| 1. |
- Aad, G., et al.
(author)
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- 2012
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In: Journal of High Energy Physics. - 1029-8479 .- 1126-6708. ; :12
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Journal article (peer-reviewed)
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| 2. |
- Storasta, Liutauras
(author)
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Electrically active defects in 4H silicon carbide
- 2003
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Doctoral thesis (other academic/artistic)abstract
- Development of future technology needs to widen the application areas of semiconductor devices. The increased requirements are beyond the limits of the most common semiconductors today like silicon or gallium arsenide. Use of new materials could resolve many performance issues and also offer increased reliability and reduced cost of the devices. Silicon carbide (SiC) is a wide bandgap semiconductor with properties suitable for high-power, high-temperature and high frequency applications. However, many material related issues have to be solved before SiC could compete in the semiconductor market. Understanding and controlling intrinsic defects and residual impurities is one of the remaining issues limiting progress and applications of this material. Intrinsic defects is a very important issue for all semiconducting materials, since they are unintentionally introduced during different device processing steps or are present directly after the growth, where the amount and nature of the defects is a very sensitive function of the growth parameters. These defects can act as effective trapping and recombination centers and therefore have negative influence on the carrier lifetime. Detailed knowledge about the defect dynamics is needed to be able to control and remove them. The concentration of the intrinsic defects is usually very low in SiC material grown in horizontal hot-wall CVD reactor due to the low growth rate and temperature. Therefore great attention must be paid to reduction of residual impurities, since even a small amount can degrade the electronic properties of the material.This thesis contributes to the increased understanding of some major intrinsic defects and residual boron acceptor in 4H-SiC. It is divided into introduction and seven papers. In paper I, an energy-level scheme in the bandgap for the D1 defect is established. Using Minority Carrier Transient Spectroscopy (MCTS) we show that the D1 defect luminescence is correlated to a hole trap at about 0.35 eV above the valence band, proving that the D1 defect is a pseudodonor.In paper II, studies of intrinsic and impurity related defects in SiC epilayers grown using chemical vapor deposition (CVD) with high growth rate in a vertical hot-wall reactor are presented. Using capacitance transient techniques, the concentration of electrically active defects as a function of growth parameters are investigated.Defects, created by low energy electron irradiation in the range of 80 300 keV are investigated in papers III and IV. We report face-dependent introduction rates of point defects in 4H-SiC in paper III. Clear difference for the defect introduction rates is obtained for irradiations performed from silicon and carbon faces. Energy dependence of the ratio of introduction rates from different faces has been investigated. In paper IV, irradiation energy dependence of the defect introduction rates and annealing dynamics are presented. Defects, caused by carbon displacements are identified, and their possible microstructure is discussed.Recombination enhanced defect annealing is reported in paper V. The signal from the HS2 trap, which usually needs 900°C to anneal out, disappears after introducing nonequilibrium density of minority carriers and indicates it being an effective recombination center. Other defects, labeled as EHi and EH3, also anneal out by recombination enhanced reaction, but at a lower rate.One of the most common trace impurities in SiC is boron. Electrical properties of residual boron acceptor in high quality epitaxial layers have been examined by MCTS in paper VI. Comparison with the optical decay measurements shows that boron is related to the observed lateral variations of the minority carrier lifetime in low doped 4H-SiC epilayers. Boron related photoluminescence and capacitance transient spectroscopy peaks are investigated around SIMS craters in paper VII. Enhancement of boron and hydrogen related PL is observed in the vicinity of the crater, whereas the concentration of electrically active boron as measured by MCTS was found to decrease considerably. Possible models of boron luminescence center are discussed.
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| 3. |
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| 4. |
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| 5. |
- Coube, Olivier, et al.
(author)
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Case studies : discussion and guidelines
- 2007
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In: Modelling of Powder Die Compaction. - London : Encyclopedia of Global Archaeology/Springer Verlag. - 9781846280986 - 9781846280993 ; , s. 197-222
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Book chapter (other academic/artistic)
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| 6. |
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| 7. |
- Agius, Stephanie C, et al.
(author)
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The internal rotenone-insensitive NADPH dehydrogenase contributes to malate oxidation by potato tuber and pea leaf mitochondria
- 1998
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In: Physiologia Plantarum. - : Wiley. - 0031-9317. ; 104:3, s. 329-336
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Journal article (peer-reviewed)abstract
- Inside-out submitochondrial particles from both potato (Solanum tuberosum L. cv. Bintje) tubers and pea (Pisum sativum L. cv. Oregon) leaves possess three distinct dehydrogenase activities: Complex I catalyzes the rotenone-sensitive oxidation of deamino-NADH, NDin(NADPH) catalyzes the rotenone-insensitive and Ca2+-dependent oxidation of NADPH and NDin(NADH) catalyzes the rotenone-insensitive and Ca2+-independent oxidation of NADH. Diphenylene iodonium (DPI) inhibits complex I, NDin(NADPH) and NDin (NADH) activity with a Ki of 3.7, 0.17 and 63 µM, respectively, and the 400-fold difference in Ki between the two NDin made possible the use of DPI inhibition to estimate NDin (NADPH) contribution to malate oxidation by intact mitochondria. The oxidation of malate in the presence of rotenone by intact mitochondria from both species was inhibited by 5 µM DPI. The maximum decrease in rate was 10–20 nmol O2 mg-1 min-1. The reduction level of NAD(P) was manipulated by measuring malate oxidation in state 3 at pH 7.2 and 6.8 and in the presence and absence of an oxaloacetate-removing system. The inhibition by DPI was largest under conditions of high NAD(P) reduction. Control experiments showed that 125 µM DPI had no effect on the activities of malate dehydrogenase (with NADH or NADPH) or malic enzyme (with NAD+ or NADP+) in a matrix extract from either species. Malate dehydrogenase was unable to use NADP+ in the forward reaction. DPI at 125 µM did not have any effect on succinate oxidation by intact mitochondria of either species. We conclude that the inhibition caused by DPI in the presence of rotenone in plant mitochondria oxidizing malate is due to inhibition of NDin(NADPH) oxidizing NADPH. Thus, NADP turnover contributes to malate oxidation by plant mitochondria.
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| 8. |
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| 9. |
- Berndt, Kurt D, et al.
(author)
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Conformational sampling by NMR solution structures calculated with the program DIANA evaluated by comparison with long-time molecular dynamics calculations in explicit water
- 1996
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In: Proteins. - 0887-3585 .- 1097-0134. ; 24, s. 304-313
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Journal article (peer-reviewed)abstract
- The NMR solution structure of bovine pancreatic trypsin inhibitor (BPTI) obtained by distance geometry calculations with the program DIANA is compared with groups of conformers generated by molecular dynamics (MD) simulations in explicit water at ambient temperature and pressure. The MD simulations started from a single conformer and were free or restrained either by the experimental NOE distance restraints or by time-averaged restraints; the groups of conformers were collected either in 10 ps intervals during 200 ps periods of simulation, or in 50 ps intervals during a 1 ns period of simulation. Overall, these comparisons show that the standard protein structure determination protocol with the program DIANA provides a picture of the protein structure that is in agreement with MD simulations using "realistic" potential functions over a nanosecond timescale. For well-constrained molecular regions there is a trend in the free MD simulation of duration 1 ns that the sampling of the conformation space is slightly increased relative to the DIANA calculations. In contrast, for surface-exposed side-chains that are less extensively constrained by the NMR data, the DIANA conformers tend to sample larger regions of conformational space than conformers selected from any of the MD trajectories. Additional insights into the behavior of surface side-chains come from comparison of the MD runs of 200 ps or 1 ns duration. In this time range the sampling of conformation space by the protein surface depends strongly on the length of the simulation, which indicates that significant side-chain transitions occur on the nanosecond timescale and that much longer simulations will be needed to obtain statistically significant data on side-chain dynamics.
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| 10. |
- Chen, Zihan, et al.
(author)
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Design of Compact Passive Tag Antenna for Practical RFID Applications
- 2014
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In: PIERS 2014 GUANGZHOU. - : ELECTROMAGNETICS ACAD. - 9781934142288 ; , s. 680-685
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Conference paper (peer-reviewed)abstract
- The communication quality between an RFID tag and a reader in a RFID network, especially the parameters of the passive tag antenna such as reading range, directivity and return loss, is affected by several factors from the environment. For practical RFID application, since the environment is complex and volatile, these factors include metallic surface of products, absorptions and impacts from neighbor tag antennas like scattering and mutual coupling. In this paper, it consists of the analysis of impacts caused by these factors and the design of passive tag antennas with resonant frequency 915 MHz able to be used in practical RFID applications against those impacts. Comparing with former ones, the proposed antenna reduces the size of the tag antenna to approximately commercial standard (18 mm x 48 mm x 3 mm) by using certain structures applied in the unit cell of metamaterial or HIS, while the properties including directivity, return loss and input impedance are still appropriate for RFID applications. Simulation results from HFSS indicates that at 915 MHz, the return loss can be about 21 dB, as most of the power can be radiated into the space towards the receiver. Meanwhile, the input impedance Z(0) = 9.4738 + j143.9189 Omega, perfectly matching the impedance of the RFID chip placed on the top surface of the antenna. The above improved parameters play an important role in prolonging the reading range.
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