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Full-Text Articles in Physics

Hydrostatic And Uniaxial Pressure Dependence Of Superconducting Transition Temperature Of Kfe2as2 Single Crystals, Sergey L. Bud'ko, Yong Liu, Thomas A. Lograsso, Paul C. Canfield Dec 2012

Hydrostatic And Uniaxial Pressure Dependence Of Superconducting Transition Temperature Of Kfe2as2 Single Crystals, Sergey L. Bud'ko, Yong Liu, Thomas A. Lograsso, Paul C. Canfield

Ames Laboratory Publications

We present heat capacity, c-axis thermal expansion and pressure-dependent, low-field, temperature-dependent magnetization for pressures up to ∼12 kbar, data for KFe2As2 single crystals. Tc decreases under pressure with dTc/dP≈−0.10 K/kbar. The inferred uniaxial, c-axis, pressure derivative is positive, dTc/dpc≈0.11 K/kbar. The data are analyzed in comparison with those for overdoped Fe-based superconductors. Arguments are presented that superconductivity in KFe2As2 may be different from the other overdoped, Fe-based materials in the 122 family.


Effects Of Transition Metal Substitutions On The Incommensurability And Spin Fluctuations In Bafe2as2 By Elastic And Inelastic Neutron Scattering, Min Gyu Kim, Jagat Lamsal, T. W. Heitmann, Gregory S. Tucker, Daniel K. Pratt, Suffian N. Khan, Y. B. Lee, Aftab Alam, Alexander N. Thaler, Ni Ni, Sheng Ran, Sergey L. Bud'ko, K. J. Marty, M. D. Lumsden, Paul C. Canfield, Bruce N. Harmon, Duane D. Johnson, Andreas Kreyssig, Robert J. Mcqueeney, Alan I. Goldman Oct 2012

Effects Of Transition Metal Substitutions On The Incommensurability And Spin Fluctuations In Bafe2as2 By Elastic And Inelastic Neutron Scattering, Min Gyu Kim, Jagat Lamsal, T. W. Heitmann, Gregory S. Tucker, Daniel K. Pratt, Suffian N. Khan, Y. B. Lee, Aftab Alam, Alexander N. Thaler, Ni Ni, Sheng Ran, Sergey L. Bud'ko, K. J. Marty, M. D. Lumsden, Paul C. Canfield, Bruce N. Harmon, Duane D. Johnson, Andreas Kreyssig, Robert J. Mcqueeney, Alan I. Goldman

Ames Laboratory Publications

The spin fluctuation spectra from nonsuperconducting Cu-substituted, and superconducting Co-substituted, BaFe2As2 are compared quantitatively by inelastic neutron scattering measurements and are found to be indistinguishable. Whereas diffraction studies show the appearance of incommensurate spin-density wave order in Co and Ni substituted samples, the magnetic phase diagram for Cu substitution does not display incommensurate order, demonstrating that simple electron counting based on rigid-band concepts is invalid. These results, supported by theoretical calculations, suggest that substitutional impurity effects in the Fe plane play a significant role in controlling magnetism and the appearance of superconductivity, with Cu distinguished by enhanced impurity scattering and ...


Weak Anti-Localization And Quantum Oscillations Of Surface States In Topological Insulator Bi2se2te, Lihong Bao, Liang He, Nicholas R. Meyer, Xufeng Kou, Peng Zhang, Zhi-Gang Chen, Alexei V. Fedorov, Trevor M. Riedemann, Thomas A. Lograsso, Kang L. Wang, Gary Tuttle, Faxian Xiu Oct 2012

Weak Anti-Localization And Quantum Oscillations Of Surface States In Topological Insulator Bi2se2te, Lihong Bao, Liang He, Nicholas R. Meyer, Xufeng Kou, Peng Zhang, Zhi-Gang Chen, Alexei V. Fedorov, Trevor M. Riedemann, Thomas A. Lograsso, Kang L. Wang, Gary Tuttle, Faxian Xiu

Ames Laboratory Publications

Topological insulators, a new quantum state of matter, create exciting opportunities for studying topological quantum physics and for exploring spintronic applications due to their gapless helical metallic surface states. Here, we report the observation of weak anti-localization and quantum oscillations originated from surface states in Bi2Se2Te crystals. Angle-resolved photoemission spectroscopy measurements on cleaved Bi2Se2Te crystals show a well-defined linear dispersion without intersection of the conduction band. The measured weak anti-localization effect agrees well with the Hikami-Larkin-Nagaoka model and the extracted phase coherent length shows a power-law dependence with temperature ( ∼T−0.44), indicating the presence of the surface states. More ...


Evolution Of Precipitate Morphology During Heat Treatment And Its Implications For The Superconductivity In Kxfe1.6+Yse2 Single Crystals, Yong Liu, Qingfeng Xing, Kevin W. Dennis, R. William Mccallum, Thomas A. Lograsso Oct 2012

Evolution Of Precipitate Morphology During Heat Treatment And Its Implications For The Superconductivity In Kxfe1.6+Yse2 Single Crystals, Yong Liu, Qingfeng Xing, Kevin W. Dennis, R. William Mccallum, Thomas A. Lograsso

Ames Laboratory Publications

We study the relationship between precipitate morphology and superconductivity in KxFe1.6+ySe2 single crystals grown by self-flux method. Scanning electron microscopy (SEM) measurements revealed that the superconducting phase forms a network in the samples quenched above iron vacancy order-disorder transition temperature Ts, whereas it aggregates into micrometer-sized rectangular bars and aligns as disconnected chains in the furnace-cooled samples. Accompanying this change in morphology the superconducting shielding fraction is strongly reduced. By post-annealing above Ts followed by quenching in room temperature water, the network recovers with a superconducting shielding fraction approaching 80% for ...


Reply To “Comment On ‘Accurate And Fast Numerical Solution Of Poisson's Equation For Arbitrary, Space-Filling Voronoi Polyhedra: Near-Field Corrections Revisited’ ”, Aftab Alam, Brian G. Wilson, Duane D. Johnson Sep 2012

Reply To “Comment On ‘Accurate And Fast Numerical Solution Of Poisson's Equation For Arbitrary, Space-Filling Voronoi Polyhedra: Near-Field Corrections Revisited’ ”, Aftab Alam, Brian G. Wilson, Duane D. Johnson

Ames Laboratory Publications

This is a Reply to the Comment by Gonis and Zhang on our recent paper. They discuss supposed issues with our “accurate and fast numerical solution of Poisson’s equation for arbitrary Voronoi polyhedra” (VP).


High Superconducting Anisotropy And Weak Vortex Pinning In Co-Doped Lafeaso, G. Li, G. Grissonnanche, J.-Q. Yan, R. William Mccallum, Thomas A. Lograsso, H. D. Zhou, L. Balicas Aug 2012

High Superconducting Anisotropy And Weak Vortex Pinning In Co-Doped Lafeaso, G. Li, G. Grissonnanche, J.-Q. Yan, R. William Mccallum, Thomas A. Lograsso, H. D. Zhou, L. Balicas

Ames Laboratory Publications

Here, we present an electrical transport study in single crystals of LaFe0.92Co0.08AsO (Tc≃9.1 K) under high magnetic fields. In contrast to most of the previously reported Fe based superconductors, and despite its relatively low Tc, LaFe0.92Co0.08AsO shows a superconducting anisotropy which is comparable to those seen, for instance, in the cuprates or γH=Hc2ab/Hc2c=mc/mab≃9, where mc/mab is the effective-mass anisotropy, although, in the present case and as in all Fe ...


Reversible Tuning Of The Surface State In A Pseudobinary Bi2(Te-Se)3 Topological Insulator, Rui Jiang, Lin-Lin Wang, Mianliang Huang, R. S. Dhaka, Duane D. Johnson, Thomas A. Lograsso, Adam Kaminski Aug 2012

Reversible Tuning Of The Surface State In A Pseudobinary Bi2(Te-Se)3 Topological Insulator, Rui Jiang, Lin-Lin Wang, Mianliang Huang, R. S. Dhaka, Duane D. Johnson, Thomas A. Lograsso, Adam Kaminski

Ames Laboratory Publications

We use angle-resolved photoemission spectroscopy to study a nontrivial surface state in a pseudobinary Bi2Te2.8Se0.2 topological insulator. We show that, unlike previously studied binaries, this is an intrinsic topological insulator with the conduction bulk band residing well above the chemical potential. Our data indicate that under a good vacuum condition there are no significant aging effects for more than two weeks after cleaving. We also demonstrate that the shift of the Kramers point at low temperature is caused by UV-assisted absorption of molecular hydrogen. Our findings pave the way for applications of these ...


Creating Nanoscale Ag Patterns On The Si(111)–(√3 × √3)R30°-Ag Surface Via Guided Self-Assembly, Alex Belianinov, Barış Ünal, Michael C. Tringides, Patricia A. Thiel Jul 2012

Creating Nanoscale Ag Patterns On The Si(111)–(√3 × √3)R30°-Ag Surface Via Guided Self-Assembly, Alex Belianinov, Barış Ünal, Michael C. Tringides, Patricia A. Thiel

Chemistry Publications

Patterns of Ag nanostructures can be created on the Si(111)–(√3 × √3)R30°-Ag surface, using a simple two-step process in ultrahigh vacuum. First, patterns are created using the tip of a scanning tunneling microscope. Second, Ag is deposited at room temperature. The Ag diffuses over long distances on the surface and selectively aggregates at the patterned regions. The size of the Ag features is ∼3–4 nm.


Nanoalloy Composition-Temperature Phase Diagram For Catalyst Design: Case Study Of Ag-Au, Lin-Lin Wang, Teck L. Tan, Duane D. Johnson Jul 2012

Nanoalloy Composition-Temperature Phase Diagram For Catalyst Design: Case Study Of Ag-Au, Lin-Lin Wang, Teck L. Tan, Duane D. Johnson

Ames Laboratory Publications

By coupling a cluster expansion with density functional theory (DFT) calculations, we determine the configurational thermodynamics (site preferences and occupations) for alloyed nanoparticles (NPs) as functions of composition (c) and temperature (T), exemplified using a 55-atom Ag-Au truncated cuboctahedron NP. The c−T phase diagram for site occupations gives detailed design information for alloyed NP, especially the thermodynamically stable active sites for catalysis and how they change with stoichiometry and processing temperature. Generally, Ag prefers core and Au prefers shell, agreeing with our universal core-shell preference assessed from DFT impurity segregation energies but with interesting multishell configurations having specific active ...


Effects Of Cold Work On Near-Surface Conductivity Profiles In Laser Shock Peened And Shot Peened Nickel-Base Superalloy, Tyler J. Lesthaeghe, Brian F. Larson, Ramya Chandrasekar, Anatoli M. Frishman, Chester C.H. Lo, Norio Nakagawa Jul 2012

Effects Of Cold Work On Near-Surface Conductivity Profiles In Laser Shock Peened And Shot Peened Nickel-Base Superalloy, Tyler J. Lesthaeghe, Brian F. Larson, Ramya Chandrasekar, Anatoli M. Frishman, Chester C.H. Lo, Norio Nakagawa

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

This paper reports on a study of the effects of cold work induced by surface enhancement treatment on conductivity profiles in nickel-base superalloys, as part of the on-going efforts aimed at evaluating the feasibility of characterizing near-surface residual stress profiles in peened engine components using a swept frequency eddy current (SFEC) technique. The approach is based on the empirical piezoresistivity effect that correlates conductivity changes with residual stress, but recent studies have shown that conductivity changes induced by peening processes are also influenced by metallurgical factors such as cold work. In this study, conductivity deviation profiles were obtained by model-based ...


X-Ray Diffuse Scattering Measurements Of Chemical Short-Range Order And Lattice Strains In A Highly Magnetostrictive Fe0.813ga0.187 Alloy In An Applied Magnetic Field, Yingzhou Du, Mianliang Huang, Thomas A. Lograsso, Robert J. Mcqueeney Jun 2012

X-Ray Diffuse Scattering Measurements Of Chemical Short-Range Order And Lattice Strains In A Highly Magnetostrictive Fe0.813ga0.187 Alloy In An Applied Magnetic Field, Yingzhou Du, Mianliang Huang, Thomas A. Lograsso, Robert J. Mcqueeney

Ames Laboratory Publications

The rapid growth of the magnetostriction coefficient of ferromagnetic Fe1−xGax alloys that occurs at a composition range from 0


Photonic Crystal: Energy-Related Applications, Zhuo Ye, Joong Mok Park, Kristen P. Constant, Tae Guen Kim, Kai-Ming Ho Jun 2012

Photonic Crystal: Energy-Related Applications, Zhuo Ye, Joong Mok Park, Kristen P. Constant, Tae Guen Kim, Kai-Ming Ho

Materials Science and Engineering Publications

We review recent work on photonic-crystal fabrication using soft-lithography techniques. We consider applications of the resulting structures in energy-related areas such as lighting and solar-energy harvesting. In general, our aim is to introduce the reader to the concepts of photonic crystals, describe their history, development, and fabrication techniques and discuss a selection of energy-related applications.


Structural Properties And Relative Stability Of (Meta)Stable Ordered, Partially Ordered, And Disordered Al-Li Alloy Phases, Aftab Alam, Duane D. Johnson Apr 2012

Structural Properties And Relative Stability Of (Meta)Stable Ordered, Partially Ordered, And Disordered Al-Li Alloy Phases, Aftab Alam, Duane D. Johnson

Ames Laboratory Publications

We resolve issues that have plagued reliable prediction of relative phase stability for solid solutions and compounds. Due to its commercially important phase diagram, we showcase the Al-Li system because historically density-functional theory (DFT) results show large scatter and limited success in predicting the structural properties and stability of solid solutions relative to ordered compounds. Using recent advances in an optimal basis-set representation of the topology of electronic charge density (and, hence, atomic size), we present DFT results that agree reasonably well with all known experimental data for the structural properties and formation energies of ordered, off-stoichiometric partially ordered, and ...


Magnetic And Structural Properties Of Single-Crystalline Er5si4, Yaroslav Mudryk, Niraj K. Singh, Vitalij K. Pecharsky, Deborah L. Schlagel, Thomas A. Lograsso, Karl A. Gschneidner Jr. Mar 2012

Magnetic And Structural Properties Of Single-Crystalline Er5si4, Yaroslav Mudryk, Niraj K. Singh, Vitalij K. Pecharsky, Deborah L. Schlagel, Thomas A. Lograsso, Karl A. Gschneidner Jr.

Ames Laboratory Publications

The magnetization of the oriented Er5Si4 single crystal, measured along the three principal crystallographic directions, reveals strong magnetocrystalline anisotropy. The b axis is the easy magnetization direction. The possible presence of the crystal-field effect and the noncollinear alignment of magnetic moments result in a lower than gJ magnetization along all crystallographic directions, even in a 70-kOe applied magnetic field, with the lowest moment (4.22 μB/Er3+) recorded along the a axis. The magnetization measurements show that even in the true paramagnetic state there is a weak magnetic field dependence of the structural-only transition when the ...


Temperature Dependence Of Magnetoelastic Properties Of Fe100−Xsix (5 < X < 20), G. Petculescu, P. K. Lambert, A. E. Clark, K. B. Hathaway, Qingfeng Xing, Thomas A. Lograsso, J. B. Restorff, M. Wun-Fogle Feb 2012

Temperature Dependence Of Magnetoelastic Properties Of Fe100−Xsix (5 < X < 20), G. Petculescu, P. K. Lambert, A. E. Clark, K. B. Hathaway, Qingfeng Xing, Thomas A. Lograsso, J. B. Restorff, M. Wun-Fogle

Ames Laboratory Conference Papers, Posters, and Presentations

Tetragonal magnetostriction (λγ,2) and elastic constants (c′, c44, and c11) for Fe100−xSixwere measured as a function of temperature (T). Compositions corresponding to the disordered A2 (x = 5), ordered D03 (x = 19.8), and mixed (x = 11.6) phases, were investigated. The magnetoelastic coupling (−b1) was determined for 77 < T < 300 K and compared with those of Fe-Ga, Fe-Ge, and Fe-Al. Both λγ,2(T) and −b1(T) of Fe-Si behave similarly to those of Fe-Ge, while other notable differences exist between the measured properties of Fe-Si and those of the other three alloys. Due to the early establishment of short ...


Anisotropic Magnetic Deflagration In Single Crystals Of Gd5ge4, S. Vélez, J. M. Hernandez, A. García-Santiago, J. Tejada, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., Deborah L. Schlagel, Thomas A. Lograsso, P. V. Santos Feb 2012

Anisotropic Magnetic Deflagration In Single Crystals Of Gd5ge4, S. Vélez, J. M. Hernandez, A. García-Santiago, J. Tejada, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., Deborah L. Schlagel, Thomas A. Lograsso, P. V. Santos

Ames Laboratory Publications

Experimental evidence of the anisotropy of the magnetic deflagration associated with the low-temperature first-order antiferromagnetic (AFM) → ferromagnetic (FM) phase transition in single crystals of Gd5Ge4 is reported. The deflagrations were induced by controlled pulses of surface acoustic waves (SAW) allowing to explore both the magnetic field and temperature dependencies on the characteristic times of the phenomenon. The study was done using samples with different geometries and configurations between the SAW pulses and the direction of the applied magnetic field with respect to the three main crystallographic directions of the samples. The effect of temperature is nearly negligible ...


Coexistence Of Charge-Density Wave And Ferromagnetism In Ni2mnga, S. W. D'Souza, Abhishek Rai, J. Nayak, M. Maniraj, R. S. Dhaka, S. R. Barman, Deborah L. Schlagel, Thomas A. Lograsso, Aparna Chakrabarti Feb 2012

Coexistence Of Charge-Density Wave And Ferromagnetism In Ni2mnga, S. W. D'Souza, Abhishek Rai, J. Nayak, M. Maniraj, R. S. Dhaka, S. R. Barman, Deborah L. Schlagel, Thomas A. Lograsso, Aparna Chakrabarti

Ames Laboratory Publications

We demonstrate the existence of a charge-density-wave (CDW) associated with an incommensurate periodic lattice distortion on Ni2MnGa surface in the ferromagnetic state. Our temperature-dependent photoemission spectra provide compelling evidence of a pseudogap at the Fermi level for TCDW ⩽ 270 K that appears at the onset of the premartensite phase and persists in the martensite phase. While the width of the pseudogap is about 25 meV, a spectral weight transfer is observed over a much wider energy range that is associated with the CDW.


Tetragonal Magnetostriction And Magnetoelastic Coupling In Fe-Al, Fe-Ga, Fe-Ge, Fe-Si, Fe-Ga-Al, And Fe-Ga-Ge Alloys, J. B. Restorff, M. Wun-Fogle, K. B. Hathaway, A. E. Clark, Thomas A. Lograsso, G. Petculescu Jan 2012

Tetragonal Magnetostriction And Magnetoelastic Coupling In Fe-Al, Fe-Ga, Fe-Ge, Fe-Si, Fe-Ga-Al, And Fe-Ga-Ge Alloys, J. B. Restorff, M. Wun-Fogle, K. B. Hathaway, A. E. Clark, Thomas A. Lograsso, G. Petculescu

Ames Laboratory Publications

This paper presents a comparative study on the tetragonal magnetostriction constant,λγ,2, [ = (3/2)λ100] and magnetoelastic coupling, b1, of binary Fe100-xZx (0 < x < 35, Z = Al, Ga, Ge, and Si) and ternary Fe-Ga-Al and Fe-Ga-Ge alloys. The quantities are corrected for magnetostrains due to sample geometry (the magnetostrictive form effect). Recently published elastic constant data along with magnetization measurements at both room temperature and 77 K make these corrections possible. The form effect correction lowers the magnetostriction by ∼10 ppm for high-modulus alloys and by as much as 30 ppm for low-modulus ...


A Comprehensive Search For Stable Pt–Pd Nanoalloy Configurations And Their Use As Tunable Catalysts, Teck L. Tan, Lin-Lin Wang, Duane D. Johnson, Kewu Bai Jan 2012

A Comprehensive Search For Stable Pt–Pd Nanoalloy Configurations And Their Use As Tunable Catalysts, Teck L. Tan, Lin-Lin Wang, Duane D. Johnson, Kewu Bai

Ames Laboratory Publications

Using density-functional theory, we predict stable alloy configurations (ground states) for a 1 nm Pt–Pd cuboctahedral nanoparticle across the entire composition range and demonstrate their use as tunable alloy catalysts via hydrogen-adsorption studies. Unlike previous works, we use simulated annealing with a cluster expansion Hamiltonian to perform a rapid and comprehensive search that encompasses both high and low-symmetry configurations. The ground states show Pt(core)–Pd(shell) type configurations across all compositions but with specific Pd patterns. For catalysis studies at room temperatures, the ground states are more realistic structural models than the commonly assumed random alloy configurations. Using ...


The Morphotropic Phase Boundary In The (1-X)Pbzro3–X[0.3bi(Zn1/2ti1/2)O3–0.7pbtio3] Perovskite Solid Solution, T. Sareein, W. Hu, Xiaoli Tan, R. Yimnirun Jan 2012

The Morphotropic Phase Boundary In The (1-X)Pbzro3–X[0.3bi(Zn1/2ti1/2)O3–0.7pbtio3] Perovskite Solid Solution, T. Sareein, W. Hu, Xiaoli Tan, R. Yimnirun

Materials Science and Engineering Publications

Ceramics in the (1-x)PbZrO3–x[0.3Bi(Zn1/2Ti1/2)O3–0.7PbTiO3] solid solution system with 0.48  x  0.56 were investigated. A morphotropic phase boundary separating rhombohedral and tetragonal perovskite phases was identified at x = 0.52. This composition displays the maximum remanent polarization Pr of 40.7 μC/cm2 and the best piezoelectric coefficient d33 of 311 pC/N in the pseudo-binary system. However, the Curie temperature Tc for this MPB composition is 291 °C, much lower than initially expected.


Nmr And Conductivity Studies Of The Mixed Glass Former Effect In Lithium Borophosphate Glasses, Michael Storek, Roland Böhmer, Steve W. Martin, Dirk Larink, Hellmut Eckert Jan 2012

Nmr And Conductivity Studies Of The Mixed Glass Former Effect In Lithium Borophosphate Glasses, Michael Storek, Roland Böhmer, Steve W. Martin, Dirk Larink, Hellmut Eckert

Materials Science and Engineering Publications

Alkali ion charge transport has been studied in a series of mixed glass former lithium borophosphate glasses of composition 0.33Li2O + 0.67[xB2O3 + (1 – x)P2O5]. The entire concentration range, 0.0 ≤ x ≤ 1.0, from pure glassy Li2P4O11 to pure glassy Li2B4O7 has been examined while keeping the molar fraction of Li2O constant. Electrical conductivity measurements and nuclear magnetic resonance techniques such as spin relaxometry, line shape analysis, and stimulated-echo spectroscopy were used to examine the temperature ...


Surface And Particle-Size Effects On Hydrogen Desorption From Catalyst-Doped Mgh2, J. M. Reich, Lin-Lin Wang, Duane D. Johnson Jan 2012

Surface And Particle-Size Effects On Hydrogen Desorption From Catalyst-Doped Mgh2, J. M. Reich, Lin-Lin Wang, Duane D. Johnson

Ames Laboratory Publications

With their high capacity, light-metal hydrides like MgH2 remain under scrutiny as reversible H-storage materials, especially to develop control of H-desorption properties by decreasing size (ball-milling) and/or adding catalysts. By employing density functional theory and simulated annealing, we study initial H2 desorption from semi-infinite stepped rutile (110) surface and Mg31H62 nanoclusters, with(out) transition-metal catalyst dopants (Ti or Fe). While Mg31H62structures are disordered (amorphous), the semi-infinite surfaces and nanoclusters have similar single, double, and triple H-to-metal bond configurations that yield similar H-desorption energies. Hence, there is no size effect on desorption energetics with reduction in sample size, but dopants ...


Growth Morphology And Thermal Stability Of Metal Islands On Graphene, Xiaojie Liu, Myron Hupalo, Cai-Zhuang Wang, Wen-Cai Lu, Patricia A. Thiel, Kai-Ming Ho, Michael C. Tringides Jan 2012

Growth Morphology And Thermal Stability Of Metal Islands On Graphene, Xiaojie Liu, Myron Hupalo, Cai-Zhuang Wang, Wen-Cai Lu, Patricia A. Thiel, Kai-Ming Ho, Michael C. Tringides

Chemistry Publications

We performed an experiment to study the thermal stability of metal on graphene. We show that Fe, Gd, Dy, and Eu on graphene exhibit island growth morphology. The 3D islands of Fe, Gd, and Dy show a small decrease in island density and an increase in the height/width aspect ratio upon thermal annealing. By contrast, coarsening of Eu islands to a close flat film is observed after annealing to 365 K. By investigating the fundamental interactions (i.e., adsorption energies and diffusion barriers) between the metal adatoms and graphene using ab initio calculations, we predict that most of the ...


High Island Densities And Long Range Repulsive Interactions: Fe On Epitaxial Graphene, Steven Michael Binz, Myron Hupalo, Xiaojie Liu, Cai-Zhuang Wang, Wen-Cai Lu, Patricia A. Thiel, Kai-Ming Ho, E. H. Conrad, Michael C. Tringides Jan 2012

High Island Densities And Long Range Repulsive Interactions: Fe On Epitaxial Graphene, Steven Michael Binz, Myron Hupalo, Xiaojie Liu, Cai-Zhuang Wang, Wen-Cai Lu, Patricia A. Thiel, Kai-Ming Ho, E. H. Conrad, Michael C. Tringides

Chemistry Publications

The understanding of metal nucleation on graphene is essential for promising future applications, especially of magnetic metals which can be used in spintronics or computer storage media. A common method to study the grown morphology is to measure the nucleated island density n as a function of growth parameters. Surprisingly, the growth of Fe on graphene is found to be unusual because it does not follow classical nucleation: n is unexpectedtly high, it increases continuously with the deposited amount θ and shows no temperature dependence. These unusual results indicate the presence of long range repulsive interactions. Kinetic Monte Carlo simulations ...