“Significant effect of stacking on the electronic and optical properties of few-layer black phosphorus”. Çakir D, Sevik C, Peeters FM, Physical review : B : condensed matter and materials physics 92, 165406 (2015). http://doi.org/10.1103/PhysRevB.92.165406
Abstract: The effect of the number of stacking layers and the type of stacking on the electronic and optical properties of bilayer and trilayer black phosphorus are investigated by using first-principles calculations within the framework of density functional theory. We find that inclusion of many-body effects (i.e., electron-electron and electron-hole interactions) modifies strongly both the electronic and optical properties of black phosphorus. While trilayer black phosphorus with a particular stacking type is found to be a metal by using semilocal functionals, it is predicted to have an electronic band gap of 0.82 eV when many-body effects are taken into account within the G(0)W(0) scheme. Though different stacking types result in similar energetics, the size of the band gap and the optical response of bilayer and trilayer phosphorene are very sensitive to the number of layers and the stacking type. Regardless of the number of layers and the type of stacking, bilayer and trilayer black phosphorus are direct band gap semiconductors whose band gaps vary within a range of 0.3 eV. Stacking arrangements that are different from the ground state structure in both bilayer and trilayer black phosphorus exhibit significant modified valence bands along the zigzag direction and result in larger hole effective masses. The optical gap of bilayer (trilayer) black phosphorus varies by 0.4 (0.6) eV when changing the stacking type. The calculated binding energy of the bound exciton hardly changes with the type of stacking and is found to be 0.44 (0.30) eV for bilayer (trilayer) phosphorous.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 127
DOI: 10.1103/PhysRevB.92.165406
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“Spin- and valley-dependent transport through arrays of ferromagnetic silicene junctions”. Missault N, Vasilopoulos P, Vargiamidis V, Peeters FM, Van Duppen B, Physical review : B : condensed matter and materials physics 92, 195423 (2015). http://doi.org/10.1103/PhysRevB.92.195423
Abstract: We study ballistic transport of Dirac fermions in silicene through arrays of barriers, of width d, in the presence of an exchange field M and a tunable potential of height U or depth-U. The spin-and valley-resolved conductances as functions of U or M, exhibit resonances away from the Dirac point (DP) and close to it a pronounced dip that becomes a gap when a critical electric field E-z is applied. This gap widens by increasing the number of barriers and can be used to realize electric field-controlled switching of the current. The spin p(s) and valley p(v) polarizations of the current near the DP increase with Ez or M and can reach 100% for certain of their values. These field ranges widen significantly by increasing the number of barriers. Also, ps and pv oscillate nearly periodically with the separation between barriers or wells and can be inverted by reversing M.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 54
DOI: 10.1103/PhysRevB.92.195423
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“Structural and phononic characteristics of nitrogenated holey graphene”. Sahin H, Physical review : B : condensed matter and materials physics 92, 085421 (2015). http://doi.org/10.1103/PhysRevB.92.085421
Abstract: Recent experimental studies showed that formation of a two-dimensional crystal structure of nitrogenated holey graphene (NHG) is possible. Similar to graphene, NHGs have an atomically thin and strong crystal structure. Using first-principles calculations, we investigate the structural, phononic, and thermal properties of monolayer NHG crystal. Our charge analysis reveals that the charged holey sites of NHG provide a reactive ground for further functionalization by adatoms or molecules. We also found that similar to graphene, the NHG structure has quite high-frequency phonon modes and the presence of nitrogen atoms leads to the emergence of additional vibrational modes. Our phonon analysis reveals the presence of three characteristic Raman-active modes of NHG. Furthermore, the analysis of constant-volume heat capacity showed that the NHG structure has a linear temperature dependence in the low-temperature region. The strong lattice structure and unique thermal properties of the NHG crystal structure are desirable in nanoscale device applications.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 49
DOI: 10.1103/PhysRevB.92.085421
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“TiS3 nanoribbons : width-independent band gap and strain-tunable electronic properties”. Kang J, Sahin H, Ozaydin HD, Senger RT, Peeters FM, Physical review : B : condensed matter and materials physics 92, 075413 (2015). http://doi.org/10.1103/PhysRevB.92.075413
Abstract: The electronic properties, carrier mobility, and strain response of TiS3 nanoribbons (TiS3 NRs) are investigated by first-principles calculations. We found that the electronic properties of TiS3 NRs strongly depend on the edge type (a or b). All a-TiS3 NRs are metallic with a magnetic ground state, while b-TiS3 NRs are direct band gap semiconductors. Interestingly, the size of the band gap and the band edge position are almost independent of the ribbon width. This feature promises a constant band gap in a b-TiS3 NR with rough edges, where the ribbon width differs in different regions. The maximum carrier mobility of b-TiS3 NRs is calculated by using the deformation potential theory combined with the effective mass approximation and is found to be of the order 10(3) cm(2) V-1 s(-1). The hole mobility of the b-TiS3 NRs is one order of magnitude lower, but it is enhanced compared to the monolayer case due to the reduction in hole effective mass. The band gap and the band edge position of b-TiS3 NRs are quite sensitive to applied strain. In addition we investigate the termination of ribbon edges by hydrogen atoms. Upon edge passivation, the metallic and magnetic features of a-TiS3 NRs remain unchanged, while the band gap of b-TiS3 NRs is increased significantly. The robust metallic and ferromagnetic nature of a-TiS3 NRs is an essential feature for spintronic device applications. The direct, width-independent, and strain-tunable band gap, as well as the high carrier mobility, of b-TiS3 NRs is of potential importance in many fields of nanoelectronics, such as field-effect devices, optoelectronic applications, and strain sensors.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 55
DOI: 10.1103/PhysRevB.92.075413
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“Theory of anharmonic phonons in two-dimensional crystals”. Michel KH, Costamagna, Peeters FM, Physical review : B : condensed matter and materials physics 91, 134302 (2015). http://doi.org/10.1103/PhysRevB.91.134302
Abstract: Anharmonic effects in an atomic monolayer thin crystal with honeycomb lattice structure are investigated by analytical and numerical lattice dynamical methods. Starting from a semiempirical model for anharmonic couplings of third and fourth orders, we study the in-plane and out-of-plane (flexural) mode components of the generalized wave vector dependent Gruneisen parameters, the thermal tension and the thermal expansion coefficients as a function of temperature and crystal size. From the resonances of the displacement-displacement correlation functions, we obtain the renormalization and decay rate of in-plane and flexural phonons as a function of temperature, wave vector, and crystal size in the classical and in the quantum regime. Quantitative results are presented for graphene. There, we find that the transition temperature T-alpha from negative to positive thermal expansion is lowered with smaller system size. Renormalization of the flexural mode has the opposite effect and leads to values of T-alpha approximate to 300 K for systems of macroscopic size. Extensive numerical analysis throughout the Brillouin zone explores various decay and scattering channels. The relative importance of normal and umklapp processes is investigated. The work is complementary to crystalline membrane theory and computational studies of anharmonic effects in two-dimensional crystals.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 38
DOI: 10.1103/PhysRevB.91.134302
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“Tuning the magnetic anisotropy in single-layer crystal structures”. Torun E, Sahin H, Bacaksiz C, Senger RT, Peeters FM, Physical review : B : condensed matter and materials physics 92, 104407 (2015). http://doi.org/10.1103/PhysRevB.92.104407
Abstract: The effect of an applied electric field and the effect of charging are investigated on themagnetic anisotropy (MA) of various stable two-dimensional (2D) crystals such as graphene, FeCl2, graphone, fluorographene, and MoTe2 using first-principles calculations. We found that themagnetocrystalline anisotropy energy of Co-on-graphene and Os-doped-MoTe2 systems change linearly with electric field, opening the possibility of electric field tuningMAof these compounds. In addition, charging can rotate the easy-axis direction ofCo-on-graphene andOs-doped-MoTe2 systems from the out-of-plane (in-plane) to in-plane (out-of-plane) direction. The tunable MA of the studied materials is crucial for nanoscale electronic technologies such as data storage and spintronics devices. Our results show that controlling the MA of the mentioned 2D crystal structures can be realized in various ways, and this can lead to the emergence of a wide range of potential applications where the tuning and switching of magnetic functionalities are important.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 37
DOI: 10.1103/PhysRevB.92.104407
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“Two-shell vortex and antivortex dynamics in a Corbino superconducting disk”. Cabral LRE, de Aquino BRCHT, de Souza Silva CC, Milošević, MV, Peeters FM, Physical review : B : condensed matter and materials physics 93, 014515 (2016). http://doi.org/10.1103/PhysRevB.93.014515
Abstract: We examine theoretically the dynamics of two vortex shells in pinning-free superconducting thin disks in the Corbino geometry. In the first considered case, the inner shell is composed of vortices and the outer one of antivortices, corresponding to a state induced by the stray field of an off-plane magnetic dipole placed on top of the superconductor. In the second considered case, both shells comprise vortices induced by a homogeneous external field. We derive the equation of motion for each shell within the Bardeen-Stephen model and study the dynamics analytically by assuming both shells are rigid and commensurate. In both cases, two distinct regimes for vortex shell motion are identified: For low applied currents the entire configuration rotates rigidly, while above a threshold current the shells decouple from each other and rotate at different angular velocities. Analytical expressions for the decoupling current, the recombination time in the decoupled phases, as well as the voltage-current characteristics are presented. Our analytical results are in excellent agreement with numerical molecular dynamics simulations of the full many-vortex problem.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 7
DOI: 10.1103/PhysRevB.93.014515
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“Depth strain profile with sub-nm resolution in a thin silicon film using medium energy ion scattering”. Jalabert D, Pelloux-Gervais D, Béché, A, Hartmann JM, Gergaud P, Rouvière JL, Canut B, Physica Status Solidi A-Applications And Materials Science 209, 265 (2012). http://doi.org/10.1002/PSSA.201127502
Abstract: The depth strain profile in silicon from the Si (001) substrate to the surface of a 2 nm thick Si/12 nm thick SiGe/bulk Si heterostructure has been determined by medium energy ion scattering (MEIS). It shows with sub-nanometer resolution and high strain sensitivity that the thin Si cap presents residual compressive strain caused by Ge diffusion coming from the fully strained SiGe layer underneath. The strain state of the SiGe buffer have been checked by X-ray diffraction (XRD) and nano-beam electron diffraction (NBED) measurements.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.775
Times cited: 3
DOI: 10.1002/PSSA.201127502
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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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“From spin-polarized interfaces to giant magnetoresistance in organic spin valves”. Çakir D, Otalvaro DM, Brocks G, Physical review : B : condensed matter and materials physics 89, 115407 (2014). http://doi.org/10.1103/PHYSREVB.89.115407
Abstract: We calculate the spin-polarized electronic transport through a molecular bilayer spin valve from first principles, and establish the link between the magnetoresistance and the spin-dependent interactions at the metal-molecule interfaces. The magnetoresistance of a Fe vertical bar bilayer-C-70 vertical bar Fe spin valve attains a high value of 70% in the linearresponse regime, but it drops sharply as a function of the applied bias. The current polarization has a value of 80% in linear response and also decreases as a function of bias. Both these trends can be modeled in terms of prominent spin-dependent Fe vertical bar C-70 interface states close to the Fermi level, unfolding the potential of spinterface science to control and optimize spin currents.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 14
DOI: 10.1103/PHYSREVB.89.115407
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“Vortex states in mesoscopic three-band superconductors”. Gillis S, Jaykka J, Milošević, MV, Physical review : B : condensed matter and materials physics 89, 024512 (2014). http://doi.org/10.1103/PHYSREVB.89.024512
Abstract: Using multicomponent Ginzburg-Landau simulations, we show a plethora of vortex states possible in mesoscopic three-band superconductors. We find that mesoscopic confinement stabilizes chiral states, with nontrivial phase differences between the band condensates, as the ground state of the system. As a consequence, we report the broken-symmetry vortex states, the chiral states where vortex cores in different band condensates do not coincide (split-core vortices), as well as fractional-flux vortex states with broken time-reversal symmetry.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 26
DOI: 10.1103/PHYSREVB.89.024512
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Sankaran KJ, Hoang DQ, Srinivasu K, Korneychuk S, Turner S, Drijkoningen S, Pobedinskas P, Verbeeck J, Leou KC, Lin IN, Haenen K, Physica status solidi : A : applications and materials science 213, 2654 (2016). http://doi.org/10.1002/PSSA.201600233
Abstract: Utilization of Au and nanocrystalline diamond ( NCD) as interlayers noticeably modifies the microstructure and field electron emission ( FEE) properties of hexagonal boron nitride nanowalls ( hBNNWs) grown on Si substrates. The FEE properties of hBNNWs on Au could be turned on at a low turn-on field of 14.3V mu m(-1), attaining FEE current density of 2.58mAcm(-2) and life-time stability of 105 min. Transmission electron microscopy reveals that the Au-interlayer nucleates the hBN directly, preventing the formation of amorphous boron nitride ( aBN) in the interface, resulting in enhanced FEE properties. But Au forms as droplets on the Si substrate forming again aBN at the interface. Conversely, hBNNWs on NCD shows superior in life-time stability of 287 min although it possesses inferior FEE properties in terms of larger turn-on field and lower FEE current density as compared to that of hBNNWs-Au. The uniform and continuous NCD film on Si also circumvents the formation of aBN phases and allows hBN to grow directly on NCD. Incorporation of carbon in hBNNWs from the NCD-interlayer improves the conductivity of hBNNWs, which assists in transporting the electrons efficiently from NCD to hBNNWs that results in better field emission of electrons with high life-time stability. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.775
Times cited: 5
DOI: 10.1002/PSSA.201600233
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“Oxygen vacancies effects in a-IGZO : formation mechanisms, hysteresis, and negative bias stress effects”. de de Meux AJ, Bhoolokam A, Pourtois G, Genoe J, Heremans P, Physica status solidi : A : applications and materials science 214, 1600889 (2017). http://doi.org/10.1002/PSSA.201600889
Abstract: The amorphous oxide semiconductor Indium-Gallium-Zinc-Oxide (a-IGZO) has gained a large technological relevance as a semiconductor for thin-film transistors in active-matrix displays. Yet, major questions remain unanswered regarding the atomic origin of threshold voltage control, doping level, hysteresis, negative bias stress (NBS), and negative bias illumination stress (NBIS). We undertake a systematic study of the effects of oxygen vacancies on the properties of a-IGZO by relating experimental observations to microscopic insights gained from first-principle simulations. It is found that the amorphous nature of the semiconductor allows unusually large atomic relaxations. In some cases, oxygen vacancies are found to behave as perfect shallow donors without the formation of structural defects. Once structural defects are formed, their transition states can vary upon charge and discharge cycles. We associate this phenomenon to a possible presence of hysteresis in the transfer curve of the devices. Under NBS, the creation of oxygen vacancies becomes energetically very stable, hence thermodynamically very likely. This generation process is correlated with the occurrence of the negative bias stress instabilities observed in a-IGZO transistors. While oxygen vacancies can therefore be related to NBS and hysteresis, it appears unlikely from our results that they are direct causes of NBIS, contrary to common belief.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 1.775
Times cited: 8
DOI: 10.1002/PSSA.201600889
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“Surface passivation of CIGS solar cells using gallium oxide”. Garud S, Gampa N, Allen TG, Kotipalli R, Flandre D, Batuk M, Hadermann J, Meuris M, Poortmans J, Smets A, Vermang B, Physica status solidi : A : applications and materials science 215, 1700826 (2018). http://doi.org/10.1002/PSSA.201700826
Abstract: This work proposes gallium oxide grown by plasma-enhanced atomic layer deposition, as a surface passivation material at the CdS buffer interface of Cu(In,Ga)Se-2 (CIGS) solar cells. In preliminary experiments, a metal-insulator-semiconductor (MIS) structure is used to compare aluminium oxide, gallium oxide, and hafnium oxide as passivation layers at the CIGS-CdS interface. The findings suggest that gallium oxide on CIGS may show a density of positive charges and qualitatively, the least interface trap density. Subsequent solar cell results with an estimated 0.5nm passivation layer show an substantial absolute improvement of 56mV in open-circuit voltage (V-OC), 1mAcm(-2) in short-circuit current density (J(SC)), and 2.6% in overall efficiency as compared to a reference (with the reference showing 8.5% under AM 1.5G).
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.775
Times cited: 8
DOI: 10.1002/PSSA.201700826
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“Introducton to the special issue on electron crystallography”. Hadermann J, Palatinus L, And Materials 75, 462 (2019). http://doi.org/10.1107/S2052520619010783
Keywords: Editorial; Electron microscopy for materials research (EMAT)
Times cited: 2
DOI: 10.1107/S2052520619010783
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“Structure solution and refinement of metal-ion battery cathode materials using electron diffraction tomography”. Hadermann J, Abakumov AM, And Materials 75, 485 (2019). http://doi.org/10.1107/S2052520619008291
Abstract: The applicability of electron diffraction tomography to the structure solution and refinement of charged, discharged or cycled metal-ion battery positive electrode (cathode) materials is discussed in detail. As these materials are often only available in very small amounts as powders, the possibility of obtaining single-crystal data using electron diffraction tomography (EDT) provides unique access to crucial information complementary to X-ray diffraction, neutron diffraction and high-resolution transmission electron microscopy techniques. Using several examples, the ability of EDT to be used to detect lithium and refine its atomic position and occupancy, to solve the structure of materials ex situ at different states of charge and to obtain in situ data on structural changes occurring upon electrochemical cycling in liquid electrolyte is discussed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 2
DOI: 10.1107/S2052520619008291
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“Enhanced transmission versus localization of a light pulse by a subwavelength metal slit”. Kukhlevsky SV, Mechler M, Csapo L, Janssens K, Samek O, Physical review : B : condensed matter and materials physics 70, 195428 (2004). http://doi.org/10.1103/PHYSREVB.70.195428
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.836
Times cited: 17
DOI: 10.1103/PHYSREVB.70.195428
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“Resonant backward scattering of light by a subwavelength metallic slit with two open sides”. Kukhlevsky SV, Mechler M, Csapó, L, Janssens K, Samek O, Physical review : B : condensed matter and materials physics 72, 165421 (2005). http://doi.org/10.1103/PHYSREVB.72.165421
Abstract: The backward scattering of TM-polarized light by a two-side-open subwavelength slit in a metal film is analyzed. We show that the reflection coefficient versus wavelength possesses a Fabry-Perot-like dependence that is similar to the anomalous behavior of transmission reported in the study [Y. Takakura, Phys. Rev. Lett. 86, 5601 (2001)]. The open slit totally reflects the light at the near-to-resonance wavelengths. In addition, we show that the interference of incident and resonantly backward-scattered light produces in the near-field diffraction zone a spatially localized wave whose intensity is 10103 times greater than the incident wave, but one order of magnitude smaller than the intracavity intensity. The amplitude and phase of the resonant wave at the slit entrance and exit are different from that of a Fabry-Perot cavity.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 3.836
Times cited: 7
DOI: 10.1103/PHYSREVB.72.165421
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“Precipitation behaviors in Ti-2.3 Wt Pct Cu alloy during isothermal and two-step aging”. Akamine H, Mitsuhara M, Nishida M, Samaee V, Schryvers D, Tsukamoto G, Kunieda T, Fujii H, Metallurgical And Materials Transactions A-Physical Metallurgy And Materials Science 52, 2760 (2021). http://doi.org/10.1007/S11661-021-06265-X
Abstract: Time evolution of precipitates related to age-hardening in Ti-2.3 wt pct Cu alloys was investigated by electron microscopy. In isothermal aging at 723 K, the hardness increases continuously owing to precipitation strengthening, whereas in two-step aging where the aging temperature is switched from 673 K to 873 K after 100 hours, the hardness is found to drastically drop after the aging temperature switches. In isothermal aging, metastable and stable precipitates are independently nucleated, whereas characteristic V-shaped clusters of precipitates are observed during the two-step aging. It is revealed by atomic-scale observations that the V-shaped clusters are composed of metastable and stable precipitates and each type of precipitate has a different orientation relationship with the alpha phase: (10 (3) over bar)//(0001)(alpha) and [0 (1) over bar0]//respectively. The drop in hardness during two-step aging can be explained by a synergistic effect of decreased precipitation strengthening and solid solution strengthening. (C) The Minerals, Metals & Materials Society and ASM International 2021
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 1.874
DOI: 10.1007/S11661-021-06265-X
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“Polytypism in mcalpineite : a study of natural and synthetic Cu₃TeO₆”. Missen OP, Mills SJ, Canossa S, Hadermann J, Nenert G, Weil M, Libowitzky E, Housley RM, Artner W, Kampf AR, Rumsey MS, Spratt J, Momma K, Dunstan MA, Acta Crystallographica. Section B: Structural Science, Crystal Engineering and Materials (Online) 78 (2022). http://doi.org/10.1107/S2052520621013032
Abstract: Synthetic and naturally occurring forms of tricopper orthotellurate, (Cu3TeO6)-Te-II-O-IV (the mineral mcalpineite) have been investigated by 3D electron diffraction (3D ED), X-ray powder diffraction (XRPD), Raman and infrared (IR) spectroscopic measurements. As a result of the diffraction analyses, (Cu3TeO6)-Te-II-O-IV is shown to occur in two polytypes. The higher-symmetric (Cu3TeO6)-Te-II-O-IV-1C polytype is cubic, space group 1a (3) over bar, with a = 9.537 (1) angstrom and V = 867.4 (3) angstrom(3) as reported in previous studies. The 1C polytype is a well characterized structure consisting of alternating layers of (CuO6)-O-II octahedra and both (CuO6)-O-II and (TeO6)-O-VI octahedra in a patchwork arrangement. The structure of the lower-symmetric orthorhombic (Cu3TeO6)-Te-II-O-IV-2O polytype was determined for the first time in this study by 3D ED and verified by Rietveld refinement. The 2O polytype crystallizes in space group Pcca, with a = 9.745 (3) angstrom, b = 9.749 (2) angstrom, c = 9.771 (2) angstrom and V = 928.3 (4) angstrom(3) . High-precision XRPD data were also collected on (Cu3TeO6)-Te-II-O-IV-2O to verify the lower-symmetric structure by performing a Rietveld refinement. The resultant structure is identical to that determined by 3D ED, with unit-cell parameters a = 9.56157 (19) angstrom, b = 9.55853 (11) angstrom, c = 9.62891 (15) angstrom and V = 880.03 (2) angstrom(3) . The lower symmetry of the 2O polytype is a consequence of a different cation ordering arrangement, which involves the movement of every second (CuO6)-O-II and (TeO6)-O-VI octahedral layer by (1/4, 1/4, 0), leading to an offset of (TeO6)-O-VI and (CuO6)-O-II octahedra in every second layer giving an ABAB* stacking arrangement. Syntheses of (Cu3TeO6)-Te-II-O-IV showed that low-temperature (473 K) hydrothermal conditions generally produce the 2O polytype. XRPD measurements in combination with Raman spectroscopic analysis showed that most natural mcalpineite is the orthorhombic 2O polytype. Both XRPD and Raman spectroscopy measurements may be used to differentiate between the two polytypes of (Cu3TeO6)-Te-II-O-IV. In Raman spectroscopy, (Cu3TeO6)-Te-II-O-IV-1C has a single strong band around 730 cm(-1), whereas (Cu3TeO6)-Te-II-O-IV-2O shows a broad double maximum with bands centred around 692 and 742 cm(-1).
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.9
DOI: 10.1107/S2052520621013032
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“On amorphization as a deformation mechanism under high stresses”. Idrissi H, Carrez P, Cordier P, Current opinion in solid state and materials science 26, 100976 (2022). http://doi.org/10.1016/J.COSSMS.2021.100976
Abstract: In this paper we review the work related to amorphization under mechanical stress. Beyond pressure, we highlight the role of deviatoric or shear stresses. We show that the most recent works make amorphization appear as a deformation mechanism in its own right, in particular under extreme conditions (shocks, deformations under high stresses, high strain-rates).
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 11
DOI: 10.1016/J.COSSMS.2021.100976
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“0 and &pi, phase Josephson coupling through an insulating barrier with magnetic impurities”. Vávra O, Gaži S, Golubović, DS, Vávra I, Dérer J, Verbeeck J, Van Tendeloo G, Moshchalkov VV, Physical review : B : condensed matter and materials physics 74, 020502 (2006). http://doi.org/10.1103/PhysRevB.74.020502
Abstract: We have studied the temperature and field dependencies of the critical current I(C) in the Nb-Fe(0.1)Si(0.9)-Nb Josephson junction with a tunneling barrier formed by a paramagnetic insulator. We demonstrate that in these junctions coexistence of both the 0 and the pi states within one tunnel junction occurs, and leads to the appearance of a sharp cusp in the temperature dependence I(C)(T), similar to the I(C)(T) cusp found for the 0-pi transition in metallic pi junctions. This cusp is not related to the 0-pi temperature-induced transition itself, but is caused by the different temperature dependencies of the opposing 0 and pi supercurrents through the barrier.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 27
DOI: 10.1103/PhysRevB.74.020502
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“Grain size tuning of nanocrystalline chemical vapor deposited diamond by continuous electrical bias growth : experimental and theoretical study”. Mortet V, Zhang L, Eckert M, D'Haen J, Soltani A, Moreau M, Troadec D, Neyts E, De Jaeger JC, Verbeeck J, Bogaerts A, Van Tendeloo G, Haenen K, Wagner P, Physica status solidi : A : applications and materials science 209, 1675 (2012). http://doi.org/10.1002/pssa.201200581
Abstract: In this work, a detailed structural and spectroscopic study of nanocrystalline diamond (NCD) thin films grown by a continuous bias assisted CVD growth technique is reported. This technique allows the tuning of grain size and phase purity in the deposited material. The crystalline properties of the films are characterized by SEM, TEM, EELS, and Raman spectroscopy. A clear improvement of the crystalline structure of the nanograined diamond film is observed for low negative bias voltages, while high bias voltages lead to thin films consisting of diamond grains of only ∼10 nm nanometer in size, showing remarkable similarities with so-called ultrananocrystalline diamond. These layers arecharacterized by an increasing amount of sp2-bonded carbon content of the matrix in which the diamond grains are embedded. Classical molecular dynamics simulations support the observed experimental data, giving insight in the underlying mechanism for the observed increase in deposition rate with bias voltage. Furthermore, a high atomic concentration of hydrogen has been determined in these films. Finally, Raman scattering analyses confirm that the Raman line observed at ∼1150 cm−1 cannot be attributed to trans-poly-acetylene, which continues to be reported in literature, reassigning it to a deformation mode of CHx bonds in NCD.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 1.775
Times cited: 31
DOI: 10.1002/pssa.201200581
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“Hysteresis in mesoscopic superconducting disks: the Bean-Livingston barrier”. Deo PS, Schweigert VA, Peeters FM, Physical review : B : condensed matter and materials physics 59, 6039 (1999). http://doi.org/10.1103/PhysRevB.59.6039
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 59
DOI: 10.1103/PhysRevB.59.6039
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“Mapping electronic reconstruction at the metal-insulator interface in LaVO3/SrVO3 heterostructures”. Tan H, Egoavil R, Béché, A, Martinez GT, Van Aert S, Verbeeck J, Van Tendeloo G, Rotella H, Boullay P, Pautrat A, Prellier W, Physical review : B : condensed matter and materials physics 88, 155123 (2013). http://doi.org/10.1103/PhysRevB.88.155123
Abstract: A (LaVO3)6/(SrVO3)(3) superlattice is studied with a combination of sub-A resolved scanning transmission electron microscopy and monochromated electron energy-loss spectroscopy. The V oxidation state is mapped with atomic spatial resolution enabling us to investigate electronic reconstruction at the LaVO3/SrVO3 interfaces. Surprisingly, asymmetric charge distribution is found at adjacent chemically symmetric interfaces. The local structure is proposed and simulated with a double channeling calculation which agrees qualitatively with our experiment. We demonstrate that local strain asymmetry is the likely cause of the electronic asymmetry of the interfaces. The electronic reconstruction at the interfaces extends much further than the chemical composition, varying from 0.5 to 1.2 nm. This distance corresponds to the length of charge transfer previously found in the (LaVO3)./(SrVO3). metal/insulating and the (LaAlO3)./(SrTiO3). insulating/insulating interfaces.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 15
DOI: 10.1103/PhysRevB.88.155123
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“Mapping spin-polarized transitions with atomic resolution”. Schattschneider P, Schaffer B, Ennen I, Verbeeck J, Physical review : B : condensed matter and materials physics 85, 134422 (2012). http://doi.org/10.1103/PhysRevB.85.134422
Abstract: The coupling of angstrom-sized electron probes with spin-polarized electronic transitions shows that the inelastically scattered probe electron is in a mixed state containing electron vortices with nonzero orbital angular momentum. These electrons create an asymmetric intensity distribution in energy filtered diffraction patterns, giving access to maps of the magnetic moments with atomic resolution. A feasibility experiment shows evidence of the predicted effect. Potential applications are column-by-column maps of magnetic ordering, and the creation of angstrom-sized free electrons with orbital angular momentum by inelastic scattering in a thin ferromagnetic foil.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 41
DOI: 10.1103/PhysRevB.85.134422
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“Mixed pairing symmetries and flux-induced spin current in mesoscopic superconducting loops with spin correlations”. Zha G-Q, Covaci L, Peeters FM, Zhou S-P, Physical review : B : condensed matter and materials physics 91, 214504 (2015). http://doi.org/10.1103/PhysRevB.91.214504
Abstract: We numerically investigate the mixed pairing symmetries inmesoscopic superconducting loops in the presence of spin correlations by solving the Bogoliubov-de Gennes equations self-consistently. The spatial variations of the superconducting order parameters and the spontaneous magnetization are determined by the band structure. When the threaded magnetic flux turns on, the charge and spin currents both emerge and depict periodic evolution. In the case of a mesoscopic loop with dominant triplet p(x) +/- ip(y)-wave symmetry, a slight change of the chemical potential may lead to novel flux-dependent evolution patterns of the ground-state energy and the magnetization. The spin-polarized currents show pronounced quantum oscillations with fractional periods due to the appearance of energy jumps in flux, accompanied with a steplike feature of the enhanced spin current. Particularly, at some appropriate flux, the peaks of the zero-energy local density of states clearly indicate the occurrence of the odd-frequency pairing. In the case of a superconducting loop with dominant singlet d(x2-y2)-wave symmetry, the spatial profiles of the zero-energy local density of states and the magnetization show spin-dependent features on different sample diagonals. Moreover, the evolution of the flux-induced spin current always exhibits an hc/e periodicity.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 15
DOI: 10.1103/PhysRevB.91.214504
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“Model-based determination of dielectric function by STEM low-loss EELS”. Zhang L, Turner S, Brosens F, Verbeeck J, Physical review : B : condensed matter and materials physics 81, 035102 (2010). http://doi.org/10.1103/PhysRevB.81.035102
Abstract: Dielectric properties of materials are crucial in describing the electromagnetic response of materials. As devices are becoming considerably smaller than the optical wavelength, the conventional measuring methods based on optical response are limited by their spatial resolution. Electron energy loss spectroscopy performed in a scanning transmission electron microscope is a good alternative to obtain the dielectric properties with excellent spatial resolution. Due to the overlap of diffraction discs in scanning transmission electron microscopy, it is difficult to apply conventional experimental settings to suppress retardation losses. In this contribution, a relativistic dielectric model for the loss function is presented which is used in a model based optimization scheme to estimate the complex dielectric function of a material. The method is applied to experiments on bulk diamond and SrTiO3 and shows a good agreement with optical reference data when retardation effects are included. Application of this technique to nanoparticles is possible but several theoretical assumptions made in the model of the loss function are violated and interpretation becomes problematic.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Theory of quantum systems and complex systems
Impact Factor: 3.836
Times cited: 9
DOI: 10.1103/PhysRevB.81.035102
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“Superconducting current and proximity effect in ABA and ABC multilayer graphene Josephson junctions”. Muñoz WA, Covaci L, Peeters FM, Physical review : B : condensed matter and materials physics 88, 214502 (2013). http://doi.org/10.1103/PhysRevB.88.214502
Abstract: Using a numerical tight-binding approach based on the Chebyshev–Bogoliubov–de Gennes method we describe Josephson junctions made of multilayer graphene contacted by top superconducting gates. Both Bernal (ABA) and rhombohedral (ABC) stacking are considered and we find that the type of stacking has a strong effect on the proximity effect and the supercurrent flow. For both cases the pair amplitude shows a polarization between dimer and nondimer atoms, being more pronounced for rhombohedral stacking. Even though the proximity effect in nondimer sites is enhanced when compared to single-layer graphene, we find that the supercurrent is suppressed. The spatial distribution of the supercurrent shows that for Bernal stacking the current flows only in the topmost layers while for rhombohedral stacking the current flows throughout the whole structure.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 4
DOI: 10.1103/PhysRevB.88.214502
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“Disordered graphene Josephson junctions”. Muñoz WA, Covaci L, Peeters FM, Physical review : B : condensed matter and materials physics 91, 054506 (2015). http://doi.org/10.1103/PhysRevB.91.054506
Abstract: A tight-binding approach based on the Chebyshev-Bogoliubov-de Gennes method is used to describe disordered single-layer graphene Josephson junctions. Scattering by vacancies, ripples, or charged impurities is included. We compute the Josephson current and investigate the nature of multiple Andreev reflections, which induce bound states appearing as peaks in the density of states for energies below the superconducting gap. In the presence of single-atom vacancies, we observe a strong suppression of the supercurrent, which is a consequence of strong intervalley scattering. Although lattice deformations should not induce intervalley scattering, we find that the supercurrent is still suppressed, which is due to the presence of pseudomagnetic barriers. For charged impurities, we consider two cases depending on whether the average doping is zero, i.e., existence of electron-hole puddles, or finite. In both cases, short-range impurities strongly affect the supercurrent, similar to the vacancies scenario.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 7
DOI: 10.1103/PhysRevB.91.054506
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