257 research outputs found
Single ion implantation for single donor devices using Geiger mode detectors
Electronic devices that are designed to use the properties of single atoms
such as donors or defects have become a reality with recent demonstrations of
donor spectroscopy, single photon emission sources, and magnetic imaging using
defect centers in diamond. Improving single ion detector sensitivity is linked
to improving control over the straggle of the ion as well as providing more
flexibility in lay-out integration with the active region of the single donor
device construction zone by allowing ion sensing at potentially greater
distances. Using a remotely located passively gated single ion Geiger mode
avalanche diode (SIGMA) detector we have demonstrated 100% detection efficiency
at a distance of >75 um from the center of the collecting junction. This
detection efficiency is achieved with sensitivity to ~600 or fewer
electron-hole pairs produced by the implanted ion. Ion detectors with this
sensitivity and integrated with a thin dielectric, for example 5 nm gate oxide,
using low energy Sb implantation would have an end of range straggle of <2.5
nm. Significant reduction in false count probability is achieved by modifying
the ion beam set-up to allow for cryogenic operation of the SIGMA detector.
Using a detection window of 230 ns at 1 Hz, the probability of a false count
was measured as 1E-1 and 1E-4 for operation temperatures of 300K and 77K,
respectively. Low temperature operation and reduced false, dark, counts are
critical to achieving high confidence in single ion arrival. For the device
performance in this work, the confidence is calculated as a probability of >98%
for counting one and only one ion for a false count probability of 1E-4 at an
average ion number per gated window of 0.015.Comment: 10 pages, 5 figures, submitted to Nanotechnolog
Magneto-Optical Studies of Exciton Effects in Layer-Type Semiconductors
Both experimental and theoretical works were performed with particular reference to a layer-type semiconductor, GaSe, for a coherent treatment of the exciton-like and the oscillatory Landau-like spectra appearing in a form of their combination in semiconductors in magnetic fields. The interband magneto-absorption and the Faraday rotation were measured in pulsed magnetic fields up to ~200 kOe at low temperatures. The theoretical analysis was based mainly on the exact solution for an extremely anisotropic semiconductor in the magnetic field of arbitrary intensity. The exciton effects are discussed in terms of the energy spectrum, the spectral intensity, and the spectral width by the use of the band parameters deduced from the experimental results
Real-time, Software-Defined, GPU-Based Receiver Field Trial
We demonstrate stable real-time operation of a software-defined, GPU-based
receiver over a metropolitan network. Massive parallelization is exploited for
implementing direct-detection and coherent Kramers-Kronig detection in real
time at 2 and 1 GBaud, respectively.Comment: Accepted for presentation at the European Conference on Optical
Communications (ECOC) 202
Field Trial of a Flexible Real-time Software-defined GPU-based Optical Receiver
We introduce a flexible, software-defined real-time multi-modulation format
receiver implemented on an off-the-shelf general-purpose graphics processing
unit (GPU). The flexible receiver is able to process 2 GBaud 2-, 4-, 8-, and
16-ary pulse-amplitude modulation (PAM) signals as well as 1 GBaud 4-, 16- and
64-ary quadrature amplitude modulation (QAM) signals, with the latter detected
using a Kramers-Kronig (KK) coherent receiver. Experimental performance
evaluation is shown for back-to-back. In addition, by using the JGN high speed
R&D network testbed, performance is evaluated after transmission over 91 km
field-deployed optical fiber and reconfigurable optical add-drop multiplexers
(ROADMs).Comment: Accepted for publication at Journal of Lightwave Technology, already
available via JLT Early Access, see supplied DOI. This v2 version of the
article is improved w.r.t. v1 after JLT peer-review. This article is a longer
journal version of the conference paper: S.P. van der Heide, et al.,
Real-time, Software-Defined, GPU-Based Receiver Field Trial, ECOC 2020 paper
We1E5, also via arXiv:2010.1433
GeVn complexes for silicon-based room-temperature single-atom nanoelectronics
We propose germanium-vacancy complexes (GeVn) as a viable ingredient to exploit single-atom quantum effects in silicon devices at room temperature. Our predictions, motivated by the high controllability of the location of the defect via accurate single-atom implantation techniques, are based on ab-initio Density Functional Theory calculations within a parameterfree screened-dependent hybrid functional scheme, suitable to provide reliable bandstructure energies and defect-state wavefunctions. The resulting defect-related excited states, at variance with those arising from conventional dopants such as phosphorous, turn out to be deep enough to ensure device operation up to room temperature and exhibit a far more localized wavefunction
Real-time transmission of geometrically-shaped signals using a software-defined GPU-based optical receiver
A software-defined optical receiver is implemented on an off-the-shelf commercial graphics processing unit (GPU). The receiver provides real-time signal processing functionality to process 1 GBaud minimum phase (MP) 4-, 8-, 16-, 32-, 64-, 128-ary quadrature amplitude modulation (QAM) as well as geometrically shaped (GS) 8- and 128-QAM signals using Kramers-Kronig (KK) coherent detection. Experimental validation of this receiver over a 91 km field-deployed optical fiber link between two Tokyo locations is shown with detailed optical signal-to-noise ratio (OSNR) investigations. A net data rate of 5 Gbps using 64-QAM is demonstrated.</p
Global associations between regional gray matter volume and diverse complex cognitive functions: evidence from a large sample study
Correlations between regional gray matter volume (rGMV) and psychometric test scores have been measured to investigate the neural bases for individual differences in complex cognitive abilities (CCAs). However, such studies have yielded different rGMV correlates of the same CCA. Based on the available evidence, we hypothesized that diverse CCAs are all positively but only weakly associated with rGMV in widespread brain areas. To test this hypothesis, we used the data from a large sample of healthy young adults [776 males and 560 females; mean age: 20.8 years, standard deviation (SD) = 0.8] and investigated associations between rGMV and scores on multiple CCA tasks (including non-verbal reasoning, verbal working memory, Stroop interference, and complex processing speed tasks involving spatial cognition and reasoning). Better performance scores on all tasks except non-verbal reasoning were associated with greater rGMV across widespread brain areas. The effect sizes of individual associations were generally low, consistent with our previous studies. The lack of strong correlations between rGMV and specific CCAs, combined with stringent corrections for multiple comparisons, may lead to different and diverse findings in the field
Refractive error is associated with intracranial volume
Myopia is part of the spectrum of refractive error. Myopia is associated with psychometric intelligence and, the link between brain anatomy and myopia has been hypothesized. Here we aimed to identify the associations between brain structures and refractive error in developed young adults. In a study cohort of 1,319 normal educated young adults, the refractive error showed a signifcant negative correlation with total intracranial volume and total cerebrospinal fuid (CSF) volume but not with total gray matter volume (GMV) or total white matter volume (WMV). Time spent studying was associated with refractive error but could not explain the aforementioned associations with brain volume parameters. The R2 values of the simple regression between spherical equivalent and outcome variables for each sex in non-whole brain imaging analyses were less than 0.05 in all cases and thus were weak. Psychometric intelligence was not associated with refractive error or total CSF volume, but it weakly positively correlated with total GMV and total WMV in this study population. Thus, refractive error appears to be primarily (weakly) associated with the volume of the cranium, whereas psychometric intelligence was associated with the volume of the brain
Recommended from our members
Regional homogeneity, resting-state functional connectivity and amplitude of low frequency fluctuation associated with creativity measured by divergent thinking in a sex-specific manner
Brain connectivity is traditionally thought to be important for creativity. Here we investigated the associations of creativity measured by divergent thinking (CMDT) with resting-state functional magnetic imaging (fMRI) measures and their sex differences. We examined these relationships in the brains of 1277 healthy young adults. Whole-brain analyses revealed a significant interaction between verbal CMDT and sex on (a) regional homogeneity within an area from the left anterior temporal lobe (b) on the resting state functional connectivity (RSFC) between the mPFC and the left inferior frontal gyrus and (c) on fractional amplitude of low frequency fluctuations (fALFF) in several distinct areas, including the precuneus and middle cingulate gyrus, left middle temporal gyrus, right middle frontal gyrus, and cerebellum. These interactions were mediated by positive correlations in females and negative correlations in males. These findings suggest that greater CMDT in females is reflected by (a) regional coherence (regional homogeneity) of brain areas responsible for representing and combining concepts as well as (b) the efficient functional connection (RSFC) between the key areas for the default state of cognitive activity and speech production, and (c) greater spontaneous neural activity (fALFF) during the resting of brain areas involved in frontal lobe functions, default cognitive activities, and language functions. Furthermore, these findings suggest that the associations between creativity and resting state brain connectivity patterns are different between males and females
- …