65 research outputs found
Test-retest reliability of evoked heat stimulation bold functional magnetic resonance imaging
To date, the blood oxygenated-level dependent (BOLD) functional magnetic resonance imaging (fMRI) technique has enabled an objective and deeper understanding of pain processing mechanisms embedded within the human central nervous system (CNS). In order to further comprehend the benefits and limitations of BOLD fMRI in the context of pain as well as the corresponding subjective pain ratings, we evaluated the univariate response, test-retest reliability and confidence intervals (CIs) at the 95% level of both data types collected during evoked stimulation of 40°C (non-noxious), 44°C (mildly noxious) and a subject-specific temperature eliciting a 7/10 pain rating. The test-retest reliability between two scanning sessions was determined by calculating group-level interclass correlation coefficients and at the single-subject level.
Across the three stimuli, we initially observed a graded response of increasing magnitude for both visual analogue scale (VAS) pain ratings and fMRI data. Test-retest reliability was observed to be highest for VAS pain ratings obtained during the 7/10 pain stimulation (intraclass correlation coefficient (ICC) = 0.938), while ICC values of pain fMRI data for a distribution of CNS structures ranged from 0.5 to 0.859 (p < 0.05). Importantly, the upper and lower CI bounds reported herein could be utilized in subsequent trials involving healthy volunteers to hypothesize the magnitude of effect required to overcome inherent variability of either VAS pain ratings or BOLD responses evoked during innocuous or noxious thermal stimulation
All CVD Boron Nitride Encapsulated Graphene FETs with CMOS Compatible Metal Edge Contacts
We report on the fabrication and characterization of field effect transistors
(FETs) based on chemical vapor deposited (CVD) graphene encapsulated between
few layer CVD boron nitride (BN) sheets with complementary metal oxide
semiconductor (CMOS) compatible nickel edge contacts. Non-contact Tera-hertz
time domain spectroscopy (THz-TDS) of large-area BN/graphene/BN (BN/G/BN)
stacks reveals average sheet conductivity >1 mS/sq and average mobility of 2500
cm/Vs. Improved output conductance is observed in direct current (DC)
measurements under ambient conditions, indicating potential for radio-frequency
(RF) applications. Moreover, we report a maximum voltage gain of 6 dB from a
low frequency signal amplifier circuit. RF characterization of the GFETs yields
an f x L product of 2.64 GHzm and an f x L
product of 5.88 GHzm. This study presents for the first time THz-TDS usage
in combination with other characterization methods for device performance
assessment on BN/G/BN stacks. The results serve as a step towards scalable, all
CVD 2D material-based FETs for CMOS compatible future nanoelectronic circuit
architectures.Comment: 6 page
A Resonant Graphene NEMS Vibrometer
Measuring vibrations is essential to ensuring building structural safety and machine stability. Predictive maintenance is a central internet of things (IoT) application within the new industrial revolution, where sustainability and performance increase over time are going to be paramount. To reduce the footprint and cost of vibration sensors while improving their performance, new sensor concepts are needed. Here, double-layer graphene membranes are utilized with a suspended silicon proof demonstrating their operation as resonant vibration sensors that show outstanding performance for a given footprint and proof mass. The unveiled sensing effect is based on resonant transduction and has important implications for experimental studies involving thin nano and micro mechanical resonators that are excited by an external shaker
Terahertz Rectennas on Flexible Substrates Based on One-Dimensional Metal–Insulator–Graphene Diodes
Flexible energy harvesting devices fabricated in scalable thin-film processes are crucial for wearable electronics and the Internet of Things. We present a flexible rectenna based on a one-dimensional junction metal–insulator–graphene diode, offering low-noise power detection at terahertz (THz) frequencies. The rectennas are fabricated on a flexible polyimide film in a scalable process by photolithography using graphene grown by chemical vapor deposition. A one-dimensional junction reduces the junction capacitance and enables operation up to 170 GHz. The rectenna shows a maximum responsivity of 80 V/W at 167 GHz in free space measurements and minimum noise equivalent power of 80 pW/√Hz
Stacking Polymorphism in PtSe2 Drastically Affects Its Electromechanical Properties
PtSe2 is one of the most promising materials for the next generation of piezoresistive sensors. However, the large-scale synthesis of homogeneous thin films with reproducible electromechanical properties is challenging due to polycrystallinity. It is shown that stacking phases other than the 1T phase become thermodynamically available at elevated temperatures that are common during synthesis. It is shown that these phases can make up a significant fraction in a polycrystalline thin film and discuss methods to characterize them, including their Seebeck coefficients. Lastly, their gauge factors, which vary strongly and heavily impact the performance of a nanoelectromechanical device are estimated
Wide spectral photoresponse of layered platinum diselenide-based photodiodes
Platinum diselenide (PtSe2) is a group-10 transition metal dichalcogenide (TMD) that has unique electronic properties, in particular a semimetal-to-semiconductor transition when going from bulk to monolayer form. We report on vertical hybrid Schottky barrier diodes (SBDs) of two-dimensional (2D) PtSe2 thin films on crystalline n-type silicon. The diodes have been fabricated by transferring large-scale layered PtSe2 films, synthesized by thermally assisted conversion of predeposited Pt films at back-end-of-the-line CMOS compatible temperatures, onto SiO2/Si substrates. The diodes exhibit obvious rectifying behavior with a photoresponse under illumination. Spectral response analysis reveals a maximum responsivity of 490 mA/W at photon energies above the Si bandgap and relatively weak responsivity, in the range of 0.1–1.5 mA/W, at photon energies below the Si bandgap. In particular, the photoresponsivity of PtSe2 in infrared allows PtSe2 to be utilized as an absorber of infrared light with tunable sensitivity. The results of our study indicate that PtSe2 is a promising option for the development of infrared absorbers and detectors for optoelectronics applications with low-temperature processing conditions
CVD Graphene Contacts for Lateral Heterostructure MoS Field Effect Transistors
Intensive research is carried out on two-dimensional materials, in particular
molybdenum disulfide, towards high-performance transistors for integrated
circuits. Fabricating transistors with ohmic contacts is challenging due to the
high Schottky barrier that severely limits the transistors' performance.
Graphene-based heterostructures can be used in addition or as a substitute for
unsuitable metals. We present lateral heterostructure transistors made of
scalable chemical vapor-deposited molybdenum disulfide and chemical
vapor-deposited graphene with low contact resistances of about 9
k{\Omega}{\mu}m and high on/off current ratios of 10${^8}. We also present a
theoretical model calibrated on our experiments showing further potential for
scaling transistors and contact areas into the few nanometers range and the
possibility of a strong performance enhancement by means of layer optimizations
that would make transistors promising for use in future logic circuits.Comment: 23 page
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