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The semiconductor industry is undergoing a transformative phase, marked by the relentless drive for miniaturization and a constant demand for higher performance and energy efficiency. However, the reduction of metal–oxide–semiconductor field-effect transistor sizes for advanced technology nodes below 10 nm presents several challenges. In response, strained silicon technology has emerged as a key player, exploiting strain induction in the silicon crystal lattice to improve device performance. At the same time, there has been a growing need for characterization techniques that allow in-line monitoring of sample conditions during semiconductor manufacturing, as an alternative to traditional methods such as transmission electron microscopy or high-resolution X-ray diffraction, which have several limitations in terms of measurement time and sample destructiveness. This paper explores the application of advanced spectroscopic characterization techniques, in particular µ-Raman spectroscopy and tip-enhanced Raman spectroscopy (TERS), to meet the evolving needs of the semiconductor industry for quality control and failure analysis, increasingly requiring faster and non-destructive characterization techniques. µ-Raman provides insight into strain values and distributions of strained layers with different thicknesses and germanium concentrations, but its lateral resolution is constrained by the Abbe diffraction limit. TERS, on the other hand, emerges as a powerful non-destructive technique capable of overcoming diffraction limits by exploiting the combination of an atomic force microscope with a Raman spectrometer. This breakthrough makes it possible to estimate the chemical composition and induced strain in the lattice by evaluating the Raman peak position shifts in strained and unstrained silicon layers, providing crucial insights for nanoscale strain control. In particular, this paper focuses on the TERS characterization of Si0.7Ge0.3 epitaxial layers grown on a silicon-on-insulator device, demonstrating the effectiveness of this technique and the high lateral resolution that can be achieved. [ABSTRACT FROM AUTHOR]

First-principles simulations are conducted to explore the structural stability, electronic properties, and optical responses of pristine and boron- or nitrogen-doped monolayers graphene. The computed electronic density of states revealed that the substitutional doping of boron impurity atoms on monolayer graphene (MLG) shifts the Dirac point upward, although the substitution of nitrogen impurity atoms in graphene pushes the Dirac point downward the Fermi level. This could exhibit that upon the doping of MLG with boron or nitrogen, respectively, p-type or n-type semimetal is acquired. The overall optical spectral properties of the substituted graphene with boron or nitrogen atoms are simulated and compared with the optical spectra results of pure graphene. The optical features of pristine and doped MLG are determined by taking the interband and intra-band transitions into account ranging from the far-infrared to the ultraviolet regime of the electromagnetic radiation. A remarkable red shift in the optical spectra of the doped MLG towards the visible regime of radiation is established. An enhanced reflectivity illustrated that concentration-dependent optical properties of boron and nitrogen-doped MLG happen at lower electromagnetic radiation regimes. In addition, we explored the thermoelectric behaviors of the pristine/doped graphene monolayers with 4 × 4 supercells. We found a significant improvement in the electrical conductivity of graphene when doped with boron or nitrogen impurities. However, an increase in the electrical conductivity has textured a decrease in the Seebeck coefficients. Improvement in the electrical conductivity is attributed to an interesting effect on the graphene monolayers' power factor (PF). These findings indicate a positive impact of the dopants on the thermoelectric properties of graphene monolayers and reveal that they are potential materials for thermoelectric applications and nanodevices. [ABSTRACT FROM AUTHOR]

It is recently shown that when a drop of Glenlivet whisky evaporates, it leaves behind a uniform deposit [Phys. Rev. Lett. 116, 124501 (2016)]. This fascinating finding is utilized in the fabrication of electrochemical metallization memory (ECM) cells. The top (Ag) and bottom (Co) electrodes in the proposed structure are separated by a layer of Glenlivet whisky deposit (an insulator). Measurements show the device response is typical of ECM cells that involve threshold‐type switching, pinched hysteresis loops, and a large difference between the high‐ and low‐resistance states. The surface coating process used in these experiments simplifies the device fabrication and results in a biodegradable insulating layer, which may facilitate the recovery of recyclable materials at the end of the device's use. [ABSTRACT FROM AUTHOR]

The performance of nanoelectronic and molecular electronic devices relies strongly on the employed functional units and their addressability, which is often a matter of appropriate interfaces and device design. Here, we compare two promising designs to build solid-state electronic devices utilizing the same functional unit. Optically addressable Ru-terpyridine complexes were incorporated in supramolecular wires or employed as ligands of gold nanoparticles and contacted by nanoelectrodes. The resulting small-area nanodevices were thoroughly electrically characterized as a function of temperature and light exposure. Differences in the resulting device conductance could be attributed to the device design and the respective transport mechanism, that is, thermally activated hopping conduction in the case of Ru-terpyridine wire devices or sequential tunneling in nanoparticle-based devices. Furthermore, the conductance switching of nanoparticle-based devices upon 530 nm irradiation was attributed to plasmon-induced metal-to-ligand charge transfer in the Ru-terpyridine complexes used as switching ligands. Finally, our results reveal a superior device performance of nanoparticle-based devices compared to molecular wire devices based on Ru-terpyridine complexes as functional units.

The dielectric properties of polyvinyl alcohol/polyethylene glycol/TiN (PVA/PEG/TiN) nanocomposites are studied to use them in different electronic nanodevices. The PVA/PEG/TiN nanocomposites’ films are synthesized by using the casting method. The dielectric properties of PVA/PEG/TiN nanocomposites are tested at frequency (f) ranged from 100 Hz to 5 MHz. The results demonstrate that the dielectric properties of fabricated nanocomposites (ε′, ε″ and σA.C.) are improved with increase in the TiN-nanoparticles’ concentration. Components (ε′ and ε″) of complex dielectric constant are decreased, while the A.C. electrical conductivity (σA.C.) is increased with increase in the frequency. The results indicate that the PVA/PEG/TiN nanocomposites can be useful in different electronic nanodevices. [ABSTRACT FROM AUTHOR]

We study spin- and valley-dependent transport properties in a n-p–n junction of 8-pmmn borophene monolayer. We show that an exchange magnetic field can generate spin polarization in the system and a gate voltage, as a potential barrier, induces valley polarization. The valley polarization, induced by the gate voltage, is due to the anisotropic and tilted Dirac cones of borophene structure. This property is the advantage of borophene over the other 2D materials with isotropic and non-tilted Dirac cones such as graphene in which a gate potential cannot induce valley polarization. We also show that the proposed device (borophene-based n-p–n junction) can work as perfect spin and perfect valley filters. The spin and valley filters can be controlled by changing the gate voltage and/or Fermi energy. The results of this study show that borophene has a suitable potential to be used in spintronic and valleytronic devices. • Our npn junction can work as perfect spin and perfect valley filters. • Spin-up filter changes to the spin-down filter and vice versa via gate voltage. • Valley filtering by applying gate voltage is due to tilted Dirac cones. • Above property cannot occur in 2D materials with isotropic and non-tilted cones. • Borophene shows a great potential for use in spintronic and valleytronic devices. [ABSTRACT FROM AUTHOR]

In this investigation, we have analyzed the structural, electrical, and optical behaviors of pure and composite thin films which are obtained from 2D monolayer molybdenum disulfide (MoS2) flakes, conjugated oligomer (CO) 1,4-Bis(9-ethyl-3-carbazo-vinylene)-9,9-dihexyl-fluorene (BECV-DHF), and by combining CO (BECV-DHF) with MoS2 in forms of CO/MoS2 composites. All the samples are coated on SiO2/Si substrates using the spin coating procedure where a spin-coating solution has been obtained by dispersing CO and MoS2 in ethanol or toluene. The structural morphology of MoS2 films and CO/MoS2 films of various thicknesses are analyzed using field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), and profilometer. These experimental results confirm the formation of MoS2 layer composite with oligomer nanocrystals. The optical properties of MoS2, CO, and CO/MoS2 films showed that the increased film thickness shifted the spectral peaks towards near infrared (NIR) and ultraviolet–visible (UV) regions of the electromagnetic spectrum. Moreover, devices such as solar cells, flexible memory cell and MOSFET were designed. The I-V characteristics of these devices show that CO/MoS2 composite films could serve as potential candidates for organic-inorganic nano-electronic device applications.

• O/F impurities effect revealed an opening of band gap at Dirac cone of graphene. • O/F impurity defects showed a shift of lower conduction states with p-type nature. • Optical spectra of doped graphene are found to absorb light in the infrared region. • F-doped graphene with the lowest formation energy is experimentally feasible. • Further experiments on sensors and electrocatalysts may benefit from these findings. In order to gain a systematic comprehension of the impacts of low-level defects in graphene, ab-initio calculations were performed on monolayer graphene sheets to examine how oxygen and fluorine substitutional impurities affect their energetic stability, electronic and optical characteristics. The optimal configurations, structural stability, electronic band structures, spatial charge density, and optical spectra of graphene single-layer materials doped with oxygen and fluorine atoms are investigated. The fluorine-doped graphene, therefore, showed a lower formation energy than its oxygen-doped counterpart. Additionally, F-doped graphene shows a higher charge density around the fluorine atom than O-doped graphene. Based on band structure analysis, the lower conduction bands of graphene sheets shift below the Fermi state (E F) when two O or F impurities are substituted into it. With two O/F impurity atoms doped into graphene, the conduction states are farther displaced below the E F , resulting in n-type behavior. Consequently, altering graphene structure via an O/F-substituting scheme results from the disruption of the Dirac cone near E F , which has become flat along the high symmetry point (K-point) in the Brillouin zone. Furthermore, the substitution of graphene sheets via O or F impurities exhibit markedly modified optical spectra and refractive indices at low photon energies. As a result, with one or two O/F impurity elements inserted into graphene sheets, the reflectivity and optical conductivity spectra differ at the lowest electromagnetic radiation ranges. Additionally, the electron energy loss functions as well as X-ray absorption spectra of clean and doped graphene monolayers revealed spectral variations at a moderate energy span. These investigations surmise that novel chemical modifications to graphene sheets doped with light non-metallic elements (O/F) may offer the opportunity to tailor their optical characteristics in the infrared spectrum, which may be beneficial in sensor and electrocatalyst uses. [ABSTRACT FROM AUTHOR]

Long metallic nanowires combine crucial factors for nonconservative current-driven atomic motion. These systems have degenerate vibrational frequencies, clustered about a Kohn anomaly in the dispersion relation, that can couple under current to form nonequilibrium modes of motion growing exponentially in time. Such motion is made possible by nonconservative current-induced forces on atoms, and we refer to it generically as the waterwheel effect. Here the connection between the waterwheel effect and the stimulated directional emission of phonons propagating along the electron flow is discussed in an intuitive manner. Nonadiabatic molecular dynamics show that waterwheel modes self-regulate by reducing the current and by populating modes in nearby frequency, leading to a dynamical steady state in which nonconservative forces are counter-balanced by the electronic friction. The waterwheel effect can be described by an appropriate effective nonequilibrium dynamical response matrix. We show that the current-induced parts of this matrix in metallic systems are long-ranged, especially at low bias. This nonlocality is essential for the characterisation of nonconservative atomic dynamics under current beyond the nanoscale.

In this paper, the authors present a simulation study in order to carry out static and dynamic analysis of CNTFET-based digital circuits, in the semi-empirical compact model for CNTFETs, which was already proposed with, both the quantum capacitance effects and the sub-threshold currents. To verify the validity of the obtained results, they are compared with those of the Stanford-Source Virtual Carbon Nanotube Field-Effect Transistor (VS-CNFET) model. This comparison is made through some simulations of digital circuits. In particular they have considered XOR gate, but emphasizing that the proposed procedure can be applied to any logic gate based on CNTFET. As regards the static conditions, the two models behave in a manner virtually identical, while, as regards the dynamic analysis, there is a remarkable differences between two models in terms of propagation delays and rise and fall times. [ABSTRACT FROM AUTHOR]

Arrays of magnetic nanowires in porous alumina can be used to store information inscribed on the system by orienting the magnetization of selected wires pointing in a desired direction, so symbols can be read as ferromagnetic sectors. However, this information is subject to aging and the stored information could be gradually lost. We investigate here two mechanisms proposed to improve the prevalence of the stored information: opposite ferromagnetic band at the center of the symbol and bi-segmented nanowires acting as two layers of nanowires storing the same information. Both mechanisms prove to increase resistance to the action of external magnetic fields for the case of Ni wires in a geometry compatible with actually grown nanowires. Advantages and disadvantages of these mechanisms are discussed. [ABSTRACT FROM AUTHOR]

Quantitative electrical admittance measurements of diffusive superconductor-normal-metal-superconductor (SNS) junctions at gigahertz frequencies and millikelvin temperatures are reported. The gold-palladium-based SNS junctions are arranged into a chain of superconducting quantum interference devices. The chain is coupled strongly to a multimode microwave resonator with a mode spacing of approximately 0.6 GHz. By measuring the resonance frequencies and quality factors of the resonator modes, the dissipative and reactive parts of the admittance of the chain are extracted. The phase and temperature dependence of the admittance near 1 GHz are compared with theory based on the time-dependent Usadel equations. This comparison allows the identification of important discrepancies between theory and experiment that are not resolved by including inelastic scattering or elastic spin-flip scattering in the theory. [ABSTRACT FROM AUTHOR]

First-principles calculations based on density-functional theory reveal some superior physical properties of hydrogen and fluorine co-decorated silicene (HSiF) monolayer and bilayer. Our simulated results reveal that the HSiF monolayer is a large direct band gap semiconductor greatly differing from the gapless semi-metallic silicene. There exists strong interlayer coupling in HSiF bilayer, leading to the good stabilities of HSiF bilayer even beyond bilayer graphene. The proposed HSiF bilayer exhibits a moderate direct band gap of 0.296 eV which is much lower than that of HSiF monolayer. Encouragingly, HSiF layers all have a direct band gap nature, irrespective of stacking pattern, thickness and external electric fields, which is an advantage over MoS 2 layers. Furthermore, an out-of-plane electric field has an evident impact on the band structures of the HSiF monolayer and bilayer. Especially, the band gap of HSiF bilayer can be effectively tuned by external electric field, even a semiconductor–metal transition occurs. More importantly, the HSiF bilayer exhibits a significant improved visible light adsorption peak with respect to that of HSiF monolayer, and the superior optical properties is robust, independent of stacking pattern. The complete electron-hole separation also enhances the photocatalytic efficiency of HSiF bilayer. In a word, the moderate band gap, effective band gap modification by external electric field, robust direct band gap nature, suitable band edge positions, electron-hole separation, and fascinating visible light adsorption, which enable HSiF bilayer to have great potential applications in the field of solar energy conversion, high performance photocatalysis and nanoelectronic devices, and we call for more concern over this kind of 2D Janus materials which possesses excellent properties. [ABSTRACT FROM AUTHOR]

The durability of the stored information in magnetic systems is one important feature in firmware applications such as security codes, magnetic keys and other similar products. In the present paper we discuss two different ways of preserving patterns in the set of magnetic wires trapped in the porous membranes used to produce them. One of the techniques is the inscription of an opposite magnetic band of about 1/3 the width of the stored pattern which minimizes the repulsive energy among the ferromagnetic cylinders still leaving a potent magnetic signal to be read. The other technique makes use of segmented nanowires which present a competition of repulsive energy of segments within the same layer while the interaction is attractive with the closer segments of the other layer; such a competition can lead to stabilization if the geometrical parameters are properly controlled. The first technique is cheaper and faster to implement, while the second technique needs a more complete fabrication process but can lead to more durable stored information. [ABSTRACT FROM AUTHOR]

We study electron transport through a single-molecule magnet (SMM) and the interplay of its anisotropic spin with quantized vibrational distortions of the molecule. Based on numerical renormalization group calculations we show that, despite the longitudinal anisotropy barrier and small transverse anisotropy, vibrational fluctuations can induce quantum spin-tunneling (QST) and a QST-Kondo effect. The interplay of spin scattering, QST and molecular vibrations can strongly enhance the Kondo effect and induce an anomalous magnetic field dependence of vibrational Kondo side-bands.

Silicon-based quantum-computer architectures have attracted attention because of their promise for scalability and their potential for synergetically utilizing the available resources associated with the existing Si technology infrastructure. Electronic and nuclear spins of shallow donors (e.g. phosphorus) in Si are ideal candidates for qubits in such proposals due to the relatively long spin coherence times. For these spin qubits, donor electron charge manipulation by external gates is a key ingredient for control and read-out of single-qubit operations, while shallow donor exchange gates are frequently invoked to perform two-qubit operations. More recently, charge qubits based on tunnel coupling in P+2 substitutional molecular ions in Si have also been proposed. We discuss the feasibility of the building blocks involved in shallow donor quantum computation in silicon, taking into account the peculiarities of silicon electronic structure, in particular the six degenerate states at the conduction band edge. We show that quantum interference among these states does not significantly affect operations involving a single donor, but leads to fast oscillations in electron exchange coupling and on tunnel-coupling strength when the donor pair relative position is changed on a lattice-parameter scale. These studies illustrate the considerable potential as well as the tremendous challenges posed by donor spin and charge as candidates for qubits in silicon.Arquiteturas de computadores quânticos baseadas em silício vêm atraindo atenção devido às suas perspectivas de escalabilidade e utilização dos recursos já instalados associados à tecnologia do Si. Spins eletrônicos e nucleares de doadores rasos (por exemplo fósforo) em Si são candidatos ideais para bits quânticos (qubits) nestas propostas, devido aos tempos de coerência relativamente longos dos spins em matrizes de Si. Para estes qubits de spin, a manipulação da carga do elétron do doador por eletrodos externos é um ingrediente importante para controle e leitura das operações de um-qubit, enquanto que as portas de troca são frequentemente invocadas para as operações de dois-qubits. Mais recentemente, qubits de carga baseados no tunelamento do elétron no íon molecular P+2 em Si foram também propostos. Discutimos aqui as operações elementares envolvidas na computação quântica baseada em doadores rasos em Si, levando em consideração as peculiaridades da estrutura eletrônica do Si, em particular a degenerescência sextupla do mínimo da banda de condução. Mostramos que a interferência quântica entre estes seis estados não afeta significativamente as operações envolvendo um único doador, mas leva a oscilações no acoplamento de troca e no acoplamento via tunelamento quando a posição relativa do par é modificada na escala de distâncias do parâmetro de rede. Nossos estudos ilustram as potencialidades bem como os enormes desafios envolvidos na implementação de qubits de spin e carga em Si.

A set of magnetic nanowires trapped in the membrane used to produce them can be employed to inscribe information in the form of sectors of wires with the same ferromagnetic orientation (Cisternas and Vogel, 2013 [1] ). However, such a system relays on the shape anisotropy of each nanowire as the stabilizing mechanism avoiding magnetization reversal. Such stabilization mechanism weakens as the size of the nanowires decrease. In the present paper we introduce a way of using segmented nanowires to produce a self-stabilization mechanism based on the fact that interactions among segments of different layers can contribute with negative energies. Then, for some particular geometries it is possible to make this interaction the most important one producing a more stable system with respect to spontaneous magnetization reversal. Such inscribed ferromagnetic sector will then last longer than other ferromagnetic sectors formed by exclusively repelling elements. We make use of available algebraic expressions to calculate the energy contribution of noncoaxial segments. For the coaxial segments a similar expression is developed here and it is applied to real systems. The total interaction energy for all segments in the system is calculated for different geometrical possibilities. Application to two particular symbols (letters T and O) is fully discussed bringing out general aspects that could be applied to other symbols. Projections of this work are finally mentioned. [ABSTRACT FROM AUTHOR]

The high yield assembly and fabrication method for Cu/CuO nanowires for nanoelectronic devices was implemented. Assembly of Cu/CuO nanowires nano-electronic devices were realized by floating potential and dielectrophoresis approach. The simulation of floating potential distribution of the chip was performed by comsol multiphysics coupling software. Six hundred devices were assembled on the area of less than one square centimeter. The assembled devices were characterized by scanning electron microscopy. The experimental results showed that high yield assembly had been realized, and the success rate of Cu/CuO nanowires ideal assembly for nanoelectronic devices had been assessed. [ABSTRACT FROM AUTHOR]

Single nanowire solar cells (SNSCs) are typical nanoscale optoelectronic devices with unique photonic and electronic properties, which require precise designs in terms of a comprehensive simulation technique. We present a coupled model for silicon-based SNSCs which solves both Maxwell and semiconductor equations self-consistently using the finite-element method. The light-trapping behavior (e.g., leaky-mode resonances) and carrier generation/recombination inside the nanowire cavity are simulated and analyzed especially by addressing the effects of semiconductor doping, surface recombination, and device dimension on the performance of the solar cells. The absorption efficiency, external quantum efficiency, and current–voltage characteristics have been obtained for a complete evaluation of SNSCs. [ABSTRACT FROM PUBLISHER]

Abstract: We present a model of Carbon Nanotube Field Effect Transistors (CNTFETs) directly and easily implementable in simulation SPICE software for electronic circuit design. The model is based on analytical approximations and parameters extracted from quantum mechanical simulations of the device and depending on the nanotube diameter and the oxide capacitance. Comparison of the simulated output and transfer characteristics with those of a numerical model available online and with experimental data shows a relative error less than 5% in both cases. In order to determine the values of CNTFET equivalent circuit elements a new procedure, based on a best-fitting between the measured and simulated values of output device characteristics, has been proposed. To verify the versatility of the proposed model we use it in the SPICE simulator to design some A/D electronic circuits, demonstrating the importance of the quantum capacitance dependence on polarisation voltages and examining the effects of the CNT quantum resistances. [Copyright &y& Elsevier]

In this study, the ability of Haloarcula sp. IRU1 isolated from Urmia lake, Iran, for production of cruxrhodopsin as a biomacromolecule with nanofunction from textile wastewater was evaluated and optimized by Taguchi experimental design. According to Taguchi method, the optimum conditions at which high cruxrhodopsin production could be achieved were observed to be in the presence of textile wastewater at 0.25% (volume/volume), yeast extract at 0.025% (weight/volume) and KH2PO4 at 0.005% (weight/volume). In conclusion, Haloarcula sp. IRU1 is capable of cruxrhodopsin production from textile wastewater in different conditions. [ABSTRACT FROM AUTHOR]

We present a compact, semiempirical model of carbon nanotube field effect transistor easily implementable in simulation SPICE software to design analog and digital circuits. The model is based on analytical approximations and parameters extracted from quantum mechanical simulations, having compared the results with those of the numerical model online available and of experimental data. [ABSTRACT FROM PUBLISHER]

In this article, we report the recent progress on decoherence dynamics of electrons in quantum dot quantum computing systems using the exact master equation we derived recently based on the Feynman–Vernon influence functional approach. The exact master equation is valid for general nanostructure systems coupled to multi-reservoirs with arbitrary spectral densities, temperatures and biases. We take the double quantum dot charge qubit system as a specific example, and discuss in details the decoherence dynamics of the charge qubit under coherence controls. The decoherence dynamics risen from the entanglement between the system and the environment is mainly non-Markovian. We further discuss the decoherence of the double-dot charge qubit induced by quantum point contact (QPC) measurement where the master equation is re-derived using the Keldysh non-equilibrium Green function technique due to the non-linear coupling between the charge qubit and the QPC. The non-Markovian decoherence dynamics in the measurement processes is extensively discussed as well. [ABSTRACT FROM AUTHOR]

In this paper we perform a simulation study on the limits of graphene-nanoribbon field-effect transistors (GNR-FETs) for post-CMOS digital applications. Both conventional and tunneling FET architectures are considered. Simulations of conventional narrow GNR-FETs confirm the high potential of these devices, but highlight at the same time OFF-state leakage problems due to various tunneling mechanisms, which become more severe as the width is made larger and require a careful device optimization. Such OFF-state problems are partially solved by the tunneling FETs, which allow subthreshold slopes better than 60 mV/dec, at the price of a reduced ON-current. The importance of a very good control on edge roughness is highlighted by means of a direct simulation of devices with non-ideal edges. [ABSTRACT FROM AUTHOR]

Abstract: The design rules in nanoscale integrated circuits have now reached the depletion regions widths in semiconductors devices. In order to describe the complete behavior of junctions, we present the analytic resolution of Poisson–Boltzmann equation in n–p and n–p–n junctions in thermal equilibrium. The main point of this resolution is the exact determination of the boundary conditions at each n–p interface. In n–p–n junction, it appears that under a few hundred of nanometers, the positive potential of the n-type region can overlap the negative potential of the p-type region. This result appears in n–p–n (or p–n–p) structures when the intermediate region is less doped in regard to the opposite regions. An illustration in the evolution of nanoscale metal–oxide–semiconductor field effect transistor (MOSFET) is presented. [Copyright &y& Elsevier]

Coherent transport in mesoscopic devices is well described by the Schrödinger equation supplemented by open boundary conditions. When electronic devices are operated at room temperature, however, a realistic transport model needs to include carrier scattering. In this work the kinetic equation for the Wigner function is employed as a model for dissipative quantum transport. Carrier scattering is treated in an approximate manner through a Boltzmann collision operator. A Monte Carlo technique for the solution of this kinetic equation has been developed, based on an interpretation of the Wigner potential operator as a generation term for numerical particles. Including a multi-valley semiconductor model and a self-consistent iteration scheme, the described Monte Carlo simulator can be used for routine device simulations. Applications to single barrier and double barrier structures are presented. The limitations of the numerical Wigner function approach are discussed. [ABSTRACT FROM AUTHOR]

We present the Vienna Schrödinger-Poisson Solver (VSP), a multi-purpose quantum mechanical solver for investigations on nano-scaled device structures. VSP includes a quantum mechanical solver for closed as well as open boundary problems on fairly arbitrary one-dimensional cross sections within the effective mass framework. For investigations on novel gate dielectrics VSP holds models for bulk and interface trap charges, and direct and trap assisted tunneling. Hetero-structured semiconductor devices, like resonant tunneling diodes (RTD), can be treated within the closed boundary model for quick estimation of resonant energy levels. The open boundary model allows evaluation of current voltage characteristics. [ABSTRACT FROM AUTHOR]

We are encountering tremendous opportunities and challenges in combining emerging nanotechnology for developing nanoelectronic devices. Researchers are designing nanoelectronic circuits based on newly discovered nanoscale building blocks, such as spintronic devices. In this paper, we calculate conductance in spintronic gates using the nonequilibrium Green's function and show useful operations for "multiterminal" logic gates. These spintronic devices can be used to design complicated spin circuits [ABSTRACT FROM PUBLISHER]

Abstract: For our previously proposed method of forming an artificially sized and positioned Ge dot array by the use of inverse-pyramid shape pits as an anchor for Ge dot positioning, we cleared the Ge dot positioning behavior, which depends on the anchor pit pitch and the Ge growth temperature. The results suggest that, with the pits, Ge dot positioning behavior still relates to the dot self-organizing mechanism itself in addition to the Ge migration behavior. On the basis of the results, their artificial positioning can be controlled by setting the pit pitch within the range between the self-organized Ge dot space and the Ge migration length. Using this method, an artificially aligned multiply-stacked Ge dot array was also demonstrated. [Copyright &y& Elsevier]

Abstract: A Si1− x Ge x sputter epitaxy method using an ultra-high-vacuum-compatible magnetron sputtering technique with an Ar and H2 mixture working gas has been introduced. The crystallinity and strain-relaxation controllability of a Si1− x Ge x layer grown on n-type Si(001) by our sputter epitaxy method is well comparable to those of a Si1− x Ge x layer grown by a standard molecular beam epitaxy (MBE) method. In the device level evaluation by forming an electron-tunneling Si/Si1− x Ge x asymmetric double quantum well resonant tunneling diode (ASDQW RTD), the fabricated RTD exhibits a high peak-to-valley current ratio (PVCR) of ∼26 with low background current, the performance of which is also close to that of our recent high PVCR ASDQW RTD fabricated by gas-source MBE. On the basis of these results, our proposed method is very promising for its application to various kinds of SiGe devices. [Copyright &y& Elsevier]

We have successfully developed an "all-laser" processing for the localized growth of suspended single-wall carbon nanotubes (SWCNTs) on prepatterned SiO2/Si substrates. Our "all-laser" process stands out by its exclusive use of the same KrF excimer laser, first, to deposit the embedded-catalyst electrodes with a controllable architecture and, second, to grow SWCNTs through the pulsed laser ablation of a pure graphite target. Under the optimal growth conditions, the suspended SWCNTs are shown to bridge laterally adjacent electrodes separated by a gap of ∼2 μm. These SWCNTs (having diameters in the 1.25-1.64-nm range) generally tend to auto-assemble into bundles of ∼5--15 nm in diameter. The "all-laser" process here developed offers the advantage of a direct integration of the SWCNTs into field-effect-transistor-like devices with no postprocessing, thereby permitting the investigation of their electrical transport properties. Thus, the suspended SWCNT bundles are shown to behave collectively as an ambipolar transistor with ON/OFF switching ratios as high as ∼104. [ABSTRACT FROM PUBLISHER]

Recently there has been tremendous progress made in the research of novel nanotechnology for future nanoelectronic applications. In particular, several emerging nanoelectronic devices such as carbon-nanotube field-effect transistors (FETs), Si nanowire FETs, and planar III-V compound semiconductor (e.g., InSb, InAs) FETs, all hold promise as potential device candidates to be integrated onto the silicon platform for enhancing circuit functionality and also for extending Moore's Law. For high-performance and low-power logic transistor applications, it is important that these research devices are frequently benchmarked against the existing Si logic transistor data in order to gauge the progress of research. In this paper, we use four key device metrics to compare these emerging nanoelectronic devices to the state-of-the-art planar and nonplanar Si logic transistors. These four metrics include: 1) CV/I or intrinsic gate delay versus physical gate length Lg; 2) energy-delay product versus Lg; 3) subthreshold slope versus Lg; and 4) CV/I versus on-to-off-state current ratio ION/IOFF. The results of this benchmarking exercise indicate that while these novel nanoelectronic devices show promise and opportunities for future logic applications, there still remain shortcomings in the device characteristics and electrostatics that need to be overcome. We believe that benchmarking is a key element in accelerating the progress of nanotechnology research for logic transistor applications. [ABSTRACT FROM PUBLISHER]

We investigated the Ge migration and Ge dot positioning behavior on a patterned Si(001) over a wide Ge growth temperature range. Ge migration length was directly measured using Si(001) with a sink structure for Ge, and Ge migrated over 2.8 μm at surface temperatures of more than 700 °C. At higher temperatures, Ge migrated and Ge dots formed at more stable positions such as in convex and concave structures which function as an anchor for thermal excitation. On the basis of the results, we proposed a new method of Ge dot formation using the Ge long migration and Ge dot-anchoring effects. With this method, we demonstrated the Ge dot array formation using small pyramids or pits as an anchor. The sizes and positions of the dots are artificially determined by the amount of Ge growth and anchor position. A pit is most effective as a position-controlling anchor. [Copyright &y& Elsevier]