Abstract: Spintronics, which manipulate spins but not electron charge, are highly valued as energy and thermal dissipationless systems. A variety of materials are challenging the realization of spintronic devices. Among those, graphene, a carbon mono-atomic layer, is very promising for efficient spin manipulation and the creation of a full spectrum of beyond-CMOS spin-based nano-devices. In the present article, the recent advancements in graphene spintronics are reviewed, introducing the observation of spin coherence and the spin Hall effect. Some research has reported the strong spin coherence of graphene. Avoiding undesirable influences from the substrate are crucial. Magnetism and spintronics arising from graphene edges are reviewed based on my previous results. In spite of carbon-based material with only sp2 bonds, the zigzag-type atomic structure of graphene edges theoretically produces spontaneous spin polarization of electrons due to mutual Coulomb interaction of extremely high electron density of states (edge states) localizing at the flat energy band. We fabricate honeycomb-like arrays of low-defect hexagonal nanopores (graphene nanomeshes; GNMs) on graphenes, which produce a large amount of zigzag pore edges, by using a nonlithographic method (nanoporous alumina templates) and critical temperature annealing under high vacuum and hydrogen atmosphere. We observe large-magnitude ferromagnetism, which arises from polarized spins localizing at the hydrogen-terminated zigzag-nanopore edges of the GNMs, even at room temperature. Moreover, spin pumping effects are found for magnetic fields applied in parallel with the few-layer GNM planes. Strong spin coherence and spontaneously polarized edge spins of graphene can be expected to lead to novel spintronics with invisible, flexible, and ultra-light (wearable) features.
Abstract: Excellent electrical performance and extreme sensitivity to chemical species in semiconducting Single-Walled Carbon NanoTubes (s-SWCNTs) motivated the study of using them to replace silicon as a next generation field effect transistor (FET) for electronic, optoelectronic, and biological applications. In addition, use of SWCNTs in the recently studied flexible electronics appears more promising because of SWCNTs’ inherent flexibility and superior electrical performance over silicon-based materials. All these applications require SWCNT-FETs to have a wafer-scale uniform and reliable performance over time to a level that is at least comparable with the currently used silicon-based nanoscale FETs. Due to similarity in device configuration and its operation, SWCNT-FET inherits most of the variability and reliability concerns of silicon-based FETs, namely the ones originating from line edge roughness, metal work-function variation, oxide defects, etc. Additional challenges arise from the lack of chirality control in as-grown and post-processed SWCNTs and also from the presence of unstable hydroxyl (–OH) groups near the interface of SWCNT and dielectric. In this review article, we discuss these variability and reliability origins in SWCNT-FETs. Proposed solutions for mitigating each of these sources are presented and a future perspective is provided in general, which are required for commercial use of SWCNT-FETs in future nanoelectronic applications.
Abstract: Current-perpendicular-to-plane (CPP) magnetoresistance (MR) effects are often exploited in various state-of-the-art magnetic field sensing and data storage technologies. Most of the CPP-MR devices are artificial layered structures of ferromagnets and non-magnets, and in these devices, MR manifests, due to spin-dependent carrier transmission through the constituent layers. In this work, we explore another class of artificial layered structure in which multilayer graphene (MLG) is grown on a metallic substrate by chemical vapor deposition (CVD). We show that depending on the nature of the graphene-metal interaction, these devices can also exhibit large CPP-MR. Magnetoresistance ratios (>100%) are at least two orders of magnitude higher than “transferred” graphene and graphitic samples reported in the literature, for a comparable temperature and magnetic field range. This effect is unrelated to spin injection and transport and is not adequately described by any of the MR mechanisms known to date. The simple fabrication process, large magnitude of the MR and its persistence at room temperature make this system an attractive candidate for magnetic field sensing and data storage applications and, also, underscore the need for further fundamental investigations on graphene-metal interactions.
Abstract: Carbon allotropes have generated much interest among different scientific communities due to their peculiar properties and potential applications in a variety of fields. Carbon nanotubes and more recently graphene have shown very interesting electrical properties along with the possibility of being grown and/or deposited at a desired location. In this Review, we will focus our attention on carbon-based nanostructures (in particular, carbon nanotubes and graphene nanoribbons) which could play an important role in the technological quest to replace copper/low-k for interconnect applications. We will provide the reader with a number of possible architectures, including single-wall as well as multi-wall carbon nanotubes, arranged in horizontal and vertical arrays, regarded as individual objects as well as bundles. Modification of their functional properties in order to fulfill interconnect applications requirements are also presented. Then, in the second part of the Review, recently discovered graphene and in particular graphene and few-graphene layers nanoribbons are introduced. Different architectures involving nanostructured carbon are presented and discussed in light of interconnect application in terms of length, chirality, edge configuration and more.
Abstract: As an alternative to both classical PID-type and modern model-based approaches to solving control problems, active disturbance rejection control (ADRC) has gained significant traction in recent years. With its simple tuning method and robustness against process parameter variations, it puts itself forward as a valuable addition to the toolbox of control engineering practitioners. This article aims at providing a single-source introduction and reference to linear ADRC with this audience in mind. A simulative study is carried out using generic first- and second-order plants to enable a quick visual assessment of the abilities of ADRC. Finally, a modified form of the discrete-time case is introduced to speed up real-time implementations as necessary in applications with high dynamic requirements.
Abstract: This paper investigates total ionizing dose (TID) effects in top-gated epitaxial graphene field-effect-transistors (GFETs). Measurements reveal voltage shifts in the current-voltage (I-V) characteristics and degradation of carrier mobility and minimum conductivity, consistent with the buildup of oxide-trapped charges. A semi-empirical approach for modeling radiation-induced degradation in GFETs effective carrier mobility is described in the paper. The modeling approach describes Coulomb and short-range scattering based on calculations of charge and effective vertical field that incorporate radiation-induced oxide trapped charges. The transition from the dominant scattering mechanism is correctly described as a function of effective field and oxide trapped charge density. Comparison with experimental data results in good qualitative agreement when including an empirical component to account for scatterer transparency in the low field regime.