scholarly journals A study of the initial stages of the electrochemical deposition of thallium on copper, Part V. The potential step results: Overpotential deposition on (111), (110) and (100) oriented copper single cry

2005 ◽  
Vol 3 (2) ◽  
pp. 169-182
Author(s):  
Jovan Jovicevic ◽  
Alan Bewick
Keyword(s):  
Single Crystal ◽  
Limiting Current ◽  
Current Time ◽  
Single Crystal Surfaces ◽  
Potential Step ◽  
Response Characteristics ◽  
Rate Of Increase ◽  
Instantaneous Nucleation ◽  
The Individual ◽  
A Charge

The over potential deposition of thallium onto carefully chemically polished single crystal copper (111), (110) and (100) electrode from sulfate and perchlorate solutions have been investigated using single and double potential step techniques. It appears that the different anions used did not change the current-time response characteristics significantly. The charge corresponding to UPD monolayers of thallium (?210?10-6 Ascm-2 for the first, and ?400?10-6 Ascm-2 for both, first and second, monolayers on all three orientations of the copper substrates used) were observed under the initial falloff seen on the current-time transients obtained at very short times, preceding the currenttime relationships for the overpotential deposition. Indication of a rising i-t transient reflecting bulk thallium deposition on Cu(111) and Cu(100) were usually observed at ?=-9mVvs.Tl while an over potential of ?=-10mVvs. Tl was needed for similar effects on Cu(110). The observed i vs. t2 linearity is characteristic to 3D instantaneous nucleation and further growth of 3D centres. The results show no appreciable 3D nucleation occurring until the UPD monolayers were completed. It must be concluded, therefore, that thallium over potential deposition on copper single crystal surfaces starts with a charge transfer controlled 3D instantaneous nucleation and proceeds by 3D growth. After some time the individual 3D centres overlap and the rate of increase of current falls off until finally the limiting current is reached. Similarly to the cases of lead deposition on Ag18 and Cu30 crystals, bulk deposition of thallium commences only after the two UPD close-packed thallium monolayers have been completed on the underlying substrate. Formation of the two UPD thallium close-packed monolayers, in the case of copper (111), (110) and (100) substrates, is an essential precursor to thicker thallium deposits their influence on the initiation of the over potential deposition and its growth mechanism, was shown to be very significant.

scholarly journals A study of the initial stages of the electrochemical deposition of thallium on copper, Part IV. The potential step results: Underpotential deposition on (111), (110) and (100) oriented copper single c

2005 ◽  
Vol 3 (2) ◽  
pp. 157-168 ◽  
Author(s):  
Jovan Jovicevic ◽  
Alan Bewick
Keyword(s):  
Single Crystal ◽  
Bulk Diffusion ◽  
Underpotential Deposition ◽  
Crystal Formation ◽  
Formation Processes ◽  
Growth Step ◽  
Current Time ◽  
Single Crystal Surfaces ◽  
Potential Step ◽  
Response Characteristics

The underpotential deposition and dissolution of thallium onto carefully chemically polished single crystal copper (111), (110) and (100) electrode surfaces from acetate, sulphate and perchlorate solutions have been investigated using single and double potential step techniques. It appeared that the different anions used did not change the current-time response characteristics significantly. Current-time responses to the potential steps applied strongly resemble those observed in the case of thallium underpotential deposition on silver single crystals [1]. The characteristics of i-t transients obtained by single potential step suggest very fast 2D crystal growth processes taking place. Sharp linear voltammetry peaks, which are observed for both thallium and lead deposition on Cu(111) [3,8] and on Ag(111) [1,3], probably always indicate nucleative phase formation processes but the rate of the lattice growth step will vary from system to system. Comparison of the obtained results with those for lead underpotential deposition [8-13] on Cu(111), (110) and (100) suggests that, in the present case, the rate of the 2D lattice building process for both thallium underpotential monolayers formed on three copper single crystal surfaces examined is so fast that it becomes controlled by diffusive processes; this will probably be surface diffusion [24,25] initially and, at longer times planar bulk diffusion. Double pulse experiments did not help significantly in attempts to obtain i-t transients capable of providing data suitable for showing conclusively the occurrence of 2D crystal formation processes. A similar situation occurred also with silver substrates [1].

Field ion microscope investigations of atomic processes at surfaces

1989 ◽  
Vol 47 ◽  
pp. 228-229
Author(s):  
G. L. Kellogg ◽  
P. R. Schwoebel
Keyword(s):  
Single Crystal ◽  
Crystal Surface ◽  
Linear Chain ◽  
Atom Probe ◽  
Nucleation And Growth ◽  
Single Atom ◽  
Initial Structure ◽  
Atomic Processes ◽  
Single Crystal Surfaces ◽  
Field Ion Microscope

Although no longer unique in its ability to resolve individual single atoms on surfaces, the field ion microscope remains a powerful tool for the quantitative characterization of atomic processes on single-crystal surfaces. Investigations of single-atom surface diffusion, adatom-adatom interactions, surface reconstructions, cluster nucleation and growth, and a variety of surface chemical reactions have provided new insights to the atomic nature of surfaces. Moreover, the ability to determine the chemical identity of selected atoms seen in the field ion microscope image by atom-probe mass spectroscopy has increased or even changed our understanding of solid-state-reaction processes such as ordering, clustering, precipitation and segregation in alloys. This presentation focuses on the operational principles of the field-ion microscope and atom-probe mass spectrometer and some very recent applications of the field ion microscope to the nucleation and growth of metal clusters on metal surfaces.The structure assumed by clusters of atoms on a single-crystal surface yields fundamental information on the adatom-adatom interactions important in crystal growth. It was discovered in previous investigations with the field ion microscope that, contrary to intuition, the initial structure of clusters of Pt, Pd, Ir and Ni atoms on W(110) is a linear chain oriented in the <111> direction of the substrate.

Experiments on REM and SREM using a Tem/Stem Microscope with a Configurable Angle-Resolving Detector

1990 ◽  
Vol 48 (1) ◽  
pp. 338-339
Author(s):  
H. Banzhof ◽  
I. Daberkow
Keyword(s):  
Electron Microscopy ◽  
Single Crystal ◽  
Crystal Surface ◽  
High Energy ◽  
Contrast Effects ◽  
Atomic Steps ◽  
Single Crystal Surfaces ◽  
Platinum Single Crystal ◽  
Reflection Electron Microscopy ◽  
Beam Reflection

A Philips EM 420 electron microscope equipped with a field emission gun and an external STEM unit was used to compare images of single crystal surfaces taken by conventional reflection electron microscopy (REM) and scanning reflection electron microscopy (SREM). In addition an angle-resolving detector system developed by Daberkow and Herrmann was used to record SREM images with the detector shape adjusted to different details of the convergent beam reflection high energy electron diffraction (CBRHEED) pattern.Platinum single crystal spheres with smooth facets, prepared by melting a thin Pt wire in an oxyhydrogen flame, served as objects. Fig. 1 gives a conventional REM image of a (111)Pt single crystal surface, while Fig. 2 shows a SREM record of the same area. Both images were taken with the (555) reflection near the azimuth. A comparison shows that the contrast effects of atomic steps are similar for both techniques, although the depth of focus of the SREM image is reduced as a result of the large illuminating aperture. But differences are observed at the lengthened images of small depressions and protrusions formed by atomic steps, which give a symmetrical contrast profile in the REM image, while an asymmetric black-white contrast is observed in the SREM micrograph. Furthermore the irregular structures which may be seen in the middle of Fig. 2 are not visible in the REM image, although it was taken after the SREM record.

scholarly journals Interface Structures and Electronic States of Epitaxial Tetraazanaphthacene on Single-Crystal Pentacene

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1088
Author(s):  
Yuki Gunjo ◽  
Hajime Kamebuchi ◽  
Ryohei Tsuruta ◽  
Masaki Iwashita ◽  
Kana Takahashi ◽  
...  
Keyword(s):  
Single Crystal ◽  
Photoelectron Spectroscopy ◽  
Grazing Incidence ◽  
Force Microscopy ◽  
Interface Dipole ◽  
Atomic Force ◽  
Interfacial Structures ◽  
Donor And Acceptor ◽  
A Charge ◽  
Interface Structures

The structural and electronic properties of interfaces composed of donor and acceptor molecules play important roles in the development of organic opto-electronic devices. Epitaxial growth of organic semiconductor molecules offers a possibility to control the interfacial structures and to explore precise properties at the intermolecular contacts. 5,6,11,12-tetraazanaphthacene (TANC) is an acceptor molecule with a molecular structure similar to that of pentacene, a representative donor material, and thus, good compatibility with pentacene is expected. In this study, the physicochemical properties of the molecular interface between TANC and pentacene single crystal (PnSC) substrates were analyzed by atomic force microscopy, grazing-incidence X-ray diffraction (GIXD), and photoelectron spectroscopy. GIXD revealed that TANC molecules assemble into epitaxial overlayers of the (010) oriented crystallites by aligning an axis where the side edges of the molecules face each other along the [1¯10] direction of the PnSC. No apparent interface dipole was found, and the energy level offset between the highest occupied molecular orbitals of TANC and the PnSC was determined to be 1.75 eV, which led to a charge transfer gap width of 0.7 eV at the interface.

scholarly journals nnOn the behavior of CTAB/CTAOH adlayers on gold single crystal surfaces

2021 ◽  
pp. 138947
Author(s):  
José M. Gisbert-González ◽  
María V. Oliver-Pardo ◽  
Francisco J. Sarabia ◽  
Víctor Climent ◽  
Juan M. Feliu ◽  
...  
Keyword(s):  
Single Crystal ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces

scholarly journals Reactions on single-crystal surfaces

1976 ◽  
Vol 9 (7) ◽  
pp. 248-256 ◽  
Author(s):  
Gabor A. Somorjai
Keyword(s):  
Single Crystal ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces

On The Optimized Nucleation of Near-Single-Crystal Cvd Diamond Film

1995 ◽  
Vol 416 ◽  
Author(s):  
L. C. Chen ◽  
C. C. Juan ◽  
J. Y. Wu ◽  
K. H. Chen ◽  
J. W. Teng
Keyword(s):  
Single Crystal ◽  
Photoelectron Spectroscopy ◽  
Morphological Evolution ◽  
Present Report ◽  
Ex Situ ◽  
Nucleation Density ◽  
Induced Current ◽  
Current Time ◽  
Single Crystal Diamond

ABSTRACTNear-single-crystal diamond films have been obtained in a number of laboratories recently. The optimization of nucleation density by using a bias-enhanced nucleation (BEN) method is believed to be a critical step. However, the condition of optimized nucleation has never been clearly delineated. In the present report, a novel quantitative technique was established to monitor the nucleation of diamond in-situ. Specifically, the induced current was measured as a function of nucleation time during BEN. The timedependence of induced current was studied under various methane concentrations as well as substrate temperatures. The optimized nucleation condition can be unambiguously determined from the current-time plot. Besides the in-situ current probe, ex-situ x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were also used to investigate the chemical and morphological evolution. Characteristic XPS and AFM features of optimized nucleation is discussed.

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