| 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. |
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| 3. |
- Stanaway, Jeffrey D., et al.
(författare)
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Global, regional, and national comparative risk assessment of 84 behavioural, environmental and occupational, and metabolic risks or clusters of risks for 195 countries and territories, 1990-2017: A systematic analysis for the Global Burden of Disease Study 2017
- 2018
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Ingår i: The Lancet. - 1474-547X .- 0140-6736. ; 392:10159, s. 1923-1994
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Tidskriftsartikel (refereegranskat)abstract
- Background The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2017 comparative risk assessment (CRA) is a comprehensive approach to risk factor quantification that offers a useful tool for synthesising evidence on risks and risk-outcome associations. With each annual GBD study, we update the GBD CRA to incorporate improved methods, new risks and risk-outcome pairs, and new data on risk exposure levels and risk- outcome associations. Methods We used the CRA framework developed for previous iterations of GBD to estimate levels and trends in exposure, attributable deaths, and attributable disability-adjusted life-years (DALYs), by age group, sex, year, and location for 84 behavioural, environmental and occupational, and metabolic risks or groups of risks from 1990 to 2017. This study included 476 risk-outcome pairs that met the GBD study criteria for convincing or probable evidence of causation. We extracted relative risk and exposure estimates from 46 749 randomised controlled trials, cohort studies, household surveys, census data, satellite data, and other sources. We used statistical models to pool data, adjust for bias, and incorporate covariates. Using the counterfactual scenario of theoretical minimum risk exposure level (TMREL), we estimated the portion of deaths and DALYs that could be attributed to a given risk. We explored the relationship between development and risk exposure by modelling the relationship between the Socio-demographic Index (SDI) and risk-weighted exposure prevalence and estimated expected levels of exposure and risk-attributable burden by SDI. Finally, we explored temporal changes in risk-attributable DALYs by decomposing those changes into six main component drivers of change as follows: (1) population growth; (2) changes in population age structures; (3) changes in exposure to environmental and occupational risks; (4) changes in exposure to behavioural risks; (5) changes in exposure to metabolic risks; and (6) changes due to all other factors, approximated as the risk-deleted death and DALY rates, where the risk-deleted rate is the rate that would be observed had we reduced the exposure levels to the TMREL for all risk factors included in GBD 2017.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
- Borg, Mattias, et al.
(författare)
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Influence of doping on the electronic transport in GaSb/InAs(Sb) nanowire tunnel devices
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:4
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Tidskriftsartikel (refereegranskat)abstract
- The effect of various doping profiles on the electronic transport in GaSb/InAs(Sb) nanowire tunnel diodes is investigated. Zn-doping of the GaSb segment increases both the peak current density and the current level in reverse bias. Top-gated diodes exhibit peak current modulation with a threshold voltage which can be controlled by Zn-doping the InAs(Sb) segment. By intentionally n-doping the InAs(Sb) segment degenerate doping on both sides of the heterojunction can be achieved, as well as tunnel diodes with peak current of 420 kA/cm(2) at V-DS = 0.16V and a record-high current density of 3.6 MA/cm(2) at V-DS = -0.5V. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4739082]
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| 8. |
- Dey, Anil, et al.
(författare)
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15 nm diameter InAs nanowire MOSFETs
- 2011
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Ingår i: [Host publication title missing]. - 1548-3770. ; , s. 21-22
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Konferensbidrag (refereegranskat)abstract
- InAs is an attractive channel material for III–V nanowire MOSFETs and early prototype high performance nanowire transistors have been demonstrated1. As the gate length is reduced, the nanowire diameter must be scaled quite aggressively in order to suppress short-channel effects2. However, a reduction in transconductance (gm) and drive current (ION) could be expected due to increased surface scattering for thin wires. We present data for the device properties of thin InAs nanowires, with diameters in the 15 nm range, and investigate possible improvements of the performance focusing on transistor applications. In order to boost ION, the source and drain resistance need to be reduced. Several doping sources were therefore evaluated in the study, among them selenium (Se), tin (Sn) and sulphur (S) to form n-i-n structures. We report very high current densities, up to 33 MA/cm2, comparable to modern HEMTs3, and a normalized transconductance of 1.8 S/mm for a nanowire with an intrinsic segment of nominally 150 nm and a diameter of 15 nm.
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| 9. |
- Dey, Anil, et al.
(författare)
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Combining axial and radial nanowire heterostructures: Radial Esaki diodes and tunnel field-effect transistors
- 2013
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 13:12, s. 5919-5924
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Tidskriftsartikel (refereegranskat)abstract
- The ever-growing demand on high-performance electronics has generated transistors with very impressive figures of merit. The continued scaling of the supply voltage of field-effect transistors, such as tunnel field-effect transistors (TFETs), requires the implementation of advanced transistor architectures including FinFETs and nanowire devices. Moreover, integration of novel materials with high electron mobilities, such as III-V semiconductors and graphene, are also being considered to further enhance the device properties. In nanowire devices, boosting the drive current at a fixed supply voltage or maintaining a constant drive current at a reduced supply voltage may be achieved by increasing the cross-sectional area of a device, however at the cost of deteriorated electrostatics. A gate-all-around nanowire device architecture is the most favorable electrostatic configuration to suppress short channel effects, however, the arrangement of arrays of parallel vertical nanowires to address the drive current predicament will require additional chip area. The use of a core-shell nanowire with a radial heterojunction in a transistor architecture provides an attractive means to address the drive current issue without compromising neither chip area nor device electrostatics. In addition to design advantages of a radial transistor architecture, we in this work illustrate the benefit in terms of drive current per unit chip area and compare the experimental data for axial GaSb/InAs Esaki diodes and TFETs to their radial counterparts and normalize the electrical data to the largest cross-sectional area of the nanowire, i.e. the occupied chip area, assuming a vertical device geometry. Our data on lateral devices show that radial Esaki diodes deliver almost 7 times higher peak current, Jpeak = 2310 kA/cm2, than the maximum peak current of axial GaSb/InAs(Sb) Esaki diodes per unit chip area. The radial TFETs also deliver high peak current densities Jpeak = 1210 kA/cm2 while their axial counterparts at most carry Jpeak = 77 kA/cm2, normalized to the largest cross-sectional area of the nanowire.
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| 10. |
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| 11. |
- Dey, Anil, et al.
(författare)
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GaSb nanowire pFETs for III-V CMOS
- 2013
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Ingår i: IEEE Device Research Conference. Proceedings. - 1548-3770. ; , s. 13-14
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Konferensbidrag (refereegranskat)
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| 12. |
- Dey, Anil, et al.
(författare)
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High Current Density InAsSb/GaSb Tunnel Field Effect Transistors
- 2012
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Ingår i: Device research conference. - 1548-3770. ; , s. 205-206
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Konferensbidrag (refereegranskat)abstract
- Steep-slope devices, such as tunnel field-effect transistors (TFETs), have recently gained interest due to their potential for low power operation at room temperature. The devices are based on inter-band tunneling which could limit the on-current since the charge carriers must tunnel through a barrier to traverse the device. The InAs/GaSb heterostructure forms a broken type II band alignment which enables inter-band tunneling without a barrier, allowing high on-currents. We have recently demonstrated high current density (Ion,reverse = 17.5 mA/µm) nanowire Esaki diodes and in this work we investigate the potential of InAs/GaSb heterostructure nanowires to operate as TFETs. We present device characterization of InAs 0.85 Sb 0.15 /GaSb nanowire TFETs, which exhibit record-high on-current levels.
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| 13. |
- Dey, Anil, et al.
(författare)
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High-Current GaSb/InAs(Sb) Nanowire Tunnel Field-Effect Transistors
- 2013
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Ingår i: IEEE Electron Device Letters. - 0741-3106. ; 34:2, s. 211-213
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Tidskriftsartikel (refereegranskat)abstract
- We present electrical characterization of GaSb/InAs(Sb) nanowire tunnel field-effect transistors. The broken band alignment of the GaSb/InAs(Sb) heterostructure is exploited to allow for interband tunneling without a barrier, leading to high ON-current levels. We report a maximum drive current of 310 μA/μm at Vds = 0.5 V. Devices with scaled gate oxides display transconductances up to gm = 250 mS/mm at Vds = 300 mV, which are normalized to the nanowire circumference at the axial heterojunction.
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| 14. |
- Dey, Anil, et al.
(författare)
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High-performance 15 nm diameter InAs nanowire Ω-gate MOSFETs
- 2012
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Konferensbidrag (refereegranskat)abstract
- In this paper we present 15 nm InAs nanowire lateral MOSFETs with an Ω-gate. The nanowires are grown from size-selected Au-aerosols by means of metal-organic vapor phase epixtaxy (MOVPE). In order to reduce the source and drain resistances, n-type dopants were introduced in the bottom and top parts of the nanowire forming a n-i-n structure. We report experimental data for 15 nm InAs nanowire MOSFETs, LG = 150 nm, with a normalized transconducatance gm = 0.7 S/mm (normalized to the circumference) and a current density Je = 24 MA/cm, comparable to modern high electron mobility transistors (HEMTs)
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| 15. |
- Dey, Anil, et al.
(författare)
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High-Performance InAs Nanowire MOSFETs
- 2012
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Ingår i: IEEE Electron Device Letters. - 0741-3106. ; 33:6, s. 791-793
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, we present a 15-nm-diameter InAs nanowire MOSFET with excellent on and off characteristics. An n-i-n doping profile was used to reduce the source and drain resistances, and an Al2O3/HfO2 bilayer was introduced in the high-k process. The nanowires exhibit high drive currents, up to 1.25 A/mm, normalized to the nanowire circumference, and current densities up to 34 MA/cm2 (VD = 0.5 V). For a nominal LG = 100 nm, we observe an extrinsic transconductance (gm) of 1.23 S/mm and a subthreshold swing of 93 mV/decade at VD = 10 mV.
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| 16. |
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| 17. |
- Dey, Anil, et al.
(författare)
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Laboratory instructions as a cause of student dissonance
- 2010
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Ingår i: [Host publication title missing].
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Konferensbidrag (refereegranskat)abstract
- Improving the quality of education is the goal of all pedagogical research. By using student surveys and course evaluations problem areas can be identified in most courses offered by universities. In this paper we perform a large-scale student survey in order to find the causes of, and remedies to, a widespread student dissonance in a mandatory course with over 100 students at Lund University. Our research shows that aiming for deeper learning, without providing time and a stimulating environment, can be worse than settling for expository learning. This problem has persisted for years despite attempts by the course administrators to solve the problem. We propose that major improvements can be achieved, both in learning and pass rates, primarily by improving the lab instructions but also by using a more intellectually stimulating lab equipment.
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| 18. |
- Dey, Anil
(författare)
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Low-Power Nanowire Circuits and Transistors
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis explores several novel material systems and innovative device concepts enabled by nanowire technology. State-of-the-art fabrication techniques such as electron beam lithography and atomic layer deposition are utilized to achieve high control and quality in the device fabrication. The devices in this thesis are based on two main types of design geometries, lateral and vertical, each of which have strengths and weaknesses. The first part of the thesis describes the goals of future metal-oxide-semiconductor field-effect transistors (MOSFETs) and discusses the ultimate scalability surrounding experimental results for 15-nm-diameter InAs nanowires and how they compare to other state-of-the-art transistors. The extracted on-resistance (Ron = 250 Ω·µm) and drive currents (Ion = 1250 µA/µm) are comparable to state-of-the-art high-electron-mobility transistors (HEMTs) from MIT and quantum-well field-effect transistors from Intel. The outstanding performance is mainly attributed to the reduced access resistance achieved through an n+-i-n+ doping profile. The extracted mobilities also agree well with state-of-the-art and theoretical predictions for extremely scaled devices. The second part of the thesis discusses how nanowires may be employed to enable III-V complementary metal-oxide-semiconductor (CMOS) digital logic. Nanowires enable the formation of both n-type semiconductors and p-type semiconductors, which are a requirement for CMOS, in a single nanowire and allow for integration on a Si platform. III-V MOSFETs are frequently employed for analog applications, but there is a disconnect regarding p-type devices, which are also required for digital logic. The individual segments of the nanowire are evaluated as well as the entire nanowire in an inverter configuration. This thesis then presents a strategy for matching the drive currents n- and p-type MOSFETs. The final part of the thesis deals with a family of devices that operate according to principles fundamentally different from those of a traditional MOSFET, namely tunnel FETs (TFETs). There is a demand for steep-slope devices such as TFETs to enable supply-voltage scaling to reduce the power dissipation. Although devices have demonstrated <60 mV/decade operation, they commonly suffer from low on-currents. To maximize the drive current, the broken band gap alignment of GaSb/InAs is exploited to allow for a direct tunneling mechanism. The material system is first explored as Esaki diodes and in various doping profiles to understand the influence of doping on device performance. The devices are further evolved into TFETs by the addition of a high-k gate dielectric and an additional terminal. Experimental results display high on-currents of Ion = 310 µA/µm comparable to other state-of-the-art TFETs. Finally, an innovative design concept combining axial and radial heterostructures is utilized to design a radial TFET with a small footprint. A radial GaSb/InAs core/shell TFET provides an attractive way to increase the drive current of a TFET without compromising either device electrostatics or chip area. The functionality of radial Esaki diodes and TFETs is demonstrated and evaluated by the maximum peak currents, which are much improved as compared to their axial counterparts when normalized to the largest cross-sectional area of the nanowire, assuming a vertical device geometry, illustrating the advantage of a core--shell architecture. The dimensions of the InAs shells are below 15-nm and display clear quantization effects revealed in low-temperature electrical characterization.
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| 19. |
- Dey, Anil, et al.
(författare)
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Single InAs/GaSb Nanowire Low-Power CMOS Inverter
- 2012
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984.
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Tidskriftsartikel (refereegranskat)abstract
- III − V semiconductors have so far predom- inately been employed for n-type transistors in high-frequency applications. This development is based on the advantageous transport properties and the large variety of heterostructure combinations in the family of III − V semiconductors. In contrast, reports on p-type devices with high hole mobility suitable for complementary metal − oxide − semiconductor (CMOS) circuits for low-power operation are scarce. In addition, the di ffi culty to integrate both n- and p-type devices on the same substrate without the use of complex bu ff er layers has hampered the development of III − V based digital logic. Here, inverters fabricated from single n-InAs/p-GaSb hetero- structure nanowires are demonstrated in a simple processing scheme. Using undoped segments and aggressively scaled high- κ dielectric, enhancement mode operation suitable for digital logic is obtained for both types of transistors. State-of-the-art on- and o ff -state characteristics are obtained and the individual long-channel n- and p-type transistors exhibit minimum subthreshold swings of SS = 98 mV/dec and SS = 400 mV/dec, respectively, at V ds = 0.5 V. Inverter characteristics display a full signal swing and maximum gain of 10.5 with a small device-to-device variability. Complete inversion is measured at low frequencies although large parasitic capacitances deform the waveform at higher frequencies.
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| 20. |
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| 21. |
- Dhama, Kuldeep, et al.
(författare)
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SARS-CoV-2 emerging Omicron subvariants with a special focus on BF.7 and XBB.1.5 recently posing fears of rising cases amid ongoing COVID-19 pandemic
- 2022
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Ingår i: Journal of Experimental Biology and Agricultural Sciences. - : JEBAS. - 2320-8694. ; 10:6, s. 1215-1221
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Tidskriftsartikel (refereegranskat)abstract
- The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron versions have been the sole one circulating for quite some time. Subvariants BA.1, BA.2, BA.3, BA.4, and BA.5 of the Omicron emerged over time and through mutation, with BA.1 responsible for the most severe global pandemic between December 2021 and January 2022. Other Omicron subvariants such as BQ.1, BQ.1.1, BA.4.6, BF.7, BA.2.75.2, XBB.1 appeared recently and could cause a new wave of increased cases amid the ongoing COVID-19 pandemic. There is evidence that certain Omicron subvariants have increased transmissibility, extra spike mutations, and ability to overcome protective effects of COVID-19 neutralizing antibodies through immunological evasion. In recent months, the Omicron BF.7 subvariant has been in the news due to its spread in China and a small number of other countries, raising concerns about a possible rebound in COVID-19 cases. More recently, the Omicron XBB.1.5 subvariant has captured international attention due to an increase in cases in the United States. As a highly transmissible sublineage of Omicron BA.5, as well as having a shorter incubation time and the potential to reinfect or infect immune population, BF.7 has stronger infection ability. It appears that the regional immunological landscape is affected by the amount and timing of previous Omicron waves, as well as the COVID-19 vaccination coverage, which in turn determines whether the increased immune escape of BF.7 and XBB.1.5 subvariants is sufficient to drive new infection waves. Expanding our understanding of the transmission and efficacy of vaccines, immunotherapeutics, and antiviral drugs against newly emerging Omicron subvariants and lineages, as well as bolstering genomic facilities for tracking their spread and maintaining a constant vigilance, and shedding more light on their evolution and mutational events, would help in the development of effective mitigation strategies. Importantly, reducing the occurrence of mutations and recombination in the virus can be aided by bolstering One health approach and emphasizing its significance in combating zoonosis and reversal zoonosis linked with COVID-19. This article provides a brief overview on Omicron variant, its recently emerging lineages and subvairants with a special focus on BF.7 and XBB.1.5 as much more infectious and highly transmissible variations that may once again threaten a sharp increase in COVID-19 cases globally amid the currently ongoing pandemic, along with presenting salient mitigation measures.
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| 22. |
- Egard, Mikael, et al.
(författare)
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Vertical InAs nanowire wrap gate transistors with f(t) > 7 GHz and f(max) > 20 GHz.
- 2010
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 10:3, s. 809-812
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Tidskriftsartikel (refereegranskat)abstract
- In this letter we report on high-frequency measurements on vertically standing III-V nanowire wrap-gate MOSFETs (metal-oxide-semiconductor field-effect transistors). The nanowire transistors are fabricated from InAs nanowires that are epitaxially grown on a semi-insulating InP substrate. All three terminals of the MOSFETs are defined by wrap around contacts. This makes it possible to perform high-frequency measurements on the vertical InAs MOSFETs. We present S-parameter measurements performed on a matrix consisting of 70 InAs nanowire MOSFETs, which have a gate length of about 100 nm. The highest unity current gain cutoff frequency, f(t), extracted from these measurements is 7.4 GHz and the maximum frequency of oscillation, f(max), is higher than 20 GHz. This demonstrates that this is a viable technique for fabricating high-frequency integrated circuits consisting of vertical nanowires.
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| 23. |
- Ek, Martin, et al.
(författare)
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Formation of the axial heterojunction in GaSb/InAs(Sb) nanowires with high crystal quality
- 2011
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Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 11:10, s. 4588-4593
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Tidskriftsartikel (refereegranskat)abstract
- Switching of the group-III element in III-V nanowire heterostructures is difficult due to the high solubility of group-III atoms in the Au seed particle. In addition, switching from Sb to a different group-V element has not been achieved in binary materials, largely due to its high solubility in Au. In MOVPE growth the use of Sb precursors presents further complications due to reactor background contamination. In this paper we demonstrate growth of GaSb/InAs(Sb) nanowire heterostructures with potential applications in tunneling devices, and study the processes occurring during the transition from GaSb to InAs growth. We show how the heterostructure can be grown with a sharp transition by taking advantage of a growth stop, which occurs naturally as the Au seed particle is emptied of Ga and filled with In. The remaining Sb background in the reactor during the InAs growth results in a finite Sb incorporation into this segment. This has the advantage of suppressing stacking faults in the InAs(Sb) segment, making the entire heterostructure a single zincblende crystal.
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| 24. |
- Ganjipour, Bahram, et al.
(författare)
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Electrical properties of GaSb/InAsSb core/shell nanowires
- 2014
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 25:42
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Tidskriftsartikel (refereegranskat)abstract
- Temperature dependent electronic properties of GaSb/InAsSb core/shell and GaSb nanowires have been studied. Results from two-probe and four-probe measurements are compared to distinguish between extrinsic (contact-related) and intrinsic (nanowire) properties. It is found that a thin (2-3 nm) InAsSb shell allows low barrier charge carrier injection to the GaSb core, and that the presence of the shell also improves intrinsic nanowire mobility and conductance in comparison to bare GaSb nanowires. Maximum intrinsic field effect mobilities of 200 and 42 cm(2) Vs(-1) were extracted for the GaSb/InAsSb core/shell and bare-GaSb NWs at room temperature, respectively. The temperature-dependence of the mobility suggests that ionized impurity scattering is the dominant scattering mechanism in bare GaSb while phonon scattering dominates in core/shell nanowires. Top-gated field effect transistors were fabricated based on radial GaSb/InAsSb heterostructure nanowires with shell thicknesses in the range 5-7 nm. The fabricated devices exhibited ambipolar conduction, where the output current was studied as a function of AC gate voltage and frequency. Frequency doubling was experimentally demonstrated up to 20 kHz. The maximum operating frequency was limited by parasitic capacitance associated with the measurement chip geometry.
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| 25. |
- Ganjipour, Bahram, et al.
(författare)
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High current density Esaki tunnel diodes based on GaSb-InAsSb heterostructure nanowires
- 2011
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 11:10, s. 4222-4226
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Tidskriftsartikel (refereegranskat)abstract
- We present electrical characterization of broken gap GaSb-InAsSb nanowire heterojunctions. Esaki diode characteristics with maximum reverse current of 1750 kA/cm2 at 0.50 V, maximum peak current of 67 kA/cm2 at 0.11 V, and peak-to-valley ratio (PVR) of 2.1 are obtained at room temperature. The reverse current density is comparable to that of state-of-the-art tunnel diodes based on heavily doped p-n junctions. However, the GaSb-InAsSb diodes investigated in this work do not rely on heavy doping, which permits studies of transport mechanisms in simple transistor structures processed with high-κ gate dielectrics and top-gates. Such processing results in devices with improved PVR (3.5) and stability of the electrical properties.
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| 26. |
- Jung, Christian, et al.
(författare)
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A comparison of very old patients admitted to intensive care unit after acute versus elective surgery or intervention
- 2019
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Ingår i: Journal of critical care. - : W B SAUNDERS CO-ELSEVIER INC. - 0883-9441 .- 1557-8615. ; 52, s. 141-148
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Tidskriftsartikel (refereegranskat)abstract
- Background: We aimed to evaluate differences in outcome between patients admitted to intensive care unit (ICU) after elective versus acute surgery in a multinational cohort of very old patients (80 years; VIP). Predictors of mortality, with special emphasis on frailty, were assessed.Methods: In total, 5063 VIPs were induded in this analysis, 922 were admitted after elective surgery or intervention, 4141 acutely, with 402 after acute surgery. Differences were calculated using Mann-Whitney-U test and Wilcoxon test. Univariate and multivariable logistic regression were used to assess associations with mortality.Results: Compared patients admitted after acute surgery, patients admitted after elective surgery suffered less often from frailty as defined as CFS (28% vs 46%; p < 0.001), evidenced lower SOFA scores (4 +/- 5 vs 7 +/- 7; p < 0.001). Presence of frailty (CFS >4) was associated with significantly increased mortality both in elective surgery patients (7% vs 12%; p = 0.01), in acute surgery (7% vs 12%; p = 0.02).Conclusions: VIPs admitted to ICU after elective surgery evidenced favorable outcome over patients after acute surgery even after correction for relevant confounders. Frailty might be used to guide clinicians in risk stratification in both patients admitted after elective and acute surgery.
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| 27. |
- Lind, Erik, et al.
(författare)
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High Frequency Performance of Vertical InAs Nanowire MOSFET
- 2010
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Ingår i: 2010 22Nd International Conference On Indium Phosphide And Related Materials (Iprm). - 1092-8669. - 9781424459193
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Konferensbidrag (refereegranskat)abstract
- We report on RF characterization of vertical, 100-nm-gate length InAs nanowire MOSFETs, utilizing wrap-gate technology and Al2O3 high-kappa gate oxide. The transistors show f(t)=5.6 GHz and f(max)=22 GHz, mainly limited by parasitic capacitances. The RF device performance is described using a hybrid-pi model taking hole generation at the drain into account. Electrostatic modeling of the parasitic capacitances for arrays of vertical nanowires indicates that a strong reduction in extrinsic capacitances can be achieved for devices with a small inter-wire separation.
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| 28. |
- Lind, Erik, et al.
(författare)
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III-V Heterostructure Nanowire Tunnel FETs
- 2015
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Ingår i: IEEE Journal of the Electron Devices Society. - 2168-6734. ; 3:3, s. 96-102
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, InAs/GaSb nanowire tunnel field-effect transistors (TFETs) are studied theoretically and experimentally. A 2-band 1-D analytic tunneling model is used to calculate the on- and off-current levels of nanowire TFETs with staggered source/channel band alignment. Experimental results from lateral InAs/GaSb are shown, as well as first results on integration of vertical InAs/GaSb nanowire TFETs on Si substrates.
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| 29. |
- Mandl, Bernhard, et al.
(författare)
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Growth Mechanism of Self-Catalyzed Group III-V Nanowires.
- 2010
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 10:Online October 7, 2010, s. 4443-4449
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Tidskriftsartikel (refereegranskat)abstract
- Group III-V nanowires offer the exciting possibility of epitaxial growth on a wide variety of substrates, most importantly silicon. To ensure compatibility with Si technology, catalyst-free growth schemes are of particular relevance, to avoid impurities from the catalysts. While this type of growth is well-documented and some aspects are described, no detailed understanding of the nucleation and the growth mechanism has been developed. By combining a series of growth experiments using metal-organic vapor phase epitaxy, as well as detailed in situ surface imaging and spectroscopy, we gain deeper insight into nucleation and growth of self-seeded III-V nanowires. By this mechanism most work available in literature concerning this field can be described.
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| 30. |
- Mandl, Bernhard, et al.
(författare)
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Self-seeded, position-controlled InAs nanowire growth on Si: A growth parameter study
- 2011
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 334:1, s. 51-56
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the nucleation and growth of InAs nanowires on patterned SiO2/Si(111) substrates is studied. It is found that the nanowire yield is strongly dependent on the size of the etched holes in the SiO2, where openings smaller than 180 nm lead to a substantial decrease in nucleation yield, while openings larger than View the MathML source promote nucleation of crystallites rather than nanowires. We propose that this is a result of indium particle formation prior to nanowire growth, where the size of the indium particles, under constant growth parameters, is strongly influenced by the size of the openings in the SiO2 film. Nanowires overgrowing the etched holes, eventually leading to a merging of neighboring nanowires, shed light into the growth mechanism.
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| 31. |
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| 32. |
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| 33. |
- Persson, Karl-Magnus, et al.
(författare)
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Low-frequency noise in vertical InAs nanowire FETs
- 2010
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Ingår i: IEEE Electron Device Letters. - 0741-3106. ; 31:5, s. 428-430
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Tidskriftsartikel (refereegranskat)abstract
- This letter presents dc characteristics and low-frequency noise (LFN) measurements on single vertical InAs nanowire MOSFETs with 35-nm gate length and HfO2 high-kappa dielectric. The average normalized transconductance for three devices is 0.16 S/mm, with a subthreshold slope of 130 mV/decade. At 10 Hz, the normalized noise power S-I/I-d(2) measures 7.3 x 10(-7) Hz(-1). Moreover, the material-dependent Hooge's parameter at room temperature is estimated to be 4.2 x 10(-3).
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| 34. |
- Svensson, Johannes, et al.
(författare)
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III-V Nanowire Complementary Metal-Oxide Semiconductor Transistors Monolithically Integrated on Si
- 2015
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 15:12, s. 7898-7904
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Tidskriftsartikel (refereegranskat)abstract
- III-V semiconductors have attractive transport properties suitable for low-power, high-speed complementary metal oxide-semiconductor (CMOS) implementation, but major challenges related to cointegration of III-V n- and p-type metal-oxide-semiconductor field-effect transistors (MOSFETs) on low-cost Si substrates have so far hindered their use for large scale logic circuits. By using a novel approach to grow both InAs and InAs/GaSb vertical nanowires of equal length simultaneously in one single growth step, we here demonstrate n- and p-type III-V MOSFETs monolithically integrated on a Si substrate with high I-on/I-off ratios using a dual channel, single gate-stack design processed simultaneously for both types of transistors. In addition, we demonstrate fundamental CMOS logic gates, such as inverters and NAND gates, which illustrate the viability of our approach for large scale III-V MOSFET circuits on Si.
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| 35. |
- Thelander, Claes, et al.
(författare)
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Effects of crystal phase mixing on the electrical properties of InAs nanowires
- 2011
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 11:April 29, 2011, s. 2424-2429
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Tidskriftsartikel (refereegranskat)abstract
- We report a systematic study of the relationship between crystal quality and electrical properties of InAs nanowires grown by MOVPE and MBE, with crystal structure varying from wurtzite to zinc blende. We find that mixtures of these phases can exhibit up to 2 orders of magnitude higher resistivity than single-phase nanowires, with a temperature-activated transport mechanism. However, it is also found that defects in the form of stacking faults and twin planes do not significantly affect the resistivity. These findings are important for nanowire-based devices, where uncontrolled formation of particular polytype mixtures may lead to unacceptable device variability.
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