共查询到20条相似文献,搜索用时 31 毫秒
1.
M. Danckwerts E. Savinova B. Pettinger K. Doblhofer 《Applied physics. B, Lasers and optics》2002,74(7-8):635-639
We combine in situ electrochemical second-harmonic generation (SHG) with voltammetry measurements using the hanging meniscus
configuration. This setup is used to investigate the interface between a Ag (111) electrode and an alkaline electrolyte. The
study offers a new in situ insight into the electrochemical processes at the Ag (111) electrode during OH adsorption and subsequent
oxidation. The behavior of SHG isotropic and anisotropic contributions as a function of potential is discussed and related
to the interfacial electric field. Comparison of the results with previous investigations of the Ag underpotential oxidation
in alkaline solutions shows that submonolayer oxidation is followed by bulk oxidation.
Received: 16 October 2001 / Revised version: 26 March 2002 / Published online: 6 June 2002 相似文献
2.
Based on a parameterized electronic many-body theory we calculate the spectrum of optical second-harmonic generation (SHG)
on an antiferromagnetic (AF) surface: NiO (001). The occurrence of AF spectral lines is further exploited for the calculation
of ultra-fast spin dynamics. This spin dynamics is observable in SHG. It is characterized by both a sharp drop of the AF signal
within a few femtoseconds and a long persistence (up to nanoseconds) of the spin coherence. These two features constitute
an ideal system for possible applications in both magnetic recording and quantum computing.
Received: 16 October 2001 / Revised version: 21 March 2002 / Published online: 6 June 2002 相似文献
3.
Y.G. Fokin T.V. Murzina O.A. Aktsipetrov S. Soria G. Marowsky 《Applied physics. B, Lasers and optics》2002,74(7-8):777-781
Ferroelectric properties of thin (1.5–4 μm planar cells of a ferroelectric liquid crystal (FLC) mixture are studied using
electro-optic measurements, second-harmonic generation (SHG) and SHG interferometry. A switching behaviour of the FLC cells
in external dc electric fields is observed. It is characterised by rotation of the polarisation plane of the transmitted light
and by changes in the SHG intensity, phase and anisotropy dependences, which are attributed to a collective motion of the
system as a ferroelectric uniform state with C2 symmetry.
Received: 16 October 2001 / Revised version: 18 March 2002 / Published online: 6 June 2002 相似文献
4.
J.S. Gibb G. Hancock A. Hutchinson R. Peverall G.A.D. Ritchie 《Applied physics. B, Lasers and optics》2003,76(1):97-105
A simple technique is demonstrated for the accurate determination of pressure-induced line shifts of water in air. High- and
low-pressure water samples are simultaneously probed on selected overtone transitions at 1.32 μm using a current-modulated
distributed-feedback diode laser and harmonic detection. The resultant profiles yield an average line shift of -293±30 MHz/atm
for the 3,3,0 (002)2,2,1 (000)transition at 227251 GHz and -134±7 MHz/atm for the 3,2,1 (002)2,1,2 (000) transition at 227027 GHz.
Comparisons are made between first- and second-harmonic detection, and wavelength- and frequency-modulation regimes. The effect
of modulation broadening on the returned line shifts is quantified.
Received: 12 August 2002 / Revised version: 21 October 2002 / Published online: 8 January 2003
RID="*"
ID="*"Corresponding author. Fax: +44-01865/275410, E-mail: gus.hancock@chemistry.ox.ac.uk 相似文献
5.
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
6.
G. Tsilimis J. Kutzner H. Zacharias 《Applied Physics A: Materials Science & Processing》2003,76(5):743-749
An extreme ultraviolet (EUV) laser light source based on high-harmonic generation is presented. Coherent radiation in the
photon energy range hν=20–120 eV is produced in the conversion media argon, neon and helium. High-harmonic radiation in the
energy range 20–50 eV is applied to investigate photoemission spectra of Pt (111) and CO/Pt (111). In the photoemission spectra
of the clean surface, new secondary electron emission structures are found which influence the cross section analysis of the
CO states. When taking these Pt resonances into consideration, the 4σ and 5σ CO shape resonances are found at photon energies
of 37 eV and 28 eV, respectively. Additionally, a resonance at hν=31 eV is also observed for the CO 1π state, in contrast
to formerly published experimental data. Experimental and theoretical data suggest that this resonance is not connected to
the well-known shape resonances in the σ-channel. Based on theoretical approaches, it is identified as an autoionization resonance.
Received: 8 April 2002 / Accepted: 22 May 2002 / Published online: 22 November 2002
RID="*"
ID="*"Corresponding author. Fax: +49-251/833-3604, E-mail: kutzner@uni-muenster.de 相似文献
7.
Second-harmonic generation (SHG) results for Ni and Co films on Cu (001) have been reinvestigated regarding the depth sensitivity
of this technique for thin films. We find that tangential components of the nonlinear susceptibility are much more sensitive
to real film properties than normal components, which are confined to surfaces and interfaces. In consequence, for SHG experiments
on ultra-thin metal films, polarization combinations should be favored that possess only tangential susceptibility components,
even though the yield is weaker. Additional phase measurements are necessary to obtain full information about the film.
Received: 20 January 2002 / Published online: 6 June 2002 相似文献
8.
E.D. Mishina A.I. Morosov Q.-K. Yu S. Nakabayashi T. Rasing 《Applied physics. B, Lasers and optics》2002,74(7-8):765-775
A general approach of second-harmonic generation (SHG) studies for surface phase transitions (PTs) is presented, with a thermodynamic
classification of surface PTs and their relation to SHG parameters. The symmetry aspects of SHG near a surface PT are discussed,
including issues connected with separation of surface and bulk contributions and the role of atomic and mesoscopic inhomogeneities.
This approach is illustrated by applying it to two systems revealing a (near-) surface PT: single-crystalline SrTiO3 near a bulk structural PT and single-crystalline Au in an electrochemical cell revealing an order–disorder and a reconstructive
PT.
Received: 15 January 2002 / Published online: 11 June 2002 相似文献
9.
Time-resolved pump–probe second-harmonic (SH) response following optical excitation has been studied in nickel and permalloy
films. Experimental data indicate that the odd SH field represents the transient magnetization, i.e. the behavior of the spin
subsystem, while the electron subsystem generates the even SH field. Delays between odd and even SH fields of about 200 fs
and 650 fs were detected for nickel and permalloy films, respectively. We found that the dynamics of the odd SH field is influenced
by the polarization of the pump pulse. This dependence on excitation conditions suggests a difference in surface and bulk
magnetization dynamics.
Received: 25 November 2001 / Revised version: 27 March 2002 / Published online: 11 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.
W.G. Schmidt 《Applied Physics A: Materials Science & Processing》2002,75(1):89-99
There has been renewed interest in the structure of III-V compound semiconductor (001) surfaces caused by recent experimental
and theoretical findings, which indicate that geometries different from the seemingly well-established dimer models describe
the surface ground state for specific preparation conditions. I review briefly the structure information available on the
(001) surfaces of GaP, InP, GaAs and InAs. These data are complemented with first-principles total-energy calculations. The
calculated surface phase diagrams are used to explain the experimental data and reveal that the stability of specific surface
structures depends largely on the relative size of the surface constituents. Several structural models for the Ga-rich GaAs (001)(4×6)
surface are discussed, but dismissed on energetic grounds. I discuss in some detail the electronic properties of the recently
proposed cation-rich GaAs (001)ζ(4×2) geometry.
Received: 18 May 2001 / Revised version: 23 July 2001 / Published online: 3 April 2002 相似文献
12.
T. Eimüller P. Fischer M. Köhler M. Scholz P. Guttmann G. Denbeaux S. Glück G. Bayreuther G. Schmahl D. Attwood G. Schütz 《Applied Physics A: Materials Science & Processing》2001,73(6):697-701
X-ray magnetic circular dichroism (X-MCD) was used as a large, element-specific and quantitative magnetic contrast mechanism
in the soft X-ray microscopes at BESSY I (Berlin) and the ALS (Berkeley). The present state and potential of magnetic transmission
X-ray microscopy (MTXM) is outlined. The possibility to record images in varying magnetic fields and the high spatial resolution
down to 25 nm were used to image out-of-plane magnetized (4 ?Fe / 4 ?Gd)×75 systems. Magnetic domains could be studied in
arrays of circular and square dots with lateral dimensions down to 180 nm. Hysteresis loops of individual dots were deduced
using the direct proportionality of the X-MCD contrast to the sample magnetization. Images of a 3 nmCr / 50 nmFe / 6 nmCr
film demonstrate for the first time that MTXM is also able to observe in-plane magnetized domains. In the future the possible
applications of MTXM will be extended with regard to the strength of the external field, the available energy range and the
sample conditions by building a dedicated transmission X-ray microscope for magnetic imaging at BESSY II.
Received: 22 May 2001 / Accepted: 4 July 2001 / Published online: 5 October 2001 相似文献
13.
W. Cheikh-Rouhou L.C. Sampaio B. Bartenlian P. Beauvillain A. Brun J. Ferré P. Georges J.-P. Jamet V. Mathet A. Stupakewicz 《Applied physics. B, Lasers and optics》2002,74(7-8):665-670
The optical and magneto-optical second harmonic reflectivity response of Au/Co/Au/Cu multilayers grown on vicinal Si (111)
substrates has been studied. These azimuthal optical non-linear experiments check the uniaxial character of the crystallinity
of the Au buffer layer and the magnetic behavior of the ultrathin Co films in the metallic multilayer. They clearly show the
strong dependence of the growth parameters and the misorientation of the vicinal surface on the SHG reflectivity signals.
This uniaxial behavior is also correlated to linear MOKE experiments on the magnetic anisotropy with an easy magnetization
axis parallel to the step edges.
Received: 16 October 2001 / Published online: 29 May 2002 相似文献
14.
V. Venkataramanan K. Noguchi M. Aono T. Suzuki 《Applied physics. B, Lasers and optics》2002,74(7-8):683-689
We describe the instrumentation related to the first observation of magnetization-induced enhancement of surface second-harmonic
generation (SHG) from the paramagnetic Si(111)-7×7 surfaces. A judicious choice of polarization and sample orientation enabled
us to isolate the magnetic-field-dependent tensor element of the nonlinear susceptibility. A conductive liquid-nitrogen system,
coupled to an ultrahigh-vacuum system that is immune to the high magnetic field of 10 T, cooled the sample to about 120 K.
A high extinction that is necessary to detect the magnetization-induced SHG (MSHG) was accomplished by minimizing stray optical
effects such as Faraday rotation, photoluminescence and thermal birefringence in all optical components, with extra care taken
for the UHV window. Consistent and stable operation of this sensitive measurement system permitted experiments involving MSHG
at multiple wavelengths and temperatures. Probing the magnetization-induced optical nonlinearity was validated by quenching
the surface states by oxidation of the surface layers. From MSHG measurements at two wavelengths resonant with different surface-state
transitions, we were able to suggest that the observed MSHG is proportional to the number of dangling bond states of Si(111)-7×7.
Received: 15 January 2002 / Published online: 2 May 2002 相似文献
15.
T.V. Murzina I.E. Razdolski A.M. Grishin 《Journal of magnetism and magnetic materials》2009,321(7):836-839
Nonlinear magneto-optical properties of all-garnet magnetophotonic crystals composed of alternating layers of ferromagnetic Bi3Fe5O12 (BIG) and Sm3Ga5O12 quarter-wavelength layers with a half-wavelength BIG microcavity mode are presented. The samples are grown by rf-magnetron sputtering on non-magnetic GGG substrate. Many-fold enhancement of the magnetization-induced effects in second-harmonic generation (SHG) as compared with linear magneto-optical effects are observed: the SHG magnetic contrast up to 50% and magnetization-induced rotation of the polarization plane of about 90° are measured at the resonance microcavity wavelengh of λ=779 nm. 相似文献
16.
D.M. Newman M.L. Wears R.J. Matelon D. McHugh 《Applied physics. B, Lasers and optics》2002,74(7-8):719-722
The behaviour of the reflectivity and Kerr magneto-optic effects in the non-linear second-harmonic (SH) field diffracted from
nano-scale structured ferromagnetic interfaces is reported. Measurements are made in both the linear and non-linear fields
at two different fundamental wavelengths (1064 nm and 800 nm) and their associated harmonics. Resonant behaviour observed
as a function of angle of incidence is identified with surface-plasmon production that is known to intensify the local field
within the interface. Radiation incident at angles of incidence that optimise coupling to the electron plasma produces an
increase in the SH field radiated in the vicinity of those angles. Similarly, at those angles of incidence where radiation
at the SH wavelengths (532 nm and 400 nm) couples optimally to the electron plasma, troughs are seen in the angular spectrum
of the generated SH radiation. Kerr magneto-optic measurements taken in both the linear field and the SH field both show very
significant enhancement at angles meeting the plasma-resonance condition. The totality of experimental data presented allows
the conclusion that intensification of the interface electric field due to plasmon creation enhances not only the SH reflection
coefficient, as was already known, but also the magneto-optic reflection coefficients in both linear and SH fields.
Received: 16 October 2001 / Revised version: 14 March 2002 / Published online: 29 May 2002 相似文献
17.
I.F. Salakhutdinov L. Kotačka H.J.W.M. Hoekstra J. Čtyroký V.A. Sychugov O. Parriaux 《Applied physics. B, Lasers and optics》2001,73(5-6):541-545
Abnormal reflecting mirror (ARM) structures, consisting of a corrugated optical waveguiding structure, can serve as a wavelength-selective
end mirror in a laser cavity. The ARM structure shows, for each wavelength in a certain region, 100% reflection at a certain
angle of incidence. In the vicinity of this angle the waveguide is resonantly excited, leading to strong enhancement of the
optical field in the layer structure, which is interesting for efficient second-harmonic generation (SHG). In this paper,
experimental results of a first prototype, exhibiting Čerenkov SHG, are reported.
Received: 16 May 2001 / Revised version: 28 August 2001 / Published online: 30 October 2001 相似文献
18.
K. Jacobi L. Geelhaar J. Márquez 《Applied Physics A: Materials Science & Processing》2002,75(1):113-127
We present a brief overview of surface structures of high-index GaAs surfaces, putting emphasis on recent progress in our
own laboratory. By adapting a commercial scanning tunneling microscope (STM) to our molecular beam epitaxy and ultra high
vacuum analysis chamber system, we have been able to atomically resolve the GaAs(
)B (8 ×1), (114)Aα2(2×1), (137), (3 7 15), and (2 5 11) surface structures. In cooperation with P. Kratzer and M. Scheffler
from the Theory Department of the Fritz-Haber Institute we determined the structure of some of these surfaces by comparing
total-energy calculations and STM image simulations with the atomically resolved STM images. We present the results for the
{112}, {113}, and {114} surfaces. Then we describe what led us to proceed into the inner parts of the stereographic triangle
and to discover the hitherto unknown stable GaAs (2 5 11) surface.
Received: 16 May 2001 / Accepted: 23 July 2001 / Published online: 3 April 2002 相似文献
19.
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
20.
S. Heinze P. Kurz D. Wortmann G. Bihlmayer S. Blügel 《Applied Physics A: Materials Science & Processing》2002,75(1):25-36
In this paper we present a density functional theory investigation of complex magnetic structures in ultra-thin films. The
focus is on magnetically frustrated antiferromagnetic Cr and Mn monolayers deposited on a triangular lattice provided by a
Ag (111) substrate. This involves non-collinear magnetic structures, which we treat by first-principles calculations on the
basis of the vector spin-density formulation of the density functional theory. We find for Cr/Ag (111) a coplanar non-collinear
periodic 120° Néel structure, for Mn/Ag (111) a row-wise antiferromagnetic structure, and for Fe/Ag (111) a ferromagnetic
structure as magnetic ground states. The spin-polarized scanning tunneling microscope (SP–STM) operated in the constant-current
mode is proposed as a powerful tool to investigate complex atomic-scale magnetic structures of otherwise chemically equivalent
atoms. We discuss a recent application of this operation mode of the SP–STM on Mn/W (110), which led to the first observation
of a two-dimensional antiferromagnet on a non-magnetic metal. The future potential of this approach is demonstrated by calculating
SP–STM images for different magnetic structures of Cr/Ag (111). The results show that the predicted non-collinear magnetic
ground state structure can clearly be discriminated from competing magnetic structures. A general discussion of the application
of different operation modes of the SP–STM is presented on the basis of the model of Tersoff and Hamann.
Received: 07 May 2001 / Accepted: 23 July 2001 / Published online: 3 April 2002 相似文献