Search

Recent studies have shown that proximity effects are able to substantially modulate the superconducting properties of various quasi-two-dimensional layered materials such as FeSe, FeSeTe, NbSe2, and NbS2. Due to their high surface charge concentration and high dielectric constants, ferroelectric materials provide an interesting avenue for inducing proximity effects in layered superconductors. In this study, we explore the interactions between FeSeTe and the two-dimensional ferroelectrics CuInP2S6 and CuInP2Se6. We found that contrary to the normal behavior of FeSeTe, FeSeTe/CuInP2S6, and FeSeTe/CuInP2Se6 heterostructures display a peculiar two-step superconducting transition. Further testing revealed a hysteresis loop in the IV curves of these samples when measured below the critical temperature indicating the presence of disorder and domains within FeSeTe. We conclude that these domains are responsible for the two-step transition in FeSeTe and hypothesize that they are induced by the domain structure of the aforementioned ferroelectric materials. [ABSTRACT FROM AUTHOR]

The effects of tensile strain and contact transmissivity on the performance limits of monolayer molybdenum disulfide ( MoS 2) nanoscale n-channel MOSFETs are studied using a semi-classical Monte Carlo method. Density functional theory calculations were performed to parametrize the electronic band structure of MoS 2 subject to tensile and shear strain. Tensile strain decreases the bandgap, increases the inter-valley band-edge energy separation between the light-mass K-valleys and heavier-mass Q-valleys, and decreases the K-valley effective mass in a way that depends on the direction and the amount of the applied strain. Biaxial tensile strain and uniaxial tensile strain along the x- or y-directions are found to have the largest effect. In bulk materials, low-field phonon-limited electron mobility is enhanced, peak and saturation drift velocities are increased, and high-field negative differential resistance becomes more pronounced. Both 200 and 15 nm gate length MoS 2 MOSFETs with end-contacts with ideal (unity) and more realistic (significantly sub-unity) contact interface transmissivity were simulated. These MoS 2 devices exhibited substantial sensitivity to strain with ideal contact transmissivity, and more so for the 15 nm quasi-ballistic device scale than 200 nm long-channel devices. However, the results showed much less strain sensitivity for devices with more realistic contact transmissivities, which may be good or bad depending on whether strain-insensitive or strain-sensitive performance is desired for a particular application and may be possible to modify with improved contact geometries. [ABSTRACT FROM AUTHOR]

The conventional theory of superconductivity holds that Cooper pairs form due to electron–phonon coupling; however, this description may not be adequate to describe certain unconventional superconductors such as cuprates and iron chalcogenides. In these unconventional superconductors, it has been proposed that spin fluctuations may be responsible for the formation of Cooper pairs. In this study, we explore spin interactions in the transition metal, dichalcogenide niobium disulfide, induced through proximity effects by fabricating antiferromagnet/NbS2 heterostructures. We tested three different 2D antiferromagnetic materials, each with different spin textures: anganese phosphorus trisulfide, manganese phosphorus triselenide, and chromium trichloride. Our results showed a substantial reduction in the critical temperature in the case of NbS2/MnPSe3. We hypothesize that this could be due to spin fluctuations in MnPSe3 inducing proximity effects in NbS2. [ABSTRACT FROM AUTHOR]

Synaptic plasticity forms the basis of memory retention in the human brain. Whereas a low "rehearsal" rate causes short-term changes in the synaptic connections such that the synapse soon "forgets," a high rehearsal rate ensures long-term retention of memory in the brain. In this paper, we propose an artificial short- and long-term memory magnetic tunnel junction (SALT-MTJ) synapse. Changes in the synaptic strength are mapped to the SALT-MTJ conductance, which is varied stochastically via spin-transfer torque resulting from input current stimuli. A meta-stable intermediate magnetic state of the SALT-MTJ synapse provides short-term synaptic plasticity and the associated forgetting behavior as in a biological synapse. Repeated spin-current stimulations, while the SALT-MTJ remains in the short-term state, then can cause a near-permanent change in the magnetic state and associated conductance to provide long-term potentiation. The synaptic weight sensitivity to the input stimulus and the forgetting behavior of these short- and long-term states can be controlled via shape engineering of the artificial synapse. [ABSTRACT FROM AUTHOR]

The effects of contact geometry and specific contact resistivity on In0.53Ga0.47As (InGaAs) and silicon (Si) nanoscale (18 nm channel length) n-channel FinFETs performance, and the effects of models thereof, are studied using a quantum-corrected semiclassical Monte Carlo method. Saddle/slot, raised source and drain (RSD), and reference end contacts are modeled. Both ideal perfectly injecting and absorbing contacts and those with more realistic specific contact resistivities are considered. Far-from-equilibrium degenerate statistics, quantum-confinement effects on carrier distributions in real-space and among energy valleys and on scattering, and quasiballistic transport are modeled. Silicon ⟨ 110 ⟩ channel and Si ⟨ 100 ⟩ channel FinFETs, multivalley InGaAs channel FinFETs with conventionally reported InGaAs energy valley offsets, and reference idealized Γ-valley-only InGaAs (Γ-InGaAs) channel FinFETs are simulated. Among our findings, InGaAs channel FinFETs are highly sensitive to modeled contact geometry and specific contact resistivity and to the band structure model, while Si channel FinFETs showed still significant but much less sensitivity to the contact models. For example, for idealized unity transmissivity contacts, Γ-InGaAs channel FinFETs performed best for all contact geometries, at least in terms of transconductance, and end contacts provided the best performance for all considered channel materials. For realistic contact resistivities, however, the results are essentially reversed. Silicon channel FinFETs performed best for all contact geometries, and saddle/slot and RSD contacts outperformed end contacts. [ABSTRACT FROM AUTHOR]

Surface passivation using intrinsic a-Si:H (i a-Si:H) films plays a key role in high efficiency c-Si heterojunction solar cells. In this study, we demonstrate improved passivation quality using i a-Si:H films with a gradient-layered structure consisting of interfacial, transition, and capping layers deposited on c-Si surfaces. The H2 dilution ratio (R) during deposition was optimized individually for the interfacial and capping layers, which were separated by a transition layer for which R changed gradually between its values for the interfacial and capping layers. This approach yielded a significant reduction in surface carrier recombination, resulting in improvement of the minority carrier lifetime from 1480 μs for mono-layered i a-Si:H passivation to 2550 μs for the gradient-layered passivation approach. [ABSTRACT FROM AUTHOR]

In this study, we report the fabrication and characterization of a vertical resonant interlayer tunneling field-effect transistor created using exfoliated, few-layer rhenium disulfide (ReS2) flakes as the electrodes and hexagonal boron nitride as the tunnel barrier. Due to the Γ-point conduction band minimum, the ReS2 based system offers the possibility of resonant interlayer tunneling and associated low-voltage negative differential resistance (NDR) without rotational alignment of the electrode crystal orientations. Substantial NDR is observed, which appears consistent with inplane crystal momentum conserving tunneling, although considerably broadened by scattering consistent within low mobility ReS2 flakes. [ABSTRACT FROM AUTHOR]

The quest of obtaining sustainable, clean energy is an ongoing challenge. While silicon-based solar cells have widespread acceptance in practical commercialization, continuous research is important to expand applicability beyond fixed-point generation to other environments while also improving power conversion efficiency (PCE), stability, and cost. In this work, graphene-on-silicon Schottky junction and graphene-insulator-silicon (GIS) solar cells are demonstrated on flexible, thin foils, which utilize the electrical conductivity and optical transparency of graphene as the top transparent contact. Multi-layer graphene was grown by chemical vapor deposition on Cu-Ni foils, followed by p-type doping with Au nanoparticles and encapsulated in poly(methyl methacrylate), which showed high stability with minimal performance degradation over more than one month under ambient conditions. Bendable silicon film substrates were fabricated by a kerf-less exfoliation process based on spalling, where the silicon film thickness could be controlled from 8 to 35 lm based on the process recipe. This method allows for re-exfoliation from the parent Si wafer and incorporates the process for forming the backside metal contact of the solar cell. GIS cells were made with a thin insulating Al2O3 atomic layer deposited film, where the thin Al2O3 film acts as a tunneling barrier for holes, while simultaneously passivating the silicon surface, increasing the minority carrier lifetime from 2 to 27 μs. By controlling the Al2O3 thickness, an optimized cell with 7.4% power conversion efficiency (PCE) on a 35 lm thick silicon absorber was fabricated. [ABSTRACT FROM AUTHOR]

Particle-based ensemble semi-classical Monte Carlo (MC) methods employ quantum corrections (QCs) to address quantum confinement and degenerate carrier populations to model tomorrow's ultra-scaled metal-oxide-semiconductor-field-effect-transistors. Here, we present the most complete treatment of quantum confinement and carrier degeneracy effects in a three-dimensional (3D) MC device simulator to date, and illustrate their significance through simulation of n-channel Si and III-V FinFETs. Original contributions include our treatment of far-from-equilibrium degenerate statistics and QC-based modeling of surface-roughness scattering, as well as considering quantum-confined phonon and ionized-impurity scattering in 3D. Typical MC simulations approximate degenerate carrier populations as Fermi distributions to model the Pauli-blocking (PB) of scattering to occupied final states. To allow for increasingly far-from-equilibrium non-Fermi carrier distributions in ultra-scaled and III-V devices, we instead generate the final-state occupation probabilities used for PB by sampling the local carrier populations as function of energy and energy valley. This process is aided by the use of fractional carriers or sub-carriers, which minimizes classical carrier-carrier scattering intrinsically incompatible with degenerate statistics. Quantumconfinement effects are addressed through quantum-correction potentials (QCPs) generated from coupled Schrödinger-Poisson solvers, as commonly done. However, we use these valley- and orientation-dependent QCPs not just to redistribute carriers in real space, or even among energy valleys, but also to calculate confinement-dependent phonon, ionized-impurity, and surfaceroughness scattering rates. FinFET simulations are used to illustrate the contributions of each of these QCs. Collectively, these quantum effects can substantially reduce and even eliminate otherwise expected benefits of considered In0:53Ga0:47As FinFETs over otherwise identical Si FinFETs despite higher thermal velocities in In0:53Ga0:47As. It also may be possible to extend these basic uses of QCPs, however calculated, to still more computationally efficient drift-diffusion and hydrodynamic simulations, and the basic concepts even to compact device modeling. [ABSTRACT FROM AUTHOR]

Quantum interference effects and electron-electron interactions are found to play an important role in two-dimensional (2D) bulk transport of topological insulator (TI) thin films, which were previously considered as 2D electron gas (2DEG) and explained on basis of Hikami-Larkin-Nagaoka formula and Lee-Ramakrishnan theory. The distinct massive Dirac-type band structure of the TI bulk state gives rise to quantum corrections to conductivity due to interference and interaction effects, which are quite different from that of a 2DEG. We interpret the experimental findings employing Lu-Shen theory particularly derived for the TI system in the 2D limit. The surface and the bulk conductions are identified based on slopes of logarithmic temperature-dependent conductivities with magnetic fields. The perpendicular field magnetoresistance is analyzed considering suppression of weak antilocalization/localization of the surface/bulk electrons by the applied field. We propose corresponding theoretical models to explain the parallel and tilted field magnetoresistance. The effect of the band structure is found to be crucial for an accurate explanation of the magnetotransport results in the TI thin film. [ABSTRACT FROM AUTHOR]

Van der Waal's heterostructures allow for novel devices such as two-dimensional-to-two-dimensional tunnel devices, exemplified by interlayer tunnel FETs. These devices employ channel/tunnel-barrier/channel geometries. However, during layer-by-layer exfoliation of these multi-layer materials, rotational misalignment is the norm and may substantially affect device characteristics. In this work, by using density functional theory methods, we consider a reduction in tunneling due to weakened coupling across the rotationally misaligned interface between the channel layers and the tunnel barrier. As a prototypical system, we simulate the effects of rotational misalignment of the tunnel barrier layer between aligned channel layers in a graphene/hBN/graphene system. We find that the rotational misalignment between the channel layers and the tunnel barrier in this van der Waal's heterostructure can significantly reduce coupling between the channels by reducing, specifically, coupling across the interface between the channels and the tunnel barrier. This weakened coupling in graphene/hBN/graphene with hBN misalignment may be relevant to all such van der Waal's heterostructures. [ABSTRACT FROM AUTHOR]

In this article, we consider through simulation low-energy switching of nanomagnets via electrostatically gated inter-magnet Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions on the surface of three-dimensional topological insulators, for possible memory and nonvolatile logic applications. We model the possibility and dynamics of RKKY-based switching of one nanomagnet by coupling to one or more nanomagnets of set orientation. Potential applications to both memory and nonvolatile logic are illustrated. Sub-attojoule switching energies, far below conventional spin transfer torque (STT)-based memories and even below CMOS logic appear possible. Switching times on the order of a few nanoseconds, comparable to times for STT switching, are estimated for ferromagnetic nanomagnets, but the approach also appears compatible with the use of antiferromagnets which may allow for faster switching. [ABSTRACT FROM AUTHOR]

Although the diffusion control and dopant activation of Ge p-type junctions are straightforward when using B+ implantation, the use of the heavier BF2+ ions or even BF+ is still favored in terms of shallow junction formation and throughput—because implants can be done at higher energies, which can give higher beam currents and beam stability—and thus the understanding of the effect of F co-doping becomes important. In this work, we have investigated diffusion and end-of-range (EOR) defect formation for B+, BF+, and BF2+ implants in crystalline and pre-amorphized Ge, employing rapid thermal annealing at 600 °C and 800 °C for 10 s. It is demonstrated that the diffusion of B is strongly influenced by the temperature, the presence of F, and the depth of amorphous/crystalline interface. The B and F diffusion profiles suggest the formation of B-F complexes and enhanced diffusion by interaction with point defects. In addition, the strong chemical effect of F is found only for B in Ge, while such an effect is vanishingly small for samples implanted with F alone, or co-implanted with P and F, as evidenced by the high residual F concentration in the B-doped samples after annealing. After 600 °C annealing for 10 s, interstitial-induced compressive strain was still observed in the EOR region for the sample implanted with BF+, as measured by X-ray diffraction. Further analysis by cross-sectional transmission electron microscopy showed that the {311} interstitial clusters are the majority type of EOR defects. The impact of these {311} defects on the electrical performance of Ge p+/n junctions formed by BF+ implantation was evaluated. [ABSTRACT FROM AUTHOR]

Many factors have been identified to influence the electrical transport characteristics of graphene field-effect transistors. In this report, we examine the influence of the exposure current level used during electron beam lithography (EBL) for active region patterning. In the presence of a self-assembled hydrophobic residual layer generated by oxygen plasma etching covering the top surface of the graphene channel, we show that the use of low EBL current level results in higher mobility, lower residual carrier density, and charge neutrality point closer to 0V, with reduced device-to-device variations. We show that this correlation originates from the resist heating dependent release of radicals from the resist material, near its interface with graphene, and its subsequent trapping by the hydrophobic polymer layer. Using a general model for resist heating, we calculate the difference in resist heating for different EBL current levels. We further corroborate our argument through control experiments, where radicals are either intentionally added or removed by other processes. We also utilize this finding to obtain mobilities in excess of 18 000 cm2/V s on silicon dioxide substrates. We believe these results are applicable to other 2D materials such as transition metal dichalcogenides and nanoscale devices in general. [ABSTRACT FROM AUTHOR]

We report on van der Waals epitaxial growth, materials characterization, and magnetotransport experiments in crystalline nanosheets of Bismuth Telluro-Sulfide (BTS). Highly layered, good-quality crystalline nanosheets of BTS are obtained on SiO2 and muscovite mica. Weak-antilocalization (WAL), electron-electron interaction-driven insulating ground state and universal conductance fluctuations are observed in magnetotransport experiments on BTS devices. Temperature, thickness, and magnetic field dependence of the transport data indicate the presence of two-dimensional surface states along with bulk conduction, in agreement with theoretical models. An extended-WAL model is proposed and utilized in conjunction with a two-channel conduction model to analyze the data, revealing a surface component and evidence of multiple conducting channels. A facile growth method and detailed magnetotransport results indicating BTS as an alternative topological insulator material system are presented. [ABSTRACT FROM AUTHOR]

We consider a thermally stable, metallic nanoscale ferromagnet (FM) subject to spin-polarized current injection and exchange coupling from the spin-helically locked surface states of a topological insulator (TI) to evaluate possible non-volatile memory applications. We consider parallel transport in the TI and the metallic FM, and focus on the efficiency of magnetization switching as a function of transport between the TI and the FM. Transport is modeled as diffusive in the TI beneath the FM, consistent with the mobility in the TI at room temperature, and in the FM, which essentially serves as a constant potential region albeit spin-dependent except in the low conductivity, diffusive limit. Thus, it can be captured by drift-diffusion simulation, which allows for ready interpretation of the results. We calculate switching time and energy consumed per write operation using self-consistent transport, spin-transfer-torque (STT), and magnetization dynamics calculations. Calculated switching energies and times compare favorably to conventional spin-torque memory schemes for substantial interlayer conductivity. Nevertheless, we find that shunting of current from the TI to a metallic nanomagnet can substantially limit efficiency. Exacerbating the problem, STT from the TI effectively increases the TI resistivity. We show that for optimum performance, the sheet resistivity of the FM layer should be comparable to or larger than that of the TI surface layer. Thus, the effective conductivity of the FM layer becomes a critical design consideration for TI-based non-volatile memory. [ABSTRACT FROM AUTHOR]

We study the transport properties of monolayer MX2 (M = Mo, W; X = S, Se, Te) n- and p-channel metal-oxide-semiconductor field effect transistors (MOSFETs) using full-band ballistic non-equilibrium Green's function simulations with an atomistic tight-binding Hamiltonian with hopping potentials obtained from density functional theory. We discuss the subthreshold slope, drain-induced barrier lowering (DIBL), as well as gate-induced drain leakage (GIDL) for different monolayer MX2 MOSFETs. We also report the possibility of negative differential resistance behavior in the output characteristics of nanoscale monolayer MX2 MOSFETs. [ABSTRACT FROM AUTHOR]

Graphene intercalation materials are potentially promising for the implementation of the ultra-low power, excitonic-condensate-based Bilayer pseudoSpin Field-Effect Transistor (BiSFETs) concept, as well as other novel device concepts requiring a graphene interlayer dielectric. Using density functional theory, we study the structural and electronic properties of bilayer graphene intercalated with iodine monochloride (ICl) and iodine monobromide (IBr). We determine the structural configuration of ICl and IBr graphene intercalation compounds (GICs). We also conduct an in-depth exploration of inter-layer electronic coupling, using ab initio calculations. The presence of intercalants dopes the graphene layer. It also reduces, but does not eliminate, the electronic coupling between graphene layers, which may enable BiSFET operation. In addition, we present experimental results for ICl-GIC synthesis and characterization. [ABSTRACT FROM AUTHOR]

We study spin-transfer-torque (STT) switching of a cross-shaped ferromagnet with unequal branches as the free layer in a magnetic tunnel junction using micromagnetic simulations. The free layer in the magnetic tunnel junction is thus designed to have four stable energy states using shape anisotropy. Switching shows distinct regions with increasing current density. Stability of the states against thermal fluctuations is considered, and the validity of the results for different dimensions and material parameters of the free layer ferromagnet is investigated. The results could be useful for a multi-bit STT-based memory. [ABSTRACT FROM AUTHOR]

Three-dimensional (3-D) topological insulators (TIs) are characterized by the presence of metallic surface states and a bulk band gap. Recently, theoretical and experimental studies have shown an induced gap in the surface state bands of TI thin films. The gap results from interaction of conduction band and valence band surface states from the opposite surfaces of a thin film, and its size is determined by the film thickness. This gap formation could open the possibility of thin-film TI-based metal-oxide-semiconductor field-effect transistors (MOSFETs). Here we explore the performance of MOSFETs based on TI thin films, specifically Bi2Se3, using quantum ballistic transport simulations with the tight-binding Hamiltonian in the atomic orbital basis. Our simulations indicate that Bi2Se3 MOSFET will be vulnerable to short-channel effects due to the high relative dielectric constant of Bi2Se3 (∼100) despite its expected excellent electrostatic integrity inherent in a two-dimensional system, and will have other limitations as compared to silicon-based MOSFETs. However, Bi2Se3 MOSFETs, and presumably other TI-based MOSFETs, appear to provide reasonable performance that perhaps could provide novel device opportunities when combined with novel TI properties such as spin-polarized surface states. [ABSTRACT FROM AUTHOR]

A quantum transport simulator, Schrödinger equation Monte Carlo (SEMC) in three dimensions, is presented that provides a rigorous yet reasonably computationally efficient quantum mechanical treatment of real scattering processes within quantum transport simulations of nanoscale three-dimensional (3D) metal oxide semiconductor field-effect transistor (MOSFET) geometries such as quantum wire and multigate field-effect transistors. This work represents an extension of earlier versions of SEMC for simulating quantum transport and scattering in systems with relatively simpler quasi-one-dimensional and quasi-two-dimensional geometries such as quantum-cascade lasers (via SEMC in one dimension) and silicon-on-insulator or dual-gate MOSFETs (via SEMC in two dimensions), respectively. However, the limiting computational considerations can be significantly different. The SEMC approach represents a variation in nonequilibrium Green’s function techniques with scattering as well as carrier injection into the simulation region treated via Monte Carlo techniques. Scattering mechanisms include intravalley and intervalley scatterings, intrasubband and intersubband scatterings via acoustic and optical phonons, and, in the former case, surface roughness scattering. SEMC-3D simulations of a silicon omega-gate nanoscale n-channel MOSFET are provided to illustrate the modeling technique as well as the complexity of scattering effects in such nanoscale devices. [ABSTRACT FROM AUTHOR]

A kinetic arsenic-interstitial interaction model has been developed to study and predict arsenic transient enhanced diffusion (TED) and deactivation behavior during ultrashallow junction (USJ) formation. This model is based on density functional theory and has been verified by previous experiments in which the significant role of interstitial mechanism in arsenic TED was revealed. The mechanism of enhanced and retarded arsenic diffusion in different point defect environments is investigated by utilizing this model in kinetic Monte Carlo simulation. The arsenic-interstitial pair, with low binding energy and low migration energy, is shown to be the major contributor to arsenic TED in silicon interstitial-rich situations. In addition, by using this model, we demonstrate the transient existence of arsenic-interstitial clusters (AsnIm) during postimplant annealing and propose their possible role in deactivation for short time annealings such as laser annealing and spike annealing. Moreover, we have developed a novel surface-trap based kinetic Monte Carlo model to simulate arsenic uphill diffusion in proximity of the Si/SiO2 interface. The simulation results show that the activation behavior of the uphill portion of arsenic has considerable impact on the junction sheet resistance. The activation behavior of this arsenic is expected to become more important when USJ depth is scaled down further. [ABSTRACT FROM AUTHOR]

A quantum transport simulator, Schrödinger equation Monte Carlo in two dimensions (SEMC-2D), is presented that provides a rigorous yet reasonably computationally efficient quantum mechanical treatment of real scattering processes within quantum transport simulations of nanoscale metal-oxide-semiconductor field effect transistors (MOSFETs). This work represents an extension of an early version of SEMC for simulating quantum transport and scattering in quasi-one-dimensional device geometries such as encountered in conventional and quantum-cascade lasers. In many respects SEMC is simply a variation on nonequilibrium Green’s function techniques, with scattering as well as carrier injection into the simulation region treated via Monte Carlo techniques. In this regard, SEMC also represents a quantum analog of semiclassical Monte Carlo. Scattering mechanisms considered include crystal momentum randomizing acoustic and optical intra- and intervalley scattering (and intra- and intersubband scattering), and nonrandomizing surface roughness scattering. Simulation results for nanoscale dual-gate MOSFET geometries are provided that illustrate the method and the continuing need for accurate modeling of scattering even in nanoscale MOSFETs. [ABSTRACT FROM AUTHOR]

We investigate B diffusion in strained Si by using first-principles density functional theory calculations. An enhancement and an anisotropy of B diffusion in biaxial tensile strained Si are found. The diffusion barrier along the strain plane (channel) is decreased while the barrier in the vertical direction (depth) remains unchanged. This anisotropy comes from the orientation dependence of the saddle point in the diffusion pathway. The formation enthalpy of B-I pair also decreases in strained Si. According to our calculations, for strained Si on a Si0.8Ge0.2 buffer layer, which is widely used in strained metal oxide semiconductor field-effect-transistor, an enhancement of B diffusivity along the channel by a factor ∼4 and a factor ∼2 in the vertical direction are expected for typical rapid thermal anneals. [ABSTRACT FROM AUTHOR]

Using plane-wave pseudopotential density functional theory calculations, we have investigated the behaviors of neutral interstitials and vacancies at the amorphous-crystalline (a–c) Si interface. A continuous random network model is employed in the construction of defect-free a-c interface structure. We find that both vacancies and interstitials prefer to reside on the amorphous side of the interface. In both cases, the most stable defects occur 3–4 Å from the a-c interface. Vacancy stabilization is found to be due to strain relief provided to the substrate lattice while interstitial stabilization is due largely to bond rearrangement arising from interstitial integration into the substrate lattice. We also discuss the effect of the “spongelike” behavior of the amorphous phase toward native defects on ultrashallow junction formation in the fabrication of ever-shrinking electronic devices. [ABSTRACT FROM AUTHOR]

The characteristics of CoSi2 poycide gates were investigated. The results showed that the sample was capable of monitoring the diffusion of electrically activated dopants from the silicide towards the polycrystalline silicon-SiO2 interface. In addition, the CoSi2 polycide was also capable of doping polycrystalline silicon gates without any observed degradation in resistivity.

A quantum transport simulator, Schrodinger equation Monte Carlo (SEMC) in three dimensions, has provided a computationally efficient quantum mechanical treatment of real scattering processes with quantum transport simulations of nanoscale three-dimensional (3D) metal oxide semiconductor field-effect transistor (MOSFET) geometries like quantum wire and multigate field-effect transistors. SEMC-3D simulations of a silicon omega-gate nanoscale n-channel MOSFET have illustrated the modeling method as well as the complexity of scattering effects in such nanoscale devices.

A kinetic arsenic-interstitial interaction model is developed for analyzing and predicting arsenic transient enhanced diffusion (TED) and deactivation behavior during ultrashallow junction (USJ) formation. The results have shown that the activation behavior of the uphill portion of arsenic has major impact on the junction sheet resistance.

A quantum transport simulator, Schrodinger equation Monte Carlo in two dimensions (SEMC-2D), is described that has provided an efficient quantum mechanical treatment of real scattering processing within quantum transport simulations of nanoscale metal-oxide-semiconductor field effect transistors (MOSFET). Simulation results for nanoscale dual-gate MOSFET geometries have illustrated the method and the need for accurate modeling of scattering even in nanoscale MOSFETs.

We studied spin-transfer-torque (STT) switching of a cross-shaped magnetic tunnel junction in a recent report [Roy et al., J. Appl. Phys. 113, 223904 (2013)]. In that structure, the free layer is designed to have four stable energy states using the shape anisotropy of a cross. STT switching showed different regions with increasing current density. Here, we employ the micromagnetic spectral mapping technique in an attempt to understand how the asymmetry of cross dimensions and spin polarization direction of the injected current affect the magnetization dynamics. We compute spatially averaged frequency-domain spectrum of the time-domain magnetization dynamics in the presence of the current-induced STT term. At low currents, the asymmetry of polarization direction and that of the arms are observed to cause a splitting of the excited frequency modes. Higher harmonics are also observed, presumably due to spin-wave wells caused by the regions of spatially non-uniform effective magnetic field. The results could be used towards designing a multi-bit-per-cell STT-based random access memory with an improved storage density. [ABSTRACT FROM AUTHOR]