67 results on '"Toyo Kazu Yamada"'
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2. Improving MgO/Fe insulator-metal interface structure through oxygen-precoating of Fe(0 0 1)
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Nana K. M. Nazriq, Peter Krüger, and Toyo Kazu Yamada
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General Physics and Astronomy ,Surfaces and Interfaces ,General Chemistry ,Condensed Matter Physics ,Surfaces, Coatings and Films - Published
- 2023
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3. Unzipping Process of Wet Carbon Nanotubes Adsorbed on Cu(111) in Ultra-High Vacuum : an STM/STS study
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Keiju Kakugawa, Yuto Goto, Shigeru Takahara, Saeko Ando, and Toyo Kazu Yamada
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Materials science ,business.industry ,law ,Optoelectronics ,Carbon nanotube ,Scanning tunneling microscope ,business ,law.invention - Published
- 2021
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4. Direct Imaging of Precursor Adcomplex States during Cryogenic-Temperature On-Surface Metalation: Scanning Tunneling Microscopy Study on Porphyrin Array with Fe Adsorption at 78.5 K
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Toyo Kazu Yamada, Masataka Yamaguchi, Eiichi Inami, Ryohei Nemoto, Peter Krüger, and Hideki Yorimitsu
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Materials science ,Metalation ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,01 natural sciences ,Porphyrin ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,General Energy ,Adsorption ,Planar ,chemistry ,Transition metal ,law ,Tetraphenylporphyrin ,Molecule ,Physical and Theoretical Chemistry ,Scanning tunneling microscope ,0210 nano-technology - Abstract
On-surface metalation of metal-free π-conjugated planar molecules, such as metal-free tetraphenylporphyrin (2HTPP), using 3d transition metals prepared in ultrahigh vacuum (UHV), attracted signific...
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- 2020
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5. Well-Ordered Monolayer Growth of Crown-Ether Ring Molecules on Cu(111) in Ultra-High Vacuum: An STM, UPS, and DFT Study
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Takuya Hosokai, Peter Krüger, Masaki Horie, Satoshi Kera, Ayu Novita Putri Hartini, Ryohei Nemoto, and Toyo Kazu Yamada
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chemistry.chemical_classification ,Materials science ,Chemical substance ,Ultra-high vacuum ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Ring (chemistry) ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Crystallography ,General Energy ,chemistry ,Monolayer ,Molecular film ,Molecule ,Physical and Theoretical Chemistry ,0210 nano-technology ,Science, technology and society ,Crown ether - Abstract
Crown-ether (CR) ring molecules are known as host molecules for capturing guest species inside the ring. So far CR molecular films have only been grown by drop-casting a CR solution on an inert sub...
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- 2019
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6. Interplay between point symmetry, oxidation state, and the Kondo effect in 3d transition metal acetylacetonate molecules on Cu(111)
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Toyo Kazu Yamada, Timo Frauhammer, Hongyan Chen, Satoru Sasaki, and Wulf Wulfhekel
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Physics ,Point symmetry ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Resonance (chemistry) ,01 natural sciences ,Metal ,Crystallography ,Transition metal ,Oxidation state ,visual_art ,0103 physical sciences ,visual_art.visual_art_medium ,Molecule ,Kondo effect ,010306 general physics ,0210 nano-technology ,Single crystal - Abstract
We report that the occurrence of a Kondo effect in magnetic molecules crucially depends on the point symmetry and oxidation state of the adsorbed species. Two different transition metal acetylacetonate (acac) compounds [$M{(\mathrm{acac})}_{3}$, with $M=\mathrm{Cr}(\mathrm{III})$ or Co(III)] adsorbed on a Cu(111) single crystal were investigated to demonstrate the interplay. After deposition, $\mathrm{Cr}{(\mathrm{acac})}_{3}$ molecules formed threefold symmetric $\mathrm{Cr}{(\mathrm{acac})}_{3}$ and twofold symmetric $\mathrm{Cr}{(\mathrm{acac})}_{2}$ by releasing a ligand, while $\mathrm{Co}{(\mathrm{acac})}_{3}$ molecules only formed twofold symmetric $\mathrm{Co}{(\mathrm{acac})}_{2}$. Threefold symmetric $\mathrm{Cr}{(\mathrm{acac})}_{3}$ molecules with a total electron spin $S=\frac{3}{2}$ exhibited no Kondo effect, while a clear Kondo resonance was observed in twofold $\mathrm{Cr}{(\mathrm{acac})}_{2}$ molecules. $\mathrm{Co}{(\mathrm{acac})}_{2}$ molecules surprisingly showed no Kondo resonance, even in the case of twofold symmetry, which is explained by a low-spin state of $S$ = 0. To analyze the results, a simple model is proposed based on the total electron spin and the symmetry of magnetic molecule. The present approach provides a feasible design strategy for single molecule magnets on metallic surfaces.
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- 2021
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7. Carbon Monoxide Stripe Motion Driven by Correlated Lateral Hopping in a 1.4 × 1.4 Monolayer Phase on Cu(111)
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Peter Krüger, Toyo Kazu Yamada, and Nana K. M. Nazriq
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Materials science ,Dynamics (mechanics) ,technology, industry, and agriculture ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,Adsorption ,chemistry ,Chemical physics ,law ,Phase (matter) ,Monolayer ,Molecule ,General Materials Science ,Physical and Theoretical Chemistry ,Scanning tunneling microscope ,0210 nano-technology ,Carbon monoxide - Abstract
We report an ultra-high-vacuum low-temperature (4.6 K) scanning tunneling microscopy study of the molecular structure and dynamics of a carbon monoxide (CO) monolayer adsorbed at 20 K on Cu(111). We observe the well-known 1.4 × 1.4 phase of CO/Cu(111) for the first time in real-space imaging. At 4.6 K, the hexagonal symmetry of the monolayer is locally broken by the formation of stripes made of single and double CO rows of different apparent heights. Using density functional theory calculations, we assign the high rows to CO molecules adsorbed mostly at off-center top sites and the low rows to bridge sites. Groups of three or four very high molecules appear randomly and are assigned to nearest-neighbor, titled top site molecules. We observe simultaneous hopping of a few CO molecules between adjacent top and bridge sites, which produces the apparent motion of the stripe pattern.
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- 2020
8. Spin-Polarized STM Overview and Issues for Next Developments
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Toyo Kazu Yamada
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General Materials Science ,Surfaces and Interfaces ,Instrumentation ,Spectroscopy - Published
- 2017
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9. Oxidative vaporization etching for molybdenum tip formation in air
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Toyo Kazu Yamada, Yutaka Noguchi, Yuto Goto, and Rie Suizu
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Materials science ,Vapor pressure ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,Atmospheric temperature range ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Adiabatic flame temperature ,law.invention ,Field electron emission ,chemistry ,Molybdenum ,law ,Vaporization ,Ligand cone angle ,Composite material ,Scanning tunneling microscope ,0210 nano-technology - Abstract
Oxidative vaporization in air using a flame with a temperature range of 1950–2300 K was employed for controlling the tip shape made from a nipper-cut metal molybdenum (Mo) wire edge. An extremely high vapor pressure of MoO3 generated on the Mo surface in flame is a driving force behind the tip shape formation. Since the MoO3 vaporization rate follows the flame temperature gradient, we could control the tip apex shape by selecting the proper flame etching condition. The best condition to obtain a sharp tip apex based on statistical tests of dozens of Mo tips was obtained by Mo wire edge insertion into the 2100 K flame from the side for one second. This was repeated twice, which reproducibly provided a tip apex with a radius of 50–100 nm and a cone angle of 20–30 degrees. The present Mo tips, fabricated without aqueous solutions, were examined for their suitability as probe tips through air-scanning tunneling microscopy (STM), ultrahigh vacuum STM, field emission spectroscopy, and conductance measurements.
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- 2021
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10. Instability of skyrmions in magnetic fields
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Timofey Balashov, Ryohei Nemoto, Wulf Wulfhekel, Patrick M. Buhl, Toyo Kazu Yamada, Loic Mougel, Marie Hervé, Julian Skolaut, Bertrand Dupé, Karlsruhe Institute of Technology (KIT), Johannes Gutenberg - Universität Mainz (JGU), Chiba University, Karlsruher Institut für Technologie (KIT), Institut des Nanosciences de Paris (INSP), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Spectroscopie des nouveaux états quantiques (INSP-E2), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), and Fonds National de la Recherche Scientifique [Bruxelles] (FNRS)
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010302 applied physics ,Physics ,Magnetization dynamics ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Field (physics) ,Texture (cosmology) ,Skyrmion ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Instability ,Magnetic field ,0103 physical sciences ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,0210 nano-technology ,Ground state ,ComputingMilieux_MISCELLANEOUS ,Topological quantum number - Abstract
In this combined experimental and theoretical work, we report on the evolution of the skyrmion radius and its destruction in the system Co/Ru(0001) when an out-of-plane magnetic field is applied. At low fields, skyrmions are metastable and display an elliptical instability in which along the short axis, the spin texture approaches that of the spin-spiral phase and the long axis expands in order to go back to the spin-spiral ground state. At high fields, we observe round skyrmions of finite size up to the collapse field Bc, where they are destroyed and the topological charge is annihilated. We estimate Bc via numerical methods based on magnetization dynamics simulations parametrized by density functional theory calculations and compare it to experimental scanning tunneling microscopy observations obtained at ≈ 30 mK.
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- 2020
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11. Controlled Deposition Number of Organic Molecules Using Quartz Crystal Microbalance Evaluated by Scanning Tunneling Microscopy Single-Molecule-Counting
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Eiichi Inami, Mikio Shimasaki, Toyo Kazu Yamada, Masataka Yamaguchi, and Takayuki Yamaguchi
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Chemistry ,Analytical chemistry ,Single molecule counting ,02 engineering and technology ,Quartz crystal microbalance ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,law.invention ,Organic molecules ,Metal ,Adsorption ,law ,visual_art ,visual_art.visual_art_medium ,Molecule ,Sublimation (phase transition) ,Scanning tunneling microscope ,0210 nano-technology - Abstract
Precise control of organic molecule deposition on a substrate is quite important for fabricating single-molecule-based devices. In this study, we demonstrate whether a quartz-crystal microbalance (QCM) widely used for a film growth calibration has the ability to precisely measure the number of organic molecules adsorbed on a substrate. The well-known Sauerbrey’s equation is extended to formulate the relation between QCM resonant frequency shift and the number of adsorbed molecules onto the QCM surface. The formula is examined by QCM measurements of sublimation of π-conjugated organic molecules and direct counting of the deposited molecules one by one onto metal substrates, using ultrahigh vacuum low-temperature scanning tunneling microscopy (STM). It is revealed that the number of adsorbed molecules evaluated by QCM (NQCM) show good agreement with those counted from the STM images (NSTM) within the error of ±25%. The results ensure the QCM capability for controlling the deposition number of organic molecu...
- Published
- 2018
12. Spin-Polarized Scanning Tunneling Microscopy
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Toyo Kazu Yamada
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Condensed Matter::Materials Science ,Materials science ,Condensed matter physics ,Spin polarization ,law ,Magnetism ,Condensed Matter::Superconductivity ,Condensed Matter::Strongly Correlated Electrons ,Spin polarized scanning tunneling microscopy ,Scanning tunneling microscope ,Sample (graphics) ,law.invention - Abstract
Spin-polarized scanning tunneling microscopy (SP-STM) is a powerful tool to visualize spin-polarization vectors of sample surface atoms.
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- 2018
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13. Energy gap opening by crossing drop cast single-layer graphene nanoribbons
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Kohji Nakamura, Seiya Kasai, Amadeo L. Vázquez de Parga, Polin Liu, Hideto Fukuda, Hirofumi Tanaka, Taizo Fujiwara, and Toyo Kazu Yamada
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Materials science ,Local density of states ,Condensed matter physics ,Graphene ,Band gap ,Mechanical Engineering ,Drop (liquid) ,Bioengineering ,Fermi energy ,02 engineering and technology ,General Chemistry ,Carbon nanotube ,021001 nanoscience & nanotechnology ,01 natural sciences ,law.invention ,Mechanics of Materials ,law ,0103 physical sciences ,General Materials Science ,Electrical and Electronic Engineering ,Scanning tunneling microscope ,010306 general physics ,0210 nano-technology ,Spectroscopy - Abstract
Band gap opening of a single-layer graphene nanoribbon (sGNR) sitting on another sGNR, fabricated by drop casting GNR solution on Au(111) substrate in air, was studied by means of scanning tunneling microscopy and spectroscopy in an ultra-high vacuum at 78 K and 300 K. GNRs with a width of ~45 nm were prepared by unzipping double-walled carbon nanotubes (diameter ~15 nm) using the ultrasonic method. In contrast to atomically-flat GNRs fabricated via the bottom-up process, the drop cast sGNRs were buckled on Au(111), i.e., some local points of the sGNR are in contact with the substrate (d ~ 0.5 nm), but other parts float (d ~ 1–3 nm), where d denotes the measured distance between the sGNR and the substrate. In spite of the fact that the nanoribbons were buckled, dI/dV maps confirmed that each buckled sGNR had a metallic character (~3.5 Go) with considerable uniform local density of states, comparable to a flat sGNR. However, when two sGNRs crossed each other, the crossed areas showed a band gap between −50 and +200 meV around the Fermi energy, i.e., the only upper sGNR electronic property changed from metallic to p-type semiconducting, which was not due to the bending, but the electronic interactions between the up and down sGNRs.
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- 2018
14. How to Get Molecular Spin-Polarization Using Spin-Polarized STM
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Toyo Kazu Yamada
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Materials science ,Condensed matter physics ,Spin polarization ,Spin-½ - Published
- 2015
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15. Room temperature stable film formation of π-conjugated organic molecules on 3d magnetic substrate
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Mikio Shimasaki, Toyo Kazu Yamada, Eiichi Inami, and Hideki Yorimitsu
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Materials science ,lcsh:Medicine ,02 engineering and technology ,Substrate (electronics) ,Conjugated system ,01 natural sciences ,Article ,Organic molecules ,law.invention ,chemistry.chemical_compound ,law ,Whisker ,0103 physical sciences ,Molecule ,Kinetic Monte Carlo ,lcsh:Science ,010306 general physics ,Multidisciplinary ,lcsh:R ,021001 nanoscience & nanotechnology ,chemistry ,Chemical physics ,Phthalocyanine ,lcsh:Q ,Scanning tunneling microscope ,0210 nano-technology - Abstract
An important step toward molecule-based electronics is to realize a robust and well-ordered molecular network at room temperature. To this end, one key challenge is tuning the molecule–substrate electronic interactions that influence not only the molecular selfassembly but also the stability of the resulting structures. In this study, we investigate the film formation of π-conjugated metal-free phthalocyanine molecules on a 3d-bcc-Fe(001) whisker substrate at 300 K by using ultra-high-vacuum scanning tunneling microscopy. On bare Fe(001), hybridization between the molecular π and the Fe(001) d-states prevents the molecular assembly, resulting in the disordered patchy structures. The second- and third-layer molecules form densely packed films, while the morphologies show clear difference. The second-layer molecules partially form p(5 × 5)-ordered films with the rectangular edges aligned along the [100] and [010] directions, while the edges of the third-layer films are rounded. Remarkably, such film morphologies are stable even at 300 K. These findings suggest that the molecular self-assembly and the resulting morphologies in the second and third layers are affected by the substrate bcc(001), despite that the Fe-d states hybridize only with the first-layer molecules. The possible mechanism is discussed with the kinetic Monte Carlo simulation.
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- 2017
16. Spin Polarization of Single Organic Molecule Using Spin-Polarized STM
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Toyo Kazu Yamada
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Materials science ,Magnetic Phenomena ,Condensed matter physics ,Spin polarization ,Spintronics ,Magnetic domain ,Electrode ,Molecule ,Giant magnetoresistance ,Spin (physics) - Abstract
One-nm-size single organic molecules have attracted interest as a key material to realize ultra-small spintronic devices such as single-molecule giant magnetoresistance memory. The origin of such magnetic phenomena is spin polarization vector in the single molecules induced by contacting magnetic electrodes. Atomically resolved spin-polarized STM has been used to measure quantitatively the spin polarization; however, in this study we point out that the reported method includes crucial ambiguity. By using the normalized differential conductance (dI/dV)/T, the true spin polarization of the single molecules on magnetic domains is revealed.
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- 2017
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17. Fabrication of tungsten tip probes within 3 s by using flame etching
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Eiichi Inami, Satoru Sasaki, Toyo Kazu Yamada, Teruaki Ohno, Yuta Sakai, Takayuki Yamaguchi, and Yuto Goto
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010302 applied physics ,Fabrication ,Materials science ,Scanning electron microscope ,Analytical chemistry ,chemistry.chemical_element ,Tungsten ,01 natural sciences ,Isotropic etching ,010305 fluids & plasmas ,Field electron emission ,Scanning probe microscopy ,chemistry ,Etching (microfabrication) ,0103 physical sciences ,Vaporization ,Instrumentation - Abstract
A tungsten (W) tip has been used as a standard tip probe because of its robustness at the highest boiling temperature; the use cases include a field emission (FE) electron source for scanning electron microscopy (SEM) and a scanning probe microscopy tip. The W tip probe has generally been fabricated through a chemical etching process with aqueous solutions. In this study, we propose a new method—flame etching. Without using aqueous solutions, a W tip probe was successfully fabricated within 3 s in air, which is very fast and convenient, and beneficial for mass production (additionally, no expensive setup is necessary). A W tip probe was obtained simply by putting a W wire into an oxygen-liquefied petroleum (O2+LP) gas flame (giving the highest temperature of ∼2300 K) through a microtorch for a few seconds. The obtained W tip provided atomically resolved scanning tunneling microscopic images. Also, since FE electrons were detected by applying ∼106 V/m, the tip can be used as an FE-SEM source. Generation and vaporization of WO3 on the W surface are important processes to form a tip shape.
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- 2019
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18. Single Molecular Magnetoresistance
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Toyo Kazu Yamada
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Materials science ,Magnetoresistance ,Condensed matter physics ,law ,Scanning tunneling microscope ,law.invention - Published
- 2013
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19. Role of π−d hybridization in a 300-K organic-magnetic interface: Metal-free phthalocyanine single molecules on a bcc Fe(001) whisker
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Toyo Kazu Yamada, Y. Yamagishi, S. Nakashima, Kohji Nakamura, and Yukie Kitaoka
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Molecular diffusion ,Local density of states ,Materials science ,Molecular electronics ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,law.invention ,chemistry.chemical_compound ,chemistry ,Ab initio quantum chemistry methods ,law ,Phthalocyanine ,Scanning tunneling microscope ,0210 nano-technology ,Spectroscopy ,Single crystal - Abstract
The realization of single molecular electronics is considered the next frontier to addressing and sustaining the storage needs of the future. In order to realize a single molecular device working at 300 K, two conditions must be satisfied: first, there must be no molecular diffusion, i.e., robust bonding between molecules and the contacting electrode, and second, stable electronic interface states. In this study, using a combination of 7-K and 300-K ultrahigh vacuum scanning tunneling microscopy/spectroscopy experiments and theoretical ab initio calculations, we investigated the adsorption of $\ensuremath{\pi}$-conjugated metal-free phthalocyanine (Pc) single molecules onto an Fe(001) whisker single crystal along with the resulting electronic interface structures. The Pc/Fe(001) system was found to prevent molecular diffusion even at 300 K, due to strong adsorption as well as the presence of a larger diffusion barrier than that of the Pc/Ag(001) system, in which molecules are known to diffuse at 300 K. The origin of such a robust bonding was studied by recovering the sample local density of states (LDOS) with the normalized $(dI/dV)/T$ curves, where the LDOS peaks are successfully explained by theoretical calculations.
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- 2016
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20. Electron-bombarded ⟨110⟩-oriented tungsten tips for stable tunneling electron emission
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Toyo Kazu Yamada, T. Abe, T. Irisawa, and N. M. K. Nazriq
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010302 applied physics ,Materials science ,Scanning electron microscope ,chemistry.chemical_element ,02 engineering and technology ,Tungsten ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Isotropic etching ,Grain size ,Field emission microscopy ,Field electron emission ,chemistry ,0103 physical sciences ,Crystallite ,0210 nano-technology ,Instrumentation ,Field ion microscope - Abstract
A clean tungsten (W) tip apex with a robust atomic plane is required for producing a stable tunneling electron emission under strong electric fields. Because a tip apex fabricated from a wire by aqueous chemical etching is covered by impurity layers, heating treatment in ultra-high vacuum is experimentally known to be necessary. However, strong heating frequently melts the tip apex and causes unstable electron emissions. We investigated quantitatively the tip apex and found a useful method to prepare a tip with stable tunneling electron emissions by controlling electron-bombardment heating power. Careful characterizations of the tip structures were performed with combinations of using field emission I-V curves, scanning electron microscopy, X-ray diffraction (transmitted Debye-Scherrer and Laue) with micro-parabola capillary, field ion microscopy, and field emission microscopy. Tips were chemically etched from (1) polycrystalline W wires (grain size ∼1000 nm) and (2) long-time heated W wires (grain size larger than 1 mm). Heating by 10-40 W (10 s) was found to be good enough to remove oxide layers and produced stable electron emission; however, around 60 W (10 s) heating was threshold power to increase the tip radius, typically +10 ± 5 nm (onset of melting). Further, the grain size of ∼1000 nm was necessary to obtain a conical shape tip apex.
- Published
- 2016
21. Electric Field Control of Iron Nano-magnets: Magneto-electric Coupling of Metal Surfaces
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Toyo Kazu Yamada
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Metal ,Materials science ,business.industry ,Electric field ,Magnet ,visual_art ,Nano ,visual_art.visual_art_medium ,Optoelectronics ,Electric coupling ,business ,Magneto - Published
- 2012
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22. Electric Field Control of Fe Nano Magnets
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Toyo Kazu Yamada, Lukas Gerhard, Wulf Wulfhekel, Arthur Ernst, and R.J.H. Wesselink
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Materials science ,business.industry ,Magnet ,Electric field ,Nano ,Optoelectronics ,Electrical and Electronic Engineering ,Condensed Matter Physics ,business ,Instrumentation ,Electronic, Optical and Magnetic Materials - Published
- 2012
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23. Electrical Control of the Magnetic State of Fe
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M. Däne, R. J. H. Wesselink, Michael Fechner, A. F. Takacs, Ingrid Mertig, Wulf Wulfhekel, Lukas Gerhard, Arthur Ernst, Timofey Balashov, Sergey Ostanin, Toyo Kazu Yamada, Faculty of Science and Technology, and Computational Materials Science
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Materials science ,Condensed matter physics ,Magnetic structure ,business.industry ,Electronic, Optical and Magnetic Materials ,law.invention ,Coupling (electronics) ,Scanning probe microscopy ,Semiconductor ,METIS-303166 ,Tunnel junction ,law ,IR-104537 ,Electric field ,Electrical and Electronic Engineering ,Scanning tunneling microscope ,business ,Quantum tunnelling - Abstract
Magneto-electric coupling offers a new pathway to information storage in magnetic memory devices. This phenomenon has been observed in various materials ranging from insulators to semiconductors. In bulk metallic systems, magneto-electric coupling has been disregarded as the electric field cannot enter bulk metals. In this work, we show that a substantial magneto-electric coupling exists in metallic Fe nano-islands grown on Cu(111). Using the electric field in the tunnel junction of a scanning tunneling microscope, the magnetic order parameter and the crystal structure of Fe was changed on the nanometer scale. This allows high density nonvolatile information storage by means of magneto-electric coupling in a simple metallic system.
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- 2011
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24. Electric Field Control of Fe Nano Magnets: Magnetoelectric Coupling at Metal Surfaces
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Toyo Kazu Yamada
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Coupling ,Condensed Matter::Materials Science ,Materials science ,Condensed matter physics ,law ,Magnet ,Bilayer ,Electric field ,Magnetoelectric effect ,Spin polarized scanning tunneling microscopy ,Scanning tunneling microscope ,Nanomagnet ,law.invention - Abstract
Magnetoelectric coupling at metal surfaces opens up a new possibility for metallic non-volatile magnetic data-storage devices, in which the magnetic bits are controlled by an electric field. We studied the atomic and magnetic order in bilayer Fe nano-islands grown on a Cu(111) substrate with a scanning tunneling microscopy setup in ultra-high vacuum at 4.5 K. Electric field pulses (108-109 V/m) were found to be able to cause a displacement of the Fe atoms, switching simultaneously the crystalline and the magnetic order, which is the prove of magnetoelectric coupling at the metallic Fe surface. We also succeeded in controlling the direction of the switching by the polarity of the electric field.
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- 2011
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25. CO-tip manipulation using repulsive interactions
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Toyo Kazu Yamada, Emi Minamitani, and Nana K. M. Nazriq
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Materials science ,Mechanical Engineering ,Nearest neighbour ,Bioengineering ,02 engineering and technology ,General Chemistry ,Substrate (electronics) ,Electron ,021001 nanoscience & nanotechnology ,01 natural sciences ,Mechanics of Materials ,Chemical physics ,Position (vector) ,0103 physical sciences ,Atom ,Microscopy ,Molecule ,General Materials Science ,Electrical and Electronic Engineering ,010306 general physics ,0210 nano-technology ,Quantum tunnelling - Abstract
Understanding the interactions between a tip apex and a target atom or molecule is crucial for the manipulation of individual molecules with precise control by using scanning tunnelling microscopy (STM) and atomic force microscopy. Herein, we demonstrate the manipulation of target CO molecules on a Cu(111) substrate using a CO-functionalized W tip with atomic-scale accuracy. All experiments were performed in a home-built ultra-high vacuum STM system at 5 K. The CO-tip was fabricated by picking up a single CO molecule from a Cu(111) surface. In contrast to a metal tip, repulsive interactions occur between the CO-tip and the target CO molecule. This repulsive interaction promises perfect lateral hopping without any vertical hopping. Hopping events were directly monitored as sudden current drops in the simultaneously measured I-z curves. A larger barrier height between the CO-tip and the target CO (∼9.5 eV) was found from the slope of the I-z curve, which decreases the electron tunnelling probability between the tip and sample. Therefore, electron-driven manipulation cannot be a major trigger for the CO-CO repulsive manipulation. The CO-tip is able to manipulate only the target CO molecule, even when another CO molecule was located ∼0.5 nm away. Statistical measurements revealed that the nearest neighbour atop site is the energetically stable position after hopping. However, if the CO target has another CO molecule in a neighbouring position (denoted as a 'pair'), the target CO hops more than twice as far. This means that the CO-tip experiences a larger repulsive interaction from the pair. These observations of CO-tip manipulation are useful for the design of two-dimensional artificial molecular networks as well as for developing a better understanding of catalytic oxidation processes.
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- 2018
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26. Surface reconstruction of clean bcc-Fe{110}: A quasi-hexagonal top-layer with periodic height modulation
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M. Shishido, H. Tamura, Tomonari Mizoguchi, Toyo Kazu Yamada, and Toshiharu Irisawa
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Phase transition ,Materials science ,Whiskers ,Surfaces and Interfaces ,Chemical vapor deposition ,Surface finish ,Condensed Matter Physics ,Molecular physics ,Surfaces, Coatings and Films ,law.invention ,Crystallography ,Transition metal ,law ,Materials Chemistry ,Scanning tunneling microscope ,Single crystal ,Surface reconstruction - Abstract
Hexagonal-pillar shaped pure Fe single crystal whiskers with six {1 1 0} side planes were obtained by means of chemical vapor deposition. Atomically resolved scanning tunneling microscopy images obtained on the {1 1 0} surface showed a quasi-hexagonal atomic array with mesoscopic-range periodic height modulation of about 1/3 of an atomic step. This height modulation was found to be a result of an interference between the quasi-hexagonal top-layer and the sub-surface bcc-Fe{1 1 0} layer. Unit vectors of the mesoscopic-range modulation turned out to be expressed as p 1 → p 2 → = 13 1 - 2 14 u 1 → u 2 → = 12 1 - 3 15 s 1 → s 2 → , where u 1 → u 2 → and s 1 → s 2 → are the primitive vectors of the two-dimensional atomic array in the top-layer and those in the sub-surface layer, respectively. The two-dimensional density of atoms in the top-layer is slightly higher by 0.46% than that in the sub-surface layer.
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- 2009
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27. Requirement of Ala Residues at g Position in Heptad Sequence of α-Helix-forming Peptide for Formation of Fibrous Structure
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Tadashi Mizoguchi, Shuichi Kojima, Mayu Arii, Toyo Kazu Yamada, and Gaku Aoki
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chemistry.chemical_classification ,Circular dichroism ,Alanine ,Stereochemistry ,Circular Dichroism ,Peptide ,Sequence (biology) ,General Medicine ,Microscopy, Atomic Force ,Fibril ,Biochemistry ,Protein Structure, Secondary ,Hydrophobic effect ,Heptad repeat ,Crystallography ,Amino Acid Substitution ,chemistry ,Helix ,Peptides ,Oligopeptides ,Molecular Biology ,Peptide sequence - Abstract
One feature of the alpha3-peptide, which has the amino acid sequence of (Leu-Glu-Thr-Leu-Ala-Lys-Ala)(3), that distinguishes it from many other alpha-helix-forming peptides is its ability to form fibrous assemblies that can be observed by transmission electron microscopy. In this study, the effects of Ala-->Gln substitution at the e (5th) or g (7th) position in the above heptad sequence of the alpha3-peptide on the formation of alpha-helix and fibrous assemblies were investigated by circular dichroism spectral measurement and atomic force microscopy. The 5Qalpha3-peptide obtained by Ala-->Gln substitution at the e position of the alpha3-peptide was found to form very short fibrils with long-elliptical shape, whereas the 7Qalpha3-peptide with Gln residues at the g position lost its ability to form such assemblies, in spite of alpha-helix formation in both peptides; the stabilities of both peptides decreased. These results indicate that Ala residues at the g position in the heptad sequence of the alpha3-peptide are key residues for the formation of fibrous assemblies, which may be due to hydrophobic interactions between alpha-helical bundle surfaces.
- Published
- 2008
- Full Text
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28. Corrigendum: Method for Controlling Electrical Properties of Single-Layer Graphene Nanoribbons via Adsorbed Planar Molecular Nanoparticles
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Ryota Negishi, Hirofumi Tanaka, Yoshihiro Kobayashi, Seiya Kasai, Minoru Fukumori, Daisuke Tanaka, Takuji Ogawa, Toyo Kazu Yamada, and Ryo Arima
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Multidisciplinary ,Materials science ,Annealing (metallurgy) ,Band gap ,Sonication ,Nanoparticle ,Carbon nanotube ,Corrigenda ,law.invention ,Adsorption ,Chemical engineering ,law ,Molecule ,Graphene nanoribbons - Abstract
A simple method for fabricating single-layer graphene nanoribbons (sGNRs) from double-walled carbon nanotubes (DWNTs) was developed. A sonication treatment was employed to unzip the DWNTs by inducing defects in them through annealing at 500 °C. The unzipped DWNTs yielded double-layered GNRs (dGNRs). Further sonication allowed each dGNR to be unpeeled into two sGNRs. Purification performed using a high-speed centrifuge ensured that more than 99% of the formed GNRs were sGNRs. The changes induced in the electrical properties of the obtained sGNR by the absorption of nanoparticles of planar molecule, naphthalenediimide (NDI), were investigated. The shape of the I-V curve of the sGNRs varied with the number of NDI nanoparticles adsorbed. This was suggestive of the existence of a band gap at the narrow-necked part near the NDI-adsorbing area of the sGNRs.
- Published
- 2015
29. Method for Controlling Electrical Properties of Single-Layer Graphene Nanoribbons via Adsorbed Planar Molecular Nanoparticles
- Author
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Ryo Arima, Minoru Fukumori, Daisuke Tanaka, Toyo Kazu Yamada, Seiya Kasai, Takuji Ogawa, Yoshihiro Kobayashi, Hirofumi Tanaka, and Ryota Negishi
- Subjects
Multidisciplinary ,Adsorption ,Materials science ,Planar ,Single layer graphene ,Nanoparticle ,Nanotechnology ,Article ,Graphene nanoribbons - Abstract
A simple method for fabricating single-layer graphene nanoribbons (sGNRs) from double-walled carbon nanotubes (DWNTs) was developed. A sonication treatment was employed to unzip the DWNTs by inducing defects in them through annealing at 500 °C. The unzipped DWNTs yielded double-layered GNRs (dGNRs). Further sonication allowed each dGNR to be unpeeled into two sGNRs. Purification performed using a high-speed centrifuge ensured that more than 99% of the formed GNRs were sGNRs. The changes induced in the electrical properties of the obtained sGNR by the absorption of nanoparticles of planar molecule, naphthalenediimide (NDI), were investigated. The shape of the I-V curve of the sGNRs varied with the number of NDI nanoparticles adsorbed. This was suggestive of the existence of a band gap at the narrow-necked part near the NDI-adsorbing area of the sGNRs.
- Published
- 2015
- Full Text
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30. Study of c(2×2)-MnAu(001) layers on Mn(001) by means of scanning tunneling microscopy/spectroscopy
- Author
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Tomonari Mizoguchi, H. van Kempen, M. M. J. Bischoff, A. L. Vázquez de Parga, and Toyo Kazu Yamada
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Local density of states ,Materials science ,Scanning tunneling spectroscopy ,Alloy ,Analytical chemistry ,chemistry.chemical_element ,Surfaces and Interfaces ,Manganese ,engineering.material ,Condensed Matter Physics ,Surfaces, Coatings and Films ,law.invention ,Crystallography ,Transition metal ,chemistry ,law ,Materials Chemistry ,engineering ,Antiferromagnetism ,Scanning tunneling microscope ,Spectroscopy - Abstract
Intermixing, growth, geometric and electronic structures of gold films grown on antiferromagnetic stacking body-centered-tetragonal manganese (0 0 1) films were studied by means of scanning tunneling microscopy/spectroscopy at room temperature in ultra-high vacuum. We found stable ordered c(2 × 2)-MnAu(0 0 1) alloy layers after depositing Au on pure Mn layers. Since at the fourth layer (5 × 23)-like Au reconstruction appears instead of the c(2 × 2) structure and local density of states peaks obtained on the c(2 × 2)-MnAu surface disappear, pure Au layers likely grow from the fourth layer.
- Published
- 2006
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31. Study of Fe/Mn/Fe multilayers by means of scanning tunneling microscopy/spectroscopy
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H. van Kempen, Toyo Kazu Yamada, A. L. Vázquez de Parga, Tadashi Mizoguchi, and M. M. J. Bischoff
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Auger electron spectroscopy ,Condensed matter physics ,Chemistry ,Scanning tunneling spectroscopy ,Analytical chemistry ,Spin polarized scanning tunneling microscopy ,Surfaces and Interfaces ,Electronic structure ,Condensed Matter Physics ,Epitaxy ,Surfaces, Coatings and Films ,law.invention ,Condensed Matter::Materials Science ,law ,Materials Chemistry ,Density of states ,Scanning tunneling microscope ,Spectroscopy - Abstract
To elucidate the magnetic properties of a magnetic multilayer film, an understanding of the local geometry, electronic structure, and possible intermixing at the interfaces is of utmost importance. By gradually increasing the Fe coverage on the Mn(001) film, we obtained this information on the interface region by means of Auger spectroscopy and scanning tunneling microscopy/spectroscopy. Intermixed atoms and various geometries and density of states are found to exist in this system.
- Published
- 2004
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32. Origin of Magnetic Contrast in Spin-Polarized Scanning Tunneling Spectroscopy: Experiments on Ultra-Thin Mn Films
- Author
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Toyo Kazu Yamada, George M. M. Heijnen, M. M. J. Bischoff, Herman van Kempen, and Tadashi Mizoguchi
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Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Chemistry ,Whiskers ,Scanning tunneling spectroscopy ,General Engineering ,General Physics and Astronomy ,chemistry.chemical_element ,Spin polarized scanning tunneling microscopy ,Manganese ,Polarization (waves) ,law.invention ,law ,Condensed Matter::Superconductivity ,Density of states ,Scanning tunneling microscope ,Quantum tunnelling - Abstract
Normalized differential tunneling conductivities obtained with Fe-coated W tips show a spin-polarized peak around +0.8 V on ultrathin bct Mn films grown on Fe(001)-whiskers. This spin-polarized peak results in a clear magnetic contrast in spectroscopic images. Our normalization removes the influence of the tunneling probability and makes the spectroscopic curves most reliable for a derivation of the spin-resolved sample density of states (DOS) at positive voltages. From this analysis we conclude that the magnetic contrast in our spectroscopic maps is caused by a highly polarized DOS. Furthermore, a tip polarization of about 15% is found.
- Published
- 2003
- Full Text
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33. STM and STS study of ultrathin Mn layers on Fe()
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H. van Kempen, M. M. J. Bischoff, Tadashi Mizoguchi, and Toyo Kazu Yamada
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Chemistry ,Scanning tunneling spectroscopy ,Surfaces and Interfaces ,Condensed Matter Physics ,Epitaxy ,Surface energy ,Surfaces, Coatings and Films ,law.invention ,Crystallography ,Lattice constant ,Transition metal ,law ,Materials Chemistry ,Scanning tunneling microscope ,Layer (electronics) ,Surface states - Abstract
The growth of ultrathin Mn films on an Fe(0 0 1) whisker at 370 K is studied by scanning tunneling microscopy (STM) and scanning tunneling spectroscopy at room temperature in ultrahigh vacuum. Atomically and chemically resolved STM images show that the Mn film grows with the same in-plane lattice constant as Fe(0 0 1) and that Fe atoms intermix with the first (14%), the second (4%), and the third Mn layer (2%), while a negligible amount of Fe atoms is found above the third layer. The growth mode changes from layer-by-layer to layer-plus-island at a coverage of 3 ML Mn. dI/dV curves which are normalized by voltage-dependent tunneling probability functions show clear peaks on each Mn layer. These peaks are tentatively ascribed to surface states. On the first Mn layer, peaks are found at +0.35 eV on pure Mn areas and at +0.28 eV on mixed MnFe areas. The second and the third Mn layer show peaks at +0.20 and +0.8 eV, respectively. Mn films thicker than three layers reveal besides a strong peak at +0.8 eV a weaker peak at −0.6 eV. Our apparent step height measurements show that the Mn film relaxes at the third layer: the interlayer spacing is ∼0.16 nm for the first two layers, and it increases to ∼0.18 nm at the third layer. Starting from the fourth layer the interlayer spacings are geometrically equivalent (∼0.165 nm).
- Published
- 2002
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34. Scanning tunneling microscopy and spectroscopy study on the submonolayer growth of Mn on Fe()
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H. van Kempen, Toyo Kazu Yamada, Aidan J. Quinn, and M. M. J. Bischoff
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Surface diffusion ,Chemistry ,Scanning tunneling spectroscopy ,Crystal growth ,Surfaces and Interfaces ,Electronic structure ,Atmospheric temperature range ,Condensed Matter Physics ,Surfaces, Coatings and Films ,law.invention ,Crystallography ,law ,Materials Chemistry ,Scanning tunneling microscope ,Spectroscopy ,Surface states - Abstract
The submonolayer growth of Mn on Fe(0 0 1) in the temperature range between 50 and 200 °C is studied by scanning tunneling microscopy and scanning tunneling spectroscopy. For growth temperatures above 100 °C, atomically resolved STM images with chemical contrast clearly reveal the incorporation of Mn atoms in the Fe(0 0 1) substrate. The fraction of place exchanged Mn atoms is observed to increase with growth temperature. Although on islands a c(2×2) structure forms locally which is attributed to an ordered MnFe surface alloy, long range order could not be obtained for the growth temperatures and coverages studied. Spectroscopy results are presented for clean Fe(0 0 1), pure Mn ad-islands, single incorporated Mn atoms and c(2×2)-ordered MnFe areas. In contrast to embedded Cr atoms in the Fe(0 0 1) surface [Phys. Rev. Lett. 76 (1996) 4175], isolated embedded Mn atoms do not lead to double peak structures in d I /d V curves. Nevertheless, on the ordered c(2×2) MnFe structure and the pure Mn monoatomic islands surface states are detected as peaks in the d I /d V and (d I /d V )/( I / V ) curves. However, due to the strong influence of a tip-dependent background on these peaks, the corresponding surface state energies cannot be found directly from those curves. The real surface state energies were recovered by normalizing the measured d I /d V curves by fitted quadratic backgrounds. Thus, surface state energies of about +0.35 and +0.25 eV are estimated for pure Mn islands and alloyed MnFe areas, respectively.
- Published
- 2002
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35. Single Molecular Spintronics
- Author
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Toyo Kazu Yamada
- Subjects
Materials science ,Spin polarization ,Condensed matter physics ,Spintronics ,Giant magnetoresistance ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,law.invention ,Condensed Matter::Materials Science ,chemistry.chemical_compound ,Ferromagnetism ,chemistry ,law ,Condensed Matter::Superconductivity ,Nano ,Phthalocyanine ,Molecule ,Scanning tunneling microscope - Abstract
Giant magnetoresistance (GMR) through a single phthalocyanine molecule (H2Pc) was studied by means of a spin-polarized scanning tunneling microscopy (STM) technique. Spin-polarized STM shows surface electronic spin and quantum structures of nano materials, such as single atoms, single molecules, nano-clusters, with an atomic resolution. Single molecular magnetic junction was fabricated by contacting a ferromagnetic STM tip to a single molecule adsorbed on nano magnets. We measured GMR of +60% and -50% through [Co/H2Pc/Co(111)] and [Fe/H2Pc/Mn(001)] junctions, respectively, in ultra-high vacuum at 4.6K. Single organic molecules can be a new material for spintronics.
- Published
- 2014
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- View/download PDF
36. STM, STS, and local work function study of Cs/p-GaAs(1 1 0)
- Author
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J. Fujii, Toyo Kazu Yamada, and Tadashi Mizoguchi
- Subjects
Scanning tunneling spectroscopy ,chemistry.chemical_element ,Surfaces and Interfaces ,Photoelectric effect ,Condensed Matter Physics ,Alkali metal ,Surfaces, Coatings and Films ,Gallium arsenide ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Caesium ,Materials Chemistry ,Work function ,Scanning tunneling microscope ,Atomic physics ,Surface states - Abstract
Various surface configurations of Cs/p-GaAs(1 1 0) have been studied by scanning tunneling microscopy and scanning tunneling spectroscopy with an interest in relation to the photoelectron emission. The local work function is found to be 4.8, 3.3, and 3.3 eV from clean p-GaAs(1 1 0), Cs one-dimensional (1D) lines (Cs coverage of 0.23 ML), and partially-ordered Cs polygons (Cs coverage of 0.5 ML), respectively. It is understood that only a coherently c(4×4)-ordered Cs-polygon surface (Cs coverage of 0.6 and 0.7 ML) can emit photoelectrons due to a sufficient reduction of the local work function down to 1.3 eV to get the negative electron affinity state. The local work function image shows that the boundary of Cs atoms has a lower local work function than at the top of Cs atoms.
- Published
- 2001
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37. Polarization of Secondary Electrons from Clean and Oxygen-Chemisorbed Ni (110)
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Y. Oshima, J. Fujii, Toyo Kazu Yamada, and Tadashi Mizoguchi
- Subjects
Materials science ,Spin polarization ,chemistry ,Condensed matter physics ,chemistry.chemical_element ,Atomic physics ,Polarization (electrochemistry) ,Oxygen ,Secondary electrons - Published
- 2001
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38. Temperature control of the growth of iron oxide nanoislands on Fe(001)
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Toyo Kazu Yamada, Lukas Gerhard, Wulf Wulfhekel, and Yuki Sakaguchi
- Subjects
Materials science ,Annealing (metallurgy) ,General Engineering ,Iron oxide ,Analytical chemistry ,Oxide ,General Physics and Astronomy ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,Surface finish ,021001 nanoscience & nanotechnology ,01 natural sciences ,Oxygen ,law.invention ,chemistry.chemical_compound ,chemistry ,Impurity ,law ,0103 physical sciences ,Scanning tunneling microscope ,010306 general physics ,0210 nano-technology ,Single crystal - Abstract
The control of atomically flat interfaces between iron (Fe) and insulating oxide films, such as the Fe/MgO(001) interface, is crucial for tunnel-magnetoresistance (TMR) devices. However, the realization of an ideal atomically flat and clean interface is rather difficult since iron easily binds to impurities such as oxygen. Atomic step defects and iron oxide at the interface could reduce TMR. In this study, the oxidization of an atomically flat and clean Fe(001)-whisker single crystal at different substrate and annealing temperatures was investigated with an ultrahigh-vacuum scanning tunneling microscope (STM). Annealing up to a temperature of 850 K was required to obtain ordered and atomically flat Fe(001)-p(1×1)O terraces after the oxidization with the coexistence of Fe–O nanoislands (∼1 nm in height, ∼50 nm in size). We found that the growth of such nanoislands, which enhances interface roughness, strongly depends on the substrate temperature (T S) during the oxidization. A T S lower than 300 K reduces the coverage by the nanoislands to less than 10%.
- Published
- 2016
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39. Use of voltage pulses to detect spin-polarized tunneling
- Author
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H. van Kempen, Tadashi Mizoguchi, M. M. J. Bischoff, and Toyo Kazu Yamada
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,Condensed matter physics ,Scanning tunneling spectroscopy ,Analytical chemistry ,Spin polarized scanning tunneling microscopy ,Conductive atomic force microscopy ,Electrochemical scanning tunneling microscope ,law.invention ,Magnetization ,Ferromagnetism ,law ,Condensed Matter::Strongly Correlated Electrons ,Scanning tunneling microscope ,Voltage - Abstract
The present letter describes a method to make a spin-polarized scanning tunneling microscopy tip by applying voltage pulses between a W tip and a magnetic sample. This spin-polarized tip has the similar characteristics as an Fe-coated W tip, which was confirmed by observations of antiferromagnetically coupled ferromagnetic Mn(001) layers (>3 ML) grown on an Fe(001) whisker at 370 K. Furthermore, we demonstrate that these voltage pulses can vary the tip magnetization direction.
- Published
- 2003
- Full Text
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40. Single molecule magnetoresistance with combined antiferromagnetic and ferromagnetic electrodes
- Author
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Toyo Kazu Yamada, Ali Jaafar, Stefan Schmaus, Ferdinand Evers, Detlef Kramczynski, Mebarek Alouani, Alexei Bagrets, and Wulf Wulfhekel
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Materials science ,Magnetoresistance ,Condensed matter physics ,Spintronics ,Mechanical Engineering ,Bioengineering ,Fermi energy ,Giant magnetoresistance ,General Chemistry ,Condensed Matter Physics ,law.invention ,Condensed Matter::Materials Science ,law ,Antiferromagnetism ,Condensed Matter::Strongly Correlated Electrons ,General Materials Science ,Density functional theory ,Scanning tunneling microscope ,HOMO/LUMO - Abstract
The magnetoresistance of a hydrogen-phthalocyanine molecule placed on an antiferromagnetic Mn(001) surface and contacted by a ferromagnetic Fe electrode is investigated using density functional theory based transport calculations and low-temperature scanning tunneling microscopy. A large and negative magnetoresistance ratio of ∼50% is observed in combination with a high conductance. The effect originates from a lowest unoccupied molecular orbital (LUMO) doublet placed almost in resonance with the Fermi energy. As a consequence, irrespective of the mutual alignment of magnetizations, electron transport is always dominated by resonant transmission of Mn-majority charge carries going through LUMO levels.
- Published
- 2012
41. Spintronics with single molecules
- Author
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Wulf Wulfhekel, Manuel Gruber, T. Miyamachi, Martin Bowen, A. Bagrets, Ferdinand Evers, Stefan Schmaus, Toyo Kazu Yamada, Eric Beaurepaire, Timofey Balashov, A. F. Takács, and V. Davesne
- Subjects
Materials science ,Magnetoresistance ,Spintronics ,Nanostructured materials ,fungi ,food and beverages ,Molecular electronics ,Nanotechnology ,law.invention ,Organic semiconductor ,Nanoelectronics ,law ,Molecule ,Scanning tunneling microscope - Abstract
We demonstrate that with the help of Scanning Tunneling Microscopy (STM), spintronic functions can be realized with single molecules.
- Published
- 2012
- Full Text
- View/download PDF
42. Robust spin crossover and memristance across a single molecule
- Author
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Eric Beaurepaire, Wulf Wulfhekel, Martin Bowen, Manuel Gruber, Loïc Joly, Fabrice Scheurer, Guillaume Rogez, V. Davesne, Toyo Kazu Yamada, Philippe Ohresser, T. Miyamachi, and Samy Boukari
- Subjects
Multidisciplinary ,Materials science ,Condensed matter physics ,Spin states ,Basis (linear algebra) ,Aucun ,General Physics and Astronomy ,Molecular electronics ,Nanotechnology ,General Chemistry ,General Biochemistry, Genetics and Molecular Biology ,Spin crossover ,Molecule ,Condensed Matter::Strongly Correlated Electrons ,Layer (electronics) ,Metallic substrate - Abstract
A nanoscale molecular switch can be used to store information in a single molecule. Although the switching process can be detected electrically in the form of a change in the molecule's conductance, adding spin functionality to molecular switches is a key concept for realizing molecular spintronic devices. Here we show that iron-based spin-crossover molecules can be individually and reproducibly switched between a combined high-spin, high-conduction state and a low-spin, low-conduction state, provided the individual molecule is decoupled from a metallic substrate by a thin insulating layer. These results represent a step to achieving combined spin and conduction switching functionality on the level of individual molecules.
- Published
- 2012
43. Giant magnetoresistance through a single molecule
- Author
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Annika Bork, Toyo Kazu Yamada, A. Bagrets, Wulf Wulfhekel, Yasmine Nahas, Martin Bowen, Stefan Schmaus, Eric Beaurepaire, and Ferdinand Evers
- Subjects
Materials science ,Colossal magnetoresistance ,Indoles ,Magnetoresistance ,Biomedical Engineering ,Bioengineering ,Giant magnetoresistance ,Metallic conduction ,Isoindoles ,Ferric Compounds ,Condensed Matter::Materials Science ,Magnetics ,Microscopy, Scanning Tunneling ,Materials Testing ,Electric Impedance ,Molecule ,Nanotechnology ,General Materials Science ,Electrical and Electronic Engineering ,Magnetite Nanoparticles ,Electrodes ,Spintronics ,Condensed matter physics ,Electric Conductivity ,Signal Processing, Computer-Assisted ,Cobalt ,Equipment Design ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Ferromagnetism ,Feasibility Studies ,Condensed Matter::Strongly Correlated Electrons ,Electronics ,Crystallization - Abstract
Magnetoresistance is a change in the resistance of a material system caused by an applied magnetic field. Giant magnetoresistance occurs in structures containing ferromagnetic contacts separated by a metallic non-magnetic spacer, and is now the basis of read heads for hard drives and for new forms of random access memory. Using an insulator (for example, a molecular thin film) rather than a metal as the spacer gives rise to tunnelling magnetoresistance, which typically produces a larger change in resistance for a given magnetic field strength, but also yields higher resistances, which are a disadvantage for real device operation. Here, we demonstrate giant magnetoresistance across a single, non-magnetic hydrogen phthalocyanine molecule contacted by the ferromagnetic tip of a scanning tunnelling microscope. We measure the magnetoresistance to be 60% and the conductance to be 0.26G(0), where G(0) is the quantum of conductance. Theoretical analysis identifies spin-dependent hybridization of molecular and electrode orbitals as the cause of the large magnetoresistance.
- Published
- 2010
44. Spin configuration in a frustrated ferromagnetic/antiferromagnetic thin-film system
- Author
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A. L. Vázquez de Parga, Andrés Vega, Toyo Kazu Yamada, Rafael Robles, E. Martinez, H. van Kempen, Daniel Stoeffler, Tadashi Mizoguchi, Masson, Beatrice, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), and Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Materials science ,Magnetism ,media_common.quotation_subject ,FOS: Physical sciences ,Frustration ,Bioengineering ,02 engineering and technology ,01 natural sciences ,law.invention ,Condensed Matter::Materials Science ,Magnetization ,Tight binding ,law ,0103 physical sciences ,Antiferromagnetism ,General Materials Science ,Electrical and Electronic Engineering ,010306 general physics ,media_common ,Condensed Matter - Materials Science ,Condensed matter physics ,Scanning Probe Microscopy ,Mechanical Engineering ,Materials Science (cond-mat.mtrl-sci) ,General Chemistry ,021001 nanoscience & nanotechnology ,Inductive coupling ,3. Good health ,Ferromagnetism ,Mechanics of Materials ,Condensed Matter::Strongly Correlated Electrons ,Scanning tunneling microscope ,0210 nano-technology - Abstract
We have studied the magnetic configuration in ultrathin antiferromagnetic Mn films grown around monoatomic steps on an Fe(001) surface by spin-polarized scanning tunneling microscopy/spectroscopy and ab-initio-parametrized self-consistent real-space tight binding calculations in which the spin quantization axis is independent for each site thus allowing noncollinear magnetism. Mn grown on Fe(001) presents a layered antiferromagnetic structure. In the regions where the Mn films overgrows Fe steps the magnetization of the surface layer is reversed across the steps. Around these defects a frustration of the antiferromagnetic order occurs. Due to the weakened magnetic coupling at the central Mn layers, the amount of frustration is smaller than in Cr and the width of the wall induced by the step does not change with the thickness, at least for coverages up to seven monolayers., 10 pages, 5 figures
- Published
- 2007
45. Study of Spin-Polarized Scanning Tunneling Microscopy / Spectroscopy on Ultrathin Magnetic Films
- Author
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A. L. Vázquez de Parga, M. M. J. Bischoff, H. van Kempen, Toyo Kazu Yamada, and Tomonari Mizoguchi
- Subjects
Materials science ,Magnetic structure ,Magnetic moment ,Condensed matter physics ,Magnetism ,Scanning tunneling spectroscopy ,Spin polarized scanning tunneling microscopy ,law.invention ,Bohr magneton ,Condensed Matter::Materials Science ,symbols.namesake ,Ferromagnetism ,law ,Condensed Matter::Superconductivity ,symbols ,Condensed Matter::Strongly Correlated Electrons ,Scanning tunneling microscope - Abstract
Spin-polarized scanning tunneling microscopy and spectroscopy (SP-STM/STS) opens up new real atomic scale magnetism. Interlayer exchange coupling of ultrathin Fe(001) films grown on the antiferromagnetically stacked bct-Mn(001) layers have been studied. The ordered c(2x2)-MnAu(001) surface alloy films were studied and found a high magnetic moment for Mn spins (>4 Bohr magneton), an antiferromagnetic coupling between layers, and a ferromagnetic coupling in the same layer.
- Published
- 2006
- Full Text
- View/download PDF
46. Spin-polarized scanning tunneling microscopy/spectroscopy study of MnAu(001) thin films
- Author
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H. van Kempen, M. M. J. Bischoff, Eduardo Martínez, Andrés Vega, Tomonari Mizoguchi, A. L. Vázquez de Parga, Roberto Robles, and Toyo Kazu Yamada
- Subjects
Materials science ,Magnetic moment ,Condensed matter physics ,Scanning tunneling spectroscopy ,Fermi level ,Spin polarized scanning tunneling microscopy ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,law.invention ,Condensed Matter::Materials Science ,symbols.namesake ,Ab initio quantum chemistry methods ,law ,Condensed Matter::Superconductivity ,symbols ,Scanning tunneling microscope ,Thin film ,Spectroscopy - Abstract
In this work we explore by means of spin-polarized scanning tunneling microcopy/spectroscopy (SP-STM/STS) and ab initio calculations the magnetic and electronic properties of thin MnAu alloyed films. The MnAu films are produced by deposition of small amounts of Au at RT on a Mn(001) surface. On the scanning tunneling microscopy images the surface of the AuMn alloy presents a $c(2\ifmmode\times\else\texttimes\fi{}2)$ reconstruction. From the SP-STM/STS measurements we find out that the MnAu alloy layers are coupled antiferromagnetically with the layers above and below. Comparing the result from the ab initio calculations with the spin-polarized measurements we found that the origin of the magnetic contrast is due to a spin-polarized peak at $0.15\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ above the Fermi level spatially placed on the Mn sites. In the calculations we also found that the magnetic moments of the Mn atoms are higher in the alloy layers than in the pure Mn films.
- Published
- 2005
- Full Text
- View/download PDF
47. Evaluation of sample spin-polarization from spin-polarized scanning tunneling spectroscopy experiments
- Author
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H. van Kempen, A. L. Vázquez de Parga, Toyo Kazu Yamada, Tadashi Mizoguchi, and M. M. J. Bischoff
- Subjects
Manganese ,Histology ,Materials science ,Magnetic structure ,Spin polarization ,Magnetic domain ,Condensed matter physics ,Scanning Probe Microscopy ,Iron ,Scanning tunneling spectroscopy ,Spin polarized scanning tunneling microscopy ,Models, Theoretical ,Polarization (waves) ,Tungsten ,law.invention ,Condensed Matter::Materials Science ,Medical Laboratory Technology ,Magnetization ,Crystallography ,Magnetics ,law ,Microscopy, Scanning Tunneling ,Anatomy ,Scanning tunneling microscope ,Instrumentation - Abstract
Spin-polarized scanning tunneling microscopy has produced a great amount of images presenting magnetic contrast between different magnetic domains with an unsurpassed spatial resolution but getting values like the surface polarization has proven to be a difficult task. We will discuss in detail how to extract this information for the case of manganese layers grown on Fe(001) whiskers. Mn layers adopt a body-centered-tetragonal (bct) structure when they are grown on the Fe(001) surface at room temperature. The Mn layers show an antiferromagnetic coupling between the layers. Comparing our spin-polarized scanning tunneling spectra measured with Fe-coated W tips with spin-resolved band structure calculations, we are able to find the value of the sample surface polarization. Also discussed is a method to change the tip magnetization. Finally, the magnetic structure around a screw dislocation on the surface is reviewed. Microsc. Res. Tech. 66:93–104, 2005. © 2005 Wiley-Liss, Inc.
- Published
- 2005
48. Characterization of Fe/W spin-polarized tips by means of holographic TEM and spin-polarized STS of optically pumped p-GaAs
- Author
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D. Okuyama, Tomonari Mizoguchi, T. Matsuda, A. Tonomura, Toyo Kazu Yamada, N. Mizuno, H. van Kempen, and A. L. Vázquez de Parga
- Subjects
Optical pumping ,Physics ,Magnetization ,Condensed matter physics ,Transmission electron microscopy ,Scanning Probe Microscopy ,Electron ,Electrical and Electronic Engineering ,Spin (physics) ,Electron holography ,Quantum tunnelling ,Electronic, Optical and Magnetic Materials ,Magnetic field - Abstract
Holographic transmission electron microscopy showed that magnetic flux does not diverge from the top of an Fe-coated W tip indicating the in-plane magnetization at the apex of successful spin-polarized tips. A dependence of differential conductivities of GaAs with Fe-coated W tips on the helicity of illuminating laser light was confirmed at negative sample bias where partially spin-polarized electrons in the conduction band of p-GaAs tunnel into spin-dependent Fe empty states while no dependence of those with nonmagnetic W tips.
- Published
- 2005
49. Analysis of the short-range order of the Au/Fe(001) surface alloy
- Author
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M. M. J. Bischoff, Toyo Kazu Yamada, and H. van Kempen
- Subjects
Surface (mathematics) ,Materials science ,Scanning tunneling spectroscopy ,Alloy ,Order (ring theory) ,engineering.material ,Molecular physics ,law.invention ,Nuclear magnetic resonance ,law ,Monolayer ,engineering ,Surface layer ,Scanning tunneling microscope ,Spectroscopy - Abstract
Scanning tunneling microscopy measurements show that the growth of about half a monolayer Au on Fe(001) at a temperature of $170\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ leads after a postanneal at $700\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ to an island free and homogeneously alloyed surface layer. The surface alloying is in contrast to the bulk where Au and Fe are immiscible. Strong chemical contrast in the images allows us to analyze the short-range order of this surface alloy. Two independent methods are considered: the first method extracts pair occupation probabilities directly from digitized images, the second method makes use of the autocorrelation of filtered images. Both methods lead to the same conclusion: only for the nearest-neighbor sites a strong preference for unlike species is found; for further sites the probabilities follow a random distribution. Scanning tunneling spectroscopy measurements on the alloyed AuFe surface are used to corroborate the interpretation of the chemical contrast. Furthermore, the spectroscopy results show that the Fe(001) surface state shifts to higher energies on areas where pure Fe patches are confined by Au atoms.
- Published
- 2003
- Full Text
- View/download PDF
50. Scanning tunneling spectroscopy study of surface states of 3d metals: Chemical identification, magnetic contrast and orbital kondo resonance states
- Author
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H. van Kempen, Alexander I. Lichtenstein, O. Yu. Kolesnychenko, G. M. M. Heijnen, Aidan J. Quinn, Toyo Kazu Yamada, Changming Fang, A.L. Vasquez de Parma, R. de Kort, R.A. de Groot, Mikhail I. Katsnelson, and M. M. J. Bischoff
- Subjects
Materials science ,Condensed matter physics ,Scanning Probe Microscopy ,Theory of Condensed Matter ,Magnetic contrast ,Scanning tunneling spectroscopy ,General Physics and Astronomy ,Condensed Matter::Strongly Correlated Electrons ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Surface states - Abstract
Scanning tunneling spectroscopy study of surface states of 3d metals: Chemical identification, magnetic contrast and orbital Kondo resonance states
- Published
- 2003
- Full Text
- View/download PDF
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