scholarly journals Unraveling the atomic structure, ripening behavior, and electronic structure of supported Au20 clusters

2020 ◽  
Vol 6 (1) ◽  
pp. eaay4289 ◽  
Author(s):  
Zhe Li ◽  
Hsin-Yi Tiffany Chen ◽  
Koen Schouteden ◽  
Thomas Picot ◽  
Ting-Wei Liao ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Gold Nanoclusters ◽  
Real Space ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Free Standing ◽  
Fundamental Information ◽  
Temperature Scanning ◽  
Homo Lumo

The free-standing Au20 cluster has a unique tetrahedral shape and a large HOMO-LUMO (highest occupied molecular orbital–lowest unoccupied molecular orbital) gap of around 1.8 electron volts. The “magic” Au20 has been intensively used as a model system for understanding the catalytic and optical properties of gold nanoclusters. However, direct real-space ground-state characterization at the atomic scale is still lacking, and obtaining fundamental information about the corresponding structural, electronic, and dynamical properties, is challenging. Here, using cluster-beam deposition and low-temperature scanning tunneling microscopy, atom-resolved topographic images and electronic spectra of supported Au20 clusters are obtained. We demonstrate that individual size-selected Au20 on ultrathin NaCl films maintains its pyramidal structure and large HOMO-LUMO gap. At higher cluster coverages, we find sintering of the clusters via Smoluchowski ripening to Au20n agglomerates. The evolution of the electron density of states deduced from the spectra reveals gap reduction with increasing agglomerate size.

scholarly journals Real-space imaging of the atomic-scale magnetic structure of Fe1+yTe

Science ◽  
2014 ◽  
Vol 345 (6197) ◽  
pp. 653-656 ◽  
Author(s):  
Mostafa Enayat ◽  
Zhixiang Sun ◽  
Udai Raj Singh ◽  
Ramakrishna Aluru ◽  
Stefan Schmaus ◽  
...  
Keyword(s):  
Magnetic Structure ◽  
Magnetic Order ◽  
Parent Compound ◽  
Iron Concentration ◽  
Orthorhombic Phase ◽  
Real Space ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Excess Iron

Spin-polarized scanning tunneling microscopy (SP-STM) has been used extensively to study magnetic properties of nanostructures. Using SP-STM to visualize magnetic order in strongly correlated materials on an atomic scale is highly desirable, but challenging. We achieved this goal in iron tellurium (Fe1+yTe), the nonsuperconducting parent compound of the iron chalcogenides, by using a STM tip with a magnetic cluster at its apex. Our images of the magnetic structure reveal that the magnetic order in the monoclinic phase is a unidirectional stripe order; in the orthorhombic phase at higher excess iron concentration (y > 0.12), a transition to a phase with coexisting magnetic orders in both directions is observed. It may be possible to generalize the technique to other high-temperature superconductor families, such as the cuprates.

Real Space Observation of Double-Helix DNA Structure Using a Low Temperature Scanning Tunneling Microscopy

1999 ◽  
Vol 38 (Part 2, No. 6A/B) ◽  
pp. L606-L607 ◽  
Author(s):  
Takashi Kanno ◽  
Hiroyuki Tanaka ◽  
Tomohiko Nakamura ◽  
Hitoshi Tabata ◽  
Tomoji Kawai
Keyword(s):  
Low Temperature ◽  
Scanning Tunneling Microscopy ◽  
Double Helix ◽  
Dna Structure ◽  
Real Space ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Temperature Scanning

scholarly journals Atomically-resolved interlayer charge ordering and its interplay with superconductivity in YBa2Cu3O6.81

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chun-Chih Hsu ◽  
Bo-Chao Huang ◽  
Michael Schnedler ◽  
Ming-Yu Lai ◽  
Yuh-Lin Wang ◽  
...  
Keyword(s):  
Carrier Transport ◽  
Charge Order ◽  
Interlayer Coupling ◽  
Real Space ◽  
Charge Ordering ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Cross Sectional ◽  
Competing Orders

AbstractHigh-temperature superconductive (SC) cuprates exhibit not only a SC phase, but also competing orders, suppressing superconductivity. Charge order (CO) has been recognized as an important competing order, but its microscopic spatial interplay with SC phase as well as the interlayer coupling in CO and SC phases remain elusive, despite being essential for understanding the physical mechanisms of competing orders and hence superconductivity. Here we report the achievement of direct real-space imaging with atomic-scale resolution of cryogenically cleaved YBa2Cu3O6.81 using cross-sectional scanning tunneling microscopy/spectroscopy. CO nanodomains are found embedded in the SC phase with a proximity-like boundary region characterized by mutual suppression of CO and superconductivity. Furthermore, SC coherence as well as CO occur on both CuO chain and plane layers, revealing carrier transport and density of states mixing between layers. The CO antiphase correlation along the c direction suggests a dominance of Coulomb repulsion over Josephson tunneling between adjacent layers.

scholarly journals Self-selective formation of ordered 1D and 2D GaBi structures on wurtzite GaAs nanowire surfaces

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yi Liu ◽  
Johan V. Knutsson ◽  
Nathaniel Wilson ◽  
Elliot Young ◽  
Sebastian Lehmann ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Selective Growth ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Precision Design ◽  
Atomic Chains ◽  
Gaas Nanowire ◽  
Temperature Scanning ◽  
New Applications

AbstractScaling down material synthesis to crystalline structures only few atoms in size and precisely positioned in device configurations remains highly challenging, but is crucial for new applications e.g., in quantum computing. We propose to use the sidewall facets of larger III–V semiconductor nanowires (NWs), with controllable axial stacking of different crystal phases, as templates for site-selective growth of ordered few atoms 1D and 2D structures. We demonstrate this concept of self-selective growth by Bi deposition and incorporation into the surfaces of GaAs NWs to form GaBi structures. Using low temperature scanning tunneling microscopy (STM), we observe the crystal structure dependent self-selective growth process, where ordered 1D GaBi atomic chains and 2D islands are alloyed into surfaces of the wurtzite (Wz) $$\{11{\bar{2}}0\}$$ { 11 2 ¯ 0 } crystal facets. The formation and lateral extension of these surface structures are controlled by the crystal structure and surface morphology uniquely found in NWs. This allows versatile high precision design of structures with predicted novel topological nature, by using the ability of NW heterostructure variations over orders of magnitude in dimensions with atomic-scale precision as well as controllably positioning in larger device structures.

scholarly journals Real-space observation of surface structuring induced by ultra-fast-laser illumination far below the melting threshold

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ch. Zaum ◽  
N. Osterloh ◽  
R. Darkins ◽  
D. M. Duffy ◽  
K. Morgenstern
Keyword(s):  
Morphological Changes ◽  
Laser Pulses ◽  
Real Space ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Laser Illumination ◽  
Surface Structuring ◽  
Structure Changes ◽  
Melting Threshold

AbstractIntense short laser pulses are an intriguing tool for tailoring surface properties via ultra-fast melting of the surface layer of an irradiated target. Despite extensive studies on the interaction of femto-second laser interaction with matter, the initial steps of the morphological changes are not yet fully understood. Here, we reveal that substantial surface structure changes occur at energy densities far below the melting threshold. By using low-temperature scanning tunneling microscopy we resolve atomic-scale changes, i.e. the creation of nanosized adatom and vacancy clusters. The two cluster types have distinct non-linear fluence-dependencies. A theoretical analysis reveals their creation and motion to be non-thermal in nature. The formation of these atomistic changes, individually resolved here for the first time, recast our understanding of how surfaces respond to low-intensity ultra-short laser illumination. A visualization and control of the initial morphological changes upon laser illumination are not only of fundamental interest, but pave the way for the designing material properties through surface structuring.

Resolution in the scanning tunneling microscope

1991 ◽  
Vol 49 ◽  
pp. 488-489
Author(s):  
R. J. Wilson ◽  
D. D. Chambliss ◽  
S. Chiang ◽  
V. M. Hallmark
Keyword(s):  
Scanning Tunneling Microscope ◽  
Fundamental Principle ◽  
Atomic Scale ◽  
Lateral Resolution ◽  
Scanning Tunneling ◽  
Electronic Noise ◽  
Vertical Resolution ◽  
Tunneling Microscopy ◽  
Spatial Profile ◽  
Theoretical Analyses

Scanning tunneling microscopy (STM) has been used for many atomic scale observations of metal and semiconductor surfaces. The fundamental principle of the microscope involves the tunneling of evanescent electrons through a 10Å gap between a sharp tip and a reasonably conductive sample at energies in the eV range. Lateral and vertical resolution are used to define the minimum detectable width and height of observed features. Theoretical analyses first discussed lateral resolution in idealized cases, and recent work includes more general considerations. In all cases it is concluded that lateral resolution in STM depends upon the spatial profile of electronic states of both the sample and tip at energies near the Fermi level. Vertical resolution is typically limited by mechanical and electronic noise.

Scanning tunneling microscopy of polymers: A status report

1989 ◽  
Vol 47 ◽  
pp. 330-331
Author(s):  
P.E. Russell ◽  
I.H. Musselman
Keyword(s):  
High Resolution ◽  
Scanning Tunneling Microscopy ◽  
Sample Surface ◽  
Atomic Scale ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Status Report ◽  
Tunneling Microscopy ◽  
Research Issues ◽  
Wide Range

Scanning tunneling microscopy (STM) has evolved rapidly in the past few years. Major developments have occurred in instrumentation, theory, and in a wide range of applications. In this paper, an overview of the application of STM and related techniques to polymers will be given, followed by a discussion of current research issues and prospects for future developments. The application of STM to polymers can be conveniently divided into the following subject areas: atomic scale imaging of uncoated polymer structures; topographic imaging and metrology of man-made polymer structures; and modification of polymer structures. Since many polymers are poor electrical conductors and hence unsuitable for use as a tunneling electrode, the related atomic force microscopy (AFM) technique which is capable of imaging both conductors and insulators has also been applied to polymers.The STM is well known for its high resolution capabilities in the x, y and z axes (Å in x andy and sub-Å in z). In addition to high resolution capabilities, the STM technique provides true three dimensional information in the constant current mode. In this mode, the STM tip is held at a fixed tunneling current (and a fixed bias voltage) and hence a fixed height above the sample surface while scanning across the sample surface.

Development of the UHV-STM

1990 ◽  
Vol 48 (1) ◽  
pp. 322-323
Author(s):  
M. Iwatsuki ◽  
S. Kitamura ◽  
A. Mogami
Keyword(s):  
Surface Science ◽  
Real Space ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Great Promise ◽  
Force Microscopy ◽  
Atomic Force ◽  
Stm Image ◽  
Surface Construction ◽  
Very High

Since Binnig, Rohrer and associates observed real-space topographic images of Si(111)-7×7 and invented the scanning tunneling microscope (STM),1) the STM has been accepted as a powerful surface science instrument.Recently, many application areas for the STM have been opened up, such as atomic force microscopy (AFM), magnetic force microscopy (MFM) and others. So, the STM technology holds a great promise for the future.The great advantages of the STM are its high spatial resolution in the lateral and vertical directions on the atomic scale. However, the STM has difficulty in identifying atomic images in a desired area because it uses piezoelectric (PZT) elements as a scanner.On the other hand, the demand to observe specimens under UHV condition has grown, along with the advent of the STM technology. The requirment of UHV-STM is especially very high in to study of surface construction of semiconductors and superconducting materials on the atomic scale. In order to improve the STM image quality by keeping the specimen and tip surfaces clean, we have built a new UHV-STM (JSTM-4000XV) system which is provided with other surface analysis capability.

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