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81.
Shubnikov-de Haas oscillations have been studied for (110) and (111) n-type silicon inversion layers. The measured cyclotron masses mc = (0.38 ± 0.03)m0 and mc = (0.40 ± 0.03)m0 for (110) and (111) planes, respectively, are larger than theoretically predicted values. The experimental valley degeneracy factor gv = 2 ± 0.2 for both orientations is also at variance with self consistent calculations. The electronic g-factor depends on the surface carrier concentration and is enhanced over its bulk value. There was no evidence for the occupation of other subbands. 相似文献
82.
Muruganathan RM Krustev R Müller HJ Möhwald H Kolaric B Klitzing RV 《Langmuir : the ACS journal of surfaces and colloids》2004,20(15):6352-6358
Foam films stabilized by a sugar-based nonionic surfactant, beta-dodecyl maltoside, are investigated. The film thickness and the film contact angle (which is formed at the transition between the film and the bulk solution) are measured as a function of NaCl concentration, surfactant concentration, and temperature. The film thickness measurements provide information about the balance of the surface forces in the film whereas the contact angle measurements provide information about the specific film interaction free energy. The use of the glass ring cell and the thin film pressure balance methods enables studies under a large variety of conditions. Thick foam films are formed at low electrolyte concentration. The film thickness decreases (respectively the absolute value of the interaction film free energy increases) with the increase of the electrolyte concentration according to the classical DLVO theory. This indicates the existence of a repulsive double layer electrostatic component of the disjoining pressure. An electrostatic double layer potential of 16 mV was calculated from the data. A decrease of the film thickness on increase of the surfactant concentration in the solution is observed. The results are interpreted on the basis of the assumption that the surface double layer potential originates in the adsorption of hydroxyl ions at the film surfaces. These ions are expelled from the surface at higher surfactant concentration. 相似文献
83.
Shvarchuck I Buggle Ch Petrov DS Dieckmann K Zielonkowski M Kemmann M Tiecke TG von Klitzing W Shlyapnikov GV Walraven JT 《Physical review letters》2002,89(27):270404
We report the formation of Bose-Einstein condensates into nonequilibrium states. Our condensates are much longer than equilibrium condensates with the same number of atoms, show strong phase fluctuations, and have a dynamical evolution similar to that of quadrupole shape oscillations of regular condensates. The condensates emerge in elongated traps as the result of local thermalization when the nucleation time is short compared to the axial oscillation time. We introduce condensate focusing as a new method to extract the phase-coherence length of Bose-Einstein condensates. 相似文献
84.
The impact of the cononsolvency effect on poly (N-isopropylacrylamide) based microgels at interfaces
Marcel Richter Melanie Hunnenmörder Regine V. Klitzing 《Colloid and polymer science》2014,292(10):2439-2452
The paper addresses the effect of solid interfaces on the cononsolvency effect for poly(N-iso propylacrylamide) based microgels containing different contents of the co-monomer allyl acetic acid (AAA). The cononsolvency effect is studied by dynamic light scattering (DLS) in solution and with atomic force microscopy (AFM) at surfaces against different mixtures of water and organic solvent (ethanol, iso-propanol, and tetrahydrofuran). For the studies at interfaces, the microgels are spin coated on silicon wafers that are precoated with poly(allylamine hydrochloride) (PAH). The minimum in particle volume due to cononsolvency shows a pronounced shift from 10–20 % of organic solvent to 40–50 % after deposition at the Si/PAH wafer. The strong shift indicates an increase of water to organic solvent ratio within the gel at the surface with respect to the bulk solution. In order to understand the increase of water to organic solvent ratio, shrinking/reswelling AFM experiments for different spin-coating conditions and under ambient conditions are carried out. Spin coating from water instead from different solvent mixtures has no effect on the cononsolvency. In ambient conditions, the cononsolvency effect disappears 相似文献
85.
R.D. Wiersma J.G.S. Lok L. Tiemann W. Dietsche K. von Klitzing D. Schuh W. Wegscheider 《Physica E: Low-dimensional Systems and Nanostructures》2006,35(2):320
Recent experiments on quantum Hall bilayers in the vicinity of total filling factor 1 (νT=1) have revealed many exciting observations characteristic of a superfluidic exciton condensate. We report on our experimental work involving the νT=1 exciton condensate in independently contacted bilayer two-dimensional electron systems. We observe previously reported phenomena as a zero-bias resonant tunneling peak, a quantized Hall drag resistivity, and in counter-flow configuration, the near vanishing of both ρxx and ρxy resistivity components. At balanced electron densities in the layers, we find for both drag and counter-flow current configurations, thermally activated transport with a monotonic increase of the activation energy for d/ℓB<1.65 with activation energies up to 0.4 K. In the imbalanced system the activation energies show a striking asymmetry around the balance point, implying that the gap to charge excitations is considerably different in the separate layers that form the bilayer condensate. This indicates that the measured activation energy is neither the binding energy of the excitons, nor their condensation energy. 相似文献
86.
87.
O. V. Volkov V. E. Zhitomirskii I. V. Kukushkin K. von Klitzing K. Eberl 《JETP Letters》1997,65(1):38-44
The recombination radiation spectra of two-dimensional electrons in an asymmetrically doped GaAs/AlGaAs quantum well are investigated
at different temperatures and laser-excitation energies. At low temperatures and in high magnetic fields the recombination
lines of the electrons from completely filled Landau levels are split into narrow sublevels. It is shown that this fine structure
of the Landau levels is due to the presence of excitonic effects in the initial and final states of the photoexcited system.
It is demonstrated that the recombination process is accompanied by the excitation of intersubband and cyclotron magnetoplasma
modes.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 1, 38–43 (10 January 1997) 相似文献
88.
M. Burghard G. Philipp S. Roth K. von Klitzing 《Applied Physics A: Materials Science & Processing》1998,67(5):591-593
Received: 4 September 1998/Accepted: 9 September 1998 相似文献
89.
V. E. Kirpichev I. V. Kukushkin V. E. Bisti K. von Klitzing K. Eberl 《JETP Letters》1996,64(11):814-819
An emission line appearing in the hot-luminescence spectrum of GaAs at a frequency shifted from the laser line by the cyclotron
energy of light holes is observed and investigated. Analysis of the magnetooscillations of the intensity of this line shows
that the line is due to the recombination of a photoexcited electron and a light hole after the hole undergoes energy relaxation
between Landau levels. The dependence of the cyclotron mass and g factor of light holes on the hole energy was measured directly and a very strong nonparabolicity of the valence band of GaAs,
several times greater than the theoretical estimates, was observed.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 11, 766–771 (10 December 1996) 相似文献
90.
J. Kvíčala J. Havelka J. Zeman J. Němec 《Journal of Radioanalytical and Nuclear Chemistry》1991,149(2):267-274
Neutron activation analysis without radiochemical separation was used for simultaneous analysis of eight trace elements in thyroid glands, obtained as necroptic material from persons not suffering from diseases of this gland. Inorganic standard solutions were used for calculations of concentrations of measured elements. Concentrations are expressed in ppm, or ppb. IAEA reference materials were used for quality assurance of analyses. From analyses of 42 thyroids concentration levels of Se, Cs, Sc, Fe, Cr, Zn, Co, and Rb and their variances in the thyroids were calculated. These results might serve as comparison material for medical research of pathological and functional changes in thyroid glands. 相似文献