Topic
Scanning tunneling spectroscopy
About: Scanning tunneling spectroscopy is a research topic. Over the lifetime, 7886 publications have been published within this topic receiving 213828 citations.
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TL;DR: The eAect of on-site Coulomb repulsion on the process of resonant tunneling is studied and it is found that the tunneling peak results from a crossover from the high-temperature Kondo phase to the lowtemperature mixed-valence phase of the system when the chemical potential is varied across the on- site localized-state energy.
Abstract: We study the eAect of on-site Coulomb repulsion on the process of resonant tunneling. We find that the tunneling peak results from a crossover from the high-temperature Kondo phase to the lowtemperature mixed-valence phase of the system when the chemical potential is varied across the on-site localized-state energy. Consequently, the line shape is non-Lorentzian, with rather unusual temperature dependence. Moreover, a magnetic field does not split the tunneling peak, but the line shape is modified. The eAect of coupling between localized states is also discussed, PACS numbers: 71.55.Jv, 73.40.QV In this Letter we discuss the effect of intra-atomic Coulomb interaction on the resonant site in the process of resonant tunneling. Resonant tunneling is thought to be the dominating mechanism for conduction at very low temperature through small systems with localized states. ' In the noninteracting case, this mechanism has been discussed by a number of authors and the phenomenon can be described by a 1D model Hamiltonian Hp, r
744 citations
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TL;DR: In this paper, pyridine-like N structures are observed to be responsible for the metallic behavior and prominent features near the Fermi level, which could pave the way to real molecular heterojunction devices.
Abstract: Nitrogen-doped carbon nanotubes have been synthesized using pyrolysis and characterized by scanning tunneling spectroscopy and transmission electron microscopy. The doped nanotubes are all metallic and exhibit strong electron donor states near the Fermi level. Using tight-binding and ab initio calculations, we observe that pyridine-like N structures are responsible for the metallic behavior and the prominent features near the Fermi level. These electron rich structures are the first example of n-type nanotubes, which could pave the way to real molecular heterojunction devices.
716 citations
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TL;DR: It is shown that, when its source is atomic-scale lattice defects, wave functions of different symmetries can mix and reflect both intravalley and intervalley scattering.
Abstract: A single sheet of carbon, graphene, exhibits unexpected electronic properties that arise from quantum state symmetries, which restrict the scattering of its charge carriers. Understanding the role of defects in the transport properties of graphene is central to realizing future electronics based on carbon. Scanning tunneling spectroscopy was used to measure quasiparticle interference patterns in epitaxial graphene grown on SiC(0001). Energy-resolved maps of the local density of states reveal modulations on two different length scales, reflecting both intravalley and intervalley scattering. Although such scattering in graphene can be suppressed because of the symmetries of the Dirac quasiparticles, we show that, when its source is atomic-scale lattice defects, wave functions of different symmetries can mix.
695 citations
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TL;DR: A combination of optical measurements, scanning tunneling spectroscopy, and theory revealed the emergence of a confined impurity band and band-tailing in semiconductor nanocrystals, enabling control of the band gap and Fermi energy.
Abstract: Doping of semiconductors by impurity atoms enabled their widespread technological application in microelectronics and optoelectronics. However, doping has proven elusive for strongly confined colloidal semiconductor nanocrystals because of the synthetic challenge of how to introduce single impurities, as well as a lack of fundamental understanding of this heavily doped limit under strong quantum confinement. We developed a method to dope semiconductor nanocrystals with metal impurities, enabling control of the band gap and Fermi energy. A combination of optical measurements, scanning tunneling spectroscopy, and theory revealed the emergence of a confined impurity band and band-tailing. Our method yields n- and p-doped semiconductor nanocrystals, which have potential applications in solar cells, thin-film transistors, and optoelectronic devices.
659 citations
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TL;DR: The results suggest that the transition and the associated magnetoresistance behavior should be viewed as a percolation of metallic ferromagnetic domains.
Abstract: Scanning tunneling spectroscopy was used to investigate single crystals and thin films of La1– x Ca x MnO3(with x of about 0.3), which exhibit colossal magnetoresistance. The different spectroscopic signatures of the insulating (paramagnetic) and metallic (ferromagnetic) phases enable their spatial extent to be imaged down to a lateral scale of the order of 10 nanometers. Above the bulk transition temperature T c, the images show mostly insulating behavior. Below T c, a phase separation is observed where inhomogeneous structures of metallic and more insulating areas coexist and are strongly field dependent in their size and structure. Insulating areas are found to persist far below T c. These results suggest that the transition and the associated magnetoresistance behavior should be viewed as a percolation of metallic ferromagnetic domains.
650 citations