Ab Initio Periodic Hartree−Fock Calculations for Interpretation of the Scanning Tunneling Microscope (STM) Images of Graphite

1998 ◽  
Vol 102 (31) ◽  
pp. 6020-6024 ◽  
Author(s):  
Kee Hag Lee ◽  
M. Causá ◽  
Sung Soo Park
Keyword(s):  
Ab Initio ◽  
Scanning Tunneling Microscope ◽  
Scanning Tunneling ◽  
Tunneling Microscope ◽  
Hartree Fock ◽  
Stm Images

Real-Space Imaging of Nanoscale Electrodeposited Ceramic Superlattices in the Scanning Tunneling Microscope

1992 ◽  
Vol 286 ◽  
Author(s):  
Teresa D. Golden ◽  
Ryne P. Raffaelle ◽  
Richard J. Phillips ◽  
Jay A. Switzer
Keyword(s):  
Cross Sections ◽  
Scanning Tunneling Microscope ◽  
Real Space ◽  
Scanning Tunneling ◽  
Nanometer Scale ◽  
X Ray Diffraction ◽  
Ceramic Oxides ◽  
Tunneling Microscope ◽  
Stm Images ◽  
Modulation Wavelength

ABSTRACTWe have imaged fractured cross-sections of electrodeposited ceramic oxides based on the TI-Pb-O system using a scanning tunneling microscope. The goal of this work is to measure both the modulation wavelength and compositional profile of the superlattices by mapping out the electronic properties in real space on a nanometer scale. Fourier analysis was done on STM images of all superlattices to yield the modulation wavelength. The modulation wavelength from STM was then compared with those obtained, by Faraday calculation and x-ray diffraction. The STM can be used to design “better” superlattices. We have found that the composition profile in superlattices deposited by modulating the potential was more square than in superlattices deposited by modulating the current.

scholarly journals The Formation of Self-Assembled Nanowire Arrays on Ge(001): a DFT Study of Pt Induced Nanowire Arrays

2009 ◽  
Vol 1177 ◽  
Author(s):  
Danny Eric Paul Vanpoucke ◽  
Geert Brocks
Keyword(s):  
Scanning Tunneling Microscope ◽  
Density Functional ◽  
Nanowire Arrays ◽  
Single Atom ◽  
Scanning Tunneling ◽  
Checkerboard Pattern ◽  
High Temperature Annealing ◽  
Functional Theory ◽  
Tunneling Microscope ◽  
Stm Images

AbstractNanowire (NW) arrays form spontaneously after high temperature annealing of a sub monolayer deposition of Pt on a Ge(001) surface. These NWs are a single atom wide, with a length limited only by the underlying beta-terrace to which they are uniquely connected. Using ab-initio density functional theory (DFT) calculations we study possible geometries of the NWs and substrate. Direct comparison to experiment is made via calculated scanning tunneling microscope (STM) images. Based on these images, geometries for the beta-terrace and the NWs are identified, and a formation path for the nanowires as function of increasing local Pt density is presented. We show the beta-terrace to be a dimer row surface reconstruction with a checkerboard pattern of Ge-Ge and Pt-Ge dimers. Most remarkably, comparison of calculated to experimental STM images shows the NWs to consist of germanium atoms embedded in the Pt-lined troughs of the underlying surface, contrary to what was assumed previously in experiments.

scholarly journals Computational scanning tunneling microscope image database

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Kamal Choudhary ◽  
Kevin F. Garrity ◽  
Charles Camp ◽  
Sergei V. Kalinin ◽  
Rama Vasudevan ◽  
...  
Keyword(s):  
Scanning Tunneling Microscope ◽  
Density Functional ◽  
Fourier Transforms ◽  
2D Materials ◽  
Scanning Tunneling ◽  
Bravais Lattice ◽  
Functional Theory ◽  
Tunneling Microscope ◽  
Experimental Data Analysis ◽  
Stm Images

AbstractWe introduce the systematic database of scanning tunneling microscope (STM) images obtained using density functional theory (DFT) for two-dimensional (2D) materials, calculated using the Tersoff-Hamann method. It currently contains data for 716 exfoliable 2D materials. Examples of the five possible Bravais lattice types for 2D materials and their Fourier-transforms are discussed. All the computational STM images generated in this work are made available on the JARVIS-STM website (https://jarvis.nist.gov/jarvisstm). We find excellent qualitative agreement between the computational and experimental STM images for selected materials. As a first example application of this database, we train a convolution neural network model to identify the Bravais lattice from the STM images. We believe the model can aid high-throughput experimental data analysis. These computational STM images can directly aid the identification of phases, analyzing defects and lattice-distortions in experimental STM images, as well as be incorporated in the autonomous experiment workflows.

Imaging molecules and metals on metal surfaces by scanning tunneling microscopy

1991 ◽  
Vol 49 ◽  
pp. 370-371
Author(s):  
S. Chiang ◽  
D. D. Chambliss ◽  
V. M. Hallmark ◽  
R. J. Wilson ◽  
J. K. Brown ◽  
...  
Keyword(s):  
High Resolution ◽  
Scanning Tunneling Microscope ◽  
Binding Sites ◽  
Near Neighbor ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Tunneling Microscope ◽  
Lattice Constants ◽  
Stm Images

Using an ultrahigh vacuum scanning tunneling microscope (STM), we have imaged naphthalene molecules adsorbed on Pt(111) and submonolayer metal coverages of Ni, Fe, Ag, and Au on Au(111). The STM is able to observe atomic scale features on both types of systems, giving information on the ordering and binding sites of atoms and molecules on the surface.High resolution STM images of naphthalene on Pt(111) show the molecules as bi-lobed features with three discrete molecular orientations on the surface, 120° apart, as shown for the ordered layer in Fig. 1. The absolute orientation of the long axis of the molecules is observed to be parallel to the near-neighbor directions of the Pt(111) lattice. The sketch of the observed features, shown in Fig. 2, with the molecules overlayed arbitrarily onto on-top sites of a Pt(111) lattice, demonstrates that the molecules are located on 3x3 lattice sites, with separation of 4 lattice constants between domains. Although the (6x3) LEED pattern reported previously was reproduced, the proposed unit cell is seldom observed in the STM images.

Analysis of Scanning Tunneling Microscope Topographs of Graphite Surfaces Roughened by Ar+ Ion Bombardment

1989 ◽  
Vol 157 ◽  
Author(s):  
Elliott A. Eklund ◽  
R. Stanley Williams ◽  
Eric J. Snyder
Keyword(s):  
Correlation Function ◽  
Quantitative Analysis ◽  
Scanning Tunneling Microscope ◽  
Large Range ◽  
Ion Bombardment ◽  
Scanning Tunneling ◽  
Two Dimensional ◽  
Tunneling Microscope ◽  
Self Similar ◽  
Stm Images

ABSTRACTThe scanning tunneling microscope (STM) has been used to investigate graphite surfaces roughened by 5 keV Ar+ ion bombardment. The (0001) surfaces of several samples were etched with the same total ion dose but with different sputter rates for each surface. STM images taken after sputtering show that the roughness of the sputtered surfaces depended on the sputter rate and that the surface topography of each sample appeared self-similar over a large range of length scales. These experimental observations agree with predictions of the recently proposed Shadow Model. The two dimensional height-height correlation function is utilized as a means of quantitative analysis for STM topographs of sputtered surfaces.

Adsorbate deformation as a contrast mechanism in stm imaging of biopolymers in an aqueous environment

1988 ◽  
Vol 46 ◽  
pp. 442-443
Author(s):  
S.M. Lindsay
Keyword(s):  
Scanning Tunneling Microscope ◽  
Metal Substrate ◽  
Scanning Tunneling ◽  
Aqueous Environment ◽  
Buffer Solution ◽  
Tunneling Microscope ◽  
Contrast Mechanism ◽  
Stm Images

The Scanning Tunneling Microscope (STM) has already been applied to several problems in biology. Examples are imaging of both stained and unstained biopolymers adsorbed on substrates such as graphite in air and in vacuo, AFM images of the surface of a polypeptide crystal and STM images of carbon-platinum replicas. Useful though these methods are, they involve dehydration of the samples and, in the case of adsorbates on graphite, the experiments are not easy to repeat. Sonnenfeld and Hansma have invented a method for operating the STM in conducting solvents'. We have been investigating the mechanism of the STM operated in a non-UHV environment and are using the STM to study aggregates of biopolymers on a metal substrate submerged under a buffer solution. Although formation of the aggregates must modify hydrated biopolymers considerably, repeatable images are obtained relatively easily, and deposition from a biochemically useful environment is straightforward.

Scanning tunneling microscope/scanning tunneling spectroscopy investigation of the structural modulation on the surface of cleaved Bi2Sr2CaCu2Oy, single crystal

1995 ◽  
Vol 10 (4) ◽  
pp. 817-822 ◽  
Author(s):  
Wu Ting ◽  
R. Itti ◽  
Y. Ishimaru ◽  
G. Gu ◽  
Y. Enomoto ◽  
...  
Keyword(s):  
Single Crystals ◽  
Scanning Tunneling Microscope ◽  
Current Mode ◽  
Scanning Tunneling Spectroscopy ◽  
Tunneling Spectroscopy ◽  
Scanning Tunneling ◽  
Electronic Density ◽  
Tunneling Microscope ◽  
Structural Modulation ◽  
Stm Images

The surface of cleaved Bi2Sr2 CaCu2O3 (Bi2212) single crystals has been studied by means of scanning tunneling microscope (STM) and scanning tunneling spectroscopy (STS) at room temperature in ultrahigh vacuum. We obtain atomic images of the BiO surface using logarithmic current mode and conventional mode. It is demonstrated that the Bi atoms in the BiO plane are not missing. Some Bi atoms are depressed down below the BiO surface. STS obtained at different places of the surface shows more or less the same feature, indicating that local electronic density of states does not change much due to the depression or the well-known structural modulation. The possible origins of the variation in the period of the structural modulation in the BiO plane of cleaved Bi2212 single crystals extracted from STM images are also studied.

Scanning tunneling microscopy of E. coli RNA polymerase deposited onto an Au substrate by an electrochemical process

1991 ◽  
Vol 49 ◽  
pp. 378-379
Author(s):  
Rebecca W. Keller ◽  
Carlos Bustamante ◽  
David Bear
Keyword(s):  
Scanning Tunneling Microscope ◽  
Biological Sample ◽  
Substrate Surface ◽  
Electrochemical Process ◽  
Atomic Resolution ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Tunneling Microscope ◽  
E Coli ◽  
Preparation Techniques

Under ideal conditions, the Scanning Tunneling Microscope (STM) can create atomic resolution images of different kinds of samples. The STM can also be operated in a variety of non-vacuum environments. Because of its potentially high resolution and flexibility of operation, it is now being applied to image biological systems. Several groups have communicated the imaging of double and single stranded DNA.However, reproducibility is still the main problem with most STM results on biological samples. One source of irreproducibility is unreliable sample preparation techniques. Traditional deposition methods used in electron microscopy, such as glow discharge and spreading techniques, do not appear to work with STM. It seems that these techniques do not fix the biological sample strongly enough to the substrate surface. There is now evidence that there are strong forces between the STM tip and the sample and, unless the sample is strongly bound to the surface, it can be swept aside by the tip.

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