scholarly journals Clustered, Terraced And Mixed Surface Phases Of The Al70Pd21Mn9 Quasicrystal

1998 ◽  
Vol 553 ◽  
Author(s):  
J. Ledieu ◽  
A. W. Munz ◽  
T. M. Parker ◽  
R. McGrath ◽  
R. D. Diehl ◽  
...  
Keyword(s):  
Atomic Resolution ◽  
Low Background ◽  
Leed Pattern ◽  
Aligned Arrays ◽  
Third Phase ◽  
Surface Phases ◽  
Stm Images

AbstractThe five-fold surface of the Al70 Pd21 Mn9 quasicrystal has been studied using STM, LEED and AES. STM images from surfaces which have been sputtered and annealed to 875 K reveal 20-30 Å protrusions that have been identified by others as Mackay-type clusters. Higher-resolution images reveal substructures in these clusters having dimensions 2-3 Å. Longer annealing times at 875 K produced large areas having flat terraces which were imaged with atomic resolution. The LEED pattern from this surface has sharp spots on a low background, and AES indicates that the surface is deficient in Mn relative to the bulk. For surfaces annealed to 1050 K for less than 2 hours, STM images indicate that cluster and terrace phases coexist, and a third phase having aligned arrays of clusters is identified which appears to be intermediate between the cluster and terrace phases.

ATOMIC RESOLUTION STM OF THE NiO (001) SURFACE STRUCTURE AND DEFECT SITES: c(2×2) PATTERNING AND EFFECTS OF COVALENT BONDING

1997 ◽  
Vol 04 (05) ◽  
pp. 1003-1008 ◽  
Author(s):  
M. R. CASTELL ◽  
S. L. DUDAREV ◽  
P. L. WINCOTT ◽  
N. G. CONDON ◽  
C. MUGGELBERG ◽  
...  
Keyword(s):  
Surface Defects ◽  
Strongly Correlated Electrons ◽  
Atomic Resolution ◽  
Correlated Electrons ◽  
Strongly Correlated ◽  
Defect Sites ◽  
Covalent Contribution ◽  
A Charge ◽  
Stm Images ◽  
Theoretical Results

Elevated temperature STM has been used to obtain atomic resolution images of flat regions, defect sites and step edges on the (001) surface of crystalline nickel oxide. Identification of surface lattice sites seen in empty and filled states (nickel and oxygen sites, respectively) is consistent with recent theoretical results according to which NiO is a charge transfer insulator with strongly correlated electrons. It has been found that certain surface defects lead to the formation of spatially delocalized hole states resulting in c(2×2) patterning in STM images. The appearance of this patterning points to the presence of a substantial covalent contribution to chemical bonding in NiO.

Triangular versus honeycomb structure in atomic-resolution STM images of graphite

Carbon ◽  
2001 ◽  
Vol 39 (3) ◽  
pp. 476-479 ◽  
Author(s):  
J.I. Paredes ◽  
A. Martı́nez-Alonso ◽  
J.M.D. Tascón
Keyword(s):  
Honeycomb Structure ◽  
Atomic Resolution ◽  
Stm Images

Vapor-Phase Grown Bundles of Carbon Nanotubes

1994 ◽  
Vol 349 ◽  
Author(s):  
Maohui Ge ◽  
Klaus Sattler
Keyword(s):  
Carbon Nanotubes ◽  
Surface Structure ◽  
Vapor Phase ◽  
Pyrolytic Graphite ◽  
Atomic Resolution ◽  
Highly Oriented Pyrolytic Graphite ◽  
Stm Images

We have produced bundles of nanotubes by vapor-phase condensation of carbon on highly-oriented pyrolytic graphite (HOPG). The bundles are found to have widths between 15 nm and 50 nm, and up to 200 nm long. They are composed of concentric tubules with 2-4 nm in diameter. Atomic resolution STM images reveal their graphitic surface structure.

Structure of Cleaved (001) USb2 Single Crystal Surface

2009 ◽  
Vol 1184 ◽  
Author(s):  
Shao-Ping Chen ◽  
Marilyn Hawley ◽  
Phil B. Van Stockum ◽  
Hari C. Manoharan ◽  
Eric Bauer
Keyword(s):  
Ab Initio Calculations ◽  
Single Crystal ◽  
Ab Initio ◽  
Basal Plane ◽  
Room Temperature ◽  
Crystal Surface ◽  
Cleavage Plane ◽  
Atomic Resolution ◽  
Single Crystal Surface ◽  
Stm Images

AbstractWe have achieved what we believe to be the first atomic resolution STM images for a uranium compound taken at room temperature. The a, b, and c lattice parameters in the images confirm that the USb2 crystals cleave on the (001) basal plane as expected. The a and b dimensions were equal, with the atoms arranged in a cubic pattern. Our calculations indicate a symmetric cut between Sb planes to be the most favorable cleavage plane and U atoms to be responsible for most of the DOS measured by STM. Some strange features observed in the STM will be discussed in conjunction with ab initio calculations.

AN STM STUDY OF THE (2×4) AND c(4×4) RECONSTRUCTIONS FORMED ON GaAs(001) BY MOLECULAR BEAM EPITAXY

1994 ◽  
Vol 01 (04) ◽  
pp. 621-624 ◽  
Author(s):  
A.R. AVERY ◽  
D.M. HOLMES ◽  
T.S. JONES ◽  
B.A. JOYCE
Keyword(s):  
Molecular Beam Epitaxy ◽  
Scanning Tunneling Microscopy ◽  
Molecular Beam ◽  
Unit Cell ◽  
Atomic Resolution ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Unit Cells ◽  
Stm Images

Atomic resolution scanning tunneling microscopy (STM) has been used to study the Asterminated (2×4) and c(4×4) reconstructions formed on GaAs(001) surfaces grown in situ by molecular beam epitaxy (MBE). Filled states STM images of the (2×4) surface always showed unit cells consisting of two As dimers in the top layer. Cooling this surface under an As flux led initially to a highly kinked (2×4) phase before the transition to the c(4×4) structure. At no point were three As dimers observed in the top layer for the (2×4) unit cell. The c(4×4) structure involves the chemisorption of a second layer of As onto an already As-terminated surface. STM images of this surface showed a series of bright rectangular blocks consisting, when complete, of three pairs of As atoms.

ORDERED AND DISORDERED Sb-RICH InSb(100) SURFACES STUDIED BY STM

1994 ◽  
Vol 01 (04) ◽  
pp. 513-516 ◽  
Author(s):  
T.S. JONES ◽  
C.F. McCONVILLE ◽  
F.M. LEIBSLE ◽  
N.V. RICHARDSON
Keyword(s):  
Surface Layer ◽  
Scanning Tunneling Microscopy ◽  
Atomic Resolution ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Subsequent Loss ◽  
Stm Images

Atomic resolution scanning tunneling microscopy (STM) has been used to study the asymmetric-(1×3) and c(4×4) Sb-terminated reconstructions of InSb(100). STM images show that these are examples of ordered and disordered reconstructions respectively. The c(4×4) structure involves the chemisorption of excess Sb onto an already Sb-terminated surface with the resultant formation of Sb-Sb bonds in the surface layer. The (1×3) structure, however, consists of short chains of individual Sb atoms in the top surface layer. The c(4×4) structure can be converted into the A-(1×3) by annealing to 500 K with the subsequent loss of Sb.

Effect of strain on ADF-STEM high-resolution images

1991 ◽  
Vol 49 ◽  
pp. 666-667
Author(s):  
M. Kelly ◽  
D.M. Bird
Keyword(s):  
High Resolution ◽  
Strong Influence ◽  
Intensity Variation ◽  
Dark Field ◽  
Atomic Resolution ◽  
Strain Fields ◽  
High Resolution Image ◽  
Annular Dark Field ◽  
High Resolution Images ◽  
Interesting Alternative

It is well known that strain fields can have a strong influence on the details of HREM images. This, for example, can cause problems in the analysis of edge-on interfaces between lattice mismatched materials. An interesting alternative to conventional HREM imaging has recently been advanced by Pennycook and co-workers where the intensity variation in the annular dark field (ADF) detector is monitored as a STEM probe is scanned across the specimen. It is believed that the observed atomic-resolution contrast is correlated with the intensity of the STEM probe at the atomic sites and the way in which this varies as the probe moves from cell to cell. As well as providing a directly interpretable high-resolution image, there are reasons for believing that ADF-STEM images may be less suseptible to strain than conventional HREM. This is because HREM images arise from the interference of several diffracted beams, each of which is governed by all the excited Bloch waves in the crystal.

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