| 1. |
- Haeggstrom, A, et al.
(författare)
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Nasal mucosal swelling and reactivity during a menstrual cycle
- 2000
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Ingår i: ORL. - : S. Karger AG. - 0301-1569 .- 1423-0275. ; 62:1, s. 39-42
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Tidskriftsartikel (refereegranskat)abstract
- <i>Introduction:</i> Nasal stuffness is a great problem for many women in the later part of pregnancy. <i>Objective:</i> This study was performed to evaluate whether oestrogen causes nasal congestion and/or a hyperreactive reaction of the nasal mucosa. <i>Material and Methods:</i> Ten healthy fertile women were examined during menstruation. Nasal mucosal congestion was studied with rhinostereometry and acoustic rhinometry. The nasal mucosa was challenged with 3 doses of histamine solution to study nasal reactivity. Measurements were made 3 times during menstruation. To find the exact time of ovulation, when oestrogen reaches its peak value, intravaginal ultrasound tests were done and blood samples taken, to determine the oestrogen and progesterone levels. <i>Results:</i> The nasal mucosa became hyperreactive to histamine in connection with ovulation, when the blood level of oestrogen reached its peak. This does not occur during the menstrual or the luteal phase. No significant alteration was found in the baseline position during the menstruation. <i>Conclusion:</i> There is a connection between high oestrogen level and nasal mucosal reactivity.
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| 2. |
- Hallen, H, et al.
(författare)
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Evaluation of a new method for assessing symptoms
- 2001
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Ingår i: ORL. - : S. Karger AG. - 0301-1569 .- 1423-0275. ; 63:2, s. 92-95
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Tidskriftsartikel (refereegranskat)abstract
- <i>Background: </i>Many studies in rhinology are based on results from symptom scoring. Numerous methods are used to estimate symptoms. With some of them the patients choose between various alternatives for estimating the severity of their symptoms, but the commonest method is the visual analogue scale (VAS), which is regarded as reliable. <i>Methods: </i>In this study, we evaluate a new method for assessing symptoms, with which the patient uses the telephone to call a computer. We compare the results using the new method with those using symptoms estimation with VAS. <i>Results: </i>The results are based on 487 observations in patients with birch pollen allergic rhinitis in the pollen season. A high correlation was found between the results using the new method and those using the VAS. In a questionnaire, the patients answered questions concerning the two methods. Most patients preferred the new telephone method. They found it easier to estimate their symptoms properly and easier to perform. <i>Conclusion: </i>We conclude that telephone scoring of symptoms is a reliable and adquate method when symptom scoring is used as hard data in a study.
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| 3. |
- Leveque, P., et al.
(författare)
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Dose-rate influence on the defect production in MeV proton-implanted float-zone and epitaxial n-type silicon
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 186, s. 375-379
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Tidskriftsartikel (refereegranskat)abstract
- The production of stable vacancy-related point defects in proton-implanted float-zone and epitaxial silicon has been studied in the low dose range ( less than or equal to 10(10)/cm(2)) as a function of dose-rate. The well-known inverse dose-rate effect has been observed in both types of materials with a decrease in the concentration of vacancy-related defects as the dose-rate increases. The effect is less pronounced in oxygen lean epitaxial silicon. Moreover, a continuous decrease of the vacancy-related defect concentration as a function of the flux was measured while a threshold was expected according to previous studies. Both or these results can be explained by a simple calculation, taking into account the influence of the oxygen concentration as well as the influence of the diffusion coefficient of point defects on the inverse dose-rate effect.
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| 4. |
- Leveque, P., et al.
(författare)
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Hydrogen-related defect centers in float-zone and epitaxial n-type proton implanted silicon
- 2001
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 174:3, s. 297-303
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen-related defects in float zone (Fz) and epitaxial (Epi) n-type silicon crystals have been studied by means of deep level transient spectroscopy. These defects, as well as the characteristic vacancy-oxygen (VO) and divacancy (V-2) centers were introduced by proton implantation (1.3 MeV) using a dose of 1 x 10(10)/cm(2). A hydrogen-related defect level located at 0.45 eV below the conduction band edge (E-c) appears in both kind of samples. Another hydrogen-related defect appears predominantly in the Fz samples with a level at E-c - 0.32 eV. Depth profiling as well as annealing studies strongly suggest that the level at E-c - 0.45 eV is due to a complex involving hydrogen and V2 The level at E-c - 0.32 eV is strongly suppressed in the high purity Epi samples and the same holds for VO center. These results together with annealing data provide substantial evidence that the E-c - 0.32 eV level originates from a VO-center partly saturated with hydrogen (a VOH complex). Finally, in the Epi samples a new level at similar toE(c) - 0.31 eV is resolved, which exhibits a concentration Versus depth profile strongly confined to the damage peak region. The origin of this level is not known but the extremely narrow depth profile may indicate a higher-order defect of either vacancy or interstitial type,
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| 5. |
- Pellegrino, P., et al.
(författare)
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Annealing kinetics of vacancy-related defects in low-dose MeV self-ion-implanted n-type silicon
- 2001
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 64:19
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Tidskriftsartikel (refereegranskat)abstract
- Silicon samples of n-type have been implanted at room temperature with 5.6-MeV Si-28 ions to a dose of 2 x 10(8) cm(-2) and then annealed at temperatures from 100 to 380 degreesC. Both isothermal and isochronal treatments were performed and the annealing kinetics of the prominent divacancy (V-2) and vacancy-oxygen (VO) centers were studied in detail using deep-level transient spectroscopy. The decrease Of V2 centers exhibits first-order kinetics in both Czochralski-grown (CZ) and float-zone (FZ) samples, and the data provide strong evidence for a process involving migration of V-2 and subsequent annihilation at trapping centers. The migration energy extracted for V-2 is similar to1.3 eV and from the shape of the concentration versus depth profiles, an effective diffusion length less than or equal to0.1 mum is obtained. The VO center displays a more complex annealing behavior where interaction with mobile hydrogen (H) plays a key role through the formation of VOH and VOH2 centers. Another contribution is migration of VO and trapping by interstitial oxygen atoms in the silicon lattice, giving rise to vacancy-dioxygen pairs. An activation energy of similar to 1.8 eV is deduced for the migration of VO, in close resemblance with results from previous studies using electron-irradiated samples. A model for the annealing of VO, involving only three reactions, is put forward and shown to yield a close quantitative agreement with the experimental data for both CZ and FZ samples over the whole temperature range studied.
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| 6. |
- Pellegrino, P., et al.
(författare)
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Separation of vacancy and interstitial depth profiles in proton- and boron-implanted silicon
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 186, s. 334-338
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Tidskriftsartikel (refereegranskat)abstract
- A new experimental method of studying shifts between concentration-versus-depth profiles of vacancy-type and interstitial-type defects in ion-implanted silicon is demonstrated. The concept is based on deep level transient spectroscopy (DLTS) measurements utilizing the filling pulse variation technique. The vacancy profile. represented by the vacancy-oxygen center and the interstitial profile, represented by the substitutional carbon-interstitial carbon pair, are obtained at the same sample temperature by varying the duration of the filling pulse, Thus the two profiles can be recorded with a high relative depth resolution, Point defects have been introduced in low doped float zone n-type silicon by implantation with 6 MeV boron ions and 1.3 MeV protons at room temperature, using low doses. For each implantation condition the peak of the interstitial profile is shown to be displaced by similar to 0.5 mum towards larger depths compared to that of the vacancy profile. This shift is primarily attributed to the preferential forward momentum of recoiling Si atoms, in accordance with theoretical predictions.
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| 7. |
- Aberg, D., et al.
(författare)
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Nitrogen deactivation by implantation-induced defects in 4H-SiC epitaxial layers
- 2001
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 78:19, s. 2908-2910
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Tidskriftsartikel (refereegranskat)abstract
- Ion implantation causes free charge carrier reduction due to damage in the crystalline structure. Here, nitrogen-doped 4H silicon carbide (n type) epitaxial layers have been investigated using low ion doses in order to resolve the initial stage of the charge carrier reduction. It was found that the reduction of free carriers per ion-induced vacancy increases with increasing nitrogen content. Nitrogen is suggested to be deactivated through reaction with migrating point defects, and silicon vacancies or alternatively interstitials are proposed as the most likely candidates.
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| 8. |
- Aberg, D., et al.
(författare)
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Nitrogen passivation by implantation-induced point defects in 4H-SiC epitaxial layers
- 2001
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 184:04-jan, s. 263-267
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Tidskriftsartikel (refereegranskat)abstract
- Ion implantation causes damage to the crystal lattice resulting in the loss of free charge carriers. In this study, low dose implantations using different ions and implantation doses are made to resolve the initial carrier loss in nitrogen-doped epitaxial layers. A strong dependence of compensation on nitrogen concentration is seen, showing that nitrogen is passivated by implantation-induced point defects. An activation energy of 3.2 eV for the dissociation of the passivated nitrogen center is obtained.
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| 9. |
- Ber, B. Y., et al.
(författare)
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Determination of nitrogen in silicon carbide by secondary ion mass spectrometry
- 2004
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Ingår i: Journal of Analytical Chemistry. - 1061-9348 .- 1608-3199. ; 59:3, s. 250-254
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Tidskriftsartikel (refereegranskat)abstract
- The emission of atomic and complex nitrogen ions, which are the main impurity determining the n type conduction of silicon carbide, is investigated. It is shown that, among all the secondary ions of the CxN and SixN kind (x = 0, 1, 2, 3), the (26)(CN)(-) fragment exhibits the highest ion yield. The use of an ion peak with a specified mass as an analytical signal provides a detection limit for nitrogen in SiC at a level of 10(16) cm(-3). This result is attained in measurements at high mass resolution (M/DeltaM = 7500, interference peak (26)(C-13(2))(-)).
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| 10. |
- Hallen, A, et al.
(författare)
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Implanted p(+)n-junctions in silicon carbide
- 2003
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Ingår i: APPLICATION OF ACCELERATORS IN RESEARCH AND INDUSTRY. ; , s. 653-657
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Konferensbidrag (refereegranskat)abstract
- Ion implantation is considered a key technology for the realisation of silicon carbide electronic devices. Here we will give an overview of the field and present some recent results of ion implanted 4H SiC epitaxial layers. Mainly Al ions of keV energies have been used at different fluence, flux and target temperature. The samples have been investigated by secondary ion mass spectrometry (SIMS), channeling Rutherford backscattering (RBS-c) and transmission electron microscopy (TEM), both as-implanted and after annealing up to 1900 degreesC. Also the electrical activation of Al-implanted and annealed material has been investigated by scanning spreading resistance microscopy (SSRM). The damage accumulation, monitored by RBS-c, is linear with ion fluence but depends strongly on implantation temperature and ion flux. Annealing at temperatures above 1700 degreesC is needed to remove the damage and to electrically activate implanted Al ions. At these high annealing temperatures, however, dislocation loops are formed that have a negative influence on device performance.
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