75 research outputs found
Magnetoconductivity of Hubbard bands induced in Silicon MOSFETs
Sodium impurities are diffused electrically to the oxide-semiconductor
interface of a silicon MOSFET to create an impurity band. At low temperature
and at low electron density, the band is split into an upper and a lower
sections under the influence of Coulomb interactions. We used
magnetoconductivity measurements to provide evidence for the existence of
Hubbard bands and determine the nature of the states in each band.Comment: In press in Physica
Design and Experimental Validation of a Software-Defined Radio Access Network Testbed with Slicing Support
Network slicing is a fundamental feature of 5G systems to partition a single
network into a number of segregated logical networks, each optimized for a
particular type of service, or dedicated to a particular customer or
application. The realization of network slicing is particularly challenging in
the Radio Access Network (RAN) part, where multiple slices can be multiplexed
over the same radio channel and Radio Resource Management (RRM) functions shall
be used to split the cell radio resources and achieve the expected behaviour
per slice. In this context, this paper describes the key design and
implementation aspects of a Software-Defined RAN (SD-RAN) experimental testbed
with slicing support. The testbed has been designed consistently with the
slicing capabilities and related management framework established by 3GPP in
Release 15. The testbed is used to demonstrate the provisioning of RAN slices
(e.g. preparation, commissioning and activation phases) and the operation of
the implemented RRM functionality for slice-aware admission control and
scheduling
Activation mechanisms in sodium-doped Silicon MOSFETs
We have studied the temperature dependence of the conductivity of a silicon
MOSFET containing sodium ions in the oxide above 20 K. We find the impurity
band resulting from the presence of charges at the silicon-oxide interface is
split into a lower and an upper band. We have observed activation of electrons
from the upper band to the conduction band edge as well as from the lower to
the upper band. A possible explanation implying the presence of Hubbard bands
is given.Comment: published in J. Phys. : Condens. Matte
Disorder and electron interaction control in low-doped silicon metal-oxide-semiconductor field effect transistors
We fabricated silicon metal-oxide-semiconductor field effect transistors
where an additional sodium-doped layer was incorporated into the oxide to
create potential fluctuations at the Si-SiO2 interface. The amplitude of these
fluctuations is controlled by both the density of ions in the oxide and their
position relative to the Si-SiO2 interface. Owing to the high mobility of the
ions at room temperature, it is possible to move them with the application of a
suitable electric field. We show that, in this configuration, such a device can
be used to control both the disorder and the electron-electron interaction
strength at the Si-SiO2 interface.Comment: 3 pages, 2 figure
Variation of the hopping exponent in disordered silicon MOSFETs
We observe a complex change in the hopping exponent value from 1/2 to 1/3 as
a function of disorder strength and electron density in a sodium-doped silicon
MOSFET. The disorder was varied by applying a gate voltage and thermally
drifting the ions to different positions in the oxide. The same gate was then
used at low temperature to modify the carrier concentration.
Magnetoconductivity measurements are compatible with a change in transport
mechanisms when either the disorder or the electron density is modified
suggesting a possible transition from a Mott insulator to an Anderson insulator
in these systems.Comment: 6 pages, 5 figure
An integrated wireless communication architecture for maritime sector
The rapid evolution of terrestrial wireless systems has brought mobile users more and more desired communication services. Maritime customers are asking for the same, such as the concepts of “Broadband at Sea” and “Maritime Internet”. Quite a lot of research work has focused on the development of new and better maritime communication technologies, but less attention has been paid on interworking of multiple maritime wireless networks or on satisfying service provisioning. To address this, an integrated wireless Communication Architecture for Maritime Sector (CAMS) has been introduced in this article. CAMS is aimed at 1) granting maritime customers uninterrupted connectivity through the best available network and 2) providing them with the best-provisioned communication services in terms of mobility, security and Quality of Experience (QoE). To address mobility challenge, the IEEE 802.21 standard is recommended to be used in CAMS in order to achieve seamless handover. CAMS provides application-level QoE support attending to the limited communication resources (e.g. bandwidth) at sea. Certain security considerations have also been proposed to supplement this architecture
Molecular basis of altered excitability in Shaker mutants of Drosophila melanogaster.
Mutations in the Shaker (Sh) locus of Drosophila melanogaster have differing effects on action potential duration and repolarization in neurons as well as on A-type K+ channels (I(A)) in muscle. The molecular basis of three exemplary Sh alleles (Sh(KS133), Sh(E62) and Sh5) has been identified. They are point mutation in the Sh transcription unit expressing aberrant voltage-gated A-type K+ channels. Replicas of each mutation have been introduced by in vitro mutagenesis into Sh cDNA. The expression of in vitro transcribed mutant Sh cRNA in Xenopus laevis oocytes reproduced the specific phenotypic traits of each Sh allele. The lack of I(A) in Sh(KS133) is due to a missense mutation within a sequence motif occurring in all hitherto characterized voltage-gated K+ channel forming proteins. The reduction of I(A) in Sh(E62) is due to a mutation in an AG acceptor site. The intervening sequence between exon 19 and 20 is not spliced in Sh(E62) RNA. As a consequence Sh(E62) flies do not contain the full complement of Sh K+ forming proteins. Finally, the Sh5 mutation leads to an altered voltage dependence of K+ channel activation and inactivation as well as to an accelerated rate of recovery from inactivation. This is due to a missense mutation altering the amino acid sequence of the proposed transmembrane segment S5 of the Sh K+ channels. Segment S5 is located adjacently to the presumed voltage sensor of voltage-gated ion channels. The results explain the altered properties of excitable cells in Sh mutants and provide a general model for the possible role of A-type K+ channels in modulation action potential profiles
Single shot measurement of a silicon single electron transistor
We have fabricated a custom cryogenic Complementary Metal-Oxide-Semiconductor
(CMOS) integrated circuit that has a higher measurement bandwidth compared with
conventional room temperature electronics. This allowed implementing single
shot operations and observe the real-time evolution of the current of a
phosphorous-doped silicon single electron transistor that was irradiated with a
microwave pulse. Relaxation times up to 90 us are observed, suggesting the
presence of well isolated electron excitations within the device. It is
expected that these are associated with long decoherence time and the device
may be suitable for quantum information processing
Evidence for multiple impurity bands in sodium-doped silicon MOSFETs
We report measurements of the temperature-dependent conductivity in a silicon
metal-oxide-semiconductor field-effect transistor that contains sodium
impurities in the oxide layer. We explain the variation of conductivity in
terms of Coulomb interactions that are partially screened by the proximity of
the metal gate. The study of the conductivity exponential prefactor and the
localization length as a function of gate voltage have allowed us to determine
the electronic density of states and has provided arguments for the presence of
two distinct bands and a soft gap at low temperature.Comment: 4 pages; 5 figures; Published in PRB Rapid-Communication
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