“The peculiar potential of transition metal dichalcogenides for thermoelectric applications : a perspective on future computational research”. Sargin GO, Sarikurt S, Sevincli H, Sevik C, Journal of applied physics 133, 150902 (2023). http://doi.org/10.1063/5.0130350
Abstract: The peculiar potential transition metal dichalcogenides in regard to sensor and device applications have been exhibited by both experimental and theoretical studies. The use of these materials, thermodynamically stable even at elevated temperatures, particularly in nano- and optoelectronic technology, is about to come true. On the other hand, the distinct electronic and thermal transport properties possessing unique coherency, which may result in higher thermoelectric efficiency, have also been reported. However, exploiting this potential in terms of power generation and cooling applications requires a deeper understanding of these materials in this regard. This perspective study, concentrated with this intention, summarizes thermoelectric research based on transition metal dichalcogenides from a broad perspective and also provides a general evaluation of future theoretical investigations inevitable to shed more light on the physics of electronic and thermal transport in these materials and to lead future experimental research.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.2
DOI: 10.1063/5.0130350
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“Energy filtering in silicon nanowires and nanosheets using a geometric superlattice and its use for steep-slope transistors”. Beckers A, Thewissen M, Sorée B, Journal of applied physics 124, 144304 (2018). http://doi.org/10.1063/1.5043543
Abstract: This paper investigates energy filtering in silicon nanowires and nanosheets by resonant electron tunneling through a geometric superlattice. A geometric superlattice is any kind of periodic geometric feature along the transport direction of the nanowire or nanosheet. Multivalley quantum-transport simulations are used to demonstrate the manifestation of minibands and minibandgaps in the transmission spectra of such a superlattice. We find that the presence of different valleys in the conduction band of silicon favors a nanowire with a rectangular cross section for effective energy filtering. The obtained energy filter can consequently be used in the source extension of a field-effect transistor to prevent high-energy electrons from contributing to the leakage current. Self-consistent Schrodinger-Poisson simulations in the ballistic limit show minimum subthreshold swings of 6 mV/decade for geometric superlattices with indentations. The obtained theoretical performance metrics for the simulated devices are compared with conventional III-V superlatticeFETs and TunnelFETs. The adaptation of the quantum transmitting boundary method to the finite-element simulation of 3-D structures with anisotropic effective mass is presented in Appendixes A and B. Our results bare relevance in the search for steep-slope transistor alternatives which are compatible with the silicon industry and can overcome the power-consumption bottleneck inherent to standard CMOS technologies. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 3
DOI: 10.1063/1.5043543
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“Tuning the bandgap and introducing magnetism into monolayer BC3 by strain/defect engineering and adatom/molecule adsorption”. Bafekry A, Shayesteh SF, Ghergherehchi M, Peeters FM, Journal of applied physics 126, 144304 (2019). http://doi.org/10.1063/1.5097264
Abstract: Using first-principles calculations, we study the structural, electronic, and optical properties of pristine BC3. Our results show that BC3 is a semiconductor which can be useful in optoelectronic device applications. Furthermore, we found that the electronic properties of BC3 can be modified by strain and the type of edge states. With increasing thickness, the indirect bandgap decreases from 0.7 eV (monolayer) to 0.27 eV (bulk). Upon uniaxial tensile strain along the armchair and zigzag directions, the bandgap slightly decreases, and with increasing uniaxial strain, the bandgap decreases, and when reaching -8%, a semiconductor-to-metal transition occurs. By contrast, under biaxial strain, the bandgap increases to 1.2 eV in +8% and decreases to zero in -8%. BC3 nanoribbons with different widths exhibit magnetism at the zigzag edges, while, at the armchair edges, they become semiconductor, and the bandgap is in the range of 1.0-1.2 eV. Moreover, we systematically investigated the effects of adatoms/molecule adsorption and defects on the structural, electronic, and magnetic properties of BC3. The adsorption of various adatoms and molecules as well as topological defects (vacancies and Stone-Wales defects) can modify the electronic properties. Using these methods, one can tune BC3 into a metal, half-metal, ferromagnetic-metal, and dilute-magnetic semiconductor or preserve its semiconducting character. Published under license by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 56
DOI: 10.1063/1.5097264
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“The role of carbon monoxide in the catalytic synthesis of endohedral carbyne”. Mehmonov K, Ergasheva A, Yusupov M, Khalilov U, Journal of applied physics 134, 144303 (2023). http://doi.org/10.1063/5.0160892
Abstract: The unique physical properties of carbyne, a novel carbon nanostructure, have attracted considerable interest in modern nanotechnology. While carbyne synthesis has been accomplished successfully using diverse techniques, the underlying mechanisms governing the carbon monoxide-dependent catalytic synthesis of endohedral carbyne remain poorly understood. In this simulation-based study, we investigate the synthesis of endohedral carbyne from carbon and carbon monoxide radicals in the presence of a nickel catalyst inside double-walled carbon nanotubes with a (5,5)@(10,10) structure. The outcome of our investigation demonstrates that the incorporation of the carbon atom within the Ni-n@(5,5)@(10,10) model system initiates the formation of an elongated carbon chain. In contrast, upon the introduction of carbon monoxide radicals, the growth of the carbyne chain is inhibited as a result of the oxidation of endohedral nickel clusters by oxygen atoms after the initial steps of nucleation. Our findings align with prior theoretical, simulation, and experimental investigations, reinforcing their consistency and providing valuable insights into the synthesis of carbyne-based nanodevices that hold promising potential for future advancements in nanotechnology.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.2
DOI: 10.1063/5.0160892
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“Investigation of voltage effect on reaction mechanisms in capacitively coupled N-2 discharges”. Liang Y-S, Liu Y-X, Zhang Y-R, Wang Y-N, Journal Of Applied Physics 127, 133301 (2020). http://doi.org/10.1063/1.5143821
Abstract: A systematic investigation of voltage effect on the plasma parameters, especially the species densities and chemical reaction mechanisms, in the capacitive N-2 discharges is performed by employing a two-dimensional self-consistent fluid model. The validity of the numerical model is first demonstrated by the qualitative agreement of the calculated and experimental results. Then, the densities, production mechanisms, and loss mechanisms of species from simulation are examined at various voltages. It is found that all the species densities increase monotonically with the voltage, whereas their spatial profiles at lower voltages are quite different from those at higher voltages. The electrons and Nthorn 2 ions are mainly generated by the electron impact ionization of N-2 gas, while the Nthorn ions, whose density is one or two orders of magnitude lower, are mostly formed by the ionization of N atoms. The electron impact dissociation of N-2 gas dominates the generation of N atoms, which are mostly destroyed for the Nthorn ion production. As for the excited N-2 levels, the level conversion processes play a very important role in their production and depletion mechanisms, except for the electron impact excitation of the ground state N-2 molecules. Published under license by AIP Publishing.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.2
DOI: 10.1063/1.5143821
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“Torque field and skyrmion motion by spin transfer torque in a quasi-2D interface in presence of strong spin-orbit interaction”. Osca J, Sorée B, Journal Of Applied Physics 130, 133903 (2021). http://doi.org/10.1063/5.0063887
Abstract: We investigate the torque field and skyrmion motion at an interface between a ferromagnet hosting a skyrmion and a material with a strong spin-orbit interaction. We analyze both semiconductor materials and topological insulators using a Hamiltonian model that includes a linear term. The spin torque-inducing current is considered to flow in the single band limit; therefore, a quantum model of current is used. Skyrmion motion due to spin transfer torque proves to be more difficult in the presence of a spin-orbit interaction in the case where only interface in-plane currents are present. However, edge effects in narrow nanowires can be used to drive the skyrmion motion and to exert a limited control on its motion direction. We also show the differences and similarities between torque fields due to electric current in the many and single band limits. Published under an exclusive license by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
DOI: 10.1063/5.0063887
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“Controlling the formation and stability of ultra-thin nickel silicides : an alloying strategy for preventing agglomeration”. Geenen FA, van Stiphout K, Nanakoudis A, Bals S, Vantomme A, Jordan-Sweet J, Lavoie C, Detavernier C, Journal of applied physics 123, 075303 (2018). http://doi.org/10.1063/1.5009641
Abstract: The electrical contact of the source and drain regions in state-of-the-art CMOS transistors is nowadays facilitated through NiSi, which is often alloyed with Pt in order to avoid morphological agglomeration of the silicide film. However, the solid-state reaction between as-deposited Ni and the Si substrate exhibits a peculiar change for as-deposited Ni films thinner than a critical thickness of t(c) = 5 nm. Whereas thicker films form polycrystalline NiSi upon annealing above 450 degrees C, thinner films form epitaxial NiSi2 films that exhibit a high resistance toward agglomeration. For industrial applications, it is therefore of utmost importance to assess the critical thickness with high certainty and find novel methodologies to either increase or decrease its value, depending on the aimed silicide formation. This paper investigates Ni films between 0 and 15 nm initial thickness by use of “thickness gradients,” which provide semi-continuous information on silicide formation and stability as a function of as-deposited layer thickness. The alloying of these Ni layers with 10% Al, Co, Ge, Pd, or Pt renders a significant change in the phase sequence as a function of thickness and dependent on the alloying element. The addition of these ternary impurities therefore changes the critical thickness t(c). The results are discussed in the framework of classical nucleation theory. Published by AIP Publishing.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 23
DOI: 10.1063/1.5009641
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“First-principles study of the optoelectronic properties and photovoltaic absorber layer efficiency of Cu-based chalcogenides”. Sarmadian N, Saniz R, Partoens B, Lamoen D, Journal of applied physics 120, 085707 (2016). http://doi.org/10.1063/1.4961562
Abstract: Cu-based chalcogenides are promising materials for thin-film solar cells with more than 20% measured
cell efficiency. Using first-principles calculations based on density functional theory, the
optoelectronic properties of a group of Cu-based chalcogenides Cu2-II-IV-VI4 is studied. They are
then screened with the aim of identifying potential absorber materials for photovoltaic applications.
The spectroscopic limited maximum efficiency (SLME) introduced by Yu and Zunger [Phys. Rev.
Lett. 108, 068701 (2012)] is used as a metric for the screening. After constructing the currentvoltage
curve, the SLME is calculated from the maximum power output. The role of the nature of
the band gap, direct or indirect, and also of the absorptivity of the studied materials on the maximum
theoretical power conversion efficiency is studied. Our results show that Cu2II-GeSe4 with
II¼ Cd and Hg, and Cu2-II-SnS4 with II ¼ Cd, Hg, and Zn have a higher theoretical efficiency
compared with the materials currently used as absorber layer.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 29
DOI: 10.1063/1.4961562
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“On the structural and electronic properties of Ir-silicide nanowires on Si(001) surface”. Fatima, Oguz IC, Çakir D, Hossain S, Mohottige R, Gulseren O, Oncel N, Journal of applied physics 120, 095303 (2016). http://doi.org/10.1063/1.4961550
Abstract: Iridium (Ir) modified Silicon (Si) (001) surface is studied with Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and Density Functional Theory (DFT). A model for Ir-silicide nanowires based on STM images and ab-initio calculations is proposed. According to our model, the Ir adatom is on the top of the substrate dimer row and directly binds to the dimer atoms. I-V curves measured at 77K shows that the nanowires are metallic. DFT calculations confirm strong metallic nature of the nanowires. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 7
DOI: 10.1063/1.4961550
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“Electric-field induced quantum broadening of the characteristic energy level of traps in semiconductors and oxides”. Mohammed M, Verhulst AS, Verreck D, Van de Put M, Simoen E, Sorée B, Kaczer B, Degraeve R, Mocuta A, Collaert N, Thean A, Groeseneken G, Journal of applied physics 120, 245704 (2016). http://doi.org/10.1063/1.4972482
Abstract: The trap-assisted tunneling (TAT) current in tunnel field-effect transistors (TFETs) is one of the crucial factors degrading the sub-60 mV/dec sub-threshold swing. To correctly predict the TAT currents, an accurate description of the trap is required. Since electric fields in TFETs typically reach beyond 10(6) V/cm, there is a need to quantify the impact of such high field on the traps. We use a quantum mechanical implementation based on the modified transfer matrix method to obtain the trap energy level. We present the qualitative impact of electric field on different trap configurations, locations, and host materials, including both semiconductors and oxides. We determine that there is an electric-field related trap level shift and level broadening. We find that these electric-field induced quantum effects can enhance the trap emission rates. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 6
DOI: 10.1063/1.4972482
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“Effect of straining graphene on nanopore creation using Si cluster bombardment: A reactive atomistic investigation”. Berdiyorov GR, Mortazavi B, Ahzi S, Peeters FM, Khraisheh MK, Journal of applied physics 120, 225108 (2016). http://doi.org/10.1063/1.4971767
Abstract: Graphene nanosheets have recently received a revival of interest as a new class of ultrathin, high-flux, and energy-efficient sieving membranes because of their unique two-dimensional and atomically thin structure, good flexibility, and outstanding mechanical properties. However, for practical applications of graphene for advanced water purification and desalination technologies, the creation of well controlled, high-density, and subnanometer diameter pores becomes a key factor. Here, we conduct reactive force-field molecular dynamics simulations to study the effect of external strain on nanopore creation in the suspended graphene by bombardment with Si clusters. Depending on the size and energy of the clusters, different kinds of topography were observed in the graphene sheet. In all the considered conditions, tensile strain results in the creation of nanopores with regular shape and smooth edges. On the contrary, compressive strain increases the elastic response of graphene to irradiation that leads to the formation of net-like defective structures with predominantly carbon atom chains. Our findings show the possibility of creating controlled nanopores in strained graphene by bombardment with Si clusters. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 10
DOI: 10.1063/1.4971767
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“Bond length variation in Ga1-xInxAs crystals from the Tersoff potential”. Titantah JT, Lamoen D, Schowalter M, Rosenauer A, Journal of applied physics 101, 123508 (2007). http://doi.org/10.1063/1.2748338
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 19
DOI: 10.1063/1.2748338
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“Calculation of gas heating in direct current argon glow discharges”. Bogaerts A, Gijbels R, Serikov VV, Journal of applied physics 87, 8334 (2000). http://doi.org/10.1063/1.373545
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.068
Times cited: 63
DOI: 10.1063/1.373545
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“Doping effect on the adsorption of NH3 molecule onto graphene quantum dot : from the physisorption to the chemisorption”. Seyed-Talebi SM, Beheshtian J, Neek-Amal M, Journal of applied physics 114, 124307 (2013). http://doi.org/10.1063/1.4822165
Abstract: The adsorption of ammonia molecule onto a graphene hexagonal flake, aluminum (Al) and boron (B) doped graphene flakes (graphene quantum dots, GQDs) are investigated using density functional theory. We found that NH3 molecule is absorbed to the hollow site through the physisorption mechanism without altering the electronic properties of GQD. However, the adsorption energy of NH3 molecule onto the Al- and B-doped GQDs increases with respect GQD resulting chemisorption. The adsorption of NH3 onto the Al-doped and B-doped GQDs makes graphene locally buckled, i.e., B-doped and Al-doped GQDs are not planar. The adsorption mechanism onto a GQD is different than that of graphene. This study reveals important features of the edge passivation and doping effects of the adsorption mechanism of external molecules onto the graphene quantum dots. (C) 2013 AIP Publishing LLC.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 10
DOI: 10.1063/1.4822165
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“Generalized phonon-assisted Zener tunneling in indirect semiconductors with non-uniform electric fields : a rigorous approach”. Vandenberghe W, Sorée B, Magnus W, Fischetti MV, Journal of applied physics 109, 124503 (2011). http://doi.org/10.1063/1.3595672
Abstract: A general framework to calculate the Zener current in an indirect semiconductor with an externally applied potential is provided. Assuming a parabolic valence and conduction band dispersion, the semiconductor is in equilibrium in the presence of the external field as long as the electron-phonon interaction is absent. The linear response to the electron-phonon interaction results in a non-equilibrium system. The Zener tunneling current is calculated from the number of electrons making the transition from valence to conduction band per unit time. A convenient expression based on the single particle spectral functions is provided, enabling the evaluation of the Zener tunneling current under any three-dimensional potential profile. For a one-dimensional potential profile an analytical expression is obtained for the current in a bulk semiconductor, a semiconductor under uniform field, and a semiconductor under a non-uniform field using the WKB (Wentzel-Kramers-Brillouin) approximation. The obtained results agree with the Kane result in the low field limit. A numerical example for abrupt p-n diodes with different doping concentrations is given, from which it can be seen that the uniform field model is a better approximation than the WKB model, but a direct numerical treatment is required for low bias conditions.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 41
DOI: 10.1063/1.3595672
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“Micro-Hall bar as a sensor to detect the interaction of nanoscale ferromagnetic disks and columns”. Hao YL, Peeters FM, Journal of applied physics 101, 123718 (2007). http://doi.org/10.1063/1.2743880
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
DOI: 10.1063/1.2743880
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“Structure and properties of artificial [(La0.7Sr0.3MnO3)m(SrTiO3)n]15 superlattices on (001)SrTiO3”. Lebedev OI, Verbeeck J, Van Tendeloo G, Dubourdieu C, Rosina M, Chaudouët P, Journal of applied physics 94, 7646 (2003). http://doi.org/10.1063/1.1628407
Abstract: Complex [(La0.7Sr0.3MnO3)(m)(SrTiO3)(n)] [(LSMO)(m)/(STO)(8)](15) superlattices with different layer thicknesses (m=5, 8, 12, 16, 32) have been prepared using pulsed liquid injection metalorganic chemical vapor deposition. Transmission electron microscopy and electron diffraction reveal a very clear and well-separated layer sequence. The remarkable microstructure, as well as the ferromagnetic transition temperature, depends on the LSMO layer thickness. Apart from a very clear layer sequence, electron microscopy shows evidence of a self-assembled nanostructure formation: SrMnO3 nanoinclusions and associated SrTiO3-SrMnO3 thin walls. A formation model and growth mechanism for the self-assembled structure is proposed, based on high resolution and energy filtered elemental imaging. (C) 2003 American Institute of Physics.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 22
DOI: 10.1063/1.1628407
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“Tunable magnetic focusing using Andreev scattering in superconductor-graphene hybrid devices”. Chaves A, Moura VN, Linard FJA, Covaci L, Milošević, MV, Journal Of Applied Physics 128, 124303 (2020). http://doi.org/10.1063/5.0020392
Abstract: We perform the wavepacket dynamics simulation of a graphene-based device where propagating electron trajectories are tamed by an applied magnetic field toward a normal/superconductor interface. The magnetic field controls the incidence angle of the incoming electronic wavepacket at the interface, which results in the tunable electron-hole ratio in the reflected wave function due to the angular dependence of the Andreev reflection. Here, mapped control of the quasiparticle trajectories by the external magnetic field not only defines an experimental probe for fundamental studies of the Andreev reflection in graphene but also lays the foundation for further development of magnetic focusing devices based on nanoengineered superconducting two-dimensional materials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 3.2
Times cited: 1
DOI: 10.1063/5.0020392
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“A perspective on the state-of-the-art functionalized 2D materials”. Duran TA, Yayak YO, Aydin H, Peeters FM, Yagmurcukardes M, Journal of applied physics 134, 120901 (2023). http://doi.org/10.1063/5.0158859
Abstract: Two-dimensional (2D) ultra-thin materials are more crucial than their bulk counterparts for the covalent functionalization of their surface owing to atomic thinness, large surface-to-volume ratio, and high reactivity of surface atoms having unoccupied orbitals. Since the surface of a 2D material is composed of atoms having unoccupied orbitals, covalent functionalization enables one to improve or precisely modify the properties of the ultra-thin materials. Chemical functionalization of 2D materials not only modifies their intrinsic properties but also makes them adapted for nanotechnology applications. Such engineered materials have been used in many different applications with their improved properties. In the present Perspective, we begin with a brief history of functionalization followed by the introduction of functionalized 2D materials. Our Perspective is composed of the following sections: the applications areas of 2D graphene and graphene oxide crystals, transition metal dichalcogenides, and in-plane anisotropic black phosphorus, all of which have been widely used in different nanotechnology applications. Finally, our Perspectives on the future directions of applications of functionalized 2D materials are given. The present Perspective sheds light on the current progress in nanotechnological applications of engineered 2D materials through surface functionalization.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.2
DOI: 10.1063/5.0158859
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“Phase formation and texture of thin nickel germanides on Ge(001) and Ge(111)”. De Schutter B, Van Stiphout K, Santos NM, Bladt E, Jordan-Sweet J, Bals S, Lavoie C, Comrie CM, Vantomme A, Detavernier C, Journal of applied physics 119, 135305 (2016). http://doi.org/10.1063/1.4945317
Abstract: We studied the solid-phase reaction between a thin Nifilm and a single crystal Ge(001) or Ge(111) substrate during a ramp anneal. The phase formation sequence was determined using in situX-ray diffraction and in situRutherford backscattering spectrometry (RBS), while the nature and the texture of the phases were studied using X-ray pole figures and transmission electron microscopy. The phase sequence is characterized by the formation of a single transient phase before NiGe forms as the final and stable phase. X-ray pole figures were used to unambiguously identify the transient phase as the ϵ-phase, a non-stoichiometric Ni-rich germanide with a hexagonal crystal structure that can exist for Ge concentrations between 34% and 48% and which forms with a different epitaxial texture on both substrate orientations. The complementary information gained from both RBS and X-ray pole figure measurements revealed a simultaneous growth of both the ϵ-phase and NiGe over a small temperature window on both substrate orientations.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 14
DOI: 10.1063/1.4945317
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“First-principles thermodynamics and defect kinetics guidelines for engineering a tailored RRAM device”. Clima S, Chen YY, Chen CY, Goux L, Govoreanu B, Degraeve R, Fantini A, Jurczak M, Pourtois G, Journal of applied physics 119, 225107 (2016). http://doi.org/10.1063/1.4953673
Abstract: Resistive Random Access Memories are among the most promising candidates for the next generation of non-volatile memory. Transition metal oxides such as HfOx and TaOx attracted a lot of attention due to their CMOS compatibility. Furthermore, these materials do not require the inclusion of extrinsic conducting defects since their operation is based on intrinsic ones (oxygen vacancies). Using Density Functional Theory, we evaluated the thermodynamics of the defects formation and the kinetics of diffusion of the conducting species active in transition metal oxide RRAM materials. The gained insights based on the thermodynamics in the Top Electrode, Insulating Matrix and Bottom Electrode and at the interfaces are used to design a proper defect reservoir, which is needed for a low-energy reliable switching device. The defect reservoir has also a direct impact on the retention of the Low Resistance State due to the resulting thermodynamic driving forces. The kinetics of the diffusing conducting defects in the Insulating Matrix determine the switching dynamics and resistance retention. The interface at the Bottom Electrode has a significant impact on the low-current operation and long endurance of the memory cell. Our first-principles findings are confirmed by experimental measurements on fabricated RRAM devices. Published by AIP Publishing.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.068
Times cited: 17
DOI: 10.1063/1.4953673
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“Inter-ribbon tunneling in graphene: An atomistic Bardeen approach”. Van de Put ML, Vandenberghe WG, Sorée B, Magnus W, Fischetti MV, Journal of applied physics 119, 214306 (2016). http://doi.org/10.1063/1.4953148
Abstract: A weakly coupled system of two crossed graphene nanoribbons exhibits direct tunneling due to the overlap of the wavefunctions of both ribbons. We apply the Bardeen transfer Hamiltonian formalism, using atomistic band structure calculations to account for the effect of the atomic structure on the tunneling process. The strong quantum-size confinement of the nanoribbons is mirrored by the one-dimensional character of the electronic structure, resulting in properties that differ significantly from the case of inter-layer tunneling, where tunneling occurs between bulk two-dimensional graphene sheets. The current-voltage characteristics of the inter-ribbon tunneling structures exhibit resonance, as well as stepwise increases in current. Both features are caused by the energetic alignment of one-dimensional peaks in the density-of-states of the ribbons. Resonant tunneling occurs if the sign of the curvature of the coupled energy bands is equal, whereas a step-like increase in the current occurs if the signs are opposite. Changing the doping modulates the onset-voltage of the effects as well as their magnitude. Doping through electrostatic gating makes these structures promising for application towards steep slope switching devices. Using the atomistic empirical pseudopotentials based Bardeen transfer Hamiltonian method, inter-ribbon tunneling can be studied for the whole range of two-dimensional materials, such as transition metal dichalcogenides. The effects of resonance and of step-like increases in the current we observe in graphene ribbons are also expected in ribbons made from these alternative two-dimensional materials, because these effects are manifestations of the one-dimensional character of the density-of-states. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 6
DOI: 10.1063/1.4953148
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“Skyrmion-induced bound states on the surface of three-dimensional topological insulators”. Andrikopoulos D, Sorée B, De Boeck J, Journal of applied physics 119, 193903 (2016). http://doi.org/10.1063/1.4950759
Abstract: The interaction between the surface of a 3D topological insulator and a skyrmion/anti-skyrmion structure is studied in order to investigate the possibility of electron confinement due to the skyrmion presence. Both hedgehog (Neel) and vortex (Bloch) skyrmions are considered. For the hedgehog skyrmion, the in-plane components cannot be disregarded and their interaction with the surface state of the topological insulator (TI) has to be taken into account. A semi-classical description of the skyrmion chiral angle is obtained using the variational principle. It is shown that both the hedgehog and the vortex skyrmion can induce bound states on the surface of the TI. However, the number and the properties of these states depend strongly on the skyrmion type and the skyrmion topological number N-Sk. The probability densities of the bound electrons are also derived where it is shown that they are localized within the skyrmion region. Published by AIP Publishing.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 8
DOI: 10.1063/1.4950759
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“Superconductor-ferromagnet bilayer under external drive : the role of vortex-antivortex matter”. Frota DA, Chaves A, Ferreira WP, Farias GA, Milošević, MV, Journal of applied physics 119, 093912 (2016). http://doi.org/10.1063/1.4943364
Abstract: Using advanced Ginzburg-Landau simulations, we study the superconducting state of a thin superconducting film under a ferromagnetic layer, separated by an insulating oxide, in applied external magnetic field and electric current. The taken uniaxial ferromagnet is organized into a series of parallel domains with alternating polarization of out-of-plane magnetization, sufficiently strong to induce vortex-antivortex pairs in the underlying superconductor in absence of other magnetic field. We show the organization of such vortex-antivortex matter into rich configurations, some of which are not matching the periodicity of the ferromagnetic film. The variety of possible configurations is enhanced by applied homogeneous magnetic field, where additional vortices in the superconductor may lower the energy of the system by either annihilating the present antivortices under negative ferromagnetic domains or by lowering their own energy after positioning under positive ferromagnetic domains. As a consequence, both the vortex-antivortex reordering in increasing external field and the evolution of the energy of the system are highly nontrivial. Finally, we reveal the very interesting effects of applied dc electric current on the vortex-antivortex configurations, since resulting Lorentzian force has opposite direction for vortices and antivortices, while direction of the applied current with respect to ferromagnetic domains is of crucial importance for the interaction of the applied and the Meissner current, as well as the consequent vortex-antivortex dynamics-both of which are reflected in the anisotropic critical current of the system. (C) 2016 AIP Publishing LLC.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 4
DOI: 10.1063/1.4943364
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“Derivatization and diffusive motion of molecular fullerenes : ab initio and atomistic simulations”. Berdiyorov G, Harrabi K, Mehmood U, Peeters FM, Tabet N, Zhang J, Hussein IA, McLachlan MA, Journal of applied physics 118, 025101 (2015). http://doi.org/10.1063/1.4923352
Abstract: Using first principles density functional theory in combination with the nonequilibrium Green's function formalism, we study the effect of derivatization on the electronic and transport properties of C-60 fullerene. As a typical example, we consider [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM), which forms one of the most efficient organic photovoltaic materials in combination with electron donating polymers. Extra peaks are observed in the density of states (DOS) due to the formation of new electronic states localized at/near the attached molecule. Despite such peculiar behavior in the DOS of an isolated molecule, derivatization does not have a pronounced effect on the electronic transport properties of the fullerene molecular junctions. Both C-60 and PCBM show the same response to finite voltage biasing with new features in the transmission spectrum due to voltage induced delocalization of some electronic states. We also study the diffusive motion of molecular fullerenes in ethanol solvent and inside poly(3-hexylthiophene) lamella using reactive molecular dynamics simulations. We found that the mobility of the fullerene reduces considerably due to derivatization; the diffusion coefficient of C-60 is an order of magnitude larger than the one for PCBM. (c) 2015 AIP Publishing LLC.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 2
DOI: 10.1063/1.4923352
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“Effects of feedstock availability on the negative ion behavior in a C4F8 inductively coupled plasma”. Zhao S-X, Gao F, Wang Y-P, Wang Y-N, Bogaerts A, Journal of applied physics 118, 033301 (2015). http://doi.org/10.1063/1.4926867
Abstract: In this paper, the negative ion behavior in a C4F8 inductively coupled plasma (ICP) is investigated using a hybrid model. The model predicts a non-monotonic variation of the total negative ion density with power at low pressure (1030 mTorr), and this trend agrees well with experiments that were carried out in many fluorocarbon (fc) ICP sources, like C2F6, CHF3, and C4F8. This behavior is explained by the availability of feedstock C4F8 gas as a source of the negative ions, as well as by the presence of low energy electrons due to vibrational excitation at low power. The maximum of the negative ion density shifts to low power values upon decreasing pressure, because of the more pronounced depletion of C4F8 molecules, and at high pressure (∼50 mTorr), the anion density continuously increases with power, which is similar to fc CCP sources. Furthermore, the negative ion composition is identified in this paper. Our work demonstrates that for a clear understanding of the negative ion behavior in radio frequency C4F8 plasma sources, one needs to take into account many factors, like the attachment characteristics, the anion composition, the spatial profiles, and the reactor configuration. Finally, a detailed comparison of our simulation results with experiments is conducted.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.068
Times cited: 1
DOI: 10.1063/1.4926867
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“Veselago lensing in graphene with a p-n junction: Classical versus quantum effects”. Milovanović, SP, Moldovan D, Peeters FM, Journal of applied physics 118, 154308 (2015). http://doi.org/10.1063/1.4933395
Abstract: The feasibility of Veselago lensing in graphene with a p-n junction is investigated numerically for realistic injection leads. Two different set-ups with two narrow leads are considered with absorbing or reflecting side edges. This allows us to separately determine the influence of scattering on electron focusing for the edges and the p-n interface. Both semiclassical and tight-binding simulations show a distinctive peak in the transmission probability that is attributed to the Veselago lensing effect. We investigate the robustness of this peak on the width of the injector, the position of the p-n interface, and different gate potential profiles. Furthermore, the influence of scattering by both short- and long-range impurities is considered.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 19
DOI: 10.1063/1.4933395
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“Ab-initio study of the segregation and electronic properties of neutral and charged B and P dopants in Si and Si/SiO2 nanowires”. Schoeters B, Leenaerts O, Pourtois G, Partoens B, Journal of applied physics 118, 104306 (2015). http://doi.org/10.1063/1.4930048
Abstract: We perform first-principles calculations to investigate the preferred positions of B and P dopants, both neutral and in their preferred charge state, in Si and Si/SiO2 core-shell nanowires (NWs). In order to understand the observed trends in the formation energy, we isolate the different effects that determine these formation energies. By making the distinction between the unrelaxed and the relaxed formation energy, we separate the impact of the relaxation from that of the chemical environment. The unrelaxed formation energies are determined by three effects: (i) the effect of strain caused by size mismatch between the dopant and the host atoms, (ii) the local position of the band edges, and (iii) a screening effect. In the case of the SiNW (Si/SiO2 NW), these effects result in an increase of the formation energy away from the center (interface). The effect of relaxation depends on the relative size mismatch between the dopant and host atoms. A large size mismatch causes substantial relaxation that reduces the formation energy considerably, with the relaxation being more pronounced towards the edge of the wires. These effects explain the surface segregation of the B dopants in a SiNW, since the atomic relaxation induces a continuous drop of the formation energy towards the edge. However, for the P dopants, the formation energy starts to rise when moving from the center but drops to a minimum just next to the surface, indicating a different type of behavior. It also explains that the preferential location for B dopants in Si/SiO2 core-shell NWs is inside the oxide shell just next to the interface, whereas the P dopants prefer the positions next to the interface inside the Si core, which is in agreement with recent experiments. These preferred locations have an important impact on the electronic properties of these core-shell NWs. Our simulations indicate the possibility of hole gas formation when B segregates into the oxide shell.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.068
Times cited: 3
DOI: 10.1063/1.4930048
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“Full-zone spectral envelope function formalism for the optimization of line and point tunnel field-effect transistors”. Verreck D, Verhulst AS, Van de Put M, Sorée B, Magnus W, Mocuta A, Collaert N, Thean A, Groeseneken G, Journal of applied physics 118, 134502 (2015). http://doi.org/10.1063/1.4931890
Abstract: Efficient quantum mechanical simulation of tunnel field-effect transistors (TFETs) is indispensable to allow for an optimal configuration identification. We therefore present a full-zone 15-band quantum mechanical solver based on the envelope function formalism and employing a spectral method to reduce computational complexity and handle spurious solutions. We demonstrate the versatility of the solver by simulating a 40 nm wide In0.53Ga0.47As lineTFET and comparing it to p-n-i-n configurations with various pocket and body thicknesses. We find that the lineTFET performance is not degraded compared to semi-classical simulations. Furthermore, we show that a suitably optimized p-n-i-n TFET can obtain similar performance to the lineTFET. (C) 2015 AIP Publishing LLC.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 9
DOI: 10.1063/1.4931890
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“Modeling surface roughness scattering in metallic nanowires”. Moors K, Sorée B, Magnus W, Journal of applied physics 118, 124307 (2015). http://doi.org/10.1063/1.4931573
Abstract: Ando's model provides a rigorous quantum-mechanical framework for electron-surface roughness scattering, based on the detailed roughness structure. We apply this method to metallic nanowires and improve the model introducing surface roughness distribution functions on a finite domain with analytical expressions for the average surface roughness matrix elements. This approach is valid for any roughness size and extends beyond the commonly used Prange-Nee approximation. The resistivity scaling is obtained from the self-consistent relaxation time solution of the Boltzmann transport equation and is compared to Prange-Nee's approach and other known methods. The results show that a substantial drop in resistivity can be obtained for certain diameters by achieving a large momentum gap between Fermi level states with positive and negative momentum in the transport direction. (C) 2015 AIP Publishing LLC.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 11
DOI: 10.1063/1.4931573
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