Search results for "Tunneling"
showing 10 items of 182 documents
High-resolution mapping of the optical near-field components at a triangular nano-aperture.
2009
A triangular nano-aperture in an aluminum film was used as a probe in a scanning near-field optical microscope (SNOM) to image single fluorescent molecules with an optical resolution down to 30 nm. The differently oriented molecules were employed as point detectors to map the vectorial components of the electric field distribution at the illuminated triangular aperture. The good agreement of the experimental results with numerical simulations enabled us to determine both the field map at a triangular aperture and the exact orientations of the probing molecules.
Probing magnetism in 2D van der Waals crystalline insulators via electron tunneling
2018
Magnetic insulators are a key resource for next-generation spintronic and topological devices. The family of layered metal halides promises varied magnetic states, including ultrathin insulating multiferroics, spin liquids, and ferromagnets, but device-oriented characterization methods are needed to unlock their potential. Here, we report tunneling through the layered magnetic insulator CrI₃ as a function of temperature and applied magnetic field.We electrically detect the magnetic ground state and interlayer coupling and observe a fieldinducedmetamagnetic transition.The metamagnetic transition results in magnetoresistances of 95, 300, and 550% for bilayer, trilayer, and tetralayer CrI₃ bar…
Atomic-resolution imaging of clean and hydrogen-terminated C(100)-(2×1)diamond surfaces using noncontact AFM
2010
Received 22 April 2010; published 14 May 2010High-purity, type IIa diamond is investigated by noncontact atomic force microscopy NC-AFM .Wepresent atomic-resolution images of both the electrically conducting hydrogen-terminated C 100 - 2 1 :Hsurface and the insulating C 100 - 2 1 surface. For the hydrogen-terminated surface, a nearly square unitcell is imaged. In contrast to previous scanning tunneling microscopy experiments, NC-AFM imaging allowsboth hydrogen atoms within the unit cell to be resolved individually, indicating a symmetric dimer alignment.Upon removing the surface hydrogen, the diamond sample becomes insulating. We present atomic-resolutionimages, revealing individual C-C dim…
Electronic structure of MgO-supported Au clusters: quantum dots probed by scanning tunneling microscopy.
2007
We investigate via density functional theory (DFT) the appearance of small MgO-supported gold clusters with 8 to 20 atoms in a scanning tunneling microscope (STM) experiment. Comparison of simulations of ultrathin films on a metal support with a bulk MgO leads to similar results for the cluster properties relevant for STM. Simulated STM pictures show the delocalized states of the cluster rather than the atomic structure. This finding is due to the presence of s- derived delocalized states of the cluster near the Fermi energy. The properties of theses states can be understood from a jellium model for monovalent gold.
Structural, electronic, and magnetic properties of pseudomorphic CrFe nanostripes on W(110)
2007
We have grown pseudomorphic binary ${\mathrm{Cr}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}$ alloy monolayers and sequences of Cr and Fe nanostripes on W(110) by molecular-beam epitaxy in ultrahigh vacuum. By coadsorption of Cr and Fe a pseudomorphic random CrFe alloy grows on the W(110) substrate. At a substrate temperature of $700\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ the CrFe alloy forms monolayer stripes in the step flow growth mode. We have measured magnetic properties of the monolayer alloy for $0.75\ensuremath{\leqslant}x\ensuremath{\leqslant}1$ using Kerr magnetometry. At a constant relative temperature $t=T∕{T}_{C}$ the saturation value of the Kerr rotation shows a maximum at $x=0.95$ an…
Magnetic Anisotropies and Coupling Mechanisms inFe/Mo(110)Nanostripes
2005
Using low-temperature (5 K) spin-polarized scanning tunneling microscopy, we have studied the morphology and magnetic properties of monolayer (ML) and double layer (DL) thick Fe nanowires grown by step flow on a Mo(110) single crystal. Magnetic contrast has been obtained using tungsten tips covered by Au/Co thin films. We find that the DL Fe nanowires, similarly to ML Fe nanowires, are perpendicularly magnetized. Because of the dipolar coupling, separated DL Fe nanowires are antiferromagnetically coupled. DL wires that are touching at step edges are ferromagnetically ordered due to direct exchange coupling. We measured the widths of the magnetic domain walls in the ML and DL Fe nanowires. T…
Atomic Structure and Mechanical Behaviour of Passive Film Formed on Stainless Steels
1995
On-Surfaces Synthesis on Insulating Substrates
2016
On-surface synthesis has attracted great attention in recent years due to its promising potential for creating functional structures on surfaces. An important aspect of on-surface synthesis is the capability to arrive at covalently linked thermally stable structures that offer the possibility for application even in harsh environments outside ultra-high vacuum conditions. Additionally, covalent linking allows for fabricating conjugated structures with superior electron transport properties. Especially, the latter is of tremendous interest when considering future applications in the field of molecular electronics. Having molecular electronics applications in mind explains the need for decoup…
Near-field study with a photon scanning tunneling microscope: Comparison between dielectric nanostructure and metallic nanostructure
2007
Abstract Scanning near-field optical microscopy (SNOM) integrates standard optical methods with scanning probe microscopy (SPM) techniques allowing to collect optical information with resolution well beyond the diffraction limit. We study the influence on image formation of several parameters in scanning near-field microscopy. The numerical calculations have been carried out using the differential method. We investigate a 2D-PSTM configuration with a dielectric rectangular object. We will focus on the collection type SNOM in a constant height scanning mode. Various oscillation patterns are observed from both sides of the nanostructure, which we interpret as interference between the diffract…
Near-field observation of evanescent light wave coupling in subwavelength optical waveguides
2002
International audience; We report the observation, in the range of visible frequencies, of the coupling of light into integrated waveguides of subwavelength cross-sections together with a subwavelength detection at the output, of such guides. Coupling in is produced by controlling the focusing of a laser beam totally reflected at the surface of the sample. Several tens of micrometres long dielectric ridges have been efficiently excited with this technique. The phenomenon is observed in direct space by a Photon Scanning Tunneling Microscope which also allows to test the principle of detection in a subwavelength volume.