Showing papers on "Nanoelectronics published in 2011"
TL;DR: A comprehensive review of the literature on one-dimensional (1D) nanostructures (nanowires, nanoribbons, nanotubes, nanobelts, and nanofibers) of π-conjugated small molecules, oligomers, and polymers is presented in this article.
Abstract: This paper presents a comprehensive review of the literature on one-dimensional (1D) nanostructures (nanowires, nanoribbons, nanotubes, nanobelts, and nanofibers) of π-conjugated small molecules, oligomers, and polymers. The diverse methods used in assembling the molecular building blocks into 1D functional nanostructures and nanodevices are discussed, including hard and soft template-assisted synthesis, electrospinning, nanolithography, self-assembly in solution and at interfaces, physical vapor transport, and other strategies. Optical, charge transport, electronic, and photoconductive properties of nanowires and nanotubes of selected classes of π-conjugated molecular systems are discussed next, highlighting unique features of the 1D nanostructures compared to 2D thin films. Overview of applications of these 1D organic nanostructures ranging from nanoscale light-emitting diodes, field-emission devices, organic photovoltaics, sensors/biosensors, spin-electronics, and nanophotonics to nanoelectronics is th...
611 citations
TL;DR: In this article, the performance limits of monolayer transition metal dichalcogenide ( MX2) transistors with a ballistic MOSFET model were examined with an ab initio theory.
Abstract: The performance limits of monolayer transition metal dichalcogenide ( MX2) transistors are examined with a ballistic MOSFET model. Using an ab initio theory, we calculate the band structures of 2-D transition MX2. We find the lattice structures of monolayer MX2 remain the same as the bulk MX2. Within the ballistic regime, the performances of monolayer MX2 transistors are better compared with those of the silicon transistors if a thin high-κ gate insulator is used. This makes monolayer MX2 promising 2-D materials for future nanoelectronic device applications.
463 citations
TL;DR: The basic functional elements needed to fabricate electronic devices are described and summarized and a high-level roadmap for device-related MOF research is proposed to stimulate thinking within the MOF community concerning the development these materials for applications including sensing, photonics, and microelectronics is proposed.
Abstract: Metal-organic frameworks (MOFs) and related material classes are attracting considerable attention for applications such as gas storage, separations, and catalysis. In contrast, research focused on potential uses in electronic devices is in its infancy. Several sensing concepts in which the tailorable chemistry of MOFs is used to enhance sensitivity or provide chemical specificity have been demonstrated, but in only a few cases are MOFs an integral part of an actual device. The synthesis of a few electrically conducting MOFs and their known structural flexibility suggest that MOF-based electronic devices exploiting these properties could be constructed. It is clear, however, that new fabrication methods are required to take advantage of the unique properties of MOFs and extend their use to the realms of electronic circuitry. In this Concepts article, we describe the basic functional elements needed to fabricate electronic devices and summarize the current state of relevant MOF research, and then review recent work in which MOFs serve as active components in electronic devices. Finally, we propose a high-level roadmap for device-related MOF research, the objective of which is to stimulate thinking within the MOF community concerning the development these materials for applications including sensing, photonics, and microelectronics.
394 citations
TL;DR: In this article, the ternary sesquichalcogenide (Bi(x)Sb(1-x))2Te3 is shown to be a tunable topological insulator system by tuning the ratio of bismuth to antimony.
Abstract: Topological insulators exhibit a bulk energy gap and spin-polarized surface states that lead to unique electronic properties, with potential applications in spintronics and quantum information processing. However, transport measurements have typically been dominated by residual bulk charge carriers originating from crystal defects or environmental doping, and these mask the contribution of surface carriers to charge transport in these materials. Controlling bulk carriers in current topological insulator materials, such as the binary sesquichalcogenides Bi2Te3, Sb2Te3 and Bi2Se3, has been explored extensively by means of material doping and electrical gating, but limited progress has been made to achieve nanostructures with low bulk conductivity for electronic device applications. Here we demonstrate that the ternary sesquichalcogenide (Bi(x)Sb(1-x))2Te3 is a tunable topological insulator system. By tuning the ratio of bismuth to antimony, we are able to reduce the bulk carrier density by over two orders of magnitude, while maintaining the topological insulator properties. As a result, we observe a clear ambipolar gating effect in (Bi(x)Sb(1-x))2Te3 nanoplate field-effect transistor devices, similar to that observed in graphene field-effect transistor devices. The manipulation of carrier type and density in topological insulator nanostructures demonstrated here paves the way for the implementation of topological insulators in nanoelectronics and spintronics.
361 citations
TL;DR: The study reveals that local changes in polarization and reduction of unit cell volume with respect to bulk values lead to the observed size effect, which has strong implication in the field of energy harvesting, as piezoelectric voltage output scales with the piezOElectric coefficient.
Abstract: Nanowires made of materials with noncentrosymmetric crystal structure are under investigation for their piezoelectric properties and suitability as building blocks for next-generation self-powered nanodevices. In this work, we investigate the size dependence of piezoelectric coefficients in nanowires of two such materials − zinc oxide and gallium nitride. Nanowires, oriented along their polar axis, ranging from 0.6 to 2.4 nm in diameter were modeled quantum mechanically. A giant piezoelectric size effect is identified for both GaN and ZnO nanowires. However, GaN exhibits a larger and more extended size dependence than ZnO. The observed size effect is discussed in the context of charge redistribution near the free surfaces leading to changes in local polarization. The study reveals that local changes in polarization and reduction of unit cell volume with respect to bulk values lead to the observed size effect. These results have strong implication in the field of energy harvesting, as piezoelectric voltage...
267 citations
TL;DR: In this paper, the authors review recent progress in the tailored assembly of carbon nanotubes and graphene into three-dimensional architectures with particular emphasis on their own research employing self-assembly principles.
Abstract: This Feature Article reviews recent progress in the tailored assembly of carbon nanotubes and graphene into three-dimensional architectures with particular emphasis on our own research employing self-assembly principles. Carbon nanotubes and graphene can be assembled into macroporous films, hollow spherical capsules, or hollow nanotubes, via directed assembly from solvent dispersion. This approach is cost-effective and beneficial for large-scale assembly, but pre-requests stable dispersion in a solvent medium. Directed growth from a nanopatterned catalyst array is another promising approach, which enables the control of morphology and properties of graphitic materials as well as their assembly. In addition, the aforementioned two approaches can be synergistically integrated to generate a carbon hybrid assembly consisting of vertical carbon nanotubes grown on flexible graphene films. Tailored assembly relying on scalable self-assembly principles offer viable routes that are scalable for mass production towards the ultimate utilization of graphitic carbon materials in nanoelectronics, displays, sensors, energy storage/conversion devices, and so on, including future flexible devices.
225 citations
TL;DR: In this article, the authors demonstrate the attosecond control of the collective electron motion and directional emission from isolated dielectric (SiO2) nanoparticles with phase-stabilized few-cycle laser fields.
Abstract: Collective electron motion in condensed matter typically unfolds on a sub-femtosecond timescale. The well-defined electric field evolution of intense, phase-stable few-cycle laser pulses provides an ideal tool for controlling this motion. The resulting manipulation of local electric fields at nanometre spatial and attosecond temporal scales offers unique spatio-temporal control of ultrafast nonlinear processes at the nanoscale, with important implications for the advancement of nanoelectronics. Here we demonstrate the attosecond control of the collective electron motion and directional emission from isolated dielectric (SiO2) nanoparticles with phase-stabilized few-cycle laser fields. A novel acceleration mechanism leading to the ejection of highly energetic electrons is identified by the comparison of the results to quasi-classical model calculations. The observed lightwave control in nanosized dielectrics has important implications for other material groups, including semiconductors and metals. A demonstration of attosecond control of the motion and directed emission of electrons from individual silica nanoparticles using few-cycle laser fields opens new possibilities to manipulate electronic processes in nanoscale systems.
223 citations
TL;DR: These circuits are designed based on the unique properties of CNFETs, such as the capability of setting the desired threshold voltage by changing the diameters of the nanotubes, which makes them very suitable for the multiple- V t design method.
Abstract: Novel high-performance ternary circuits for nanotechnology are presented here. Each of these carbon nanotube field-effect transistor (CNFET)-based circuits implements all the possible kinds of ternary logic, including negative, positive and standard ternary logics, in one structure. The proposed designs have good driving capability and large noise margins and are robust. These circuits are designed based on the unique properties of CNFETs, such as the capability of setting the desired threshold voltage by changing the diameters of the nanotubes. This property of CNFETs makes them very suitable for the multiple- V t design method. The proposed circuits are simulated exhaustively, using Synopsys HSPICE with 32 nm-CNFET technology in various test situations and different supply voltages. Simulation results demonstrate great improvements in terms of speed, power consumption and insusceptibility to process variations with respect to other conventional and state-of-the-art 32 nm complementary metal-oxide semiconductor and CNFET-based ternary circuits. For instance at 0.9 V, the proposed ternary logic and arithmetic circuits consume on average 53 and 40 less energy, respectively, compared to the CNFET-based ternary logic and arithmetic circuits, recently proposed in the literature.
202 citations
TL;DR: This review will illustrate concepts using nanowires as a platform material for investigating fundamental properties and performance limits of nanoscale quantum electronic and photovoltaic devices at the single nanowire level.
Abstract: Advances in nanoscience and nanotechnology critically depend on the development of nanostructures whose properties are controlled during synthesis. We focus on this critical concept using semiconductor nanowires, which provide the capability through design and rational synthesis to realize unprecedented structural and functional complexity in building blocks as a platform material. First, a brief review of the synthesis of complex modulated nanowires in which rational design and synthesis can be used to precisely control composition, structure, and, most recently, structural topology is discussed. Second, the unique functional characteristics emerging from our exquisite control of nanowire materials are illustrated using several selected examples from nanoelectronics and nano-enabled energy. Finally, the remarkable power of nanowire building blocks is further highlighted through their capability to create unprecedented, active electronic interfaces with biological systems. Recent work pushing the limits of both multiplexed extracellular recording at the single-cell level and the first examples of intracellular recording is described, as well as the prospects for truly blurring the distinction between nonliving nanoelectronic and living biological systems.
195 citations
TL;DR: NEMO5 as discussed by the authors is a multilevel parallelization tool for nanoelectronics modeling based on open-source packages that enables a mix and match of physical models with different length scales and varying numerical complexity.
Abstract: The development of a new nanoelectronics modeling tool, NEMO5, is reported. The tool computes strain, phonon spectra, electronic band structure, charge density, charge current, and other properties of nanoelectronic devices. The modular layout enables a mix and match of physical models with different length scales and varying numerical complexity. NEMO5 features multilevel parallelization and is based on open-source packages. Its versatility is demonstrated with selected application examples: a multimillion-atom strain calculation, bulk electron and phonon band structures, a 1-D Schrodinger-Poisson simulation, a multiphysics simulation of a resonant tunneling diode, and quantum transport through a nanowire transistor.
187 citations
TL;DR: First-principle simulations indicate that encapsulation of the GNR is energetically favorable and that the electronic structure of the encapsulated GNRs is the same as for the free-standing ones, pointing to possible applications of theGNR@SWNT structures in photonics and nanoelectronics.
Abstract: A novel material, graphene nanoribbons encapsulated in single-walled carbon nanotubes (GNR@SWNT), was synthesized using confined polymerization and fusion of polycyclic aromatic hydrocarbon (PAH) molecules. Formation of the GNR is possible due to confinement effects provided by the one-dimensional space inside nanotubes, which helps to align coronene or perylene molecules edge to edge to achieve dimerization and oligomerization of the molecules into long nanoribbons. Almost 100% filling of SWNT with GNR is achieved while nanoribbon length is limited only by the length of the encapsulating nanotube. The PAH fusion reaction provides a very simple and easily scalable method to synthesize GNR@SWNT in macroscopic amounts. First-principle simulations indicate that encapsulation of the GNRs is energetically favorable and that the electronic structure of the encapsulated GNRs is the same as for the free-standing ones, pointing to possible applications of the GNR@SWNT structures in photonics and nanoelectronics.
TL;DR: A combined plasmonics and metamaterials approach may allow light-matter interaction to be controlled at the single-photon level, and nanoscale plasmons, which can transmit classical information with unprecedented bandwidth, are also naturally conducive to quantum information processing.
Abstract: Light in a silica fiber and electrons in silicon are the backbones of current communication and computation systems. A seamless interface between the two can guarantee the use of light to overcome issues related to the resistive time delay of electrons within integrated circuits. However, a fundamental incompatibility arises between photonics and nanometer-scale electronics because light breaks free when confined to sizes below its wavelength. Instead, coupling light to the free electrons of metals can lead to a quasiparticle called a plasmon, with nanometer-scale mode volumes. The resulting possibility of efficiently interfacing photonics and nanoelectronics has been the impetus for the field of plasmonics ( 1 ). Recent work has shown that these nanoscale plasmons, which can transmit classical information with unprecedented bandwidth, are also naturally conducive to quantum information processing ( 2 ).
01 Jan 2011
TL;DR: New semiconductor-on-insulator materials have been proposed in this article, and the physics of modern SemOI devices have been discussed. Diagnostics of the SOI devices are discussed.
Abstract: New semiconductor-on-insulator materials.- Physics of modern SemOI devices.- Diagnostics of the SOI devices.- Sensors and MEMS on SOI.
TL;DR: This work combines optical microspectroscopy and electronic measurements to study how gold deposition affects the physical properties of graphene and finds that the electronic structure, the electron-phonon coupling, and the doping level in gold-plated graphene are largely preserved.
Abstract: We combine optical microspectroscopy and electronic measurements to study how gold deposition affects the physical properties of graphene. We find that the electronic structure, the electron-phonon coupling, and the doping level in gold-plated graphene are largely preserved. The transfer lengths for electrons and holes at the graphene-gold contact have values as high as 1.6 μm. However, the interfacial coupling of graphene and gold causes local temperature drops of up to 500 K in operating electronic devices.
TL;DR: This work demonstrates the 3D subdiffraction-limited laser operation in the green spectral region based on a metal-oxide-semiconductor (MOS) structure, comprising a bundle of green-emitting InGaN/GaN nanorods strongly coupled to a gold plate through a SiO(2) dielectric nanogap layer.
Abstract: Realization of smaller and faster coherent light sources is critically important for the emerging applications in nanophotonics and information technology. Semiconductor lasers are arguably the most suitable candidate for such purposes. However, the minimum size of conventional semiconductor lasers utilizing dielectric optical cavities for sustaining laser oscillation is ultimately governed by the diffraction limit (∼(λ/2n)(3) for three-dimensional (3D) cavities, where λ is the free-space wavelength and n is the refractive index). Here, we demonstrate the 3D subdiffraction-limited laser operation in the green spectral region based on a metal-oxide-semiconductor (MOS) structure, comprising a bundle of green-emitting InGaN/GaN nanorods strongly coupled to a gold plate through a SiO(2) dielectric nanogap layer. In this plasmonic nanocavity structure, the analogue of MOS-type "nanocapacitor" in nanoelectronics leads to the confinement of the plasmonic field into a 3D mode volume of 8.0 × 10(-4) μm(3) (∼0.14(λ/2n)(3)).
TL;DR: This study suggests simple (no additional doping) FETs using tiny top-down nanowires can deliver high performance for potential impact on both CMOS scaling and emerging applications such as biosensing.
Abstract: We demonstrate lithographically fabricated Si nanowire field effect transistors (FETs) with long Si nanowires of tiny cross sectional size (∼3-5 nm) exhibiting high performance without employing complementarily doped junctions or high channel doping. These nanowire FETs show high peak hole mobility (as high as over 1200 cm(2)/(V s)), current density, and drive current as well as low drain leakage current and high on/off ratio. Comparison of nanowire FETs with nanobelt FETs shows enhanced performance is a result of significant quantum confinement in these 3-5 nm wires. This study suggests simple (no additional doping) FETs using tiny top-down nanowires can deliver high performance for potential impact on both CMOS scaling and emerging applications such as biosensing.
TL;DR: The well established theories of chemisorption and interfacial electron transfer are applied as conceptual frameworks for understanding the adsorption of semiconductor nanocrystals on surfaces, paying particular attention to instances when the nonadiabatic Marcus picture breaks down.
Abstract: Semiconductor nanocrystals are called artificial atoms because of their atom-like discrete electronic structure resulting from quantum confinement. Artificial atoms can also be assembled into artificial molecules or solids, thus, extending the toolbox for material design. We address the interaction of artificial atoms with bulk semiconductor surfaces. These interfaces are model systems for understanding the coupling between localized and delocalized electronic structures. In many perceived applications, such as nanoelectronics, optoelectronics, and solar energy conversion, interfacing semiconductor nanocrystals to bulk materials is a key ingredient. Here, we apply the well established theories of chemisorption and interfacial electron transfer as conceptual frameworks for understanding the adsorption of semiconductor nanocrystals on surfaces, paying particular attention to instances when the nonadiabatic Marcus picture breaks down. We illustrate these issues using recent examples from our laboratory.
TL;DR: In this paper, the authors report on the fabrication and characterization of graphene made by electron-radiation induced cross-linking of aromatic self-assembled monolayers (SAMs) and their subsequent annealing.
Abstract: Graphene-based materials have been suggested for applications ranging from nanoelectronics to nanobiotechnology. However, the realization of graphene-based technologies will require large quantities of free-standing two-dimensional (2D) carbon materials with tunable physical and chemical properties. Bottom-up approaches via molecular self-assembly have great potential to fulfill this demand. Here, we report on the fabrication and characterization of graphene made by electron-radiation induced cross-linking of aromatic self-assembled monolayers (SAMs) and their subsequent annealing. In this process, the SAM is converted into a nanocrystalline graphene sheet with well-defined thickness and arbitrary dimensions. Electric transport data demonstrate that this transformation is accompanied by an insulator to metal transition that can be utilized to control electrical properties such as conductivity, electron mobility, and ambipolar electric field effect of the fabricated graphene sheets. The suggested route opens broad prospects toward the engineering of free-standing 2D carbon materials with tunable properties on various solid substrates and on holey substrates as suspended membranes.
TL;DR: A new and straightforward protocol for unambiguously isolating a single organic molecule on a metal surface and wiring it inside a nanojunction under ambient conditions is described.
Abstract: One of the challenging goals of molecular electronics is to wire exactly one molecule between two electrodes. This is generally nontrivial under ambient conditions. We describe a new and straightfo...
TL;DR: A new multiple-cycle chemical vapor deposition (CVD) method is presented to synthesize horizontally aligned arrays of parallel single-walled carbon nanotubes (SWNTs) with densities of 20-40 SWNT/μm over large area and a diameter distribution of 2.4 ± 0.5 nm on the quartz surface based on a methanol/ethanol CVD method.
Abstract: A dense array of parallel single-walled carbon nanotubes (SWNTs) as the device channel can carry higher current, be more robust, and have smaller device-to-device variation, thus is more desirable for and compatible with applications in future highly integrated circuits when compared with single-tube devices. The density of the parallel SWNT arrays and the diameter of SWNTs both are key factors in the determination of the device performance. In this paper, we present a new multiple-cycle chemical vapor deposition (CVD) method to synthesize horizontally aligned arrays of SWNTs with densities of 20-40 SWNT/μm over large area and a diameter distribution of 2.4 ± 0.5 nm on the quartz surface based on a methanol/ethanol CVD method. The high nucleation efficiency of catalyst particles in multiple-cycle CVD processes has been demonstrated to be the main reason for the improvements in the density of SWNT arrays. More interestingly, we confirmed the existence of an etching effect, which strongly affects the final products in the multiple-cycle growth. This etching effect is likely the reason that only large-diameter SWNTs were obtained in the multiple-cycle CVD growth. Using these high-density and large-diameter nanotube arrays, two-terminal devices with back-gates were fabricated. The performances of these devices have been greatly improved in overall resistance and on-state current, which indicates these SWNT arrays have high potential for applications such as interconnects, high-frequency devices, and high-current transistors in future micro- or nanoelectronics.
TL;DR: In this article, a review of electron transport experiments on etched graphene nanostructures is presented, focusing on transport through graphene nanoribbons and constrictions, single electron transistors as well as on graphene quantum dots including double quantum dots.
Abstract: Graphene nanostructures are promising candidates for future nanoelectronics and solid-state quantum information technology. In this review we provide an overview of a number of electron transport experiments on etched graphene nanostructures. We briefly revisit the electronic properties and the transport characteristics of bulk, i.e., two-dimensional graphene. The fabrication techniques for making graphene nanostructures such as nanoribbons, single electron transistors and quantum dots, mainly based on a dry etching “paper-cutting” technique are discussed in detail. The limitations of the current fabrication technology are discussed when we outline the quantum transport properties of the nanostructured devices. In particular we focus here on transport through graphene nanoribbons and constrictions, single electron transistors as well as on graphene quantum dots including double quantum dots. These quasi-one-dimensional (nanoribbons) and quasi-zero-dimensional (quantum dots) graphene nanostructures show a clear route of how to overcome the gapless nature of graphene allowing the confinement of individual carriers and their control by lateral graphene gates and charge detectors. In particular, we emphasize that graphene quantum dots and double quantum dots are very promising systems for spin-based solid state quantum computation, since they are believed to have exceptionally long spin coherence times due to weak spin-orbit coupling and weak hyperfine interaction in graphene.
TL;DR: A new method to manipulate the channel charge density of field-effect transistors using dipole-generating self-assembled monolayers (SAMs) with different anchor groups is presented, maintaining an ideal interface between the dipole layers and the semiconductor while changing the built-in electric potential.
Abstract: We present a new method to manipulate the channel charge density of field-effect transistors using dipole-generating self-assembled monolayers (SAMs) with different anchor groups. Our approach maintains an ideal interface between the dipole layers and the semiconductor while changing the built-in electric potential by 0.41−0.50 V. This potential difference can be used to change effectively the electrical properties of nanoelectronic devices. We further demonstrate the application of the SAM dipoles to enable air-stable operation of n-channel organic transistors.
TL;DR: CdSe is recognized as a promising light-harvesting material to be applied in optoelectronics because of its fundamental emission in the near-infrared (NIR) region, and biosensors operating in this region can avoid interference from biological media such as tissue autofl uorescence and scattering light, and thereby facilitate relatively interference-free sensing.
Abstract: One-dimensional (1D) semiconductor nanowires (NWs) have drawn considerable research attention over the past few decades because of their unique properties and potential applications in nanoelectronics, photonics, luminescent materials, lasing materials, and biological and medical sensing. [ 1–3 ] Impressive progress has been demonstrated in highly effi cient light sources (nanolasers), waveguides, fi eld-effect transistors and photodetectors based on group IV elements (Si and Ge), [ 4 ] III–V compound semiconductors (GaN and GaAs), [ 2 , 5 ] and semiconducting oxides (ZnO, SnO 2 and In 2 O 3 ). [ 6 , 7 ] Owing to its direct bandgap (ca. 1.74 eV at room temperature), good absorption ability, and excellent photosensitivity, [ 8 , 9 ] CdSe is recognized as a promising light-harvesting material to be applied in optoelectronics. Especially, the fundamental emission of CdSe falls in the near-infrared (NIR) region, and biosensors operating in this region can avoid interference from biological media such as tissue autofl uorescence and scattering light, and thereby facilitate relatively interference-free sensing. [ 10 ]
TL;DR: In this article, two new efficient ternary Full Adder cells for nanoelectronics were proposed based on the unique characteristics of the CNTFET device, such as the capability of setting the desired threshold voltages by adopting proper diameters for the nanotubes as well as the same carrier mobilities for the N-type and P-type devices.
Abstract: This paper presents two new efficient ternary Full Adder cells for nanoelectronics. These CNTFET-based ternary Full Adders are designed based on the unique characteristics of the CNTFET device, such as the capability of setting the desired threshold voltages by adopting proper diameters for the nanotubes as well as the same carrier mobilities for the N-type and P-type devices. These characteristics of CNTFETs make them very suitable for designing high-performance multiple-Vth structures. The proposed structures reduce the number of the transistors considerably and have very high driving capability. The presented ternary Full Adders are simulated using Synopsys HSPICE with 32 nm CNTFET technology to evaluate their performance and to confirm their correct operation.
TL;DR: The energy dispersion relation with the quantized electron wave vector obtained from a Fourier analysis of dI/dV maps is established and it is established that the nanoislands preserve the Dirac Fermion properties with a reduced Fermi velocity.
Abstract: One leading question for the application of graphene in nanoelectronics is how electronic properties depend on the size at the nanoscale. Direct observation of the quantized electronic states is ce...
TL;DR: The presence of a large bandgap means that a single layer of molybdenum disulphide can be used to make field-effect transistors with high on/off ratios and reasonably high mobilities.
Abstract: The presence of a large bandgap means that a single layer of molybdenum disulphide can be used to make field-effect transistors with high on/off ratios and reasonably high mobilities.
TL;DR: In this article, the authors report on the characterization of bipolar resistive switching materials and their integration into nanocrossbar structures, as well as on different memory operation schemes in terms of memory density and the challenging problem of sneak paths.
Abstract: The paper reports on the characterization of bipolar resistive switching materials and their integration into nanocrossbar structures, as well as on different memory operation schemes in terms of memory density and the challenging problem of sneak paths. TiO2, WO3, GeSe, SiO2 and MSQ thin films were integrated into nanojunctions of 100×100 nm2. The variation between inert Pt and Cu or Ag top electrodes leads to valence change (VCM) switching or electrochemical metallization (ECM) switching and has significant impact on the resistive properties. All materials showed promising characteristics with switching speeds down to 10 ns, multilevel switching, good endurance and retention. Nanoimprint lithography was found to be a suitable tool for processing crossbar arrays down to a feature size of 50 nm and 3D stacking was demonstrated. The inherent occurrence of current sneak paths in passive crossbar arrays can be circumvented by the implementation of complementary resistive switching (CRS) cells. The comparison with other operation schemes shows that the CRS concept dramatically increases the addressable memory size to about 1010 bit.
TL;DR: The proposed hardened memory cell overcomes the problems associated with the previous design by utilizing novel access and refreshing mechanisms and achieves 55% reduction in power delay product compared to the DICE cell (with 12 transistors) providing a significant improvement in soft error tolerance.
Abstract: This paper proposes a new hardening design for an 11 transistors (11T) CMOS memory cell at 32 nm feature size. The proposed hardened memory cell overcomes the problems associated with the previous design by utilizing novel access and refreshing mechanisms. Simulation shows that the data stored in the proposed hardened memory cell does not change even for a transient pulse of more than twice the charge than a conventional memory cell. Moreover it achieves 55% reduction in power delay product compared to the DICE cell (with 12 transistors) providing a significant improvement in soft error tolerance. Simulation results are provided using the predictive technology file for 32 nm feature size in CMOS.
TL;DR: In this paper, the strain-gradient induced exciton energy shift in elastically curved CdS nanowires at low temperature was investigated, and it was shown that the red-shift of the energy in the curved nanwires is proportional to the strain gradient, an index of lattice distortion.
Abstract: Although possible non-homogeneous strain effects in semiconductors have been investigated for over a half century and the strain-gradient can be over 1% per micrometer in flexible nanostructures, we still lack an understanding of their influence on energy bands. Here we conduct a systematic cathodoluminescence spectroscopy study of the strain-gradient induced exciton energy shift in elastically curved CdS nanowires at low temperature, and find that the red-shift of the exciton energy in the curved nanowires is proportional to the strain-gradient, an index of lattice distortion. Density functional calculations show the same trend of band gap reduction in curved nanostructures and reveal the underlying mechanism. The significant linear strain-gradient effect on the band gap of semiconductors should shed new light on ways to tune optical-electronic properties in nanoelectronics.
TL;DR: A complete fabrication route for atomic-scale, donor-based devices in single-crystal Ge using a combination of scanning tunneling microscope lithography and high-quality crystal growth and an innovative lithographic procedure based on direct laser patterning of the semiconductor surface.
Abstract: Despite the rapidly growing interest in Ge for ultrascaled classical transistors and innovative quantum devices, the field of Ge nanoelectronics is still in its infancy. One major hurdle has been electron confinement since fast dopant diffusion occurs when traditional Si CMOS fabrication processes are applied to Ge. We demonstrate a complete fabrication route for atomic-scale, donor-based devices in single-crystal Ge using a combination of scanning tunneling microscope lithography and high-quality crystal growth. The cornerstone of this fabrication process is an innovative lithographic procedure based on direct laser patterning of the semiconductor surface, allowing the gap between atomic-scale STM-patterned structures and the outside world to be bridged. Using this fabrication process, we show electron confinement in a 5 nm wide phosphorus-doped nanowire in single-crystal Ge. At cryogenic temperatures, Ohmic behavior is observed and a low planar resistivity of 8.3 kΩ/◻ is measured.