1,721,028 research outputs found
Strain release at the graphene-Ni(100) interface investigated by in-situ and operando scanning tunnelling microscopy
Full text linkInterface strain can significantly influence the mechanical, electronic and magnetic properties of low- dimensional materials. Here we investigated by scanning tunneling microscopy how the stress intro- duced by a mismatched interface affects the structure of a growing graphene (Gr) layer on a Ni(100) surface in real time during the process. Strain release appears to be the main factor governing morphology, with the interplay of two simultaneous driving forces: on the one side the need to obtain two-dimensional best registry with the substrate, via formation of moire patterns, on the other side the requirement of optimal one-dimensional in-plane matching with the transforming nickel carbide layer, achieved by local rotation of the growing Gr flake. Our work suggests the possibility of tuning the local properties of two-dimensional films at the nanoscale through exploitation of strain at a one-dimensional interface
Method for driving a scanning probe microscope at elevated scan frequencies
No full textA method for operating a scanning probe microscope at elevated scan frequencies has a characterization stage of sweeping a plurality of excitation frequencies of the vertical displacement of the scanning element; measuring the value attained by the reading parameter at the excitation frequencies; and identifying plateau regions of the response spectrum of the reading parameter. The reading parameter variation is limited within a predetermined range over a predefined frequency interval, thereby defining corresponding fast scanning frequency windows in which the microscope assembly is sufficiently stable to yield a lateral resolution comparable to the one obtained during slow measurements. The measurement stage includes driving the scanning element along at least a scanning trajectory over the surface of the specimen at a frequency selected among the frequencies included in a fast scanning frequency window
Dynamics of the O Induced Reconstruction of the Rh(110) Surface: a Scanning Tunneling Microscopy Study
No full textReactivity and Deconstruction of the (1x2)-Rh(110) Surface Studied by Scanning Tunneling Microscopy
No full textCarbide coating on nickel to enhance the stability of supported metal nanoclusters
Full text linkThe influence on the growth of cobalt (Co)-based nanostructures of a surface carbide (Ni2C) layer formed at the Ni(100) surface is revealed via complementary scanning tunneling microscopy (STM) measurements and first-principles calculations. On clean Ni(100) below 200 degrees C in the sub-monolayer regime, Co forms randomly distributed two-dimensional (2D) islands, while on Ni2C it grows in the direction perpendicular to the surface as well, thus forming two-atomic-layers high islands. We present a simple yet powerful model that explains the different Co growth modes for the two surfaces. A jagged step decoration, not visible on stepped Ni(100), is present on Ni2C. This contrasting behavior on Ni2C is explained by the sharp differences in the mobility of Co atoms for the two cases. By increasing the temperature, Co dissolution is activated with almost no remaining Co at 250 degrees C on Ni(100) and Co islands still visible on the Ni2C surface up to 300 degrees C. The higher thermal stability of Co above the Ni2C surface is rationalized by ab initio calculations, which also suggest the existence of a vacancy-assisted mechanism for Co dissolution in Ni(100). The methodology presented in this paper, combining systematically STM measurements with first-principles calculations and computational modelling, opens the way to controlled engineering of bimetallic surfaces with tailored properties
K-Stabilized High-Oxygen-Coverage States on Rh(110): A Low-Pressure Pathway to Formation of Surface Oxide
No full textTwo-Step Reaction on a Strained, Nano-scale segmented Surface
No full textBy means of scanning tunneling microscopy and density functional theory calculations we demonstrate that on the Rh(110)-(10×2)-O surface, a prototypical multiphase surface of an oxidized transition metal model catalyst, water formation upon H2 exposure is a two-step reaction, with each step requiring special active sites. The 1st step initiates at (2×1)p2mg-O defect islands in the (10×2) structure and propagates across the surface as a reaction front, removing half of the adsorbed oxygen. The oxygen decorated Rh ridges of the (10×2) structure lose their tensile strain upon this reduction step, whereby nanoscale patches of clean Rh become exposed and act as special reaction sites in the 2nd reaction step, which therefore initiates homogeneously over the entire surface
Initial Oxidation of a Rh(110) Surface using Atomic or Molecular Oxygen and Reduction of the Surface Oxide by Hydrogen
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