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: In this article, the authors discuss the mechanism of ESR-STM based on a direct exchange coupling between the tunneling electrons and the local precessing spin, and find that the signal-to-noise ratio in the spectral characteristic is 2--4 and is comparable to the reported signal to noise.
Abstract: Electron Spin resonance scanning tunneling microscopy (ESR-STM) is an emerging technique which is capable of detecting the precession of a single spin. We discuss the mechanism of ESR-STM based on a direct exchange coupling between the tunneling electrons and the local precessing spin $\mathbf{S}.$ We claim that since the number of tunneling electrons in a single precessing period is small $(\ensuremath{\sim}20),$ one may expect a net temporary polarization within this period that will couple via exchange interaction to the localized spin. This coupling will randomly modulate the tunneling barrier and create a dispersion in the tunneling current which is a product of a Larmor frequency component due to the precession of the single spin and the dispersion of the spin of the tunneling electrons. This noise component is spread over the whole frequency range for random white noise spin polarization of electrons. In the opposite case where the power spectrum of the spins of the tunneling electrons has a peak at zero frequency an elevated noise in the current at ${\ensuremath{\omega}}_{L}$ will appear. We discuss the possible source of this spin polarization. We find that for relevant values of parameters the signal-to-noise ratio in the spectral characteristic is 2--4 and is comparable to the reported signal to noise ${\mathrm{ratio}.}^{1,2}$ The magnitude of the current fluctuation is a relatively weak increaing function of the dc current and magnetic field. The linewidth produced by the back action effect of tunneling electrons on the precessing spin is also discussed.
55 citations
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TL;DR: Two alkyl-substituted dual oligothiophenes, quarterthiophene (4T)-trimethylene (tm) and 4T-tm-4T, were used to fabricate molecular structures on highly oriented pyrolytic graphite and Au(111) surfaces and showed the electronic property of individual molecules in the patterns.
Abstract: Two alkyl-substituted dual oligothiophenes, quarterthiophene (4T)-trimethylene (tm)-octithiophene (8T) and 4T-tm-4T, were used to fabricate molecular structures on highly oriented pyrolytic graphite and Au(111) surfaces. The resulted structures were investigated by scanning tunneling microscopy. The 4T-tm-8T and 4T-tm-4T molecules self-organize into long-range ordered structures with linear and/or quasi-hexagonal patterns on highly oriented pyrolytic graphite at ambient temperature. Thermal annealing induced a phase transformation from quasi-hexagonal to linear in 4T-tm-8T adlayer. The molecules adsorbed on Au(111) surface in randomly folded and linear conformation. Based on scanning tunneling microscopy results, the structural models for different self-organizations were proposed. Scanning tunneling spectroscopy measurement showed the electronic property of individual molecules in the patterns. These results are significant in understanding the chemistry of molecular structure, including its formation, transformation, and electronic properties. They also help to fabricate oligothiophene assemblies with desired structures for future molecular devices.
55 citations
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TL;DR: Using scanning tunneling spectroscopy and high-resolution scanning transmission electron microscopy, this article showed that the superconducting state of a conventional superconductor, NbN, spontaneously segregates into domains.
Abstract: The notion of spontaneous formation of an inhomogeneous superconducting state is at the heart of most theories attempting to understand the superconducting state in the presence of strong disorder. Using scanning tunneling spectroscopy and high resolution scanning transmission electron microscopy, we experimentally demonstrate that under the competing effects of strong homogeneous disorder and superconducting correlations, the superconducting state of a conventional superconductor, NbN, spontaneously segregates into domains. Tracking these domains as a function of temperature we observe that the superconducting domains persist across the bulk superconducting transition, Tc, and disappear close to the pseudogap temperature, T*, where signatures of superconducting correlations disappear from the tunneling spectrum and the superfluid response of the system.
55 citations
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TL;DR: In this paper, the authors investigated the perylene-tetracarboxylic-dianhydride on Ag(110) with scanning tunneling microscopy (STM) at 295 and 50 K.
Abstract: Submonolayer coverages of perylene-tetracarboxylic-dianhydride on Ag(110) were investigated with scanning tunneling microscopy (STM) at 295 and 50 K. The molecules form highly ordered rhombic islands which at 295 K coexist with molecules diffusing on the substrate terraces. At 50 K the molecular islands appear 1.4 \AA{} higher than the Ag substrate in STM images, independent of the tunneling voltages and currents. At 295 K this apparent height is observed only at high tunneling resistances. Lowering of the resistance decreases the height difference until finally the contrast between islands and the surrounding substrate is reversed. At the same time, vacancies within islands show no contrast reversal. We explain the contrast reversal by trapping of molecules below the tip apex.
55 citations
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TL;DR: The dependence of the local density of states near the Fermi energy E(F) on the width of terraces T is investigated by tunneling scanning spectroscopy on Ag(111) at 7 K, leading to a depopulation at T=3.2 nm in quantitative agreement with a Fabry-Pérot model.
Abstract: The dependence of the local density of states near the Fermi energy E(F) on the width of terraces T is investigated by tunneling scanning spectroscopy on Ag(111) at 7 K. With decreasing T, the electronic density in the occupied surface state shifts monotonically towards E(F), leading to a depopulation at T=3.2 nm in quantitative agreement with a Fabry-Perot model. Depopulation coincides with a switch from confinement by terrace modulation to step modulation.
55 citations