ORCID Profile
0000-0003-2670-7381
Current Organisations
Monash University
,
University of Cambridge
,
NHS England
,
Cambridge University Hospitals
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Publisher: National Institute for Health and Care Research
Date: 12-2022
DOI: 10.3310/LFPE3627
Abstract: Do not attempt cardiopulmonary resuscitation decisions have been widely criticised. The Recommended Summary Plan for Emergency Care and Treatment (ReSPECT) process was developed to facilitate shared decisions between patients and clinicians in relation to emergency treatments, including cardiopulmonary resuscitation. To explore how, when and why ReSPECT plans are made and what effects the plans have on patient outcomes. A mixed-methods evaluation, comprising (1) a qualitative study of ReSPECT decision-making processes, (2) an interrupted time series examining process and survival outcomes following in-hospital cardiac arrest and (3) a retrospective observational study examining factors associated with ReSPECT recommendations and patient outcomes. NHS acute hospitals and primary care and community services in England (2017–2020). Hospital doctors, general practitioners, nurses, patients and families. The following sources were used: (1) observations of ReSPECT conversations at six hospitals and conversations with clinicians, patient, families and general practitioners, (2) survey and freedom of information data from hospitals participating in the National Cardiac Arrest Audit and (3) a review of inpatient medical records, ReSPECT forms and NHS Safety Thermometer data. By December 2019, the ReSPECT process was being used in 40 of 186 (22%) acute hospitals. In total, 792 of 3439 (23%) inpatients, usually those identified at risk of deterioration, had a ReSPECT form. Involvement of the patient and/or family was recorded on 513 of 706 (73%) ReSPECT forms reviewed. Clinicians said that lack of time prevented more conversations. Observed conversations focused on resuscitation, but also included other treatments and the patient’s values and preferences. Conversation types included open-ended conversations, with clinicians actively eliciting the patients’ wishes and preferences, a persuasive approach, swaying the conversation towards a decision aligned with medical opinion, and simply informing the patient/relative about a medical decision that had already been made. The frequency of harms reported on the NHS Safety Thermometer was similar among patients with or without a ReSPECT form. Hospital doctors and general practitioners gave different views on the purpose of the ReSPECT process and the type of recommendations they would record. The research was undertaken within the first 2 years following the implementation of ReSPECT. Local policies meant that doctors led these conversations. Most patients were seriously ill, which limited opportunities for interviews. Incomplete adoption of the ReSPECT process and problems associated with the NHS Safety Thermometer tool affected the evaluation on clinical outcomes. Patients and families were involved in most ReSPECT conversations. Conversations focused on resuscitation, but also included other emergency treatments. Respect for patient autonomy and duty to protect from harm informed clinicians’ approach to varying degrees, depending on the clinical situation and their views of ReSPECT as a shared decision-making process. The complexity of these conversations and the clinical, emotional and organisational barriers observed suggest that a nuanced and multifaceted approach will be necessary to support good ReSPECT processes. Further research is needed to understand the advantages and disadvantages to the adoption of a national emergency care and treatment plan system, the most effective national and local implementation approaches, and whether or not shared decision-making approaches in the context of emergency care and treatment plans could further enhance patient and family engagement. This study is registered as ISRCTN11112933. This project was funded by the National Institute for Health and Care Research (NIHR) Health and Social Care Delivery Research programme and will be published in full in Health and Social Care Delivery Research Vol. 10, No. 40. See the NIHR Journals Library website for further project information.
Publisher: Elsevier BV
Date: 08-2022
Publisher: Elsevier BV
Date: 05-2021
Publisher: AIP Publishing
Date: 11-2018
DOI: 10.1063/1.5053621
Abstract: The higher critical electric field of β-gallium oxide (Ga2O3) gives promise to the development of next generation power electronic devices with improved size, weight, power, and efficiency over current state-of-the-art wide bandgap devices based on 4H-silicon carbide (SiC) and gallium nitride (GaN). However, it is expected that Ga2O3 devices will encounter serious thermal issues due to the poor thermal conductivity of the material. In this work, self-heating in Ga2O3 Schottky barrier diodes under different regimes of the diode operation was investigated using erse optical thermography techniques including thermoreflectance thermal imaging, micro-Raman thermography, and infrared thermal microscopy. 3D coupled electro-thermal modeling was used to validate experimental results and to understand the mechanism of heat generation for the diode structures. Measured top-side and cross-sectional temperature fields suggest that device and circuit engineers should account for the concentrated heat generation that occurs near the anode/Ga2O3 interface and/or the lightly doped drift layer under both forward and high voltage reverse bias conditions. Results of this study suggest that electro-thermal co-design techniques and top-side thermal management solutions are necessary to exploit the full potential of the Ga2O3 material system.
Publisher: AIP Publishing
Date: 19-05-2021
DOI: 10.1063/5.0041266
Abstract: Chemical and structural features of (2¯01) β-Ga2O3 interfaces with SiO2 and Al2O3 gate oxides formed by low pressure chemical vapor deposition (SiO2) and atomic layer deposition (Al2O3) were investigated by analytical electron microscopy in order to identify features that may explain electrical properties recently observed in the same s les. Cross-sectional transmission electron microscopy at the Ga2O3/SiO2 interface revealed nanoscale interfacial roughness increasing with higher post-deposition annealing temperature. At the Ga2O3/Al2O3 interface, a few nanometers of epitaxial Al2O3 was seen prior to the complete crystallization of the gate oxide film after tens of seconds exposure to the electron beam. Multivariate statistical analysis of electron energy loss spectroscopy signals showed evidence of interdiffusion between Al and Ga into the substrate and gate oxide, respectively, which was more pronounced following post-deposition annealing at elevated temperatures. The interdiffusion provides an explanation for the increased interface trap density previously reported in these devices. These results identify issues with the processing methods of the gate oxide affecting the performance and reliability of β-Ga2O3 metal–oxide–semiconductor devices.
Publisher: IOP Publishing
Date: 02-05-2018
Publisher: AIP Publishing
Date: 07-05-2018
DOI: 10.1063/1.5019270
Abstract: The electrical properties of interfaces and the impact of post-deposition annealing have been investigated in gate oxides formed by low pressure chemical vapor deposition (LPCVD SiO2) and atomic layer deposition (Al2O3) on (2¯01) oriented n-type β-Ga2O3 single crystals. Capacitance-voltage based methods have been used to extract the interface state densities, including densities of slow ‘border’ traps at the dielectric-Ga2O3 interfaces. It was observed that SiO2-β-Ga2O3 has a higher interface and border trap density than the Al2O3-β-Ga2O3. An increase in shallow interface states was also observed at the Al2O3-β-Ga2O3 interface after post-deposition annealing at higher temperature suggesting the high temperature annealing to be detrimental for Al2O3-Ga2O3 interfaces. Among the different dielectrics studied, LPCVD SiO2 was found to have the lowest dielectric leakage and the highest breakdown field, consistent with a higher conduction band-offset. These results are important for the processing of high performance β-Ga2O3 MOS devices as these factors will critically impact channel transport, threshold voltage stability, and device reliability.
Publisher: Elsevier BV
Date: 08-2023
Publisher: The Electrochemical Society
Date: 15-04-2017
DOI: 10.1149/MA2017-01/27/1290
Abstract: 4H- Silicon carbide is a promising for power electronic devices operated at high voltages, high temperatures, and high frequencies due to its attractive material properties, such as high avalanche electric breakdown field (2.5 MV/cm), high electron mobility (1000 cm 2 /V. s), high thermal conductivity (4.9 Wcm -1 K -1 ) and large bandgap (3.26 eV). While conventional double-implanted MOSFET (D-MOSFET) has been commercially successful, trench MOSFET is a fascinating device design for next-generation 4H-SiC power MOSFETs due to its low specific on resistance (R ON ) [1] and higher current density which can potentially reduce cost. Trench formation in mechanically hard and chemically stable 4H-SiC material requires reactive ion etching (RIE). This RIE step has been reported to introduce surface roughness and deep level defects [2-4] in SiC which may cause degradation of the channel mobility as well as the voltage blocking capability of the trench MOSFETs. These particular issues are critical challenges and need further attention. In this regard, we have studied the electrical properties of planer MOS capacitors fabricated on Si-face ( ) and A- face ( –20 ) 4H-SiC epitaxial layers, with and without RIE, prior to gate oxidation. Capacitance coupled plasma (CCP) RIE process was carried out to etch about 2μm of SiC, using NF 3 as the process gas. Before performing the gate oxidation, a sacrificial thermal oxidation was carried out on the etched s les to consume subsurface damage. The gate oxidation was followed annealing in nitric oxide (NO) for both etched and un-etched s les. Atomic force microscope (AFM) images revealed that almost atomically flat surfaces (RMS roughness= 0.3 nm) were obtained following RIEs as shows in Figure 1. Simultaneous high-low capacitance-voltage ( C - V ) measurements at room temperature was carried out to investigate RIE induced effects on effective charge density at the SiO 2 /4H-SiC interface and the interface trap density ( D it ) near the conduction band-edge of 4H-SiC. In addition, current-voltage ( I-V ) measurements were done at room temperature to investigate RIE induced dielectric breakdown effects. From the room temperature C-V data as shown in the Figure 2, it can be seen that C-V curves for MOS capacitors with or without RIE lie on top each with negligible flat-band voltage ( V FB ) shift which suggests that the effective interfacial charge does not change significantly due to RIE (Table 1). Furthermore, extracted D it profiles (Figure 3) with or without RIE MOS capacitors also shows no difference. In addition, comparable I-V data as shown in the Figure 4 also confirmed minimal effects induced by RIE. These results are inconsistent with previous results [4] where RIE was shown to generate significant amount of interface traps. This is most likely due to a much smoother surface obtained here after RIE as well the post-RIE sacrificial oxidation step which was implemented here. These results suggest that processes such as etching in an H 2 environment at elevated temperatures not be necessary after RIE for trench MOSFET fabrication. In the ongoing work, we are analyzing possible deep level defects in the SiC bulk, introduced by RIE using deep level transient spectroscopy measurements. In this talk, detailed discussion of the methods in the context of trench MOSFETs and analysis of the obtained results will present. [1] B. J. Baliga, Fundamentals of power semiconductor devices 2010 (Springer Science & Business Media) [2] V. Khemka et al.: J. Electron. Mater. 27 (1998) 1128-1135 [3] K. Kawahara et al.: J. Appl. Phys. 108 (2010) 023706 [4] Gang Liu et al.: Appl. Surf. Sci. 324 (2015) 30–34 Figure 1
Publisher: AOA Academic Open Access Ltd.
Date: 09-2013
DOI: 10.18052/WWW.SCIPRESS.COM/ILCPA.4.39
Abstract: For the acusto-optic interactions in liquids, an equation for the diffraction light intensity was obtained in terms of Klein Cook parameter Q. With optimized parameters for Q, incident light wave length of λ = 633 nm, sound wave length of Λ = 0.1 mm, acusto-optic interaction length L=0.1 m, and refractive index of the liquid in the range of 1 to 2, the existence of ideal Raman-Nath and Bragg diffractions were investigated in terms of phase delay and incident angle. The ideal Raman-Nath diffraction slightly deviated when the Klein Cook parameter was increased from 0 to 1 for low phase delay values and for large phase delay, the characteristics of the Bessel function disappeared. Higher value of Klein Cook parameter gave Bragg diffraction and ideal Bragg diffraction was obtained for Q ~100. A slight variation of the incident angle from Bragg angle had a considerable effect on Bragg diffraction pattern. Klein Cook parameter with the change of acoustic wave frequency was investigated for liquids with refractive index in the range1.3-1.7 and their diffraction patterns were compared with practically applicable acusto-optic crystals. For acusto-optic diffractions in liquids, sound velocity plays an important role in Bragg regime with Q increasing with increasing acoustic frequency. As acoustic wave frequency exceeded 10 MHz most of the liquids reached Bragg regime before these crystals.
Publisher: Trans Tech Publications, Ltd.
Date: 06-2018
DOI: 10.4028/WWW.SCIENTIFIC.NET/MSF.924.444
Abstract: In this work, we examined the oxidation growth rates of the (0001) Si-face and (11−20) a-faces of 4H-SiC by carrying out oxidation in the 850°C-950 °C temperature range in a plasma afterglow furnace for application to trench MOSFETs. At 900 °C, this method results in almost equal oxide thickness on the Si-face and a-face which would nominally correspond to trench bottom and sidewalls in trench devices. Our results indicate that after NO annealing, the electronic properties of the plasma oxidized SiO 2 /SiC interface is comparable to control s les with gate oxides formed by dry oxidation at 1150 °C followed by NO annealing. Next, the effect of reactive ion etching (RIE) of 4H-SiC surfaces prior to gate oxidation was investigated using planar 4H-SiC MOS capacitors. Our experiments show that oxidation followed by NO annealing of surfaces with smooth morphology following the RIE step, results in similar interface charge and trap densities as MOS capacitors which did not undergo the RIE etching.
Publisher: Elsevier BV
Date: 11-2021
Publisher: Elsevier BV
Date: 2021
Publisher: IOP Publishing
Date: 27-09-2016
Publisher: Trans Tech Publications, Ltd.
Date: 07-2019
DOI: 10.4028/WWW.SCIENTIFIC.NET/MSF.963.217
Abstract: Charge trapping at 4H-SiC/dielectric interfaces in 4H-SiC MOS capacitors has been investigated using constant capacitance deep level transient spectroscopy (CCDLTS). The experiments were focused on further understanding of the following aspects related to 4H-SiC/SiO 2 interfaces: (i) Origin of near interface oxide traps (NITs), (ii) Effect of interfacial impurity assivation methods and (iii) Characterization of near-interface oxide traps for different SiC wafer orientations. For the (0001) Si-face 4H-SiC/ SiO 2 interface, two types of NITs are typically detected by CCDLTS, named ‘O1’ and ‘O2’ traps with emission activation energies of about 0.15±0.05 eV and 0.39±0.1 eV respectively below the 4H-SiC conduction band. Based on comparison with previous ab initio calculations, the physical identities of these defects have been suggested to be carbon dimers substituted for O dimers (‘O1’) and interstitial silicon atoms (‘O2’) in the near interfacial SiO 2 respectively. In this work, it is shown for the first time that such traps are not observed for 4H-SiC/ Al 2 O 3 interfaces, proving that these traps are inherent to the near-interfacial SiO 2 . In addition, the summary of CCDLTS results for Si-face with different interface trap passivation methods are included in this study. Finally, a comparison is presented for NO annealed (0001) Si-face, (11-20) a-face and (000-1) C-face interfaces that highlight the difference of CCDLTS signatures for the different crystal faces.
Publisher: The Electrochemical Society
Date: 13-04-2018
DOI: 10.1149/MA2018-01/23/1441
Abstract: 4H-Silicon carbide is one of the enabling materials for modern high voltage and high temperature power electronic devices due to its attractive material properties. A significant drawback to SiC MOSFET performance is the low channel conductance due to trapping of carriers by the high-density of near-interface traps (NITs) at the SiO 2 /4H-SiC interface. These states are spatially located within ~1 nm from the interface and energetically positioned near the conduction band edge of 4H-SiC. Constant capacitance deep level transient spectroscopy (CCDLTS) technique is appropriate for analysis of such defects as it can differentiate between trap types and measure trapped charge emission rates. In this study, we examined SiO 2 -4HSiC interfaces formed on the polar (0001) Si- face (100% Si) and non-polar (11-20) a-face (50% Si, 50% C) oriented 4H-SiC wafers using CCDLTS. For the NO annealed Si-face interface, there are two main types of NITs detected by CCDLTS, labeled “O1” and “O2” traps by Basile et al. [1]. The physical identities of these defects have been suggested to be carbon dimers substituted for O dimers (C O =C O ) and interstitial Silicon atoms in the near interfacial SiO 2 [2]. In this work, we observed both the O1 and O2 traps in the Si-face with activation energies of about 0.15±0.01 eV and 0.35±0.01 eV respectively, which are consistent with previous results[3]. The original result obtained in this study was that for the a-face two new NITs (labeled A1 & A2) positioned very close to the O1 peak were observed but the O2 peak was absent. For this study, 4H-SiC MOS capacitors were fabricated on Si-face and a-face oriented wafers. The s les underwent dry oxidation followed by nitridation with NO annealing at 1175°C. After that, circular Al gates were evaporated as gate contact. The oxide thickness was ~62 nm and ~54 nm for Si-face and a-face respectively. CCDLTS was measured on capacitors keeping a constant capacitance in deep depletion in a temperature range of 77 K to 298 K changing pulse voltages and emission rates. Using the analysis method detailed in [1], the activation energies of the A1 and A2 peaks were found to be 0.15±0.01 eV and 0.19±0.01 eV respectively, which is in the same range as the O1 trap in the Si-face. The capture cross-sections for all traps detected was in the 10 -16 -10 -14 cm 2 range. Qualitatively, this result is similar to the results reported in [4], which shows that nitrided SiO 2 formed on the (000-1) C-face (100% C terminated) also shows only one peak very similar to the O1 trap observed on the Si-face. This result points to the importance of interface structural differences due to different wafer orientation with respect to near-interface oxide traps. Acknowledgement: This work was supported by the II-VI foundation References: [1] A. F. Basile, J. Rozen, J. R. Williams, L. C. Feldman, and P. M. Mooney, J. Appl. Phys., 109, 064514, 2011. [2] P. Deák, J. M. Knaup, T. Hornos, C. Thill, A. Gali, and T. Frauenheim,” J. Phys. Appl. Phys., 40, 6242, 2007. [3] P. M. Mooney, Z. Jiang, A. F. Basile, Y. Zheng, and S. Dhar, J. Appl. Phys., 120, 034503, 2016. [4] T. Hatakeyama, M. Sometani, Y. Yonezawa, K. Fukuda, H. Okumura, and T. Kimoto, Jpn. J. Appl. Phys., 54, 111301, 2015.
Publisher: The Electrochemical Society
Date: 2022
Abstract: Identification of biomarkers in clinical applications for diagnostics at the point-of-care (POC) setting requires the development of industry viable biosensing platform. Herein, we report such development of biosensor architecture for the detection of pharmacogenetic biomarker HLA-B*15:02 gene. The biosensor architecture comprises of an oligonucleotide stem-loop probe modified with a methylene blue redox (MB) reporter, immobilized via a rapid “printing” method on the commercially available disposable screen-printed electrodes (SPE). The square wave voltammetric measurements on the DNA sensor showed a clear peak difference of ∼80 nA with a significant difference in peak height values of the faradaic current generated for the MB redox moiety between the positive control (biotin-modified 19 based oligonucleotides with the sequence mimicking the specific region of the HLA-B*15:02 allele and complementary to the probe sequence) and negative control s les (biotin-modified 19 based oligonucleotides with the sequence unrelated to the probe sequence and the HLA-B*15:02 allele). These initial proof of concept results provide support for the possibility of using this signal-off biosensor architecture in the intended pharmacogenetic biomarker testing.
Publisher: Springer Science and Business Media LLC
Date: 26-07-2021
DOI: 10.1038/S41598-021-94652-0
Abstract: There is currently a high level of demand for rapid COVID-19 tests, that can detect the onset of the disease at point of care settings. We have developed an ultra-portable, self-contained, point-of-care nucleic acid lification test for diagnosis of active COVID-19 infection, based on the principle of loop mediated isothermal lification (LAMP). The LAMP assay is 100% sensitive and specific to detect a minimum of 300 RNA copies/reaction of SARS-CoV-2. All of the required s le transportation, lysing and lification steps are performed in a standalone disposable cartridge, which is controlled by a battery operated, pocket size (6x9x4cm 3 ) unit. The test is easy to operate and does not require skilled personnel. The total time from s le to answer is approximately 35 min a colorimetric readout indicates positive or negative results. This portable diagnostic platform has significant potential for rapid and effective testing in community settings. This will accelerate clinical decision making, in terms of effective triage and timely therapeutic and infection control interventions.
Publisher: Elsevier BV
Date: 2023
Publisher: Cold Spring Harbor Laboratory
Date: 11-05-2023
DOI: 10.1101/2023.05.08.23289442
Abstract: PHOSP-COVID is a national UK multi-centre cohort study of patients who were hospitalised for COVID-19 and subsequently discharged. PHOSP-COVID was established to investigate the medium- and long-term sequelae of severe COVID-19 requiring hospitalisation, understand the underlying mechanisms of these sequelae, evaluate the medium- and long-term effects of COVID-19 treatments, and to serve as a platform to enable future studies, including clinical trials. Data collected covered a wide range of physical measures, biological s les, and Patient Reported Outcome Measures (PROMs). Participants could join the cohort either in Tier 1 only with remote data collection using hospital records, a PROMs app and postal saliva s le for DNA, or in Tier 2 where they were invited to attend two specific research visits for further data collection and biological research s ling. These research visits occurred at five (range 2-7) months and 12 (range 10-14) months post-discharge. Participants could also participate in specific nested studies (Tier 3) at selected sites. All participants were asked to consent to further follow-up for 25 years via linkage to their electronic healthcare records and to be re-contacted for further research. In total, 7935 participants were recruited from 83 UK sites: 5238 to Tier 1 and 2697 to Tier 2, between August 2020 and March 2022. Cohort data are held in a Trusted Research Environment and s les stored in a central biobank. Data and s les can be accessed upon request and subject to approvals.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Asanka Jayawardena.