the spatial origin of photoelectrons
and the three-dimensional shape of Fermi surfaces.
Received: 11 July 2001 / Accepted: 23 July 2001 / Published online: 3 April 2002 相似文献
2.
Attenuated total reflection (ATR) is a prominent effect in examining the excitation of surface plasmons. The Kretschmann–Raether
and Otto configurations are implemented to generate surface plasmons and to examine the change of the refractive index of
liquid crystals (LCs) by an applied field. A mixture of nematic and cholesteric liquid crystals is sandwiched between two
glass substrates coated with conducting films. The minimum ATR angle changes by only 1° as the applied voltage increases to
as much as 30 V (corresponding to 6×105 Vm-1), which does not agree with the calculation based on field-induced refractive-index change. This fact suggests that the orientation
of LC molecules adjacent to an electrode surface is unaffected by the external field because of the strong-anchoring effect.
A Jones-matrix simulation together with a multilayered structure of a LC clearly adduces this fact.
Received: 30 November 2001 / Revised version: 1 February 2002 / Published online: 14 March 2002 相似文献
3.
K. Pedersen T.B. Kristensen T.G. Pedersen P. Morgen Z. Li S.V. Hoffmann 《Applied physics. B, Lasers and optics》2002,74(7-8):677-682
Thin noble metal films (Ag, Au and Cu) on Si (111) have been investigated by optical second-harmonic generation (SHG) in combination
with synchrotron radiation photoemission spectroscopy. The valence band spectra of Ag films show a quantization of the sp-band
in the 4-eV energy range from the Fermi level down to the onset of the d-bands. For Cu and Au the corresponding energy range
is much narrower and quantization effects are less visible. Quantization effects in SHG are observed as oscillations in the
signal as a function of film thickness. The oscillations are strongest for Ag and less pronounced for Cu, in agreement with
valence band photoemission spectra. In the case of Au, a reacted layer floating on top of the Au film masks the observation
of quantum well levels by photoemission. However, SHG shows a well-developed quantization of levels in the Au film below the
reacted layer. For Ag films, the relation between film thickness and photon energy of the SHG resonances indicates different
types of resonances, some of which involve both quantum well and substrate states.
Received: 16 October 2001 / Revised version: 14 March 2002 / Published online: 29 May 2002 相似文献
4.
Simulation of SET Operation in Phase-Change Random Access Memories with Heater Addition and Ring-Type Contactor for Low-Power Consumption by Finite Element Modeling 下载免费PDF全文
A three-dimensional finite element model for phase change random access memory (PCRAM) is established for comprehensive electrical and thermal analysis during SET operation. The SET behaviours of the heater addition structure (HS) and the ring-type contact in bottom electrode (RIB) structure are compared with each other. There are two ways to reduce the RESET current, applying a high resistivity interracial layer and building a new device structure. The simulation resuIts indicate that the variation of SET current with different power reduction ways is little. This study takes the RESET and SET operation current into consideration, showing that the RIB structure PCRAM cell is suitable for future devices with high heat efficiency and high-density, due to its high heat efficiency in RESET operation. 相似文献
5.
A model is proposed that treats electrons at surfaces as a combination of two-dimensional and three-dimensional degrees of
freedom. This yields a simple formula for the surface state induced resonant enhancement of the transfer of electrons through
a surface. The model also yields analytic approximations for the transition between two-dimensional and three-dimensional
distance laws in the correlations between electrons in surface states.
Received 6 August 2002 Published online 31 October 2002
RID="a"
ID="a"e-mail: rainer@sask.usask.ca 相似文献
6.
Simulation of Voltage SET Operation in Phase-Change Random Access Memories with Heater Addition and Ring-Type Contactor for Low-Power Consumption by Finite Element Modeling 下载免费PDF全文
A three-dimensional finite element model for phase change random access memory is established to simulate electric, thermal and phase state distribution during (SET) operation. The model is applied to simulate the SET behaviors of the heater addition structure (HS) and the ring-type contact in the bottom electrode (RIB) structure. The simulation results indicate that the small bottom electrode contactor (BEC) is beneficial for heat efficiency and reliability in the HS cell, and the bottom electrode contactor with size Fx=80 nm is a good choice for the RIB cell. Also shown is that the appropriate SET pulse time is lOOns for the low power consumption and fast operation. 相似文献
7.
C. Schönenberger A. Bachtold C. Strunk J.-P. Salvetat L. Forró 《Applied Physics A: Materials Science & Processing》1999,69(3):283-295
We report equilibrium electric resistance R and tunneling spectroscopy (dI/dV)measurements obtained on single multi-wall nanotubes
contacted by four metallic Au fingers from above. At low temperature quantum interference phenomena dominate the magnetoresistance.
The phase-coherence (lφ)and elastic-scattering lengths (le)are deduced. Because le is of order of the circumference of the nanotubes, transport is quasi-ballistic. This result is supported by a dI/dV spectrum
which is in good agreement with the density of states (DOS) due to the one-dimensional subbands expected for a perfect single-wall
tube. As a function of temperature T the resistance increases on decreasing T and saturates at ≈1–10 Kfor all measured nanotubes.
R(T) cannot be related to the energy-dependent DOS of graphene but is mainly caused by interaction and interference effects.
On a relatively small voltage scale of the order ≈10 meV, a pseudogap is observed in dI/dV which agrees with Luttinger-liquid
theories for nanotubes. Because we have used quantum diffusion based on Fermi-liquid as well as Luttinger-liquid theory in
trying to understand our results, a large fraction of this paper is devoted to a careful discussion of all our results.
Received: 17 May 1999 / Accepted: 18 May 1999 / Published online: 4 August 1999 相似文献
8.
E. Ozturk Y. Ergun H. Sari I. Sokmen 《Applied Physics A: Materials Science & Processing》2001,73(6):749-754
In this study, we report results of a self-consistent calculation obtained for the sub-band structure of Si δ-doped GaAs material
by using a new alternative method. We will discuss the influence of the δ-doping concentration and the δ-layerthickness on
the sub-band structure for a non-uniform distribution, which is taken as different from the known Gaussian distribution. The
confining potential, the sub-band energies, the sub-band occupations, and the Fermi energy have been calculated by solving
the Schr?dinger and Poisson equations by using the Airy functions self-consistently.
Received: 4 December 2000 / Accepted: 31 January 2001 / Published online: 26 April 2001 相似文献
9.
T.V. Dolgova D. Schuhmacher G. Marowsky A.A. Fedyanin O.A. Aktsipetrov 《Applied physics. B, Lasers and optics》2002,74(7-8):653-659
The technique of combined optical second-harmonic (SH) intensity and phase spectroscopy, which is the spectroscopic modification
of SH phase measurements, is proposed to study the nonlinear optical response of semiconductor interfaces with spectrally
close resonant contributions. The spectral dependences of SH intensity and phase from oxidised Si (111) and Ge (111) surfaces
are studied in the range of 3.5- to 5-eV SH photon energy. The resonant behaviour of combined SH spectra is associated with
a superposition of contributions from direct interband transitions at several critical points of Si and Ge band structures.
Received: 16 October 2001 / Revised version: 16 April 2002 / Published online: 6 June 2002 相似文献
10.
M. Roth M. Pickel J. Wang M. Weinelt Th. Fauster 《Applied physics. B, Lasers and optics》2002,74(7-8):661-664
Image-potential states on Cu (117) and Cu (119) surfaces were studied by means of two-photon photoelectron spectroscopy. The
regular array of steps generates a lateral potential on the vicinal surfaces, which modifies the surface-electronic structure.
Compared to Cu (001), the band bottom of the n=1 image-potential states shifts by 40 meV to lower binding energy. The periodicity
of the step-induced superlattice manifests itself as back-folding of the n=1 and 2 dispersion bands. At the surface Brillouin
zone boundary a mini-gap opens with a width of 135 meV for the first image-potential state on Cu (117). On the vicinal surfaces
the lifetime of the image-potential states is reduced by a factor of three as compared to Cu (001). This is attributed to
a narrowing of the surface-projected bulk-band gap when projected along the [11n] direction. While the dephasing rate of the
first image-potential state is close to the decay rate, higher members of the Rydberg-like series show negligible dephasing.
Received: 16 October 2001 / Revised version: 9 April 2002 / Published online: 6 June 2002 相似文献
11.
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
12.
Magnetism of Fe/Cr/Sn/Cr multilayers have been studied by the first-principles density-functional theory. Calculations by the full-potential linearized augmented plane waves (FP LAPW) and screened Korringa–Kohn–Rostoker (SKKR) methods have shown that two types of solutions may be found in these systems: a high-spin (HS) and a low-spin (LS) ones in accordance with the Cr magnetic moment magnitudes. In this work, we have concentrated our attention on the LS solution. The calculation has shown that the LS solution has a phase slip of antiferromagnetic ordering in Cr and is classified as an incommensurate spin density wave (ISDW). The dependence of the ISDW solution on the thickness of Cr, lattice parameter and boundary conditions has been investigated. 相似文献
13.
T.V. Dolgova V.G. Avramenko A.A. Nikulin G. Marowsky A.F. Pudonin A.A. Fedyanin O.A. Aktsipetrov 《Applied physics. B, Lasers and optics》2002,74(7-8):671-675
Size effects in the resonant nonlinear optical response of amorphous Si/SiO2 multiple quantum wells (MQW) are studied by second-harmonic generation (SHG) spectroscopy in a spectral interval of second-harmonic
photon energies from 2.5 to 3.4 eV. The sensitivity of SHG spectroscopy to thickness-dependent electronic structure (sub-band
energy position and density of states line shape) of MQW is demonstrated. A monotonic red shift of central energies of SHG
resonances by 120 m eV upon increase of the well thickness from 2.5 to 10 ? is observed. This is interpreted as a size dependence
of the position of singularities in the combined density of states for a 2D gas of electrons moving in an effective potential
well. It is shown that, for agreement with experiment, the simplest (rectangular) shape of the well should be modified in
order to take into account the lattice-potential distortion at the interfaces.
Received: 16 October 2001 / Revised version: 16 April 2002 / Published online: 6 June 2002 相似文献
14.
A. Castaldini D. Cavalcoli A. Cavallini E. Susi 《Applied Physics A: Materials Science & Processing》2002,75(5):601-605
Acceptor deactivation in the near-surface region of as-grown, boron-doped Si wafers was detected by in-depth profiles of the
free-carrier density obtained by capacitance–voltage measurements. As this deactivation was only observed in wafers subjected
to the standard cleaning procedures used in Si manufacturing, we ascribed it to boron passivation by an impurity introduced
during the cleaning process. From the study of the free-carrier reactivation kinetics and of the diffusion behaviour of boron–impurity
complexes, we have concluded that the impurity is possibly related to hydrogen introduced during the cleaning treatments.
The characteristics of the deep level associated with this impurity have been analysed by deep-level transient spectroscopy.
Received: 22 August 2001 / Accepted: 27 October 2001 / Published online: 29 May 2002 相似文献
15.
A. Gold 《Zeitschrift für Physik B Condensed Matter》1994,94(4):395-399
We present an analytical model for the Coulomb interaction effects in quantum wires forming a nanochannel array. We study the elementary excitations (plasmons and electron-hole excitations) of electron arrays forming three-dimensional structures. The plasmon spectrum of boson arrays is also calculated. Our model applies to bulk material with one-dimensional conduction channels as realized in organic or polymer crystals and in nanochannel array glasses. 相似文献
16.
T. Sameshima Y. Kaneko N. Andoh 《Applied Physics A: Materials Science & Processing》2002,74(6):719-723
We analyzed the rapid heating properties of 50-nm-thick silicon films via 250-nm-thick SiO2 intermediate layers by heat diffusion from joule heating induced by electrical current flow in chromium strips. Numerical
heat-flow simulation resulted in that the silicon films were heated to the melting point by a joule-heating intensity above
1 MW/cm2. A marked increase in electrical conductance associated with silicon melting was experimentally detected. Taper-shaped chromium
strips detected the temperature gradient in the lateral direction caused by the spatial distribution of the joule-heating
intensity. Crystallization occurred according to the temperature gradient. A 2–4-μm lateral crystalline grain growth was demonstrated
for the silicon films.
Received: 20 November 2001 / Accepted: 22 November 2001 / Published online: 20 March 2002 相似文献
17.
Oxygen plasma and high pressure H2O vapor heat treatment were applied to fabrication of n-channel polycrystalline silicon thin film transistors (poly-Si TFTs).
13.56 MHz-oxygen-plasma treatment at 250 °C, 100 W for 5 min effectively reduced defect states of 25-nm-thick silicon films
crystallized by 30 ns-pulsed XeCl excimer laser irradiation. 1.3×106-Pa-H2O vapor heat treatment at 260 °C for 3 h was carried out in order to improve electrical properties of SiOx gate insulators and SiOx/Si interfaces. A carrier mobility of 470 cm2/V s and a low threshold voltage of 1.8 V were achieved for TFTs fabricated with crystallization at 285 mJ/cm2.
Received: 18 November 2002 / Accepted: 25 November 2002 / Published online: 11 April 2003
RID="*"
ID="*"Corresponding author. Fax: +81-42/388-7109, E-mail: tsamesim@cc.tuat.ac.jp 相似文献
18.
Ph. Ebert 《Applied Physics A: Materials Science & Processing》2002,75(1):101-112
This work reports the measurement of the nano-scale physical properties of surface vacancies and the extraction of the types
and concentrations of dopant atoms and point defects inside compound semiconductors, primarily by cross-sectional scanning
tunneling microscopy on cleavage surfaces of III–V semiconductors. The results provide the basis to determine the physical
mechanisms governing the interactions, the formation, the electronic properties, and the compensation effects of surface as
well as bulk point defects and dopant atoms.
Received: 10 May 2001 / Accepted: 23 July 2001 / Published online: 3 April 2002 相似文献
19.
I.L. Lyubchanskii N.N. Dadoenkova M.I. Lyubchanskii E.A. Shapovalov A.E. Zabolotin K.Y. Guslienko T. Rasing 《Applied physics. B, Lasers and optics》2002,74(7-8):711-714
Nonlinear (at the second-harmonic frequency of the incident light) optical reflection by two-dimensional magnetic superstructures
is theoretically studied. A square lattice of magnetic dots and a hexagonal lattice of magnetic bubbles (cylindrical magnetic
domains) are considered. Because the periods of these structures are comparable with the wavelengths of the fundamental and
the second-harmonic radiation, it would be possible to observe diffraction at the second-harmonic frequency. A polarization
analysis of nonlinearly diffracted radiation is performed and the numbers of observable diffraction orders for the above structures
are estimated.
Received: 10 January 2002 / Published online: 11 June 2002 相似文献
20.
S. Nolte M. Will J. Burghoff A. Tuennermann 《Applied Physics A: Materials Science & Processing》2003,77(1):109-111
Using tightly focussed femtosecond laser pulses, waveguides can be fabricated inside various glasses and crystals. This technique
has the potential to generate not only planar but three-dimensional photonic devices. In this paper we present, to the best
of our knowledge, the first true three-dimensional integrated optical device, a 1×3 splitter fabricated in pure fused silica.
The optical properties of this device and possibilities for the fabrication of complex high-density integrated optical elements
are discussed.
Received: 23 December 2002 / Accepted: 6 January 2003 / Published online: 28 March 2003
RID="*"
ID="*"Corresponding author. Fax: +49-3641/65-7680, E-mail: nolte@iap.uni-jena.de 相似文献