| 1. |
- Lozano, Rafael, et al.
(författare)
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Measuring progress from 1990 to 2017 and projecting attainment to 2030 of the health-related Sustainable Development Goals for 195 countries and territories: a systematic analysis for the Global Burden of Disease Study 2017
- 2018
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Ingår i: The Lancet. - : Elsevier. - 1474-547X .- 0140-6736. ; 392:10159, s. 2091-2138
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Tidskriftsartikel (refereegranskat)abstract
- Background: Efforts to establish the 2015 baseline and monitor early implementation of the UN Sustainable Development Goals (SDGs) highlight both great potential for and threats to improving health by 2030. To fully deliver on the SDG aim of “leaving no one behind”, it is increasingly important to examine the health-related SDGs beyond national-level estimates. As part of the Global Burden of Diseases, Injuries, and Risk Factors Study 2017 (GBD 2017), we measured progress on 41 of 52 health-related SDG indicators and estimated the health-related SDG index for 195 countries and territories for the period 1990–2017, projected indicators to 2030, and analysed global attainment. Methods: We measured progress on 41 health-related SDG indicators from 1990 to 2017, an increase of four indicators since GBD 2016 (new indicators were health worker density, sexual violence by non-intimate partners, population census status, and prevalence of physical and sexual violence [reported separately]). We also improved the measurement of several previously reported indicators. We constructed national-level estimates and, for a subset of health-related SDGs, examined indicator-level differences by sex and Socio-demographic Index (SDI) quintile. We also did subnational assessments of performance for selected countries. To construct the health-related SDG index, we transformed the value for each indicator on a scale of 0–100, with 0 as the 2·5th percentile and 100 as the 97·5th percentile of 1000 draws calculated from 1990 to 2030, and took the geometric mean of the scaled indicators by target. To generate projections through 2030, we used a forecasting framework that drew estimates from the broader GBD study and used weighted averages of indicator-specific and country-specific annualised rates of change from 1990 to 2017 to inform future estimates. We assessed attainment of indicators with defined targets in two ways: first, using mean values projected for 2030, and then using the probability of attainment in 2030 calculated from 1000 draws. We also did a global attainment analysis of the feasibility of attaining SDG targets on the basis of past trends. Using 2015 global averages of indicators with defined SDG targets, we calculated the global annualised rates of change required from 2015 to 2030 to meet these targets, and then identified in what percentiles the required global annualised rates of change fell in the distribution of country-level rates of change from 1990 to 2015. We took the mean of these global percentile values across indicators and applied the past rate of change at this mean global percentile to all health-related SDG indicators, irrespective of target definition, to estimate the equivalent 2030 global average value and percentage change from 2015 to 2030 for each indicator. Findings: The global median health-related SDG index in 2017 was 59·4 (IQR 35·4–67·3), ranging from a low of 11·6 (95% uncertainty interval 9·6–14·0) to a high of 84·9 (83·1–86·7). SDG index values in countries assessed at the subnational level varied substantially, particularly in China and India, although scores in Japan and the UK were more homogeneous. Indicators also varied by SDI quintile and sex, with males having worse outcomes than females for non-communicable disease (NCD) mortality, alcohol use, and smoking, among others. Most countries were projected to have a higher health-related SDG index in 2030 than in 2017, while country-level probabilities of attainment by 2030 varied widely by indicator. Under-5 mortality, neonatal mortality, maternal mortality ratio, and malaria indicators had the most countries with at least 95% probability of target attainment. Other indicators, including NCD mortality and suicide mortality, had no countries projected to meet corresponding SDG targets on the basis of projected mean values for 2030 but showed some probability of attainment by 2030. For some indicators, including child malnutrition, several infectious diseases, and most violence measures, the annualised rates of change required to meet SDG targets far exceeded the pace of progress achieved by any country in the recent past. We found that applying the mean global annualised rate of change to indicators without defined targets would equate to about 19% and 22% reductions in global smoking and alcohol consumption, respectively; a 47% decline in adolescent birth rates; and a more than 85% increase in health worker density per 1000 population by 2030. Interpretation: The GBD study offers a unique, robust platform for monitoring the health-related SDGs across demographic and geographic dimensions. Our findings underscore the importance of increased collection and analysis of disaggregated data and highlight where more deliberate design or targeting of interventions could accelerate progress in attaining the SDGs. Current projections show that many health-related SDG indicators, NCDs, NCD-related risks, and violence-related indicators will require a concerted shift away from what might have driven past gains—curative interventions in the case of NCDs—towards multisectoral, prevention-oriented policy action and investments to achieve SDG aims. Notably, several targets, if they are to be met by 2030, demand a pace of progress that no country has achieved in the recent past. The future is fundamentally uncertain, and no model can fully predict what breakthroughs or events might alter the course of the SDGs. What is clear is that our actions—or inaction—today will ultimately dictate how close the world, collectively, can get to leaving no one behind by 2030.
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| 2. |
- Shetty, Naveen, 1988, et al.
(författare)
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Ultralow 1/f noise in epigraphene devices
- 2024
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Ingår i: Applied Physics Letters. - 0003-6951 .- 1077-3118. ; 124:9
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Tidskriftsartikel (refereegranskat)abstract
- We report the lowest recorded levels of 1/ f noise for graphene-based devices, at the level of S V / V 2 = S I / I 2 = 4.4 × 10 − 16 (1/Hz), measured at f = 10 Hz ( S V / V 2 = S I / I 2 < 10 − 16 1/Hz for f > 100 Hz) in large-area epitaxial graphene on silicon carbide (epigraphene) Hall sensors. This performance is made possible through the combination of high material quality, low contact resistance achieved by edge contact fabrication process, homogeneous doping, and stable passivation of the graphene layer. Our study explores the nature of 1/ f noise as a function of carrier density and device geometry and includes data from Hall sensors with device area range spanning over six orders of magnitude, with characteristic device length ranging from L = 1 μm to 1 mm. In optimized graphene Hall sensors, we demonstrate arrays to be a viable route to improve further the magnetic field detection: a simple parallel connection of two devices displays record-high magnetic field sensitivity at room temperature, with minimum detectable magnetic field levels down to B min = 9.5 nT/√Hz. The remarkable low levels of 1/ f noise observed in epigraphene devices hold immense capacity for the design and fabrication of scalable epigraphene-based sensors with exceptional performance.
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| 3. |
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| 4. |
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| 5. |
- He, Hans, 1989
(författare)
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Engineering Epitaxial Graphene for Quantum Metrology
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Quantum resistance metrology deals both with the precise and accurate measurement of electrical resistance, by utilizing the quantum hall effect (QHE) in two-dimensional electron gases (2DEGs) such as those based on gallium arsenide (GaAs). Due to the unique properties of graphene, and specifically epitaxial graphene grown on silicon carbide (SiC/G), quantum Hall resistance (QHR) standards based on graphene perform better in a wider parameter space (temperature, current and magnetic field) than conventional semiconducting materials. To date, this is possibly the only electronic application of graphene that surpasses previous technologies. However, due to the nature of SiC/G there are still certain issues than remain unsolved, which stand in the way for widespread use of graphene QHR devices. This work aims to discuss, and suggest solutions to, one of the major problems: charge carrier density control. Control over the charge carrier density is crucial in order to observe the QHE at sufficiently low magnetic fields. Since SiC/G is intrinsically n-doped due to interactions with the SiC substrate, external doping methods must be used in order to bring graphene closer to charge neutrality. Previous techniques such as photochemical gating, corona discharge of ions or simply electrostatic gating lack either potency, stability or tuneability. This thesis presents a new air-stable chemical gating method using the acceptor molecule 2,3,5,6-Tetrauoro-tetracyanoquinodimethane (F4TCNQ) mixed with a poly(methyl-methacrylate) (PMMA) polymer. This dopant blend can be applied to SiC/G using simple spin coating, forgoing the need for ultra-high vacuum (UHV) systems. It provides potent and homogeneous doping, with the ability to bring SiC/G close to charge neutrality, with measured mobilities reaching 70,000 cm2/Vs. Furthermore, the method is compatible with macroscopic devices with the doping being significantly homogeneous even on the millimeter scale. Interestingly, chemical analysis reveal that the doping effect is a consequence of F4TCNQ molecules diffusing through the PMMA matrix and preferentially assembling near the graphene surface. Charge transfer and doping is attributed to the formation of a charge-transfer complex between F4TCNQ and graphene. The low carrier densities and high carrier mobilities for chemically doped samples is the result of low charge disorder (± 9 meV), thus far only attainable in state-of-the-art exfoliated graphene flakes encapsulated by hexagonal boron nitride (hBN) or suspended graphene. Initial measurements performed at metrological institutes, comparing SiC/G to GaAs, suggest that the chemical dopant is compatible with precision measurements of quantized resistance with part-per-billion accuracy.
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| 6. |
- He, Hans, 1989, et al.
(författare)
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Fabrication of graphene quantum hall resistance standard in a cryogen-Table-Top system
- 2016
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Ingår i: 2016 Conference on Precision Electromagnetic Measurements, CPEM 2016; The Westin OttawaOttawa; Canada; 10-15 July 2016. - : Institute of Electrical and Electronics Engineers Inc.. - 9781467391344 ; , s. Art no 7540516-
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Konferensbidrag (refereegranskat)abstract
- We have demonstrated quantum Hall resistance measurements with metrological accuracy in a relatively easy to use and compact cryogen-free system operating at a temperature of around 3.8 K and magnetic field below 5 T. This advance in technology is due to the unique properties of epitaxial graphene on silicon carbide (SiC) which lifts the stringent requirements for quantum hall effect seen in conventional semiconductors. This paper presents the processes involved in fabrication and characterization of metrologically viable epitaxial graphene samples.
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| 7. |
- He, Hans, 1989
(författare)
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Molecular Doping of Epigraphene for Device Applications
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Epitaxial graphene grown on silicon carbide, or epigraphene, offers in principle a suitable platform for electronic applications of graphene which require scalable, reproducible, and high-quality material. However, one of the main drawbacks of epigraphene lies in the difficulty in controlling its carrier density, which hinders its usefulness in future applications. To solve this problem, this thesis introduces a novel molecular doping method which utilizes acceptor molecules mixed with a polymer. This combination results in a dopant blend that is simple to apply onto epigraphene, and capable of providing controllable, potent, and homogeneous doping over large areas. This technique opens many different avenues for potential applications, three of which are explored in this work. The doping method was successfully used to create practical graphene quantum resistance standards, based on the quantum Hall effect. It was confirmed by two independent metrology institutes that epigraphene meets the stringent criteria for use in precision measurements of resistance. Doped epigraphene was also used to develop magnetic field sensors. These Hall sensors were shown to rival and even surpass the best graphene-based Hall sensors reported in literature thus far, including record-low magnetic field detection limits at room temperature. These Hall sensors also demonstrated promising performance at high temperatures, with the potential to one day outmatch industrial sensors in the automotive and military temperature ranges. Lastly, doped epigraphene was used to create a proof-of-concept terahertz detector. The devices demonstrated highly sensitive and wide-band coherent detection of terahertz signals, with record-low power consumption requirements. It was found that an optimized device could potentially allow for the creation of detector arrays that can provide quantum limited detection across the entire terahertz range, and revolutionize sensors used in next-generation space telescopes.
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| 8. |
- He, Hans, 1989, et al.
(författare)
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The performance limits of epigraphene Hall sensors doped across the Dirac point
- 2020
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 116:22
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial graphene on silicon carbide, or epigraphene, provides an excellent platform for Hall sensing devices in terms of both high electrical quality and scalability. However, the challenge in controlling its carrier density has thus far prevented systematic studies of epigraphene Hall sensor performance. In this work, we investigate epigraphene Hall sensors where epigraphene is doped across the Dirac point using molecular doping. Depending on the carrier density, molecular-doped epigraphene Hall sensors reach room temperature sensitivities of S-V=0.23V/(VT) and S-I=1440V/(AT), with magnetic field detection limits down to B-MIN=27 nT/root Hz at 20kHz. Thermally stabilized devices demonstrate operation up to 150 degrees C with S-V=0.12V/(VT), S-I=300V/(AT), and B-MIN similar to 100 nT/root Hz at 20kHz. Our work demonstrates that epigraphene doped close to the Dirac point could potentially outperform III-V Hall elements in the extended and military temperature ranges.
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| 9. |
- He, Hans, 1989, et al.
(författare)
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Uniform doping of graphene close to the Dirac point by polymer-assisted assembly of molecular dopants
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Tuning the charge carrier density of two-dimensional (2D) materials by incorporating dopants into the crystal lattice is a challenging task. An attractive alternative is the surface transfer doping by adsorption of molecules on 2D crystals, which can lead to ordered molecular arrays. However, such systems, demonstrated in ultra-high vacuum conditions (UHV), are often unstable in ambient conditions. Here we show that air-stable doping of epitaxial graphene on SiC—achieved by spin-coating deposition of 2,3,5,6-tetrafluoro-tetracyano-quino-dimethane (F4TCNQ) incorporated in poly(methyl-methacrylate)—proceeds via the spontaneous accumulation of dopants at the graphene-polymer interface and by the formation of a charge-transfer complex that yields low-disorder, charge-neutral, large-area graphene with carrier mobilities ~70 000 cm2V−1s−1at cryogenic temperatures. The assembly of dopants on 2D materials assisted by a polymer matrix, demonstrated by spin-coating wafer-scale substrates in ambient conditions, opens up a scalable technological route toward expanding the functionality of 2D materials.
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| 10. |
- Janssen, Tjbm, et al.
(författare)
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Operation of graphene quantum Hall resistance standard in a cryogen-free table-top system
- 2015
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Ingår i: 2D Materials. - : IOP Publishing. - 2053-1583. ; 2:3, s. 035015-
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Tidskriftsartikel (refereegranskat)abstract
- Wedemonstrate quantum Hall resistance measurements with metrological accuracy in a small cryogen-free system operating at a temperature of around 3.8Kand magnetic fields below 5 T. Operating this system requires little experimental knowledge or laboratory infrastructure, thereby greatly advancing the proliferation of primary quantum standards for precision electrical metrology. This significant advance in technology has come about as a result of the unique properties of epitaxial graphene on SiC.
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| 11. |
- Janssen, Tjbm, et al.
(författare)
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Towards a cryogen-free table-top primary resistance standard
- 2016
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Ingår i: 2016 Conference on Precision Electromagnetic Measurements (Cpem 2016). - : Institute of Electrical and Electronics Engineers Inc.. - 9781467391344
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Konferensbidrag (refereegranskat)abstract
- We demonstrate quantum Hall resistance measurements with metrological accuracy in a small cryogen-free system operating at a temperature of around 3.8 K and magnetic fields below 5 T. We use this system to investigate the optimisation of graphene/SiC devices for maximum breakdown current. In addition we report the first characterisation of a cryogen-free cryogenic current comparator which enables entirely cryogen-free primary resistance metrology.
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| 12. |
- Karimi, Bayan, et al.
(författare)
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Electron-phonon coupling of epigraphene at millikelvin temperatures measured by quantum transport thermometry
- 2021
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 118:10
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the basic charge and heat transport properties of charge neutral epigraphene at sub-kelvin temperatures, demonstrating a nearly logarithmic dependence of electrical conductivity over more than two decades in temperature. Using graphene's sheet conductance as an in situ thermometer, we present a measurement of electron-phonon heat transport at mK temperatures and show that it obeys the T4 dependence characteristic for a clean two-dimensional conductor. Based on our measurement, we predict the noise-equivalent power of ∼ 10 - 22 W / Hz of the epigraphene bolometer at the low end of achievable temperatures.
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| 13. |
- Kim, Kyung Ho, 1984, et al.
(författare)
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Apparent Power Law Scaling of Variable Range Hopping Conduction in Carbonized Polymer Nanofibers
- 2016
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- We induce dramatic changes in the structure of conducting polymer nanofibers by carbonization at 800 degrees C and compare charge transport properties between carbonized and pristine nanofibers. Despite the profound structural differences, both types of systems display power law dependence of current with voltage and temperature, and all measurements can be scaled into a single universal curve. We analyze our experimental data in the framework of variable range hopping and argue that this mechanism can explain transport properties of pristine polymer nanofibers as well.
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| 14. |
- Kim, Kyung Ho, 1984, et al.
(författare)
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Chemical Sensing with Atomically Thin Platinum Templated by a 2D Insulator
- 2020
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Ingår i: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 7:12
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Tidskriftsartikel (refereegranskat)abstract
- Boosting the sensitivity of solid‐state gas sensors by incorporating nanostructured materials as the active sensing element can be complicated by interfacial effects. Interfaces at nanoparticles, grains, or contacts may result in nonlinear current–voltage response, high electrical resistance, and ultimately, electric noise that limits the sensor read‐out. This work reports the possibility to prepare nominally one atom thin, electrically continuous platinum layers by physical vapor deposition on the carbon zero layer (also known as the buffer layer) grown epitaxially on silicon carbide. With a 3–4 Å thin Pt layer, the electrical conductivity of the metal is strongly modulated when interacting with chemical analytes, due to charges being transferred to/from Pt. The strong interaction with chemical species, together with the scalability of the material, enables the fabrication of chemiresistor devices for electrical read‐out of chemical species with sub part‐per‐billion (ppb) detection limits. The 2D system formed by atomically thin Pt on the carbon zero layer on SiC opens up a route for resilient and high sensitivity chemical detection, and can be the path for designing new heterogenous catalysts with superior activity and selectivity.
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| 15. |
- Kim, Kyung Ho, 1984, et al.
(författare)
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Probing variable range hopping lengths by magneto conductance in carbonized polymer nanofibers
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Using magneto transport, we probe hopping length scales in the variable range hopping conduction of carbonized polyacetylene and polyaniline nanofibers. In contrast to pristine polyacetylene nanofibers that show vanishing magneto conductance at large electric fields, carbonized polymer nanofibers display a negative magneto conductance that decreases in magnitude but remains finite with respect to the electric field. We show that this behavior of magneto conductance is an indicator of the electric field and temperature dependence of hopping length in the gradual transition from the thermally activated to the activation-less electric field driven variable range hopping transport. This reveals magneto transport as a useful tool to probe hopping lengths in the non-linear hopping regime.
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| 16. |
- Kim, Kyung Ho, 1984, et al.
(författare)
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Thermal stability of epitaxial graphene electrodes for conductive polymer nanofiber devices
- 2017
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Ingår i: Crystals. - : MDPI AG. - 2073-4352. ; 7:12
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Tidskriftsartikel (refereegranskat)abstract
- We used large area, monolayer graphene epitaxially grown on SiC (0001) as contact electrodes for polymer nanofiber devices. Our fabrication process, which avoids polymer resist residues on the graphene surface, results in graphene-polyaniline nanofiber devices with Ohmic contacts and electrical conductivity comparable to that of Au-nanofiber devices. We further checked the thermal stability of the graphene contacts to polyaniline devices by annealing up to T = 800 °C, the temperature at which polyaniline nanofibers are carbonized but the graphene electrode remains intact. The thermal stability and Ohmic contact of polymer nanofibers are demonstrated here, which together with the chemical stability and atomic flatness of graphene, make epitaxial graphene on SiC an attractive contact material for future all-carbon electronic devices.
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| 17. |
- Lara Avila, Samuel, 1983, et al.
(författare)
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Towards quantum-limited coherent detection of terahertz waves in charge-neutral graphene
- 2019
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Ingår i: Nature Astronomy. - : Springer Science and Business Media LLC. - 2397-3366. ; 3:11, s. 983-988
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Spectacular advances in heterodyne astronomy1,2 have been largely due to breakthroughs in detector technology3. To exploit the full capacity of future terahertz (∼300 GHz–5 THz) telescope space missions4, new concepts of terahertz coherent receivers are needed, providing larger bandwidths and imaging capabilities with multipixel focal plane heterodyne arrays5. Here we show that graphene uniformly doped to the Dirac point, with material resistance dominated by quantum localization and thermal relaxation governed by electron diffusion, enables highly sensitive and wideband coherent detection of signals from 90 to 700 GHz and, prospectively, across the entire terahertz range. We measure on proof-of-concept graphene bolometric mixers an electron diffusion-limited gain bandwidth of 8 GHz (corresponding to a Doppler shift of 480 km s−1 at 5 THz) and intrinsic mixer noise temperature of 475 K (which would be equivalent to ~2 hν/kB at ν = 5 THz), limited by the residual thermal background in our setup. An optimized device will result in a mixer noise temperature as low as 36 K, with the gain bandwidth exceeding 20 GHz, and a local oscillator power of <100 pW. In conjunction with the emerging quantum-limited amplifiers at the intermediate frequency6,7, our approach promises quantum-limited sensing in the terahertz domain, potentially surpassing superconducting technologies, particularly for large heterodyne arrays
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| 18. |
- Shetty, Naveen, 1988, et al.
(författare)
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Long-term stability of molecular doped epigraphene quantum Hall standards: single elements and large arrays (R K/236 ≈ 109 Ω)
- 2023
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Ingår i: Metrologia. - : Institute of Physics. - 0026-1394 .- 1681-7575. ; 60:5
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Tidskriftsartikel (refereegranskat)abstract
- In this work we investigate the long-term stability of epitaxial graphene (epigraphene) quantum Hall resistance standards, including single devices and an array device composed of 236 elements providing R K/236 ≈ 109 Ω, with R K the von Klitzing constant. All devices utilize the established technique of chemical doping via molecular dopants to achieve homogenous doping and control over carrier density. However, optimal storage conditions and the long-term stability of molecular dopants for metrological applications have not been widely studied. In this work we aim to identify simple storage techniques that use readily available and cost-effective materials which provide long-term stability for devices without the need for advanced laboratory equipment. The devices are stored in glass bottles with four different environments: ambient, oxygen absorber, silica gel desiccant, and oxygen absorber/desiccant mixture. We have tracked the carrier densities, mobilities, and quantization accuracies of eight different epigraphene quantum Hall chips for over two years. We observe the highest stability (i.e. lowest change in carrier density) for samples stored in oxygen absorber/desiccant mixture, with a relative change in carrier density below 0.01% per day and no discernable degradation of quantization accuracy at the part-per-billion level. This storage technique yields a comparable stability to the currently established best storage method of inert nitrogen atmosphere, but it is much easier to realize in practice. It is possible to further optimize the mixture of oxygen absorber/desiccant for even greater stability performance in the future. We foresee that this technique can allow for simple and stable long-term storage of polymer-encapsulated molecular doped epigraphene quantum Hall standards, removing another barrier for their wide-spread use in practical metrology.
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| 19. |
- Shetty, Naveen, 1988, et al.
(författare)
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Scalable Fabrication of Edge Contacts to 2D Materials : Implications for Quantum Resistance Metrology and 2D Electronics
- 2023
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society. - 2574-0970. ; 6:7, s. 6292-
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Tidskriftsartikel (refereegranskat)abstract
- We report a reliable and scalable fabrication method for producing electrical contacts to two-dimensional (2D) materials based on the tri-layer resist system. We demonstrate the applicability of this method in devices fabricated on epitaxial graphene on silicon carbide (epigraphene) used as a scalable 2D material platform. For epigraphene, data on nearly 70 contacts result in median values of the one-dimensional (1D) specific contact resistances ρc ∼ 67 Ω·μm and follow the Landauer quantum limit ρc ∼ n-1/2, consistently reaching values ρc < 50 Ω·μm at high carrier densityn. As a proof of concept, we apply the same fabrication method to the transition metal dichalcogenide (TMDC) molybdenum disulfide (MoS2). Our edge contacts enable MoS2 field-effect transistor (FET) behavior with an ON/OFF ratio of >106 at room temperature (>109 at cryogenic temperatures). The fabrication route demonstrated here allows for contact metallization using thermal evaporation and also by sputtering, giving an additional flexibility when designing electrical interfaces, which is key in practical devices and when exploring the electrical properties of emerging materials. © 2023 The Authors.
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| 20. |
- Shetty, Naveen, 1988, et al.
(författare)
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Ultralow 1/f noise in epigraphene devices
- 2024
-
Ingår i: Applied Physics Letters. - : American Institute of Physics Inc.. - 0003-6951 .- 1077-3118. ; 124:9
-
Tidskriftsartikel (refereegranskat)abstract
- We report the lowest recorded levels of 1/ f noise for graphene-based devices, at the level of S V / V 2 = S I / I 2 = 4.4 × 10 − 16 (1/Hz), measured at f = 10 Hz ( S V / V 2 = S I / I 2 < 10 − 16 1/Hz for f > 100 Hz) in large-area epitaxial graphene on silicon carbide (epigraphene) Hall sensors. This performance is made possible through the combination of high material quality, low contact resistance achieved by edge contact fabrication process, homogeneous doping, and stable passivation of the graphene layer. Our study explores the nature of 1/ f noise as a function of carrier density and device geometry and includes data from Hall sensors with device area range spanning over six orders of magnitude, with characteristic device length ranging from L = 1 μm to 1 mm. In optimized graphene Hall sensors, we demonstrate arrays to be a viable route to improve further the magnetic field detection: a simple parallel connection of two devices displays record-high magnetic field sensitivity at room temperature, with minimum detectable magnetic field levels down to B min = 9.5 nT/√Hz. The remarkable low levels of 1/ f noise observed in epigraphene devices hold immense capacity for the design and fabrication of scalable epigraphene-based sensors with exceptional performance. © 2024 Author(s).
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