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“Influence of Al concentration on the optoelectronic properties of Al-doped MgO”. Sarmadian N, Saniz R, Lamoen D, Partoens B, Physical review : B : condensed matter and materials physics 86, 205129 (2012). http://doi.org/10.1103/PhysRevB.86.205129
Abstract: We use density functional theory within the local density approximation to investigate the structural, electronic, and optical properties of Al-doped MgO. The concentrations considered range from 6% to 56%. In the latter case, we also compare the optical properties of the amorphous and crystalline phases. We find that, overall, the electronic properties of the crystalline phases change qualitatively little with Al concentration. On the other hand, the changes in the electronic structure in the amorphous phase are more important, most notably because of deep impurity levels in the band gap that are absent in the crystalline phase. This leads to observable effects in, e.g., the optical absorption edge and in the refractive index. Thus, the latter can be used to characterize the crystalline to amorphous transition with Al doping level.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 5
DOI: 10.1103/PhysRevB.86.205129
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“Induced polarization and electronic properties of carbon-doped boron nitride nanoribbons”. Beheshtian J, Sadeghi A, Neek-Amal M, Michel KH, Peeters FM, Physical review : B : condensed matter and materials physics 86, 195433 (2012). http://doi.org/10.1103/PhysRevB.86.195433
Abstract: The electronic properties of boron nitride nanoribbons (BNNRs) doped with a line of carbon atoms are investigated using density functional calculations. By replacing a line of alternating B and N atoms with carbons, three different configurations are possible depending on the type of the atoms which bond to the carbons. We found very different electronic properties for these configurations: (i) the NCB arrangement is strongly polarized with a large dipole moment having an unexpected direction, (ii) the BCB and NCN arrangements are nonpolar with zero dipole moment, (iii) the doping by a carbon line reduces the band gap regardless of the local arrangement of the borons and the nitrogens around the carbon line, and (iv) the polarization and energy gap of the carbon-doped BNNRs can be tuned by an electric field applied parallel to the carbon line. Similar effects were found when either an armchair or zigzag line of carbon was introduced.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 41
DOI: 10.1103/PhysRevB.86.195433
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“Nano- and microcrystal investigations of precipitates, interfaces and strain fields in Ni-Ti-Nb by various TEM techniques”. Schryvers D, Shi H, Martinez GT, Van Aert S, Frenzel J, Van Humbeeck J, Materials science forum
T2 –, 9th European Symposium on Martensitic Transformations (ESOMAT 2012), SEP 09-16, 2012, St Petersburg, RUSSIA 738/739, 65 (2013). http://doi.org/10.4028/www.scientific.net/MSF.738-739.65
Abstract: In the present contribution several advanced electron microscopy techniques are employed in order to describe chemical and structural features of the nano- and microstructure of a Ni45.5Ti45.5Nb9 alloy. A line-up of Nb-rich nano-precipitates is found in the Ni-Ti-rich austenite of as-cast material. Concentration changes of the matrix after annealing are correlated with changes in the transformation temperatures. The formation of rows and plates of larger Nb-rich precipitates and particles is described. The interaction of a twinned martensite plate with a Nb-rich nano-precipitate is discussed and the substitution of Nb atoms on the Ti-sublattice in the matrix is confirmed.
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
Times cited: 2
DOI: 10.4028/www.scientific.net/MSF.738-739.65
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“Effect of annealing on the transformation behavior and mechanical properties of two nanostructured Ti-50.8at.%Ni thin wires produced by different methods”. Wang X, Amin-Ahmadi B, Schryvers D, Verlinden B, Van Humbeeck J, Materials science forum 738/739, 306 (2013). http://doi.org/10.4028/www.scientific.net/MSF.738-739.306
Abstract: A Ti-50.8at.%Ni wire produced using a co-drawing method and a commercial Ti-50.8at.%Ni wire were annealed at different temperatures between 450°C and 700°C. Grains with diameter less than 100nm were revealed by transmission electron microscopy for both wires before annealing treatment. However, the microstructural heterogeneity of the co-drawn wire is more obvious than that of the commercial wire. Multi-stage martensitic transformation was observed in the co-drawn wire, compared with the one-stage A↔M transformation in the commercial wire after annealing at 600°C for 30min. The differences of total elongation, plateau strain and pseudoelastic recoverable strain between the commercial wire and the co-drawn wire were also observed. The differences of the transformation behavior and mechanical properties between the commercial wire and the co-drawn wire are attributed to the microstructural difference between these two wires.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 5
DOI: 10.4028/www.scientific.net/MSF.738-739.306
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“EM characterization of precipitates in as-cast and annealed Ni45.5Ti45.5Nb9 shape memory alloys”. Shi H, Frenzel J, Schryvers D, Materials science forum 738/739, 113 (2013). http://doi.org/10.4028/www.scientific.net/MSF.738-739.113
Abstract: Nb-rich precipitates in the matrix of as-cast and annealed Ni45.5Ti45.5Nb9 alloys are investigated by scanning and scanning transmission electron microscopy, including slice-and-view and geometric phase analysis (GPA). The Nb-rich bcc nano-precipitates in the as-cast alloy have a 10% lattice parameter difference with the B2 matrix and reveal compensating interface dislocations. The 3D reconstruction of the configuration of small Nb-rich precipitates in the annealed alloy reveals a wall-like distribution of precipitates, which may increase the thermal hysteresis of the material.
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
Times cited: 1
DOI: 10.4028/www.scientific.net/MSF.738-739.113
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“Round-robin investigation of silicon-oxide on silicon reference materials for ellipsometry”. Vanhellemont J, Maes HE, Schaekers M, Armigliato A, Cerva H, Cullis A, de Sande J, Dinges H, Hallais J, Nayar V, Pickering C, Stehlé, JL, Van Landuyt J, Walker C, Werner H, Salieri P;, Applied surface science
T2 –, SYMP ON DIAGNOSTIC TECHNIQUES FOR SEMICONDUCTOR MATERIALS ANALYSIS AND, FABRICATION PROCESS CONTROL, AT THE 1992 SPRING CONF OF THE EUROPEAN, MATERIALS RESEARCH SOC, JUN 02-05, 1992, STRASBOURG, FRANCE 63, 45 (1993). http://doi.org/10.1016/0169-4332(93)90062-G
Abstract: The main results and conclusions are presented of a round robin study of silicon oxide on silicon reference samples for ellipsometry. The oxide films with nominal thicknesses of 10, 50 and 120 nm are grown by thermal oxidation. The oxide film thicknesses have been determined by single wavelength ellipsometry (SWE), by spectroscopic ellipsometry (SE) and by cross-sectional conventional and high-resolution transmission electron microscopy (TEM and HREM) in different laboratories. The main conclusions are that special precautions have to be taken in order to use TEM as a reliable thickness measurement technique; that single wavelength ellipsometry can be used with great accuracy and reproducibility for the 50 and 120 nm film thicknesses but that it shows some inherent problems for the 10 nm films; and that spectroscopic ellipsometry showed for all film thicknesses an accuracy and reproducibility which is clearly superior to that of SWE.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.711
Times cited: 13
DOI: 10.1016/0169-4332(93)90062-G
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“Ordering and defects in BanTaxTiyO3n ternary oxides”. Nistor L, Van Tendeloo G, Amelinckx S, Shpanchenko RV, van Landuyt J, Electron Microscopy 1994, Vols 2a And 2b: Applications In Materials Sciences , 869 (1994)
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
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“Nucleation and growth of Ni5Al3 in austenite and martensite matrices”. Schryvers D, Ma Y, Toth L, Tanner LE, Electron Microscopy 1994, Vols 2a And 2b: Applications In Materials Sciences , 509 (1994)
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
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“Stabilization of mercury-based superconductors by foreign cations”. Raveau B, Michel C, Hervieu M, Van Tendeloo G, Maignan A, Annales de chimie (1914)
T2 –, 4th North-African Materials Science Symposium (JMSM 94), NOV 23-24, 1994, CASABLANCA, MOROCCO 19, 487 (1994)
Abstract: The recently discovered superconducting mercury-based cuprates HgBa2Can-1CunO2n+2+delta have proved difficult to synthesize as single phases and are sensitive to environment (CO2, moisture). The present paper gives an overview of new series mercury based superconductors, whose stabilisation is based on the fact that a foreign cation with a higher valency than Hg(II) must be introduced in the mercury layers, in order to fill up partially the oxygen vacancies of these layers. By this method, several new series of superconductors involving strontium instead of barium with critical temperatures ranging from 27 K to 95 K have been isolated : Hg0.5Bi0.5Sr2-xLaxCuO4+delta, Hg(0.5)Bi(0.5)Sr(2)Ca(1-x)R(x)Cu(2)O(6+delta) (R Y, Nd, Pr), Pb0.7Hg0.3Sr2-xLaxCuO4+delta, Pb(0.7)Hg(0.3)Sr(2)Ca(1-x)R(x)Cu(2)O(6+delta) (R = Y, Nd) Hg(1-x)Pr(x)Sr(2)A(1-x')Pr(x') Cu2O6+delta (A = Sr, Ca), Pb0.7Hg0.3Sr2Cu2CO3O7 and Hg1-xCrxSr2CuO4+delta. The behaviour of the praseodymium cuprates that exhibit a rather sharp transition and reach a Tc of 85 K is especially discussed. A method to synthesize new ''Ba-Hg'' superconducting cuprates with the 1212 structure at normal pressure with a Tc up to 110 K is also presented.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 2
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“Microscopic theory of orientational disorder and lattice instability in solid C70”. Callebaut AK, Michel KH, Physical review : B : condensed matter and materials physics 52, 15279 (1995). http://doi.org/10.1103/PhysRevB.52.15279
Abstract: We have developed a microscopic theory which describes the orientational dynamics of C-70 molecules and its coupling to lattice displacements in the face-centered-cubic phase of C-70 fullerite. The single-molecule orientational density distribution in the disordered phase is calculated. The ferroelastic transition to the rhombohedral phase is investigated. The discontinuity of the orientational order parameter at the phase transition is calculated. It is found that the transition leads to a stretching of the primitive unit cell along a [111] cubic direction. A softening of the elastic constant c(44) at the transition is predicted.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.736
Times cited: 20
DOI: 10.1103/PhysRevB.52.15279
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“Microstructure of artificial [100] 45 degrees twist grain boundaries in YBa2Cu3O7-delta”. Verbist K, Tafuri F, Granozio FM, Di Chiara S, Van Tendeloo G, Electron Microscopy 1998, Vol 2: Materials Science 1 , 593 (1998)
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
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“Reduced dimensionality in different forms of carbon”. Van Tendeloo G, Bernaerts D, Amelinckx S, Fullerenes and carbon based materials , 487 (1998)
Abstract: Several TEM techniques are used to characterise the local structure of low dimensional forms of carbon. HREM is particularly useful to describe the defect structure of thin films of diamond or fullerenes and C-60-C-70 nanoclusters. A columnar form of graphite is analysed, mainly by electron diffraction which allowed us to propose a growth mechanism. Diffraction contrast dark field microscopy, in combination with electron diffraction, allows a detailed characterisation of carbon nanotubes; e.g. the chirality distribution of tubes in ropes of single wall tubes is studied by selected area electron diffraction. (C) 1998 Elsevier Science Ltd. All rights reserved.
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
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“Crystal structure of Bi6Sr8-xCa3+xO22(-0.5\leq x\leq1.7): a mixed valence bismuth oxide related to perovskite”. Luhrs CC, Molins E, Van Tendeloo G, Beltran-Porter D, Fuertes A, Chemistry of materials 10, 1875 (1998). http://doi.org/10.1021/cm9800377
Abstract: The crystal structure of BiSr8-xCa3+xO22 has been determined by single-crystal X-ray diffraction. This phase is the same as Bi9Sr11Ca5Oy that was previously studied by several authors as a secondary phase in the Bi-Sr-Ca-Cu-O system and coexists in thermodynamic equilibrium with the superconductors Bi2Sr2CuO6 and Bi2Sr2CaCu2O8 It crystallizes in the monoclinic space group P2(1)/c, with cell parameters a 11.037(3) Angstrom, b = 5.971(2) Angstrom, c = 19.703(7) Angstrom, beta = 101.46(3)degrees Z = 2. The structure was solved by direct methods and full-matrix least-squares refinement. It is built up by perovskite-related blocks of composition [Sr8-xBi2Ca3+xO16] that intergrow with double rows [Bi4O6] running along b. The perovskite blocks are formed by groups of five octahedra that are shifted from each other 3/2 root 2a(p) along [110](p) (a(p) being the parameter of the cubic perovskite subcell) in a zigzag configuration and are aligned with this direction parallel to the one forming an angle of 25" with the c axis. In turn, the perovskite blocks [Sr8-xBi2Ca3+xO16] are shifted from each other 1/2 of both a(p) and root 2a(p) along [100](p) and [110](p), respectively. In the double rows, two trivalent bismuth atoms are placed, forming dimeric anion complexes [Bi2O6].(6-).6- The oxygen atoms around bismuth in these dimers are placed in the vertexes of a distorted trigonal bipyramid, with one vacant position that would be occupied by the lone pairs characteristic for the electronic configuration of Bi(III). The B sites in the perovskite blocks are occupied by pentavalent bismuth atoms and calcium atoms; the remaining Sr and Ca ions occupy the A sites of the perovskite blocks with coordination numbers with oxygen ranging from 10 to 12. The mean valence for Bi is +3.67 [33.3% of Bi(V) and 66.7% of Bi(III)]. The oxygen vacancies are located in the boundaries between domains having the two possible configurations of the perovskite subcell as in the anionic superconductor Bi3BaO5.5. The oxidation of Bi6Sr8-xCa3+xO22 at 650 degrees C allows the complete filling of the oxygen vacancies to form the double perovskite (Sr2-xCax)Bi1.4Ca0.6O6 that shows 92.5% of bismuth in +5 oxidation state. The experimental high-resolution electon microscopy image and the electron diffraction pattern of powder samples along the [010]* zone axis are in good agreement with those calculated from the structural model obtained by single-crystal X-ray diffraction. The material is almost free of defects and the occurrence of planar defects is very exceptional.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 6
DOI: 10.1021/cm9800377
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“Size mismatch : a crucial factor for generating a spin-glass insulator in manganites”. Maignan A, Martin C, Van Tendeloo G, Hervieu M, Raveau B, Physical review : B : condensed matter and materials physics 60, 15214 (1999). http://doi.org/10.1103/PhysRevB.60.15214
Abstract: Thr structural, electronic, and magnetic properties of the highly mismatched perovskite oxides, Th(0.35)A(0.65)MnO(3), where Ais for the alkaline earth divalent cations (Ca, Ba, Sr), which are all characterized by the same large tolerance factor (t=0.934), have been investigated by using electron microscopy, electrical resistivity, magnetic susceptibility, and magnetization. It is clearly established that a transition from ferromagnetic metallic towards spin-glass insulator samples is induced as the A-site cationic size mismatch is increased. Moreover, the magnetoresistance (MR) properties of these manganites are strongly reduced for the spin-glass insulators, demonstrating that the A-sire cationic disorder is detrimental for the colossal MR properties. Based on these results, a new electronic and magnetic diagram is established that shows that the A-site disorder, rather than the A-site average cationic size (or t) is the relevant factor for generating spin-glass insulating manganites. [S0163-1829(99)01746-4].
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 75
DOI: 10.1103/PhysRevB.60.15214
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“Epitaxial growth of \beta-SiC on ion-beam synthesized \beta-SiC : structural characterization”. Romano-Rodriguez A, Perez-Rodriguez A, Serre C, van Landuyt J, et al, Materials science forum
T2 –, International Conference on Silicon Carbide and Related Materials, OCT 10-15, 1999, RES TRIANGLE PK, NORTH CAROLINA 338-3, 309 (2000)
Abstract: In this work we present for the first time, to our knowledge, the CVD epitaxial growth of beta -SiC using an ion beam synthesized (IBS) beta -SiC layer as seed, which has been formed by multiple implantation into Si wafers at 500 degreesC. The ion beam synthesized continuous layer is constituted by beta -SiC nanocrystals that are well oriented relative to the silicon substrate. Comparison of the epitaxial growth on these samples with that on silicon test samples, both on and off-axis, is performed. The results show that the epitaxial growth can be achieved on the IBS samples without the need of the carbonization step and that the structural quality of the CVD layer is comparable to that obtained on a carbonized silicon sample. Improvement of the quality of the deposited layer is proposed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 2
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“Relation between structure, charge ordering and magnetotransport properties in Nd0.5Ca0.5Mn1-xCrxO3 manganites”. Schuddinck W, Van Tendeloo G, Barnabé, A, Hervieu M, Raveau B, Journal of magnetism and magnetic materials
T2 –, Symposium G Material Physics Issues and Applications of Magnetic Oxides, at the E-MRS Spring Meeting, JUN 01-04, 1999, Strasbourg, France 211, 105 (2000). http://doi.org/10.1016/S0304-8853(99)00720-9
Abstract: The relationships between incommensurability, charge ordering and magnetotransport properties in Nd0.5Ca0.5Mn1-xCrxO3 manganites have been studied by electron diffraction and lattice imaging versus temperature with 0.02 less than or equal to x less than or equal to 0.07. All compositions show an incommensurate superstructure over the whole temperature domain, despite the fact that they are ferromagnetic and conductive below 140 K, The q-vector (1/2 – delta)a* decreases with increasing temperature for all compositions x. For a given temperature q also decreases with x. Lattice images obtained at low temperature give a clear view of the characteristics of the incommensurate structure. They also provide a better understanding of the charge ordering process. The low-temperature form of the Cr-doped manganites is not a perfectly doubled cell [[2a(p)root 2 x 2a(p) x a(p)root 2]], but defects inducing a tripled cell occur pseudo-periodically. (C) 2000 Elsevier Science B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.63
Times cited: 16
DOI: 10.1016/S0304-8853(99)00720-9
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“Electron diffraction of nanotubes bundles : unique helicity and tube-tube atomically coherent packing”. Colomer J-F, Henrard L, Lambin P, Van Tendeloo G, AIP conference proceedings
T2 –, 16th International Winterschool on Electronic Properties of Novel, Materials, MAR 02-09, 2002, KIRCHBERG, AUSTRIA , 314 (2002). http://doi.org/10.1063/1.1514131
Abstract: The atomic structure of single-wall carbon nanotube bundles produced by three different techniques has been characterized by electron diffraction and microscopy. Small bundles produced by Catalytical Chemical Vapor Deposition (CCVD) exhibit only one or two tube chiralities within a single bundle while bundles produced by arc-discharge or laser-ablation exhibit more chiralities. A detailed analysis of the central line of diffraction is also presented. The CCVD nanotubes present more intense spots around 1.7 Angstrom(-1) < k < 2Angstrom(-1) (k is the momentum transfer) compared to what is observed for nanotubes produced by other methods. Amongst the possible explanation for such an anomaly, we put forward that in this range of momentum transfer, the relative tube orientations and translations are important for what concerns the interpretation of the diffraction peaks intensities.
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
DOI: 10.1063/1.1514131
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“Correlated few-particle states in artificial bipolar molecule”. Anisimovas E, Peeters FM, Physical review : B : condensed matter and materials physics 65, 233302 (2002). http://doi.org/10.1103/PhysRevB.65.233302
Abstract: We investigate the ground and excited states of a bipolar artificial molecule composed of two vertically coupled quantum dots containing different type of carriers-electrons and holes-in equilibrium. The approach based on exact diagonalization is used and reveals an intricate pattern of ground-state angular momentum switching and a rearrangement of approximate single-particle levels as a function of the interdot coupling strength.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 14
DOI: 10.1103/PhysRevB.65.233302
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“Stationary-phase slip state in quasi-one-dimensional rings”. Vodolazov DY, Baelus BJ, Peeters FM, Physical review : B : condensed matter and materials physics 66, 054531 (2002). http://doi.org/10.1103/PhysRevB.66.054531
Abstract: The nonuniform superconducting state in a ring in which the order parameter vanishing at one point is studied. This state is characterized by a jump of the phase by pi at the point where the order parameter becomes zero. In uniform rings such a state is a saddle-point state and consequently unstable. However, for nonuniform rings with, e.g., variations of geometrical or physical parameters or with attached wires this state can be stabilized and may be realized experimentally.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 29
DOI: 10.1103/PhysRevB.66.054531
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“Orientational charge density waves and the metal-insulator transition in polymerized KC60”. Verberck B, Nikolaev AV, Michel KH, Physical review : B : condensed matter and materials physics 71, 165117 (2005). http://doi.org/10.1103/PhysRevB.71.165117
Abstract: A theoretical model is presented for the description of the metal-insulator transition which accompanies the structural phase transition at T approximate to 50 K in polymerized KC60. The model involves orientational charge density waves (along the C-60 polymer chains) which were introduced previously for a description of the structural phase transition. A satisfactory qualitative and quantitative understanding is obtained when the three-dimensionality of the crystal and the presence of the K+ counterions is properly taken into account.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 1
DOI: 10.1103/PhysRevB.71.165117
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“Spin-dependent tunneling in diluted magnetic semiconductor trilayer structures”. Krstajic P, Peeters FM, Physical review : B : condensed matter and materials physics 72, 125350 (2005). http://doi.org/10.1103/PhysRevB.72.125350
Abstract: Tunneling of holes through a trilayer structure made of two diluted magnetic semiconductors, (Ga,Mn)As, separated by a thin layer of nonmagnetic AlAs is investigated. The problem is treated within the 6x6 Luttinger-Kohn model for valence bands with the split-off band included. The influence of the spin-orbit coupling is pronounced as the spin-splitting Delta(ex) is comparable with the split-off Delta(SO) splitting. It is assumed that direct tunneling is the dominant mechanism due to the high quality of the tunnel junctions. Our theoretical results predict the correct order of magnitude for the tunneling magnetoresistance ratio, but various other effects, such as scattering on impurities and defects, should be included in order to realize a quantitative agreement with experiment.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 8
DOI: 10.1103/PhysRevB.72.125350
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“Generalized Galitskii approach for the vertex function of a Fermi gas with resonant interaction”. Vagov A, Schomerus H, Shanenko A, Physical review : B : condensed matter and materials physics 76, 214513 (2007). http://doi.org/10.1103/PhysRevB.76.214513
Abstract: We present a generalized Galitskii approach for the Bethe-Salpeter equation for the two-particle vertex function of a Fermi system with the resonant interaction by accounting for the resonant state in the scattering potential and utilizing the universal form of the resonant scattering amplitude. The procedure can be carried out both for the normal as well as for the condensate state. In both cases, the vertex function in the vicinity of the resonance is shown to formally coincide with that obtained for a weakly attractive Fermi gas. Thus we justify the popular calculational framework in which results for the weakly attractive Fermi gas are formally extrapolated into the domain of strong coupling, and further to the repulsive side of the resonance, where molecular states are formed.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 8
DOI: 10.1103/PhysRevB.76.214513
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“Calculation of binary and ternary metallic immiscible clusters with icosahedral structures”. Dzhurakhalov AA, Atanasov I, Hou M, Physical review : B : condensed matter and materials physics , 115415 (2008). http://doi.org/10.1103/PHYSREVB.77.115415
Abstract: Recently, core-shell Ag-Co, Ag-Cu, and “onionlike” Cu-Co equilibrium configurations were predicted in the case of isolated face centered cubic (fcc) bimetallic clusters, and three shell onionlike configurations were predicted in the case of ternary metallic clusters with spherical and truncated octahedral morphologies. In the present paper, immiscible binary CuCo and ternary AgCuCo clusters with icosahedral structures are studied as functions of their size and composition. Clusters studied are formed by 13, 55, 147, 309, and 561 atoms corresponding to the five smallest possible closed shell icosahedral structures. An embedded atom model potential is used to describe their cohesion. Equilibrium configurations are investigated by means of Metropolis Monte Carlo free energy minimization in the (NPT) canonical ensemble. Most simulations are achieved at 10 and 300 K. The effect of temperature on segregation ordering is systematically investigated. Selected cases are used to identify the effect of size and composition on melting. In contrast with fcc clusters, homogeneous onionlike configurations of binary clusters are not predicted. When it is allowed by the composition, a complete outer shell is formed by Cu in binary Cu-Co clusters and by Ag in ternary Ag-Cu-Co clusters. Depending on temperature, Co may precipitate into decahedral groups under the Cu vertices of the icosahedra in binary clusters, while the Co-Cu configuration in ternary clusters drastically depends on the Ag coating. Despite the multicomponent character of the clusters and the immiscibility of the species forming them, for most compositions and sizes, equilibrium structures remain close to perfectly icosahedral at 10 K as well as at 300 K.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.836
Times cited: 11
DOI: 10.1103/PHYSREVB.77.115415
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“In situ transmission electron microscopy study of the silicidation process in Co thin films on patterned (001) Si substrates”. Ghica C, Nistor L, Bender H, Steegen A, Lauwers A, Maex K, van Landuyt J, Journal of materials research 16, 701 (2001). http://doi.org/10.1557/JMR.2001.0121
Abstract: The results of an in situ transmission electron microscopy study of the formation of Co-silicides on patterned (001) Si substrates are discussed. It is shown that the results of the in situ heating experiments agreed very well with the data based on standard rapid thermal annealing experiments. Fast heating rates resulted in better definition of the silicide lines. Also, better lines were obtained for samples that received already a low-temperature ex situ anneal. A Ti cap layer gave rise to a higher degree of epitaxy in the CoSi2 silicide.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.673
Times cited: 4
DOI: 10.1557/JMR.2001.0121
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“Molecular terms and optical transitions of C60n+/- molecular ions”. Nikolaev AV, Michel KH, AIP conference proceedings
T2 –, 16th International Winterschool on Electronic Properties of Novel, Materials, MAR 02-09, 2002, KIRCHBERG, AUSTRIA , 417 (2002)
Abstract: We have studied the molecular energy terms of the hole configurations (h(u)(+))(m), m=2,3,4,5 of C-60(m+) cations and the electronic configurations (t(1u))(n) n=2,3,4, as well as (t(1u))(n-1)t(1g) of the C-60(n-) anions. The lowest terms (within an energy span of 0.03 eV) for C-60(2+) are three triplets T-3(1g), (3)G(g), T-3(2g) and for C-60(3+) are three quartets T-4(1u), (4)G(u), T-4(2u), which favor Jahn-Teller distortions. For the ground state of C-60(2-) we find a triplet T-3(1g) in agreement with Hund's rules. Our method takes into account intramolecular direct and exchange multipolar Coulomb interactions.
Keywords: P1 Proceeding; Condensed Matter Theory (CMT)
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“Superconducting properties of mesoscopic cylinders with enhanced surface superconductivity”. Baelus BJ, Yampolskii SV, Peeters FM, Montevecchi E, Indekeu JO, Physical review : B : condensed matter and materials physics 65, 024510 (2002). http://doi.org/10.1103/PhysRevB.65.024510
Abstract: The superconducting state of an infinitely long superconducting cylinder surrounded by a medium which enhances its superconductivity near the boundary is studied within the nonlinear Ginzburg-Landau theory. This enhancement can be due to the proximity of another superconductor or due to surface treatment. Quantities such as the free energy, the magnetization and the Cooper-pair density are calculated. Phase diagrams are obtained to investigate how the critical field and the critical temperature depend on this surface enhancement for different values of the Ginzburg-Landau parameter kappa. Increasing the superconductivity near the surface leads to higher critical fields and critical temperatures. For small cylinder diameters only giant vortex states nucleate, while for larger cylinders multivortices can nucleate. The stability of these multivortex states also depends on the surface enhancement. For type-I superconductors we found the remarkable result that for a range of values of the surface extrapolation length the superconductor can transit from the Meissner state into superconducting states with vorticity L > 1. Such a behavior is not found for the case of large kappa, i.e., type-II superconductivity,
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 13
DOI: 10.1103/PhysRevB.65.024510
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“Phase transition and magnetic anisotropy of (La,Sr)MnO3 thin films”. Wang Z-H, Kronmüller H, Lebedev OI, Gross GM, Razavi FS, Habermeier HU, Shen BG, Physical review : B : condensed matter and materials physics 65, 054411 (2002). http://doi.org/10.1103/PhysRevB.65.054411
Abstract: The magnetic proper-ties and their correlation with the microstructure and electrical transport are investigated in La0.88Sr0.1MnO3 films grown on (100)SrTiO3 Single crystal substrates with thickness ranging from 100 to 2500 Angstrom. The ultrathin film (t = 100 Angstrom) has a single ferromagnetic transition (FMT) at T-c of 250 K, whereas the thicker films exhibit two FMTs, with the main one at a lowered T-c of 200 K while the minor one around 300 K. Furthermore, a thickness dependent magnetic anisotropy has been found, strongly indicating the existence of strain effect, which is also revealed by the transmission electron microscopy study. The suppressed Jahn-Teller distortion (JTD) by the epitaxial strain, and the recovered JTD due to the strain relexation are suggested to explain the metallic behavior in thin films and the insulating behavior in the thick film (t = 2500 Angstrom), repectively.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 23
DOI: 10.1103/PhysRevB.65.054411
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“Dislocations in diamond : dissociation into partials and their glide motion”. Blumenau AT, Jones R, Frauenheim T, Willems B, Lebedev OI, Van Tendeloo G, Fisher D, Martineau PM, Physical review : B : condensed matter and materials physics 68, 014115 (2003). http://doi.org/10.1103/PhysRevB.68.014115
Abstract: The dissociation of 60degrees and screw dislocations in diamond is modeled in an approach combining isotropic elasticity theory with ab initio-based tight-binding total-energy calculations. Both dislocations are found to dissociate with a substantial lowering of their line energies. For the 60degrees dislocation, however, an energy barrier to dissociation is found. We investigate the core structure of a screw dislocation distinguishing “shuffle,” “mixed,” and “glide” cores. The latter is found to be the most stable undissociated screw dislocation. Further, the glide motion of 90degrees and 30degrees partials is discussed in terms of a process involving the thermal formation and subsequent migration of kinks along the dislocation line. The calculated activation barriers to dislocation motion show that the 30degrees partial is less mobile than the 90degrees partial. Finally, high-resolution electron microscopy is performed on high-temperature, high-pressure annealed natural brown diamond, allowing the core regions of 60degrees dislocations to be imaged. The majority of dislocations are found to be dissociated. However, in some cases, undissociated 60degrees dislocations were also observed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 39
DOI: 10.1103/PhysRevB.68.014115
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“Ab initio approach to superexchange interactions in alkali doped fullerides AC60”. Nikolaev AV, Michel KH, AIP conference proceedings
T2 –, 18th International Winterschool/Euroconference on Electronic Properties, of Novel Materials, MAR 06-JUN 13, 2004, Kirchberg, AUSTRIA , 393 (2004). http://doi.org/10.1063/1.1812115
Abstract: The superexchange interactions between the fullerenes arise as a result of the electron transfer from the C-60 molecule to the alkali atom and back. We present a scheme, which is a configuration interaction approach based on the valence bond (Heitler-London) method. The effect of superexchange is described together with chemical bonding by constructing and solving a secular equation, rather than by using a perturbation treatment. We have considered 180degrees and 90degrees superexchange for the C-60 Cs-C-60 pathways. The calculations account for unusual electronic properties of polymer orthorhombic and quenched cubic phases of CsC60: two lines in nuclear magnetic resonance experiments, the development of a spin-singlet ground state and a decrease of magnetic susceptibility as T-->0.
Keywords: P1 Proceeding; Condensed Matter Theory (CMT)
DOI: 10.1063/1.1812115
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“Preparation of nanocrystalline titania powder via aerosol pyrolysis of titanium tetrabutoxide”. Ahonen PP, Kauppinen EI, Joubert JC, Deschanvres JL, Van Tendeloo G, Journal of materials research 14, 3938 (1999). http://doi.org/10.1557/JMR.1999.0533
Abstract: Nanocrystalline titanium dioxide was prepared via aerosol pyrolysis of titanium alkoxide precursor at 200-580 degrees C in air and in nitrogen atmospheres. Powders were characterized by x-ray diffraction, thermogravimetric analysis, Brunauer-Emmett-Teller analysis, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, x-ray fluorescence, Raman and infrared spectroscopy, and Berner-type low-pressure impactor. The anatase phase transition was initiated at 500 degrees C in nitrogen and at 580 degrees C in air. Under other conditions amorphous powders were observed and transformed to nanocrystalline TiO2 via thermal postannealing. In air, smooth and spherical particles with 2-4-mu m diameter were formed with an as-expected tendency to convert to rutile in the thermal postannealings. In nitrogen, a fraction of the titanium tetrabutoxide precursor evaporated and formed ultrafine particles via the gas-to-particle conversion. At 500 degrees C thermally stable anatase phase was formed in nitrogen. A specific surface area as high as 280 m(2) g(-1) was observed for an as-prepared powder.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.673
Times cited: 38
DOI: 10.1557/JMR.1999.0533
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