scholarly journals Surface structure of Gd20Co80 alloy

2021 ◽  
Vol 24 (1) ◽  
pp. 56-63
Author(s):  
V.G. Kudin ◽  
◽  
S.G. Rozouvan ◽  
V.S. Staschuk ◽  
◽  
...  
Keyword(s):  
Optical Constants ◽  
Surface States ◽  
Scanning Tunneling ◽  
Quantum Mechanical ◽  
Energy Bands ◽  
Tunneling Microscopy ◽  
Spectral Ellipsometry ◽  
Configurational Interaction ◽  
Mechanical Methods ◽  
Significant Difference

Gd 20 Co 80 alloy was studied applying experimental methods of spectral ellipsometry, atomic force and scanning tunneling microscopy. The experimental results exhibit the eutectic two-phase structure of this alloy. Clusters of a phase with a lower content had a lesser concentration of free carriers, which resulted in smaller tunnel currents during the measurements. To analyze the experimental data, a theoretical approach was developed, which was based both on the quantum-mechanical methods of configurational interaction and on three-diagonal Toeplitz matrices formalism. This approach allowed us to describe in detail the energy bands formation process in solid clusters with a relatively small quantity of atoms, which as a consequence enabled to describe the Shockley surface states as well as the existence of a surface layer with partially formed energy bands. Spectral-ellipsometric measurements of Gd 20 Co 80 alloy thin films confirmed a significant difference between the measured optical constants for 20-nm thick films and larger films. Quantum-mechanical molecular calculus allowed to obtain optical constants for several supercells of Gd-Co chemical compounds and confirmed the acquired experimental and theoretical results.

Carbon Molecules on a Copper Substrate

Nano Hybrids ◽  
2014 ◽  
Vol 8 ◽  
pp. 1-14 ◽  
Author(s):  
Tamara Rozouvan ◽  
Igor Shaykevich ◽  
Stanislav Rozouvan
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Copper Substrate ◽  
Interface Layer ◽  
Scanning Tunneling ◽  
Quantum Mechanical ◽  
Tunneling Microscopy ◽  
Complicated Structure ◽  
Spectral Ellipsometry ◽  
Carbon Molecules

Semiconductor and metal carbon nanotubes were studied by scanning tunneling microscopy (STM) and spectral ellipsometry. STM measurements with spatial resolution up to 0.15 nm reveal spatially complicated structure of semiconductor nanotube-substrate interface layer. The measurements also registered graphene nanoclusters with hexagonal rings structure on copper. Quantum mechanical numerical calculations of electron density were performed on a carbon nanotube containing 40 atoms.

In-Plane Asymmetries on the Ge(111)-c(2×8) Surface Mapped with the Scanning Tunneling Microscope

1992 ◽  
Vol 295 ◽  
Author(s):  
P. Molinàs-Mata ◽  
J. Zegenhagen ◽  
M. Böhringer ◽  
N. Takeuchi ◽  
A. Selloni
Keyword(s):  
Local Density ◽  
Experimental Studies ◽  
Surface States ◽  
Small Sample ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Low Energy Electron ◽  
Tunneling Currents ◽  
Insight Into

AbstractWe report on new experimental studies of the Ge(111)-c(2×8) reconstruction performed with low-energy electron diffraction. (LEED) and scanning tunneling microscopy (STM). Weak quarter-order reflections are present in the c(2 × 8) LEED pattern in agreement with previous observations and results of ab initio calculations. In order to gain insight into the predicted splitting of dangling bond states, we compare constant current topographs (CCT's) performed at high-tunneling currents (40.nA) with first-principles calculations of the local density of states (LDOS) 1Å above the surface adatoms and obtain good qualitative agreement. We finally discuss to what extent the STM CCT's at high tunneling currents (small sample-tip distances (STD)) are sensitive to surface states outside the Г point.

Multilayered silicene: the bottom-up approach for a weakly relaxed Si(111) with Dirac surface states

Nanoscale ◽  
2015 ◽  
Vol 7 (38) ◽  
pp. 15880-15885 ◽  
Author(s):  
Huixia Fu ◽  
Lan Chen ◽  
Jian Chen ◽  
Jinglan Qiu ◽  
Zijing Ding ◽  
...  
Keyword(s):  
Scanning Tunneling Microscopy ◽  
First Principles ◽  
Van Der Waals ◽  
Surface States ◽  
Scanning Tunneling ◽  
Diamond Structure ◽  
Tunneling Microscopy ◽  
Bottom Up

Combining first principles investigations and scanning tunneling microscopy, we identify that the presumable van der Waals packed multilayered silicene sheets spontaneously transform into a diamond-structure bulk Si film due to strong interlayer couplings.

scholarly journals Polar and phase domain walls with conducting interfacial states in a Weyl semimetal MoTe2

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Fei-Ting Huang ◽  
Seong Joon Lim ◽  
Sobhit Singh ◽  
Jinwoong Kim ◽  
Lunyong Zhang ◽  
...  
Keyword(s):  
Domain Walls ◽  
Surface States ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Topological Materials ◽  
Phase Domain ◽  
Wall Structures ◽  
Transmission Electron ◽  
Interfacial States ◽  
Protected Surface

Abstract Much of the dramatic growth in research on topological materials has focused on topologically protected surface states. While the domain walls of topological materials such as Weyl semimetals with broken inversion or time-reversal symmetry can provide a hunting ground for exploring topological interfacial states, such investigations have received little attention to date. Here, utilizing in-situ cryogenic transmission electron microscopy combined with first-principles calculations, we discover intriguing domain-wall structures in MoTe2, both between polar variants of the low-temperature(T) Weyl phase, and between this and the high-T higher-order topological phase. We demonstrate how polar domain walls can be manipulated with electron beams and show that phase domain walls tend to form superlattice-like structures along the c axis. Scanning tunneling microscopy indicates a possible signature of a conducting hinge state at phase domain walls. Our results open avenues for investigating topological interfacial states and unveiling multifunctional aspects of domain walls in topological materials.

scholarly journals A new Majorana platform in an Fe-As bilayer superconductor

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Wenyao Liu ◽  
Lu Cao ◽  
Shiyu Zhu ◽  
Lingyuan Kong ◽  
Guangwei Wang ◽  
...  
Keyword(s):  
Bound States ◽  
Zero Mode ◽  
Surface States ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Iron Pnictide ◽  
Iron Chalcogenide ◽  
Zero Modes ◽  
Topological Quantum ◽  
Iron Chalcogenide Superconductors

Abstract Iron-chalcogenide superconductors have emerged as a promising Majorana platform for topological quantum computation. By combining topological band and superconductivity in a single material, they provide significant advantage to realize isolated Majorana zero modes. However, iron-chalcogenide superconductors, especially Fe(Te,Se), suffer from strong inhomogeneity which may hamper their practical application. In addition, some iron-pnictide superconductors have been demonstrated to have topological surface states, yet no Majorana zero mode has been observed inside their vortices, raising a question of universality about this new Majorana platform. In this work, through angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy measurement, we identify Dirac surface states and Majorana zero modes, respectively, for the first time in an iron-pnictide superconductor, CaKFe4As4. More strikingly, the multiple vortex bound states with integer-quantization sequences can be accurately reproduced by our model calculation, firmly establishing Majorana nature of the zero mode.

Spectroscopic Characterization of Nanoscale Modification of Passivated Si(100) Surface by STM

1994 ◽  
Vol 332 ◽  
Author(s):  
F. PÉRez-Murano ◽  
N. Barniol ◽  
X. Aymerich
Keyword(s):  
Local Density ◽  
Surface States ◽  
Spectroscopic Characterization ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Band Bending ◽  
Sample Spacing ◽  
Current Voltage

ABSTRACTThe electrochemical modification of H-passivated Si(100) surface is produced and characterized by Scanning Tunneling Microscopy and Spectroscopy (STM/STS) operating in air. In order to better understand this nanometer scale modification, we have characterized spectroscopically the modified region. From the current-voltage (I/V) curves, dI/dV versus V curves and tip to sample spacing versus voltage (s/V) curves (at constant current) we have concluded that the modification induces a local electrochemical change on the surface, which in turn produces both, a decrease of the local density of surface states and a variation of the band bending in the silicon surface.

LOCAL ELECTRONIC PROPERTIES OF DOMAIN BOUNDARIES ON c(2 × 2) Fe(001) THIN FILM SURFACES

2006 ◽  
Vol 05 (06) ◽  
pp. 935-942 ◽  
Author(s):  
HIROFUMI OKA ◽  
AGUS SUBAGYO ◽  
KAZUHISA SUEOKA
Keyword(s):  
Bias Voltage ◽  
Surface States ◽  
Scanning Tunneling ◽  
Tunneling Conductance ◽  
Tunneling Microscopy ◽  
Voltage Range ◽  
Domain Boundaries ◽  
Voltage Dependent ◽  
The Difference

Scanning tunneling microscopy (STM) and spectroscopy have been performed on a nanostructure "line-like pattern" appearing on atomically flat terraces of bcc-Fe (001) with a c(2 × 2) reconstructed structure. Atomically resolved STM reveals that the line-like pattern consists of regularly aligned surface atoms that have a similar symmetry to the (1 × 1) structure of Fe (001). The line-like pattern plays a role of domain boundaries of c(2 × 2) domains. The patterns exhibit bias-voltage dependent image contrast in the STM topographic images. In negative sample bias-voltage range the patterns appear lower than the c(2 × 2) domains and higher in positive range. In dI/dV tunneling spectra taken on the patterns a shoulder is observed around +0.2 V. On the other hands, a small salient is distinguished around +0.4 V in the spectra taken on the c(2 × 2) domains. These features are originated from surface states existing on bcc-Fe (001) surfaces with (1 × 1) structure and c(2 × 2) reconstructed structure, respectively. Emergence of the line-like patterns results in the difference of tunneling conductance.

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