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| 2. |
- Bertilsson, Kent, et al.
(author)
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Monte Carlo simulation of vertical MESFETs in 2H, 4H and 6H-SiC
- 2001
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In: Diamond and related materials. - 0925-9635 .- 1879-0062. ; 10:3-7, s. 1283-1286
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Journal article (peer-reviewed)abstract
- The 4H-SiC static induction transistor (SIT) is a very competitive device for high frequency and high power applications (3-6 GHz range). The large breakdown voltage and the high thermal conductivity of 4H-SiC allow transistors with extremely high current density at high voltages. The SIT transistor shows better output power capabilities but the unity current-gain frequency is lower compared to a MESFET device. In this work we show, using a very accurate numerical model, that a compromise between the features given by the SIT structure and the ordinary MESFET structure can be obtained using the vertical MESFET structure. The device dimension has been selected very aggressively to demonstrate the performance of an optimized technology. We also present results from drift-diffusion simulations of devices, using transport parameters obtained from the Monte Carlo simulation. The simulations indicate that 2H-SiC is superior to both 4H and 6H-SiC for vertical devices. For lateral devices, 2H-SiC is slightly faster compared to an identical 4H-SiC device
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| 3. |
- Bertilsson, Kent, et al.
(author)
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The Effect of Different Transport Models in Simulation of High Frequency 4H-SiC and 6H-SiC Vertical MESFETs
- 2001
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In: Solid-State Electronics. - 0038-1101 .- 1879-2405. ; 45:5, s. 645-653
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Journal article (peer-reviewed)abstract
- A full band Monte Carlo (MC) study of the high frequency performance of a 4H-SiC Short channel vertical MESFET is presented. The MC model used is based on data from a full potential band structure calculation using the local density approximation to the density functional theory. The MC results have been compared with simulations using state of the art drift-diffusion and hydrodynamic transport models. Transport parameters such as mobility, saturation velocity and energy relaxation time are extracted from MC simulations
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| 4. |
- Ciamulski, T, et al.
(author)
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Parallel FDTD Processing on Shared Memory Computers
- 2007
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In: The 23rd annual review of Progress in Applied computational electromagnetics.
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Conference paper (other academic/artistic)abstract
- An ongoing European project on customization of electromagnetic simulation tool is ready to present significantly improved performance of parallel version of a professional FDTD simulator. The first stage of the work is concentrated on solution for computers with the shared memory architecture. The relevance and feasibility study of the solution for contemporary computers is shown. Possible ways to reach further performance improvements as well as solutions for distributed memory machines are discussed.
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| 5. |
- Dubaric, Ervin, et al.
(author)
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Monte Carlo simulations of the imaging properties of scintillator coated X-ray pixel detectors
- 2000
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In: IEEE Nuclear Science Symposium and Medical Imaging Conference. - : IEEE conference proceedings. - 0780365038 ; , s. 6/282-6/285
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Conference paper (peer-reviewed)abstract
- The imaging properties of X-ray pixel detectors depend on the quantum efficiency for X-rays, the generated signal for each X-ray photon and the distribution of the generated signal between different pixels. In a scintillator coated device the signal is generated both by X-ray photons captured in the scintillator and by X-ray photons captured directly in the semiconductor. Hence, the signal-to-noise ratio (SNR) in the image is then a function of the number of photons captured in each of these processes, and the yield of each process, in terms of electron-hole pairs (EHPs) produced in the semiconductor. The full process from the absorption of the X-ray photon to the final signal read out from the detector has been simulated with a combination of the Monte Carlo program MCNP and the commercial carrier transport simulation tool MEDICI. An in house program calculating the light transport between the scintillator and the semiconductor serves as a link
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| 6. |
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| 7. |
- Engholm, Magnus, et al.
(author)
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A bio-compatible fiber optic pH sensor based on a thin core interferometric technique
- 2019
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In: Photonics. - : MDPI AG. - 2304-6732. ; 6:1
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Journal article (peer-reviewed)abstract
- There is an increasing demand for compact, reliable and versatile sensor concepts for pH-level monitoring within several industrial, chemical as well as bio-medical applications. Many pH sensors concepts have been proposed, however, there is still a need for improved sensor solutions with respect to reliability, durability and miniaturization but also for multiparameter sensing. Here we present a conceptual verification, which includes theoretical simulations as well as experimental evaluation of a fiber optic pH-sensor based on a bio-compatible pH sensitive material not previously used in this context. The fiber optic sensor is based on a Mach-Zehnder interferometric technique, where the pH sensitive material is coated on a short, typically 20-25 mm thin core fiber spliced between two standard single mode fibers. The working principle of the sensor is simulated by using COMSOL Multiphysics. The simulations are used as a guideline for the construction of the sensors that have been experimentally evaluated in different liquids with pH ranging from 1.95 to 11.89. The results are promising, showing the potential for the development of bio-compatible fiber optic pH sensor with short response time, high sensitivity and broad measurement range. The developed sensor concept can find future use in many medical- or bio-chemical applications as well as in environmental monitoring of large areas. Challenges encountered during the sensor development due to variation in the design parameters are discussed. © 2019 by the authors.
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| 8. |
- Hammarling, Krister, 1968-, et al.
(author)
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Broad-range hydrogel-based pH sensor with capacitive readout manufactured on a flexible substrate
- 2018
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In: Chemosensors. - Basel, Switzerland : MDPI AG. - 2227-9040. ; 6:3
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Journal article (peer-reviewed)abstract
- Environmental monitoring of land, water and air, is an area receiving greater attention because of human health and safety concerns. Monitoring the type of pollution and concentration levels is vital, so that appropriate contingency plans can be determined. To effectively monitor the environment, there is a need for new sensors and sensor systems that suits these type of measurements. However, the diversity of sensors suitable for low, battery powered- and large area sensor systems are limited. We have manufactured and characterized a flexible pH sensor using laser processing and blade coating techniques that is able to measure pH between 2.94 and 11.80. The sensor consists of an interdigital capacitance with a pH sensitive hydrogel coating. Thin sensors can reach 95% of their final value value within 3 min, and are stable after 4 min. Good repeatability was achieved in regard to cycling of the sensor with different pH and multiple measurements from dry state. We have also studied the relation between an interdigital capacitance penetration depth and hydrogels expansion. We believe that our passive sensor is suitable to be used in low power and large area sensor networks.
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| 9. |
- Hammarling, Krister, 1968-, et al.
(author)
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Synthesis, Curing Behavior and Swell Tests of pH-Responsive Coatings from Acryl-Terminated Oligo(beta-Amino Esters)
- 2018
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In: CHEMOSENSORS. - : MDPI AG. - 2227-9040. ; 6:1
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Journal article (peer-reviewed)abstract
- The ability of acryl-terminated oligo(beta-amino esters) (AOBAE) to be coated on fibers and printed electronics without solvents and to be cross-linked to a pH-responsive coatings, makes AOBAE-based coatings a potential type of pH-sensor coating. However, there are currently no reports of AOBAEs used as a pH-responsive coating material in sensor applications. Here we present an investigation of the synthesis, curing behavior and swell tests of AOBAEs. AOBAEs were synthesized from reacting an excess of asymmetric diacrylates with piperazine without the use of any solvents. They were then cross-linked to an insoluble network by UV-curing. Nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the AOBAEs. NMR was used to clarify the irregular structure of the AOBAE. FTIR was used to monitor the effects of UV-curing dose and air exposure on monomer conversion during curing. An interferometric technique was used to monitor the swelling behavior of the coating in response to pH variations. Swell experiments showed that the AOBAE also responded to pH variations after polymerization. Therefore, AOBAE is an interesting class of material with potential use as a pH responsive coating in optical-and printed electronics pH-sensors applications.
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