Showing papers by "László Forró published in 1998"
TL;DR: In this article, the authors report on the field emission properties of single-wall carbon nanotube films, with emphasis on current-versus-voltage (I-V) characteristics and current stability.
Abstract: We report on the field emission properties of single-wall carbon nanotube films, with emphasis on current–versus–voltage (I–V) characteristics and current stability. The films are excellent field emitters, yielding current densities higher than 10 mA cm−2 with operating voltages that are far lower than for other film emitters, but show a significant degradation of their performances with time. The observed deviations from the Fowler-Nordheim behavior in the I–V characteristics point to the presence of a nonmetallic density of states at the tip of the nanotubes.
686 citations
TL;DR: In this paper, the authors investigated the field emission properties of multiwalled carbon nanotubes, in the form of both single tips and films, and found that they show low operating voltages and produce high current densities.
253 citations
TL;DR: In this paper, the light emission is caused by electron transitions between different electronic levels participating in the field emission, which is not due to blackbody radiation or current-induced heating.
Abstract: We report on the observation of luminescence during electron field emission on singlewall and multiwall carbon nanotubes. Spectra acquired at different emitted currents, as well as the dependence of the luminescence intensity with the current, show that the light emission is not due to blackbody radiation or to current-induced heating. In fact, our results suggest that the light emission is caused by electron transitions between different electronic levels participating in the field emission.
142 citations
TL;DR: In this paper, the authors show that screening by free carriers from the domain boundaries reduces Coulomb repulsion in the Ta d band by similar to 1/3, compared to pure samples, yielding a finite spectral weight at the Fermi level.
Abstract: Random defects destroy long-range phase coherence, and inhibit the metal-insulator transition in the charge density wave (CDW) system 1T-TaS2. Photoelectron spectroscopy with high resolution reveals corresponding changes in the electronic structure. Core level spectra indicate a temperature-dependent limited growth of commensurate CDW domains. Screening by free carriers from the domain boundaries reduces the Coulomb repulsion in the Ta d band by similar to 1/3, compared to pure samples, yielding a finite spectral weight at the Fermi level.
78 citations
TL;DR: In this paper, the authors performed spatially resolved measurements on multiwalled carbon nanotubes and observed at special positions on the sample Raman-active vibrational modes in the low energy region.
Abstract: We performed spatially resolved measurements on multiwalled carbon nanotubes. The first-order spectra do not reveal any characteristic, fingerprint-like signal as it is known from singlewalled nanotubes. Instead, we observed at special positions on the sample Raman-active vibrational modes in the low-energy region, which, as we show, differ from those of singlewalled nanotubes and graphite. Possible explanations for the origin of these modes will be given.
53 citations
TL;DR: In this article, the authors deduced the magnitude of the electric field across the planes induced by atoms with different valence above and below from new Raman results on YBa2Cu3O6+x and Bi2Sr2(Ca1−xYx)Cu2O8 with different O and Y doping.
15 citations
TL;DR: In this article, the Ramaman spectra of underdoped cuprate superconductors have been studied for different polarizations and temperatures Strong anisotropies show up in both the normal and superconducting state.
9 citations