共查询到20条相似文献,搜索用时 13 毫秒
1.
Th. Englert 《Solid State Communications》1981,40(9):893-897
An experimental method is presented to determine the valley splitting in n-channel Si inversion layers. The method is an extension of the “tilted field” experiment under conditions, where the valley splitting is resolved at all tilt angles. In the framework of Ohkawa and Uemura's theory, the bare splitting as well as the effective exchange interaction are obtained directly from the angles of coincidence. The bare valley splitting in the samples investigated is 0.15 meV/1012 cm-2 ·ns. Using experimentally determined parameters we have calculated the oscillatory conductivity σxx in a simplified version of Ohkawa and Uemura's model. The calculated curves reproduce the detailed structure of the experimental data for the various tilt angles of the experiment. 相似文献
2.
Zhang Y Jiang Z Small JP Purewal MS Tan YW Fazlollahi M Chudow JD Jaszczak JA Stormer HL Kim P 《Physical review letters》2006,96(13):136806
The quantum Hall (QH) effect in two-dimensional electrons and holes in high quality graphene samples is studied in strong magnetic fields up to 45 T. QH plateaus at filling factors nu = 0, +/-1, +/-4 are discovered at magnetic fields B > 20 T, indicating the lifting of the fourfold degeneracy of the previously observed QH states at nu = +/-4(absolute value(n) + 1/2), where n is the Landau-level index. In particular, the presence of the nu = 0, +/-1 QH plateaus indicates that the Landau level at the charge neutral Dirac point splits into four sublevels, lifting sublattice and spin degeneracy. The QH effect at nu = +/-4 is investigated in a tilted magnetic field and can be attributed to lifting of the spin degeneracy of the n = 1 Landau level. 相似文献
3.
The valley splitting, which lifts the degeneracy of the lowest two valley states in a SiO(2)/Si(100)/SiO(2) quantum well, is examined through transport measurements. We demonstrate that the valley splitting can be observed directly as a step in the conductance defining a boundary between valley-unpolarized and -polarized regions. This persists to well above liquid helium temperature and shows no dependence on magnetic field, indicating that single-particle valley splitting and valley polarization exist in (100) silicon even at zero magnetic field. 相似文献
4.
《Surface science》1991,245(3):L185-L189
In this Letter, both the dynamics and kinetics of the reaction of oxygen molecules on Si(100)p2 × 1 and Si(111)7 × 7 and 1× 1 surfaces are compared. In all three cases, two distinct adsorption channels were observed. For oxygen molecules with translational energies less than 0.08 eV, the initial sticking is not sensitive to the energy or the angle of incidence, but displays a high sensitivity to the surface structure. At higher energies, a second channel becomes effective. The initial sticking coefficient increases rapidly and scales with the normal component of the translational energy, but the dependence on surface structure is greatly diminished. The kinetics of SiO formation are qualitatively similar on all surfaces with slightly higher rates on Si(111). 相似文献
5.
K. Yamada N. Miura C. Hamaguchi 《Applied Physics A: Materials Science & Processing》1989,48(2):149-153
Chaotic conductivity oscillations were observed in n-Si in a narrow freeze-out temperature range between 26 K and 34 K in a pulsed high magnetic field of about 18 T. It was found that the chaotic behaviour can be drastically influenced by the magnetic field. Period-doubling bifurcations were found in these chaotic oscillations and the routes to the chaos were determined. The attractor dimensions of the chaos converged to around 1.1 to 2.3 depending on the applied electric fields. The frequency dependence of the power spectrum of the oscillations was approximately 1/f
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M. Kutschera M. Weinelt M. Rohlfing T. Fauster 《Applied Physics A: Materials Science & Processing》2007,88(3):519-526
We have identified a surface state on Si(100) (2×1) at a binding energy of 0.69±0.05 eV with respect to the vacuum level.
Band-structure calculations within the GW method reveal that almost 80% of the probability density of the resonance is located
in front of the surface. We therefore assign the surface resonance to an image-potential state. It has a lifetime of about
10 fs and contributes significantly to two-photon photoemission from Si(100).
PACS 73.20.At; 79.60.Bm; 79.60.Dp; 79.60.Ht 相似文献
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Deviations from the classical two-dimensional plasmon dispersion are observed at high wavevectors q in electron inversion layers on Si(100) MOS-capacitors with periodically structured gate electrodes. For high inversion electron densities (ns> 6 × 1012cm?2) an unexpected mass enhancement is extracted from the plasmon dispersion. In addition the plasmon linewidth is found to be significantly larger than predicted from transport experiments. On the same samples non-vertical intersubband resonance transitions are observed with radiation incident normal to the interface. They are excited by an electric field component normal to the surface that is induced by the structured gate electrode. 相似文献
10.
H. Taub 《Zeitschrift für Physik B Condensed Matter》1975,19(1):107-115
We have measured the temperature dependence of both the zero-field resistivity and the transverse magnetoresistance of polycrystalline potassium wires (?(300 K)/?(4.2 K)=140 to 6000) in fieldsH?35 kG and at temperaturesT?4.2 K. Our principal findings are: 1) The presence of a large magnetic fieldH=35 kG does not alter the temperature dependence of ? from that observed atH=0; below 4.2 K theT-dependent part of the resistivities,?T (H=0) and?T (H=35 kG), fit well to the function exp (?Θ*/T) with the same Θ*=23K. 2) Deviations from Matthiessen's rule are significantly reduced in a strong field so that the magnitude of?T (H=0) approaches that of?T (H=35 kG) as sample purity decreases. 3) The slope of the high-field linear magnetoresistance increases slightly (?8%) from 1.5 K to 4.2 K. We attribute the exponential temperature dependence of?T (H) to the freezing out of electron-phonon umklapp processes as has been shown for the zero-field resistivity. The reduction in deviations from Matthiessen's rule at high fields can be understood within semiclassical theory, but the latter cannot explain the failure of?T (H) to saturate at high fields. A proposal by Young that electron-phonon umklapp scattering may contribute aT-dependent high-field linear magnetoresistance in potassium is considered. 相似文献
11.
Magneto-transport study has been performed in topological semimetal ZrSiS single crystals under high pulsed magnetic fields. Obvious dependence of Landau level splitting on temperature and angular was investigated. The strong three-dimensional anisotropic nature of Landau level splitting under high pulsed magnetic fields was revealed by the angular dependent measurements, in which the orbital contribution is more dominant than Zeeman splitting. Our studies provide more insights into the physical properties of topological semimetals ZrSiS and shed light on future spintronic applications of ZrSiS. 相似文献
12.
The main tendencies in the formation of local magnetic moments and hyperfine magnetic fields at Fe nuclei in Fe-Sn and Fe-Si alloys at low metalloid concentrations are analyzed on the basis of “first-principles” calculations. The results of calculations are compared with experimental data. The main differences between these alloys were proved to be due to the differences in their lattice parameters. It is shown that a significant contribution to the formation of the hyperfine field comes from the orbital magnetic moment and the Ruderman-Kittel-Kasuya-Yosida polarization, which depend on the impurity concentration and the distance to an impurity atom in the crystal lattice. 相似文献
13.
M. Weinelt M. Kutschera R. Schmidt C. Orth T. Fauster M. Rohlfing 《Applied Physics A: Materials Science & Processing》2005,80(5):995-1003
The electronic structure and electron dynamics at a Si(100) surface is studied by two-photon photoemission (2PPE). At 90 K the occupied Dup dangling-bond state is located 150±50 meV below the valence-band maximum (VBM) at the center of the surface Brillouin zone ̄ and exhibits an effective hole mass of (0.5±0.15)me. The unoccupied Ddown band has a local minimum at ̄ at 650±50 meV above the VBM and shows strong dispersion along the dimer rows of the c(4×2) reconstructed surface. At 300 K the Ddown position shifts comparable to the Si conduction-band minimum by 40 meV to lower energies but the dispersion of the dangling-bond states is independent of temperature. The surface band bending for p-doped silicon is less than 30 meV, while acceptor-type defects cause significant and preparation-dependent band bending on n-doped samples. 2PPE spectra of Si(100) are dominated by interband transitions between the occupied and unoccupied surface states and emission out of transiently and permanently charged surface defects. Including electron–hole interaction in many-body calculations of the quasi-particle band structure leads us to assign a dangling-bond split-off state to a quasi-one-dimensional surface exciton with a binding energy of 130 meV. Electrons resonantly excited to the unoccupied Ddown dangling-bond band with an excess energy of about 350 meV need 1.5±0.2 ps to scatter via phonon emission to the band bottom at ̄ and relax within 5 ps with an excited hole in the occupied surface band to form an exciton living for nanoseconds. PACS 73.20.At; 79.60.Bm; 79.60.Dp; 79.60.Ht 相似文献
14.
N. Arzate J.E. Mejía B.S. Mendoza R. Del Sole 《Applied physics. B, Lasers and optics》1999,68(3):629-632
1 resonances for clean and H covered surfaces shift as a function of the dc field in agreement with experiment. This suggests
the presence of built-in electric fields whose strength depends on the H coverage, and which are strongly localized in the
subsurface region.
Received: 20 September 1998 相似文献
15.
Nuclear acoustic resonance has been observed at much higher magnetic fields than previously reported for nonmagnetic materials. Marked differences between the Δm = 1 and the Δm = 2 line shapes in tantalum were noted. 相似文献
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Morley GW van Tol J Ardavan A Porfyrakis K Zhang J Briggs GA 《Physical review letters》2007,98(22):220501
By applying a new technique for dynamic nuclear polarization involving simultaneous excitation of electronic and nuclear transitions, we have enhanced the nuclear polarization of the nitrogen nuclei in 15N@C60 by a factor of 10(3) at a fixed temperature of 3 K and a magnetic field of 8.6 T, more than twice the maximum enhancement reported to date. This methodology will allow the initialization of the nuclear qubit in schemes exploiting N@C60 molecules as components of a quantum information processing device. 相似文献
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《Surface science》1989,219(3):L560-L564
Nitrogen trifluoride is found to undergo spontaneous dissociative chemisorption at Si(100) surfaces. Both fluorine and nitrogen are incorporated at the surface. The ratio of chemisorbed N and F on the surface is non-stoichiometric for NF3, suggesting that two or more competitive reaction pathways may occur. 相似文献
20.
《Surface science》1988,206(3):L888-L894
Employing spin-resolved inverse photoemission we have observed an exchange splitting of the unoccupied oxygen-induced band in the chemisorption system (2 × 1)-O/Ni(110). At the centre of the surface Brillouin zone the splitting between the oxygen 2p-derived majority and minority band— referred to the magnetization vector of nickel-was found to be 80±20 meV. This effect is a manifestation of the strong magnetic correlation between the oxygen and nickel bands. The size of the splitting is surprising as earlier experimental work indicated a substantial reduction of the surface magnetization due to chemisorption. For the empty 2π1-derived band of CO on Ni(110) no such splitting has been observed. 相似文献