2,236 research outputs found
Application of Graphene within Optoelectronic Devices and Transistors
Scientists are always yearning for new and exciting ways to unlock graphene's
true potential. However, recent reports suggest this two-dimensional material
may harbor some unique properties, making it a viable candidate for use in
optoelectronic and semiconducting devices. Whereas on one hand, graphene is
highly transparent due to its atomic thickness, the material does exhibit a
strong interaction with photons. This has clear advantages over existing
materials used in photonic devices such as Indium-based compounds. Moreover,
the material can be used to 'trap' light and alter the incident wavelength,
forming the basis of the plasmonic devices. We also highlight upon graphene's
nonlinear optical response to an applied electric field, and the phenomenon of
saturable absorption. Within the context of logical devices, graphene has no
discernible band-gap. Therefore, generating one will be of utmost importance.
Amongst many others, some existing methods to open this band-gap include
chemical doping, deformation of the honeycomb structure, or the use of carbon
nanotubes (CNTs). We shall also discuss various designs of transistors,
including those which incorporate CNTs, and others which exploit the idea of
quantum tunneling. A key advantage of the CNT transistor is that ballistic
transport occurs throughout the CNT channel, with short channel effects being
minimized. We shall also discuss recent developments of the graphene tunneling
transistor, with emphasis being placed upon its operational mechanism. Finally,
we provide perspective for incorporating graphene within high frequency
devices, which do not require a pre-defined band-gap.Comment: Due to be published in "Current Topics in Applied Spectroscopy and
the Science of Nanomaterials" - Springer (Fall 2014). (17 pages, 19 figures
Graphene plasmonics
Two rich and vibrant fields of investigation, graphene physics and
plasmonics, strongly overlap. Not only does graphene possess intrinsic plasmons
that are tunable and adjustable, but a combination of graphene with noble-metal
nanostructures promises a variety of exciting applications for conventional
plasmonics. The versatility of graphene means that graphene-based plasmonics
may enable the manufacture of novel optical devices working in different
frequency ranges, from terahertz to the visible, with extremely high speed, low
driving voltage, low power consumption and compact sizes. Here we review the
field emerging at the intersection of graphene physics and plasmonics.Comment: Review article; 12 pages, 6 figures, 99 references (final version
available only at publisher's web site
Electrically Tunable Excitonic Light Emitting Diodes based on Monolayer WSe2 p-n Junctions
Light-emitting diodes are of importance for lighting, displays, optical
interconnects, logic and sensors. Hence the development of new systems that
allow improvements in their efficiency, spectral properties, compactness and
integrability could have significant ramifications. Monolayer transition metal
dichalcogenides have recently emerged as interesting candidates for
optoelectronic applications due to their unique optical properties.
Electroluminescence has already been observed from monolayer MoS2 devices.
However, the electroluminescence efficiency was low and the linewidth broad due
both to the poor optical quality of MoS2 and to ineffective contacts. Here, we
report electroluminescence from lateral p-n junctions in monolayer WSe2 induced
electrostatically using a thin boron nitride support as a dielectric layer with
multiple metal gates beneath. This structure allows effective injection of
electrons and holes, and combined with the high optical quality of WSe2 it
yields bright electroluminescence with 1000 times smaller injection current and
10 times smaller linewidth than in MoS2. Furthermore, by increasing the
injection bias we can tune the electroluminescence between regimes of
impurity-bound, charged, and neutral excitons. This system has the required
ingredients for new kinds of optoelectronic devices such as spin- and
valley-polarized light-emitting diodes, on-chip lasers, and two-dimensional
electro-optic modulators.Comment: 13 pages main text with 4 figures + 4 pages upplemental material
Graphene photodetectors for high-speed optical communications
While silicon has dominated solid-state electronics for more than four
decades, a variety of new materials have been introduced into photonics to
expand the accessible wavelength range and to improve the performance of
photonic devices. For example, gallium-nitride based materials enable the light
emission at blue and ultraviolet wavelengths, and high index contrast
silicon-on-insulator facilitates the realization of ultra dense and CMOS
compatible photonic devices. Here, we report the first deployment of graphene,
a two-dimensional carbon material, as the photo-detection element in a 10
Gbits/s optical data link. In this interdigitated metal-graphene-metal
photodetector, an asymmetric metallization scheme is adopted to break the
mirror symmetry of the built-in electric-field profile in conventional graphene
field-effect-transistor channels, allowing for efficient photo-detection within
the entire area of light illumination. A maximum external photo-responsivity of
6.1 mA/W is achieved at 1.55 {\mu}m wavelength, a very impressive value given
that the material is below one nanometer in thickness. Moreover, owing to the
unique band structure and exceptional electronic properties of graphene, high
speed photodetectors with an ultra-wide operational wavelength range at least
from 300 nm to 6 {\mu}m can be realized using this fascinating material.Comment: 20 pages, 3 figure
High resolution synteny maps allowing direct comparisons between the coffee and tomato genomes
Tomato (Solanum lycopersicum) and coffee (Coffea canephora) belong to the sister families Solanaceae and Rubiaceae, respectively. We report herein the mapping of a common set of 257 Conserved Ortholog Set II genes in the genomes of both species. The mapped markers are well distributed across both genomes allowing the first syntenic comparison between species from these two families. The majority (75%) of the synteny blocks are short (<4 cM); however, some extend up to 50 cM. In an effort to further characterize the synteny between these two genomes, we took advantage of the available sequence for the tomato genome to show that tomato chromosome 7 is syntenic to half of the two coffee linkage groups E and F with the putative break point in tomato localized to the boundary of the heterochromatin and euchromatin on the long arm. In addition to the new insight on genome conservation and evolution between the plant families Solanaceae and Rubiaceae, the comparative maps presented herein provide a translational tool by which coffee researchers may take benefit of DNA sequence and genetic information from tomato and vice versa. It is thus expected that these comparative genome information will help to facilitate and expedite genetic and genomic research in coffee
Proactive and politically skilled professionals: What is the relationship with affective occupational commitment?
The aim of this study is to extend research on employee affective commitment in three ways: (1) instead of organizational commitment the focus is on occupational commitment; (2) the role of proactive personality on affective occupational commitment is examined; and (3) occupational satisfaction is examined as a mediator and political skills as moderator in the relationship between proactive personality and affective occupational commitment. Two connected studies, one in a hospital located in the private sector and one in a university located in the public sector, are carried out in Pakistan, drawing on a total sample of over 400 employees. The results show that proactive personality is positively related to affective occupational commitment, and that occupational satisfaction partly mediates the relationship between proactive personality and affective occupational commitment. No effect is found for a moderator effect of political skills in the relationship between proactive personality and affective occupational commitment. Political skills however moderate the relationship between proactive personality and affective organizational commitment
Graphene Photonics and Optoelectronics
The richness of optical and electronic properties of graphene attracts
enormous interest. Graphene has high mobility and optical transparency, in
addition to flexibility, robustness and environmental stability. So far, the
main focus has been on fundamental physics and electronic devices. However, we
believe its true potential to be in photonics and optoelectronics, where the
combination of its unique optical and electronic properties can be fully
exploited, even in the absence of a bandgap, and the linear dispersion of the
Dirac electrons enables ultra-wide-band tunability. The rise of graphene in
photonics and optoelectronics is shown by several recent results, ranging from
solar cells and light emitting devices, to touch screens, photodetectors and
ultrafast lasers. Here we review the state of the art in this emerging field.Comment: Review Nature Photonics, in pres
Biology of archaea from a novel family Cuniculiplasmataceae (Thermoplasmata) ubiquitous in hyperacidic environments
The order Thermoplasmatales (Euryarchaeota) is represented by the most acidophilic organisms known so far that are poorly amenable to cultivation. Earlier culture-independent studies in Iron Mountain (California) pointed at an abundant archaeal group, dubbed 'G-plasma'. We examined the genomes and physiology of two cultured representatives of a Family Cuniculiplasmataceae, recently isolated from acidic (pH 1-1.5) sites in Spain and UK that are 16S rRNA gene sequence-identical with 'G-plasma'. Organisms had largest genomes among Thermoplasmatales (1.87-1.94 Mbp), that shared 98.7-98.8% average nucleotide identities between themselves and 'G-plasma' and exhibited a high genome conservation even within their genomic islands, despite their remote geographical localisations. Facultatively anaerobic heterotrophs, they possess an ancestral form of A-type terminal oxygen reductase from a distinct parental clade. The lack of complete pathways for biosynthesis of histidine, valine, leucine, isoleucine, lysine and proline pre-determines the reliance on external sources of amino acids and hence the lifestyle of these organisms as scavengers of proteinaceous compounds from surrounding microbial community members. In contrast to earlier metagenomics-based assumptions, isolates were S-layer-deficient, non-motile, non-methylotrophic and devoid of iron-oxidation despite the abundance of methylotrophy substrates and ferrous iron in situ, which underlines the essentiality of experimental validation of bioinformatic predictions
Observation of an Exotic Baryon in Exclusive Photoproduction from the Deuteron
In an exclusive measurement of the reaction , a
narrow peak that can be attributed to an exotic baryon with strangeness
is seen in the invariant mass spectrum. The peak is at
GeV/c with a measured width of 0.021 GeV/c FWHM, which is largely
determined by experimental mass resolution. The statistical significance of the
peak is . The mass and width of the observed peak are
consistent with recent reports of a narrow baryon by other experimental
groups.Comment: 5 pages, 5 figure
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