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.

A fascinating new field in colloid science: small ligand-stabilized metal clusters and their possible application in microelectronics: Part II: Future directions

Abstract: Small metal clusters, like Au 55 (PPh 3 ) 12 Cl 6 , which fall in the size regime of 1 - 2 nm are colloidal nanoparticles with quantum properties in the transitional range between metals and semiconductors These chemically tailored quantum dots show by the Quantum Size Effect (QSE) a level splitting between 20 and 100 meV, increasing from small particle sizes to the molecular state The organic ligand shell surrounding the cluster acts like a dielectric «spacer» generating capacitances between neighboring clusters down to 10 -18 F Therefore, charging effects superposed by level spacing effects can be observed The ligand-stabilized colloidal quantum dots in condensed state can be described as a novel kind of artificial solid with extremely narrow mini or hopping bands depending on the chemically adjustable thickness of the ligand shell and its properties Since its discovery, the Single Electron Tunneling (SET) effect has been recognized to be the fundamental concept for ultimate miniaturization in microelectronics The controlled transport of charge carriers in arrangements of ligand-stabilized clusters has been observed already at room temperature through Impedance Spectroscopy (IS) and Scanning Tunneling Spectroscopy (STS) This reveals future directions with new concepts for the realization of simple devices for Single Electron Logic (SEL) Part II presents models and connections between microscopic and macroscopic level, regardless of whether there already exist suitable nanoscale metal cluster compounds, and is aimed at the ultimate properties for a possible application in microelectronics

Visible-Light-Emitting Layered BC2N Semiconductor.

Abstract: We have examined the band gap of a layered B${\mathrm{C}}_{2}$N compound semiconductor. The spectroscopic measurements of scanning tunneling microscopy showed the characteristics of a semiconductor with a band gap energy of 2 eV. The valence band edge measured by x-ray photoelectron spectroscopy was 0.95 eV below the Fermi level. Photoluminescence spectra showed a peak at 2.1 eV at room temperature and 4.2 K. These results were compared with the calculated band structures, and good agreement was obtained. It was concluded that the B${\mathrm{C}}_{2}$N is a semiconductor with a direct band gap which emits visible light.

Imaging the electron wave function in self-assembled quantum dots.

Abstract: Magnetotunneling spectroscopy is used as a noninvasive and nondestructive probe to produce two-dimensional spatial images of the probability density of an electron confined in a self-assembled semiconductor quantum dot. The technique exploits the effect of the classical Lorentz force on the motion of a tunneling electron and can be regarded as the momentum (k) space analog of scanning tunneling microscopy imaging. The images reveal the elliptical symmetry of the ground state and the characteristic lobes of the higher energy states.

Atomic-Resolution Surface Spectroscopy with the Scanning Tunneling Microscope

Abstract: The study of surfaces has enjoyed an explosive growth during the last 2 5 years, due largely to the development of new techniques for probing the symmetry, chemical composition, and the electronic and vibrational states of surfaces and of adsorbed atomic and molecular species. Although a veritable arsenal of surface science tools is available, the study of surfaces is often so complex that even when several tools are applied simultaneously, unambiguous results may not be obtained. The study of surfaces has been greatly advanced during the last five years by the newly developed technique of scanning tunneling microscopy (STM) (1-6). In this technique, a very sharp tip (usually of tungsten) is brought to within a few atomic diameters of the surface under investigation without actual physical contact, so that there is a very small overlap of the wavefunctions of the surface with the nearest atom of the tip. When a small bias voltage (10 mV--4V) is applied between the sample and tip, electrons tunnel across this gap with a probability that increases exponentially as the tip approaches the sample. This exponential dependence of the tunneling current on the sample-tip separation provides an extremely sensitive way of detecting the small changes in the surface height due to the individual atoms, thus providing the basis for the scanning tunneling microscope. The images obtained in STM are often strongly dependent on the sample-tip bias voltage in a nontrivial manner. Although early STM stud-

Scanning tunneling microscopy single atom/molecule manipulation and its application to nanoscience and technology

Abstract: Single atom/molecule manipulation with a scanning-tunneling-microscope (STM) tip is an innovative experimental technique of nanoscience. Using a STM tip as an engineering or analytical tool, artificial atomic-scale structures can be fabricated, novel quantum phenomena can be probed, and properties of single atoms and molecules can be studied at an atomic level. The STM manipulations can be performed by precisely controlling tip–sample interactions, by using tunneling electrons, or electric field between the tip and sample. In this article, various STM manipulation techniques and some of their applications are described, and the impact of this research area on nanoscience and technology is discussed.