| 1. |
- Beyer, Franziska, et al.
(författare)
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Annealing behavior of the EB-centers and M-center in low-energy electron irradiated n-type 4H-SiC
- 2011
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Ingår i: Journal of Applied Physics. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 109:10, s. 103703-
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Tidskriftsartikel (refereegranskat)abstract
- After low-energy electron irradiation of epitaxial n-type 4H-SiC with a dose of 5 x 10(16) cm(-2), the bistable M-center, previously reported in high-energy proton implanted 4H-SiC, is detected in the deep level transient spectroscopy (DLTS) spectrum. The annealing behavior of the M-center is confirmed, and an enhanced recombination process is suggested. The annihilation process is coincidental with the evolvement of the bistable EB-centers in the low temperature range of the DLTS spectrum. The annealing energy of the M-center is similar to the generation energy of the EB-centers, thus partial transformation of the M-center to the EB-centers is suggested. The EB-centers completely disappeared after annealing temperatures higher than 700 degrees C without the formation of new defects in the observed DLTS scanning range. The threshold energy for moving Si atom in SiC is higher than the applied irradiation energy, and the annihilation temperatures are relatively low, therefore the M-center, EH1 and EH3, as well as the EB-centers are attributed to defects related to the C atom in SiC, most probably to carbon interstitials and their complexes.
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| 2. |
- Beyer, Franziska, et al.
(författare)
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Bistable defects in low-energy electron irradiated n-type 4H-SiC
- 2010
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Ingår i: PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS. - : John Wiley and Sons, Ltd. - 1862-6254. ; 4:8-9, s. 227-229
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial n-type 4H-SiC layers were irradiated at room temperature by low-energy electrons. During the annihilation process of the irradiation induced defects EH I and EH3, three new bistable centers, labeled EB centers, were detected in the DLTS spectrum. The reconfigurations of the EB centers (I -andgt; II and II -andgt; I) take place at room temperature with a thermal reconfiguration energy of about 0.95 eV. The threshold energy for moving the Si atom from its site in the SiC crystal structure is higher than the applied irradiation energy; therefore, the EB centers are attributed to carbon related complex defects.
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| 3. |
- Beyer, Franziska, et al.
(författare)
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Capacitance transient study of a bistable deep level in e(-)-irradiated n-type 4H-SiC
- 2012
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Ingår i: Journal of Physics D. - : Institute of Physics. - 0022-3727 .- 1361-6463. ; 45:45
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Tidskriftsartikel (refereegranskat)abstract
- Using capacitance transient techniques, a bistable centre, called FB centre here, was observed in electron irradiated 4H-SiC. In configuration A, the deep level known as EH5 (E-a = E-C - 1.07 eV) is detected in the deep level transient spectroscopy spectrum, whereas for configuration B no obvious deep level is observed in the accessible part of the band gap. Isochronal annealing revealed the transition temperatures to be T-A -andgt; B andgt; 730K and for the opposite process T-B -andgt; A approximate to 710 K. The energy needed to conduct the transformations were determined to be E-A(A -andgt; B) = (2.1 +/- 0.1) eV and E-A(B -andgt; A) = (2.3 +/- 0.1) eV, respectively. The pre-factor indicated an atomic jump process for the opposite transition A -andgt; B and a charge carrier-emission dominated process in the case of B -andgt; A. Minority charge carrier injection enhanced the transformation from configuration B to configuration A by lowering the transition barrier by about 1.4 eV. Since the bistable FB centre is already present after low-energy electron irradiation (200 keV), it is likely related to carbon.
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| 4. |
- Beyer, Franziska, et al.
(författare)
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Defects in low-energy electron-irradiated n-type 4H-SiC
- 2010
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Ingår i: Physica Scripta, vol. T141. - : IOP Publishing. ; , s. 014006-
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Konferensbidrag (refereegranskat)abstract
- The bistable M-center, previously observed in high-energy proton-implanted 4H-SiC, was detected in low-energy electron-irradiated 4H-SiC using deep-level transient spectroscopy (DLTS). Irradiation increased the DLTS signals of the intrinsic defects Z(1/2) and EH6/7 and introduced the frequently observed defects EH1 and EH3. After the M-center is annealed out at about 650K without bias and at about 575K with bias applied to the sample during the annealing process, a new bistable defect in the low temperature range of the DLTS spectrum, the EB-center, evolves. Since low-energy irradiation affects mainly the carbon atoms in SiC, the M-center and the newly discovered EB-center are most probably carbon-related intrinsic defects.
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| 5. |
- Ekblom Bak, Elin, 1981-, et al.
(författare)
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Sex- and age-specific associations between cardiorespiratory fitness, CVD morbidity and all-cause mortality in 266.109 adults
- 2019
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Ingår i: Preventive Medicine. - : Elsevier BV. - 0091-7435 .- 1096-0260. ; 127
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Tidskriftsartikel (refereegranskat)abstract
- The aim was to investigate sex- and age-specific associations between cardiorespiratory fitness, all-cause and cause-specific mortality, and cardiovascular disease (CVD) morbidity. 266.109 participants (47% women, 18-74 years) free from CVD, participating in occupational health service screenings in 1995-2015 were included. CRF was assessed as estimated maximal oxygen consumption (estVO(2)max) using a submaximal cycle test. Incident cases of first-time CVD event and death from any cause were ascertained through national registers. There were 4244 CVD events and 2750 cases of all-cause mortality during mean 7.6 years follow-up. Male gender, higher age and lower estVO(2)max were associated with higher all-cause mortality and CVD morbidity incidence rates. Risk reductions with increasing estVO(2)max were present in all age-groups of men and women. No obvious levelling off in risk was identified in the total cohort. However, women and older age-groups showed no further reduction in higher aggregated estVO(2)max levels. CVD specific mortality was more associated with estVO(2)max compared to tumor specific mortality. The risk for all-cause mortality and CVD morbidity decreased by 2.3% and 2.6% per increase in 1 ml.min(-) (1).kg(-1) with no significant sex-differences but more pronounced in the three lower estVO(2)max categories for all-cause mortality (9.1%, 3.8% and 3.3%, respectively). High compared to lower levels of estVO(2)max was not related to a significantly elevated mortality or morbidity. In this large cohort study, CVD morbidity and all-cause mortality were inversely related to estVO(2)max in both men and women of all age-groups. Increasing cardiorespiratory fitness is a clear public health priority.
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| 6. |
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| 7. |
- Ellison, A, et al.
(författare)
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Fast SiC epitaxial growth in a chimney CVD reactor and HTCVD crystal growth developments
- 2000
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Ingår i: Materials science Forum, Vols. 338-342. - : Trans Tech Publications Inc.. - 0878498540 ; , s. 131-136
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Konferensbidrag (refereegranskat)abstract
- The epitaxial growth of SiC is investigated in a CVD process based on a vertical hot-wall, or "chimney", reactor geometry. Carried out at increased temperatures (1650 to 1850 degreesC) and concentrations of reactants, the growth process enables epitaxial rates ranging from 10 to 50 mum/h. The growth rate is shown to be influenced by two competing processes: the supply of growth species in the presence of homogeneous gas-phase nucleation, and, the etching effect of the hydrogen carrier gas. The quality of thick (20 to 100 mum) low-doped 4H-SiC epitaxial layers grown at rates ranging between 10 and 25 mum/h are discussed in terms of thickness uniformity, surface morphology and purity. The feasibility of high voltage Schottky rectifiers (V-BR from 2 to similar to3.8 kV) on as-grown chimney CVD epilayers is reported. In a second part, recent developments of the High Temperature Chemical Vapor Deposition (HTCVD) technique for SiC crystal growth are described. Using pure gases (SiH4 and C2H4) as source material and growth temperatures of 2100-2300 degreesC, this technique enables at present growth rates ranging from 0.4 to 0.8 mm/h. 6H and 4H-SiC crystals of thickness up to 7 mm and diameters up to 40 mm have been grown. We report micropipe densities of similar to 80 cm(-2) over areas of 0.5 cm(2) in 35 mm diameter 4H-SiC wafers sliced from HTCVD grown crystals. Undoped wafer demonstrators exhibit semi-insulating behavior with a bulk resistivity higher than 7.10(9) Omega cm at room temperature.
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| 8. |
- Hemmingsson, Carl, 1964-, et al.
(författare)
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Deep-Level Defects in Electron-irradiated 4H SiC Epitaxial Layers
- 1997
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 81:9, s. 6155-6159
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Tidskriftsartikel (refereegranskat)abstract
- Deep level defects in electron-irradiated 4H SiC epitaxial layers grown by chemical vapor deposition were studied using deep level transient spectroscopy. The measurements performed on electron-irradiated p+n junctions in the temperature range 100–750 K revealed several electron traps and one hole trap with thermal ionization energies ranging from 0.35 to 1.65 eV. Most of these defects were already observed at a dose of irradiation as low as ≈5×1013 cm-2. Dose dependence and annealing behavior of the defects were investigated. For two of these electron traps, the electron capture cross section was measured. From the temperature dependence studies, the capture cross section of these two defects are shown to be temperature independent. © 1997 American Institute of Physics.
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| 9. |
- Hemmingsson, Erik, et al.
(författare)
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Bicycling but not walking is independently associated with fasting insulin in abdominally obese women
- 2011
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Ingår i: Journal of physical activity & health. - : Human Kinetics. - 1543-5474 .- 1543-3080. ; 8:6, s. 820-823
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Tidskriftsartikel (refereegranskat)abstract
- The impact of walking and bicycling on insulin resistance (IR) in women with abdominal obesity is unclear.Methods:Pooled analysis of data from a randomized trial on physically active commuting (bicycling + walking vs walking only) in women with abdominal obesity [n = 98; age:47.3 ± 7.6 yrs; waist circumference (WC):103.1 ± 7.8 cm]. Bicycling and walking data were collected during 7 consecutive days by trip meters (Trelock FC-410) and pedometers (Yamax digiwalker SW-200) at baseline, 2, 4, and 6 months. Owing to a skew distribution we analyzed bicycling as a binary dummy variable with a 10 km/week cut-off. Fasting serum insulin and homeostatic model assessment – insulin resistance (HOMA-IR) were assessed at baseline and 6 months, as were body mass index (BMI), WC, and dual x-ray absorptiometry (DXA)-assessed % whole-body fat.Results:Increased bicycling by 10 km/wk was associated with reductions in fasting serum insulin at follow-up independent of age, treatment allocation, baseline phenotype, Δ walking, and Δ % body fat (β = −10.9, P = .042), but not HOMA-IR (β = −2.0, P = .13). Increased walking was not associated with fasting serum insulin (P = .33) or HOMA-IR (P = .44) at follow-up, after adjustment for the same covariates and Δ bicycling.Conclusion:Increased bicycling but not walking was associated with reduced insulin levels at follow-up. Bicycling may be more effective than walking for reducing insulin levels in abdominally obese women.
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| 10. |
- Hemmingsson, Erik, et al.
(författare)
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Increased physical activity in abdominally obese women through support for changed commuting habits : a randomized clinical trial
- 2009
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Ingår i: International Journal of Obesity. - : Springer Science and Business Media LLC. - 0307-0565 .- 1476-5497. ; 33:6, s. 645-652
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Tidskriftsartikel (refereegranskat)abstract
- Background: Abdominally obese women can reduce their health risk through regular physical activity. There is, however, little evidence on the effectiveness of interventions that promote physical activity long-term, such as cycling and walking to and from work. Methods: This intervention focused on physically active commuting (cycling and walking) in middle-aged (30-60 years), abdominally obese (waist circumference >= 88 cm) women (n = 120), recruited by newspaper advertisement. The intervention group was a moderate-intensity programme with physician meetings, physical activity prescriptions, group counselling and bicycles. The control group was a low-intensity group support programme with pedometers. We used a randomized, controlled, 2-armed design with 18 months duration and intention-to-treat analysis (data collection 2005-2006). Treatment success was defined as bicycling >= 2 km/d (primary) or walking 10 000 steps per day (secondary). Results: At baseline, mean (s. d.) age was 48.2 years (7.4), waist circumference 103.8cm (7.8), walking 8471 steps per day (2646), bicycling 0 km per day. Attrition at 18 months was 10% for the intervention group and 25% in the control group (P = 0.03). The intervention group was more likely to achieve treatment success for cycling than controls: 38.7 vs 8.9% (odds ratio (OR) 7.8 (95% confidence interval = 4.0 to 15.0, P < 0.001)), but with no difference for compliance with the walking recommendation: 45.7 vs 39.3% (OR 1.2 (95% CI 0.7 to 2.0, P = 0.50)). Commuting by car and public transport were reduced by 34% (P < 0.01) and 37% (P < 0.001), respectively, with no differences between groups. Both groups attained similar waist reductions (-2.1 and -2.6 cm, P = 0.72). Conclusions: Abdominally obese women can increase PA long-term through moderate-intensity behavioural support aimed at changing commuting habits. International Journal of Obesity (2009) 33, 645-652; doi: 10.1038/ijo.2009.77; published online 5 May 2009
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