| 1. |
- Jönsson, Adam, et al.
(författare)
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Doping Profiles in Ultrathin Vertical VLS-Grown InAs Nanowire MOSFETs with High Performance
- 2021
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Ingår i: ACS Applied Electronic Materials. - : American Chemical Society (ACS). - 2637-6113. ; 3:12, s. 5240-5247
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Tidskriftsartikel (refereegranskat)abstract
- Thin vertical nanowires based on III-V compound semiconductors are viable candidates as channel material in metal oxide semiconductor field effect transistors (MOSFETs) due to attractive carrier transport properties. However, for improved performance in terms of current density as well as contact resistance, adequate characterization techniques for resolving doping distribution within thin vertical nanowires are required. We present a novel method of axially probing the doping profile by systematically changing the gate position, at a constant gate length Lg of 50 nm and a channel diameter of 12 nm, along a vertical nanowire MOSFET and utilizing the variations in threshold voltage VT shift (∼100 mV). The method is further validated using the well-established technique of electron holography to verify the presence of the doping profile. Combined, device and material characterizations allow us to in-depth study the origin of the threshold voltage variability typically present for metal organic chemical vapor deposition (MOCVD)-grown III-V nanowire devices.
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| 2. |
- Jönsson, Adam, et al.
(författare)
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Gate-Length Dependence of Vertical GaSb Nanowire p-MOSFETs on Si
- 2020
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Ingår i: IEEE Transactions on Electron Devices. - 0018-9383. ; 67:10, s. 4118-4122
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Tidskriftsartikel (refereegranskat)abstract
- The effect of gate-length variation on key transistor metrics for vertical nanowire p-type GaSb metal-oxide-semiconductor field-effect transistors (MOSFETs) are demonstrated using a gate-last process. The new fabrication method enables short gate-lengths (Lg = 40 nm) and allows for selective digital etching of the channel region. Extraction of material properties as well as contact resistance are obtained by systematically varying the gate-length. The fabricated transistors show excellent modulation properties with a maximum Ion/Ioff = 700 (VGS = -0.5,,V) as well as peak transconductance of 50 μS/μm with a linear subthreshold swing of 224 mV/dec.
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| 3. |
- Kilpi, Olli Pekka, et al.
(författare)
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High-Performance Vertical III-V Nanowire MOSFETs on Si with gm> 3 mS/μm
- 2020
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Ingår i: IEEE Electron Device Letters. - 0741-3106. ; 41:8, s. 1161-1164
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Tidskriftsartikel (refereegranskat)abstract
- Vertical III-V nanowire MOSFETs have demonstrated excellent performance including high transconductance and high Ion. One main bottleneck for the vertical MOSFETs is the large access resistance arising from the contacts and ungated regions. We demonstrate a process to reduce the access resistance by combining a gate-last process with ALD gate-metal deposition. The devices demonstrate fully scalable gm down to Lg = 25 nm. These vertical core/shell InAs/InGaAs MOSFETs demonstrate gm = 3.1 mS/μm and Ron = 190 Ωμm. This is the highest gm demonstrated on Si. Transmission line measurement verifies a low contact resistance with RC = 115 Ωμm, demonstrating that most of the MOSFET access resistance is located in the contact regions.
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| 4. |
- Kilpi, Olli Pekka, et al.
(författare)
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Increased Breakdown Voltage in Vertical Heterostructure III-V Nanowire MOSFETs with a Field Plate
- 2021
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Ingår i: IEEE Electron Device Letters. - 0741-3106. ; 42:11, s. 1596-1598
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Tidskriftsartikel (refereegranskat)abstract
- Vertical III-V heterostructure MOSFETs exhibit outstanding performance at reduced supply voltages. In this paper, we report on a novel process of extending high-speed device operation towards higher voltages. The device vertical geometry allows for engineering a field plate by covering the nanowire drain area with a 10-nm-thick SiO2 film. The film acts as a field moderator in the device drain region. Reference devices without a field plate exhibit a transconductance of 2.5 mS/μm, while devices with a 120-nm-long field plate show 1.5 mS/μm but a three times increase in breakdown voltage. Measurements show that the field-screening effect attributes to reduced band-to-band tunneling and impact ionization, thereby reducing the parasitic bipolar effect in the MOSFET channel as well. The devices show promise in applications in circuits and systems requiring large power-handling.
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| 5. |
- Kilpi, Olli-Pekka, et al.
(författare)
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Vertical nanowire III–V MOSFETs with improved high-frequency gain
- 2020
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 56:13, s. 669-671
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Tidskriftsartikel (refereegranskat)abstract
- High-frequency performance of vertical InAs/InGaAs heterostructure nanowire MOSFETs on Si is demonstrated for the first time for a gate-last configuration. The device architecture allows highly asymmetric capacitances, which increases the power gain. A device with Lg = 120 nm demonstrates fT = 120 GHz, fmax = 130 GHz and maximum stable gain (MSG) = 14.4 dB at 20 GHz. These metrics demonstrate the state-of-the-art performance of vertical nanowire MOSFETs.
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| 6. |
- Krishnaraja, Abinaya, et al.
(författare)
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Tuning of Source Material for InAs/InGaAsSb/GaSb Application-Specific Vertical Nanowire Tunnel FETs
- 2020
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Ingår i: ACS Applied Electronic Materials. - : American Chemical Society (ACS). - 2637-6113. ; 2:9, s. 2882-2887
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Tidskriftsartikel (refereegranskat)abstract
- Tunnel field-effect transistors (TFETs) are promising candidates that have demonstrated potential for and beyond the 3 nm technology node. One major challenge for the TFETs is to optimize the heterojunction for high drive currents while achieving steep switching. Thus far, such optimization has mainly been addressed theoretically. Here, we experimentally investigate the influence of the source segment composition on the performance for vertical nanowire InAs/InGaAsSb/GaSb TFETs. Compositional analysis using transmission electron microscopy is combined with simulations to interpret the results from electrical characterization data. The results show that subthreshold swing (S) and transconductance (gm) decrease with increasing arsenic composition until the strain due to lattice mismatch increases them both. The role of indium concentration at the junction is also examined. This systematic optimization has rendered sub-40 mV/dec operating TFETs with a record transconductance efficiency gm/ID = 100 V-1, and it shows that different source materials are preferred for various applications.
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| 7. |
- Larsson, Erik, 1983, et al.
(författare)
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The Influence of KCl and HCl on the High-Temperature Oxidation of a Fe-2.25Cr-1Mo Steel at 400 °C
- 2020
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 93:1-2, s. 29-52
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Tidskriftsartikel (refereegranskat)abstract
- The influence of alkali- and chlorine-containing compounds on the corrosion of superheater alloys has been studied extensively. The current paper instead investigates the corrosive effects of KCl and HCl under conditions relevant to waterwall conditions. A low-alloy (Fe-2.25Cr-1Mo) steel was exposed to KCl(s), 500 vppm HCl(g) and (KCl + HCl) in the presence of 5%O2 and 20% H2O at 400 °C. The results indicate that alloy chlorination by KCl occurs by an electrochemical process, involving cathodic formation of chemisorbed KOH on the scale surface and anodic formation of solid FeCl2 at the bottom of the scale. The process is accompanied by extensive cracking and delamination of the iron oxide scale, resulting in a complex, convoluted scale morphology. Adding 500 vppm HCl to the experimental environment (KCl + HCl) initially greatly accelerated the formation of FeCl2 at the scale/alloy interface. The accelerated alloy chlorination is attributed to HCl reacting with KOH at the scale surface, causing the cathodic process to be depolarized. A rapid slowing down of the rate of chlorination and corrosion in KCl + HCl environment was observed which was attributed to the electronically insulating nature of the FeCl2 layer which forms at the bottom of the scale, disconnecting the anodic and cathodic regions.
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| 8. |
- Näslund, Erik, et al.
(författare)
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Association of Metabolic Surgery With Major Adverse Cardiovascular Outcomes in Patients With Previous Myocardial Infarction and Severe Obesity A Nationwide Cohort Study
- 2021
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Ingår i: Circulation. - : Lippincott Williams & Wilkins. - 0009-7322 .- 1524-4539. ; 143:15, s. 1458-1467
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Tidskriftsartikel (refereegranskat)abstract
- Background: The number of patients with myocardial infarction and severe obesity is increasing and there is a lack of evidence how these patients should be treated. The aim of this study was to investigate the association between metabolic surgery (Roux-en-Y gastric bypass and sleeve gastrectomy) and major adverse cardiovascular events in patients with previous myocardial infarction (MI) and severe obesity.Methods: Of 566 patients with previous MI registered in the SWEDEHEART registry (Swedish Web-System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies) undergoing metabolic surgery and registered in the nationwide Scandinavian Obesity Surgery Registry, 509 patients (Roux-en-Y gastric bypass n=465; sleeve gastrectomy n=44) could be matched 1:1 to a control with MI from SWEDEHEART, but no subsequent metabolic surgery regarding sex, age (+/- 3 years), year of MI (+/- 3 years), and body mass index (+/- 3). The 2 groups were well matched, except for a lower proportion of reduced ejection fraction after MI (7% versus 12%), previous heart failure (10% versus 19%), atrial fibrillation (6% versus 10%), and chronic obstructive pulmonary disease (4% versus 7%) in patients undergoing metabolic surgery.Results: The median (interquartile range) follow-up time was 4.6 (2.7-7.1) years. The 8-year cumulative probability of major adverse cardiovascular events was lower in patients undergoing metabolic surgery (18.7% [95% CI, 15.9-21.5%] versus 36.2% [33.2-39.3%], adjusted hazard ratio, 0.44 [95% CI, 0.32-0.61]). Patients undergoing metabolic surgery had also a lower risk of death (adjusted HR, 0.45 [95% CI, 0.29-0.70]; MI, 0.24 [0.14-0.41]) and new onset heart failure, but there were no significant differences regarding stroke (0.91 [0.38-2.20]) and new onset atrial fibrillation (0.56 [0.31-1.01]).Conclusions: In severely obese patients with previous MI, metabolic surgery is associated with a low risk for serious complications, lower risk of major adverse cardiovascular events, death, new MI, and new onset heart failure. These findings need to be confirmed in a randomized, controlled trial.
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| 9. |
- Alirani, Gertrud, 1976-
(författare)
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Miljöintegrering i praktisk tillämpning : En policystudie av två lokala stadsutvecklingsprocesser
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dealing with environmental problems has become one of the most challenging political issues of our time. Since the Brundtland report in 1987, environmental policy integration (EPI) that is, the mainstreaming of environmental issues in all policy sectors has emerged as a viable policy solution. This has meant that responsibility for implementing environmental policy rests to a large extent on local authorities where environmental problems with both local and global consequences are expected to be handled. However, there is still a disagreement on what EPI means in day-to-day decision making. With a theoretical framework drawing from theory on policy change, policy entrepreneurship and the neoinstitutional “logic of appropriateness” the aim of this dissertation is to analyze how the integration of environmental considerations manifests itself in local policy processes, highlighting what factors foster or hinder EPI. To reach this aim, I have followed two urban development processes in Kristianstad. This research offers insights on how EPI varies through the policy process and how focus is placed mainly on certain environmental issues and chiefly defined as of local importance. My study suggest that arenas for coordination are critical to overcoming the perceived “gap” between EPI on a strategic level and its implementation. This can help to clarify responsibility allocation among bureaucrats and their leeway for interpretation when new issues comes up continuously during the processes and affect the conditions for EPI. Furthermore, the dissertation gives insights on how acting “entrepreneurially” can enable an environmental issue to be included and given priority. This can also be a barrier if the ones acting entrepreneurially are not part of the entire process because the issue might receive less attention. In addition, if too much attention is given to one issue it might overshadow other environmental issues. Conversely, acting according to “the logic of appropriateness” can enable EPI by enhancing a more all-encompassing perspective on environmental considerations and also function as a cautious approach to radical change by preventing measures taken in absence of democratic legitimacy. By using the two theoretical perspectives, “entrepreneurial” and “appropriate” agency, this dissertation offers important insights into how different ways of acting interact and affect EPI and its outcome.
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| 10. |
- Amombo Noa, Francoise Mystere, 1988, et al.
(författare)
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Metal-Organic Frameworks with Hexakis(4-carboxyphenyl)benzene: Extensions to Reticular Chemistry and Introducing Foldable Nets
- 2020
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 142:20, s. 9471-9481
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Tidskriftsartikel (refereegranskat)abstract
- Nine metal-organic frameworks have been prepared with the hexagon-shaped linker 1,2,3,4,5,6-hexakis(4-carboxyphenyl)-benzene (H(6)cpb) by solvothermal reactions in dimethylformamide (dmf) or dimethylacetamide (dmac) with acetic acid or formic acid as modulators: [Bi-2(cpb)(acetato)(2)(dmf)(2)]center dot 2dmf CTH-6 forms a rtl-net; 2(H2NMe2)[Cu-2(cpb)] CTH-7 forms a kgd-net; [Fe-4(cpb)-(acetato)(2)(dmf)(4)] CTH-8 and [Co-4(cpb)(acetato)(2)(dmf)(4)] CTH-9 are isostructural and form yav-nets; 2(HNEt3)[Fe-2(cpb)] CTH-10 and the two polymorphs of 2(H2NMe2)[Zn-2(cpb)]center dot 1.5dmac, Zn-MOF-888 and CTH-11, show kgd-nets; [Cu-2(cpb)-(acetato)(2)(dmf)(2)]center dot 2dmf, CTH-12, forms a mixed coordination and hydrogen-bonded sql-net; and 2(H2NMe2)[Zn-2(cpb)] CTH-13, a similarly mixed yav-net. Surface area values (Brunauer-Emmett-Teller, BET) range from 34 m(2) g(-1) for CTH-12 to 303 m(2) g(-1) for CTH-9 for samples activated at 120 degrees C in dynamic vacuum. All compounds show normal (10-fold higher) molar CO2 versus N-2 uptake at 298 K, except the 19-fold CO2 uptake for CTH-12 containing Cu(II) dinuclear paddle-wheels. We also show how perfect hexagons and triangles can combine to a new 3D topology laf, a model of which gave us the idea of foldable network topologies, as the laf-net can fold into a 2D form while retaining the local geometry around each vertex. Other foldable nets identified are cds, cds-a, ths, sqc163, clh, jem, and tfc covering the basic polygons and their combinations. The impact of this concept on "breathing" MOFs is discussed. I-2 sorption, both from gas phase and from MeOH solution, into CTH-7 were studied by time of flight secondary ion mass spectrometry (ToF-SIMS) on dried crystals. I-2 was shown to have penetrated the crystals, as layers were consecutively peeled off by the ion beam. We suggest ToF-SIMS to be a method for studying sorption depth profiles of MOFs.
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