| 1. |
- Aartsen, M. G., et al.
(författare)
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Observation of High-Energy Astrophysical Neutrinos in Three Years of IceCube Data
- 2014
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 113:10, s. 101101-
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Tidskriftsartikel (refereegranskat)abstract
- A search for high-energy neutrinos interacting within the IceCube detector between 2010 and 2012 provided the first evidence for a high-energy neutrino flux of extraterrestrial origin. Results from an analysis using the same methods with a third year (2012-2013) of data from the complete IceCube detector are consistent with the previously reported astrophysical flux in the 100 TeV-PeV range at the level of 10(-8) GeV cm(-2) s(-1) sr(-1) per flavor and reject a purely atmospheric explanation for the combined three-year data at 5.7 sigma. The data are consistent with expectations for equal fluxes of all three neutrino flavors and with isotropic arrival directions, suggesting either numerous or spatially extended sources. The three-year data set, with a live time of 988 days, contains a total of 37 neutrino candidate events with deposited energies ranging from 30 to 2000 TeV. The 2000-TeV event is the highest-energy neutrino interaction ever observed.
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| 2. |
- Aartsen, M. G., et al.
(författare)
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SEARCHES FOR EXTENDED AND POINT-LIKE NEUTRINO SOURCES WITH FOUR YEARS OF ICECUBE DATA
- 2014
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 796:2, s. 109-
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Tidskriftsartikel (refereegranskat)abstract
- We present results on searches for point-like sources of neutrinos using four years of IceCube data, including the first year of data from the completed 86 string detector. The total livetime of the combined data set is 1373 days. For an E-2 spectrum, the observed 90% C. L. flux upper limits are similar to 10(-12) TeV-1 cm(-2) s(-1) for energies between 1 TeV and 1 PeV in the northern sky and similar to 10(-11) TeV-1 cm(-2) s(-1) for energies between 100 TeV and 100 PeV in the southern sky. This represents a 40% improvement compared to previous publications, resulting from both the additional year of data and the introduction of improved reconstructions. In addition, we present the first results from an all-sky search for extended sources of neutrinos. We update the results of searches for neutrino emission from stacked catalogs of sources and test five new catalogs; two of Galactic supernova remnants and three of active galactic nuclei. In all cases, the data are compatible with the background-only hypothesis, and upper limits on the flux of muon neutrinos are reported for the sources considered.
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| 3. |
- Aartsen, M. G., et al.
(författare)
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Search for neutrino-induced particle showers with IceCube-40
- 2014
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 89:10, s. 102001-
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the search for neutrino-induced particle showers, so-called cascades, in the IceCube-40 detector. The data for this search were collected between April 2008 and May 2009 when the first 40 IceCube strings were deployed and operational. Three complementary searches were performed, each optimized for different energy regimes. The analysis with the lowest energy threshold (2 TeV) targeted atmospheric neutrinos. A total of 67 events were found, consistent with the expectation of 41 atmospheric muons and 30 atmospheric neutrino events. The two other analyses targeted a harder, astrophysical neutrino flux. The analysis with an intermediate threshold of 25 TeV leads to the observation of 14 cascadelike events, again consistent with the prediction of 3.0 atmospheric neutrino and 7.7 atmospheric muon events. We hence set an upper limit of E-2 Phi(lim) <= 7.46 x 10(-8) GeV sr(-1) s(-1) cm(-2) (90% C.L.) on the diffuse flux from astrophysical neutrinos of all neutrino flavors, applicable to the energy range 25 TeV to 5 PeV, assuming an E-nu(-2) spectrum and a neutrino flavor ratio of 1: 1: 1 at the Earth. The third analysis utilized a larger and optimized sample of atmospheric muon background simulation, leading to a higher energy threshold of 100 TeV. Three events were found over a background prediction of 0.04 atmospheric muon events and 0.21 events from the flux of conventional and prompt atmospheric neutrinos. Including systematic errors this corresponds to a 2.7 sigma excess with respect to the background-only hypothesis. Our observation of neutrino event candidates above 100 TeV complements IceCube's recently observed evidence for high-energy astrophysical neutrinos.
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| 4. |
- Aartsen, M. G., et al.
(författare)
-
Energy reconstruction methods in the IceCube neutrino telescope
- 2014
-
Ingår i: Journal of Instrumentation. - 1748-0221. ; 9, s. P03009-
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Tidskriftsartikel (refereegranskat)abstract
- Accurate measurement of neutrino energies is essential to many of the scientific goals of large-volume neutrino telescopes. The fundamental observable in such detectors is the Cherenkov light produced by the transit through a medium of charged particles created in neutrino interactions. The amount of light emitted is proportional to the deposited energy, which is approximately equal to the neutrino energy for v(e) and v(mu) charged-current interactions and can be used to set a lower bound on neutrino energies and to measure neutrino spectra statistically in other channels. Here we describe methods and performance of reconstructing charged-particle energies and topologies from the observed Cherenkov light yield, including techniques to measure the energies of uncontained muon tracks, achieving average uncertainties in electromagnetic-equivalent deposited energy of similar to 15% above 10 TeV.
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| 5. |
- Aartsen, M. G., et al.
(författare)
-
Search for a diffuse flux of astrophysical muon neutrinos with the IceCube 59-string configuration
- 2014
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 89:6, s. 062007-
-
Tidskriftsartikel (refereegranskat)abstract
- A search for high-energy neutrinos was performed using data collected by the IceCube Neutrino Observatory from May 2009 to May 2010, when the array was running in its 59-string configuration. The data sample was optimized to contain muon neutrino induced events with a background contamination of atmospheric muons of less than 1%. These data, which are dominated by atmospheric neutrinos, are analyzed with a global likelihood fit to search for possible contributions of prompt atmospheric and astrophysical neutrinos, neither of which have yet been identified. Such signals are expected to follow a harder energy spectrum than conventional atmospheric neutrinos. In addition, the zenith angle distribution differs for astrophysical and atmospheric signals. A global fit of the reconstructed energies and directions of observed events is performed, including possible neutrino flux contributions for an astrophysical signal and atmospheric backgrounds as well as systematic uncertainties of the experiment and theoretical predictions. The best fit yields an astrophysical signal flux for nu(mu) + (nu) over bar (mu) of E-2. Phi(E) = 0.25 x 10(-8) GeV cm(-2) s(-1) sr(-1), and a zero prompt component. Although the sensitivity of this analysis for astrophysical neutrinos surpasses the Waxman and Bahcall upper bound, the experimental limit at 90% confidence level is a factor of 1.5 above at a flux of E-2 . Phi(E) = 1.44 x 10(-8) GeV cm(-2) s(-1) sr(-1).
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| 6. |
- Aartsen, M. G., et al.
(författare)
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Search for non-relativistic magnetic monopoles with IceCube
- 2014
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 74:7, s. 2938-
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Tidskriftsartikel (refereegranskat)abstract
- The IceCube Neutrino Observatory is a large Cherenkov detector instrumenting of Antarctic ice. The detector can be used to search for signatures of particle physics beyond the Standard Model. Here, we describe the search for non-relativistic, magnetic monopoles as remnants of the Grand Unified Theory (GUT) era shortly after the Big Bang. Depending on the underlying gauge group these monopoles may catalyze the decay of nucleons via the Rubakov-Callan effect with a cross section suggested to be in the range of to . In IceCube, the Cherenkov light from nucleon decays along the monopole trajectory would produce a characteristic hit pattern. This paper presents the results of an analysis of first data taken from May 2011 until May 2012 with a dedicated slow-particle trigger for DeepCore, a subdetector of IceCube. A second analysis provides better sensitivity for the brightest non-relativistic monopoles using data taken from May 2009 until May 2010. In both analyses no monopole signal was observed. For catalysis cross sections of the flux of non-relativistic GUT monopoles is constrained up to a level of at a 90 % confidence level, which is three orders of magnitude below the Parker bound. The limits assume a dominant decay of the proton into a positron and a neutral pion. These results improve the current best experimental limits by one to two orders of magnitude, for a wide range of assumed speeds and catalysis cross sections.
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| 7. |
- Aartsen, M. G., et al.
(författare)
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Probing the origin of cosmic rays with extremely high energy neutrinos using the IceCube Observatory
- 2013
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:11
-
Tidskriftsartikel (refereegranskat)abstract
- We have searched for extremely high energy neutrinos using data taken with the IceCube detector between May 2010 and May 2012. Two neutrino-induced particle shower events with energies around 1 PeV were observed, as reported previously. In this work, we investigate whether these events could originate from cosmogenic neutrinos produced in the interactions of ultrahigh energy cosmic rays with ambient photons while propagating through intergalactic space. Exploiting IceCube's large exposure for extremely high energy neutrinos and the lack of observed events above 100 PeV, we can rule out the corresponding models at more than 90% confidence level. The model-independent quasidifferential 90% C. L. upper limit, which amounts to E-2 phi(nu e)+(nu mu)+(nu tau) = 1.2 x 10(-7) GeV cm(-2) s(-1) sr(-1) at 1 EeV, provides the most stringent constraint in the energy range from 10 PeV to 10 EeV. Our observation disfavors strong cosmological evolution of the highest energy cosmic-ray sources such as the Fanaroff-Riley type II class of radio galaxies.
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| 8. |
- Aartsen, M. G., et al.
(författare)
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Evidence for High-Energy Extraterrestrial Neutrinos at the IceCube Detector
- 2013
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 342:6161, s. 947-
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Tidskriftsartikel (refereegranskat)abstract
- We report on results of an all-sky search for high-energy neutrino events interacting within the IceCube neutrino detector conducted between May 2010 and May 2012. The search follows up on the previous detection of two PeV neutrino events, with improved sensitivity and extended energy coverage down to about 30 TeV. Twenty-six additional events were observed, substantially more than expected from atmospheric backgrounds. Combined, both searches reject a purely atmospheric origin for the 28 events at the 4 sigma level. These 28 events, which include the highest energy neutrinos ever observed, have flavors, directions, and energies inconsistent with those expected from the atmospheric muon and neutrino backgrounds. These properties are, however, consistent with generic predictions for an additional component of extraterrestrial origin.
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| 9. |
- Aartsen, M. G., et al.
(författare)
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Improvement in fast particle track reconstruction with robust statistics
- 2014
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 736, s. 143-149
-
Tidskriftsartikel (refereegranskat)abstract
- The IceCube project has transformed 1 km(3) of deep natural Antarctic ice into a Cherenkov detector Muon neutrinos are detected and their direction is inferred by mapping the light produced by the secondary muon track inside the volume instrumented with photomultipliers. Reconstructing the muon track from the observed light is challenging due to noise, light scattering in the ice medium, and the possibility of simultaneously having multiple muons inside the detector, resulting from the large flux of cosmic ray muons. This paper describes work on two problems: (1) the truck reconstruction problem, in which, given a set of observations, the goal is to recover the track of a muon; and (2) the coincident event problem, which is to determine how many muons are active in the detector during a time window. Rather than solving these problems by developing more complex physical models that are applied at later stages of the analysis, our approach is to augment the detector's early reconstruction with data filters and robust statistical techniques. These can be implemented at the level of on-line reconstruction and, therefore, improve all subsequent reconstructions. Using the metric of median angular resolution, a standard metric for track reconstruction, we improve the accuracy in the initial reconstruction direction by 13%. We also present improvements in measuring the number of muons in coincident events: we can accurately determine the number of muons 98% of the time.
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| 10. |
- Aartsen, M. G., et al.
(författare)
-
SEARCH FOR TIME-INDEPENDENT NEUTRINO EMISSION FROM ASTROPHYSICAL SOURCES WITH 3 yr OF IceCube DATASearch for time-independent neutrino emission from astrophysical sources with 3 yr of icecube data
- 2013
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 779:2, s. 132-
-
Tidskriftsartikel (refereegranskat)abstract
- We present the results of a search for neutrino point sources using the IceCube data collected between 2008 April and 2011 May with three partially completed configurations of the detector: the 40-, 59-, and 79-string configurations. The live-time of this data set is 1040 days. An unbinned maximum likelihood ratio test was used to search for an excess of neutrinos above the atmospheric background at any given direction in the sky. By adding two more years of data with improved event selection and reconstruction techniques, the sensitivity was improved by a factor of 3.5 or more with respect to the previously published results obtained with the 40-string configuration of IceCube. We performed an all-sky survey and a dedicated search using a catalog of a priori selected objects observed by other telescopes. In both searches, the data are compatible with the background-only hypothesis. In the absence of evidence for a signal, we set upper limits on the flux of muon neutrinos. For an E-2 neutrino spectrum, the observed limits are (0.9-5) x 10(-12) TeV-1 cm(-2) s(-1) for energies between 1 TeV and 1 PeV in the northern sky and (0.9-23.2) x 10(-12) TeV-1 cm(-2) s(-1) for energies between 10(2) TeV and 10(2) PeV in the southern sky. We also report upper limits for neutrino emission from groups of sources that were selected according to theoretical models or observational parameters and analyzed with a stacking approach. Some of the limits presented already reach the level necessary to quantitatively test current models of neutrino emission.
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| 11. |
- Aartsen, M. G., et al.
(författare)
-
First Observation of PeV-Energy Neutrinos with IceCube
- 2013
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 111:2, s. 021103-
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Tidskriftsartikel (refereegranskat)abstract
- We report on the observation of two neutrino-induced events which have an estimated deposited energy in the IceCube detector of 1.04 +/- 0.16 and 1.14 +/- 0.17 PeV, respectively, the highest neutrino energies observed so far. These events are consistent with fully contained particle showers induced by neutral-current nu(e,mu,tau) ((nu) over bar (e,mu,tau)) or charged-current nu(e) ((nu) over bar (e)) interactions within the IceCube detector. The events were discovered in a search for ultrahigh energy neutrinos using data corresponding to 615.9 days effective live time. The expected number of atmospheric background is 0.082 +/- 0.004(stat)(-0.057)(+0.041)(syst). The probability of observing two or more candidate events under the atmospheric background-only hypothesis is 2.9 x 10(-3) (2.8 sigma) taking into account the uncertainty on the expected number of background events. These two events could be a first indication of an astrophysical neutrino flux; the moderate significance, however, does not permit a definitive conclusion at this time.
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| 12. |
- Aartsen, M. G., et al.
(författare)
-
IceCube search for dark matter annihilation in nearby galaxies and galaxy clusters
- 2013
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:12
-
Tidskriftsartikel (refereegranskat)abstract
- We present the results of a first search for self-annihilating dark matter in nearby galaxies and galaxy clusters using a sample of high-energy neutrinos acquired in 339.8 days of live time during 2009/10 with the IceCube neutrino observatory in its 59-string configuration. The targets of interest include the Virgo and Coma galaxy clusters, the Andromeda galaxy, and several dwarf galaxies. We obtain upper limits on the cross section as a function of the weakly interacting massive particle mass between 300 GeV and 100 TeV for the annihilation into b (b) over bar, W+(W) over bar (-), tau(+)tau(-), mu(+)mu(-) , and nu(nu) over bar. A limit derived for the Virgo cluster, when assuming a large effect from subhalos, challenges the weakly interacting massive particle interpretation of a recently observed GeV positron excess in cosmic rays.
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| 13. |
- Aartsen, M. G., et al.
(författare)
-
Measurement of Atmospheric Neutrino Oscillations with IceCube
- 2013
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 111:8, s. 081801-
-
Tidskriftsartikel (refereegranskat)abstract
- We present the first statistically significant detection of neutrino oscillations in the high-energy regime (> 20 GeV) from an analysis of IceCube Neutrino Observatory data collected in 2010 and 2011. This measurement is made possible by the low-energy threshold of the DeepCore detector (similar to 20 GeV) and benefits from the use of the IceCube detector as a veto against cosmic-ray-induced muon background. The oscillation signal was detected within a low-energy muon neutrino sample (20-100 GeV) extracted from data collected by DeepCore. A high-energy muon neutrino sample (100 GeV-10 TeV) was extracted from IceCube data to constrain systematic uncertainties. The disappearance of low-energy upward-going muon neutrinos was observed, and the nonoscillation hypothesis is rejected with more than 5 sigma significance. In a two-neutrino flavor formalism, our data are best described by the atmospheric neutrino oscillation parameters vertical bar Delta m(32)(2)vertical bar = (2.3(-0.5)(+0.6)) x 10(-3) eV(2) and sin(2) (2 theta(23)) > 0.93, and maximum mixing is favored.
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| 14. |
- Aartsen, M. G., et al.
(författare)
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Measurement of the cosmic ray energy spectrum with IceTop-73
- 2013
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:4, s. 042004-
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Tidskriftsartikel (refereegranskat)abstract
- We report on the measurement of the all-particle cosmic ray energy spectrum with the IceTop air shower array in the energy range from 1.58 PeV to 1.26 EeV. The IceTop air shower array is the surface component of the IceCube Neutrino Observatory at the geographical South Pole. The analysis was performed using only information from IceTop. The data used in this work were taken from June 1, 2010 to May 13, 2011. During that period the IceTop array consisted of 73 stations, compared to 81 in its final configuration. The measured spectrum exhibits a clear deviation from a single power law above the knee around 4 PeV and below 1 EeV. We observe spectral hardening around 18 PeV and steepening around 130 PeV.
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| 15. |
- Aartsen, M. G., et al.
(författare)
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South Pole glacial climate reconstruction from multi-borehole laser particulate stratigraphy
- 2013
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Ingår i: Journal of Glaciology. - 0022-1430 .- 1727-5652. ; 59:218, s. 1117-1128
-
Tidskriftsartikel (refereegranskat)abstract
- The IceCube Neutrino Observatory and its prototype, AMANDA, were built in South Pole ice, using powerful hot-water drills to cleanly bore >100 holes to depths up to 2500 m. The construction of these particle physics detectors provided a unique opportunity to examine the deep ice sheet using a variety of novel techniques. We made high-resolution particulate profiles with a laser dust logger in eight of the boreholes during detector commissioning between 2004 and 2010. The South Pole laser logs are among the most clearly resolved measurements of Antarctic dust strata during the last glacial period and can be used to reconstruct paleoclimate records in exceptional detail. Here we use manual and algorithmic matching to synthesize our South Pole measurements with ice-core and logging data from Dome C, East Antarctica. We derive impurity concentration, precision chronology, annual-layer thickness, local spatial variability, and identify several widespread volcanic ash depositions useful for dating. We also examine the interval around similar to 74 ka recently isolated with radiometric dating to bracket the Toba (Sumatra) supereruption.
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| 16. |
- Aartsen, M. G., et al.
(författare)
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Observation of the cosmic-ray shadow of the Moon with IceCube
- 2014
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Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 89:10, s. 102004-
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the observation of a significant deficit of cosmic rays from the direction of the Moon with the IceCube detector. The study of this "Moon shadow" is used to characterize the angular resolution and absolute pointing capabilities of the detector. The detection is based on data taken in two periods before the completion of the detector: between April 2008 and May 2009, when IceCube operated in a partial configuration with 40 detector strings deployed in the South Pole ice, and between May 2009 and May 2010 when the detector operated with 59 strings. Using two independent analysis methods, the Moon shadow has been observed to high significance (> 6 sigma) in both detector configurations. The observed location of the shadow center is within 0.2 degrees of its expected position when geomagnetic deflection effects are taken into account. This measurement validates the directional reconstruction capabilities of IceCube.
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| 17. |
- Azarov, A. Yu., et al.
(författare)
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Structural damage in ZnO bombarded by heavy ions
- 2010
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Ingår i: Vacuum. - : Elsevier BV. - 0042-207X .- 1879-2715. ; 84:8, s. 1058-1061
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of implantation parameters on damage build-up in ZnO bombarded with Bi and Er ions is studied by Rutherford backscattering/channelling spectrometry. The results show that the damage accumulation behaviour in ZnO is different dramatically from that in other semiconductors. In particular, a variation of implantation parameters, such as collision cascade density, sample temperature and ion flux, has only a minor influence on the damage accumulation in the crystal bulk for the case of such heavy ions. Moreover, an intermediate damage peak, between the surface and bulk defect peaks, is observed for all the irradiation conditions studied. The cascade density affects the behaviour of this intermediate peak with increasing ion dose.
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| 18. |
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| 19. |
- Gustafsson, Oscar, et al.
(författare)
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Long-wavelength infrared quantum-dot based interband photodetectors
- 2011
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Ingår i: Infrared physics & technology. - : Elsevier BV. - 1350-4495 .- 1879-0275. ; 54:3, s. 287-291
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Tidskriftsartikel (refereegranskat)abstract
- We report on the design and fabrication of (Al)GaAs(Sb)/InAs tensile strained quantum-dot (QD) based detector material for thermal infrared imaging applications in the long-wavelength infrared (LWIR) regime. The detection is based on transitions between confined dot states and continuum states in a type-II band lineup, and we therefore refer to it as a dot-to-bulk (D2B) infrared photodetector with expected benefits including long carrier lifetime due to the type-II band alignment, suppressed Shockley-Read-Hall generation-recombination due to the relatively large-bandgap matrix material, inhibited Auger recombination processes due to the tensile strain and epitaxial simplicity. Metal-organic vapor-phase epitaxy was used to grow multiple (Al)GaAs(Sb) QD layers on InAs substrates at different QD nominal thicknesses, compositions, doping conditions and multilayer periods, and the material was characterized using atomic force and transmission electron microscopy, and Fourier-transform infrared absorption spectroscopy. Dot densities up to 1 x 10(11) cm(-2), 1 x 10(12) cm(-2) and 3 x 10(10) cm(-2) were measured for GaAs, AlGaAs and GaAsSb QDs, respectively. Strong absorption in GaAs, AlGaAs and GaAsSb multilayer QD samples was observed in the wavelength range 6-12 mu m. From the wavelength shift in the spectral absorption for samples with varying QD thickness and composition it is believed that the absorption is due to an intra- valance band transition. From this it is possible to estimate the type-II inter-band transition wavelength, thereby suggesting that (Al)GaAs(Sb) QD/InAs heterostructures are suitable candidates for LWIR detection and imaging.
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| 20. |
- Issa, F., et al.
(författare)
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Nuclear radiation detectors based on 4H-SiC p+-n junction
- 2014
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Ingår i: 15th International Conference on Silicon Carbide and Related Materials, ICSCRM 2013. - 9783038350101 ; , s. 1046-1049
-
Konferensbidrag (refereegranskat)abstract
- Silicon carbide (SiC) radiation detectors were realized by 10B implantation into the metal contact in order to avoid implantation-related defects within the sensitive area of the 4H-SiC pn junction. No post implantation annealing was performed. Such detectors respond to thermal neutrons showing consistent counting rates as function of external reverse bias voltages and radiation intensity.
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| 21. |
- Issa, F., et al.
(författare)
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Radiation silicon carbide detectors based on ion implantation of boron
- 2014
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Ingår i: IEEE Transactions on Nuclear Science. - 0018-9499 .- 1558-1578. ; 61:4, s. 2105-2111
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Tidskriftsartikel (refereegranskat)abstract
- Radiation detectors based on radiation-hardened semiconductor such as silicon carbide (SiC), have received considerable attention in many applications such as in outer space, high energy physics experiments, gas and oil prospection, and nuclear reactors. In the frame work of the European project I-SMART (Innovative Sensor for Material Ageing and Radiation Testing), we demonstrated for the first time the reliability of thermal neutron detectors realized by standard ion implantation of boron atoms to form a neutron converter layer (NCL). Two types of detectors were realized; the first was implanted by aluminum to create the p+ - layer, and then implanted by boron ( 10 B) to realize the NCL. The second type was based on p+ - layer, and was implanted by 10B into the aluminum metallic contact in order to avoid implantation-related defect within the sensitive area. Both kinds of detectors reveal to respond to thermal neutrons and gamma rays, showing consistent counting rates as a function of bias voltages, radiation intensity and type of shielding.
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| 22. |
- Issa, F., et al.
(författare)
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Radiation silicon carbide detectors based on ion implantation of boron
- 2013
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Ingår i: 2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and Their Applications, ANIMMA 2013. - : IEEE. - 9781479910472 ; , s. 6727997-
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Konferensbidrag (refereegranskat)abstract
- Radiation detectors based on radiation-hardened semiconductor such as silicon carbide (SiC), have received considerable attention in many applications such as in outer space, high energy physics experiments, gas and oil prospection, and nuclear reactors. For the first time it was demonstrated the reliability of thermal neutron detectors realized by standard ion implantation of boron layer as a neutron converter layer. Moreover, these detectors respond to thermal neutrons and gamma rays showing different counting rates at different voltages and under different types of shielding.
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| 23. |
- Vervisch, V., et al.
(författare)
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Nuclear radiation detector based on ion implanted p-n junction in 4H-SiC
- 2013
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Ingår i: 2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and Their Applications, ANIMMA 2013. - : IEEE. - 9781479910472 ; , s. 6728002-
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose a new device detector based on ion implanted p-n junction in 4H-SiC for nuclear instrumentation. We showed the interest to use 10Boron as a Neutron Converter Layer in order to detect thermal neutrons. We present the main results obtained during irradiation tests performed in the Belgian Reactor 1. We show the capability of our detector by means of first results of the detector response at different reverse voltage biases and at different reactor power.
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| 24. |
- Vervisch, Vanessa, et al.
(författare)
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Thermal neutron detection enhancement by 10B implantation in silicon carbide sensor
- 2014
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Ingår i: Materials Research Society Symposium Proceedings. - : Springer Science and Business Media LLC.
-
Konferensbidrag (refereegranskat)abstract
- The purpose of this paper is to propose the enhancement of device detectors based on p-n junction in 4H-SiC for nuclear instrumentation. Particular emphasis is placed on the interest on using Boron isotope 10 as a Neutron Converter Layer in order to detect thermal neutrons. Here, we present the main results obtained during several irradiation tests performed in the Belgian Reactor 1 (BR1). We show the capability of our detectors by means of first results of the detector response at different reverse voltage biases and at different reactor power.
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| 25. |
- Azarov, A. Yu, et al.
(författare)
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Annealing of ion implanted CdZnO
- 2012
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 45:23, s. 235304-
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the effect of the Cd content on the recovery of ion-induced damage in wurtzite CdxZn1-xO (x <= 0.05) films and compared with that in pure wurtzite ZnO and rock-salt CdO.200 keV Au+ and 55 keV Ar+ ion implants were performed at room temperature in the dose range of 5 x 1014-6.5 x 1015 cm-2. Rutherford backscattering/channelling spectrometry was used to characterize the damage evolution in the course of annealing (600-900 degrees C in air). A complex defect annealing behaviour is revealed in CdZnO as a function of annealing temperature, Cd content and ion dose. In particular, defects in the low dose implanted CdZnO films can be effectively removed at 800 degrees C, while the high dose implantation results in the formation of defects stable at least up to 900 degrees C. Moreover, annealing of the CdZnO films is accompanied by Cd loss at the surface for temperatures exceeding 800 degrees C. In contrast, CdO exhibits a typical damage accumulation behaviour for metals and semiconductors with high degree of ionicity, resulting in saturation and extended defect formation at high ion doses. These extended defects in pure ZnO and CdO, formed either directly during implantation or by reconstruction during post-implant annealing, are substantially more stable compared with small defects which can be efficiently removed at 700 degrees C and 600 degrees C for ZnO and CdO, respectively.
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| 26. |
- Azarov, A. Yu., et al.
(författare)
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Damage accumulation and annealing behavior in high fluence implanted MgZnO
- 2012
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 272, s. 426-429
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Tidskriftsartikel (refereegranskat)abstract
- Molecular beam epitaxy grown MgxZn1-xO (x <= 0.3) layers were implanted at room temperature with 150 keV Er-166(+) ions in a fluence range of 5 x 10(15-)3 x 10(16) cm(-2). Evolution of ion-induced damage and structural changes were studied by a combination of Rutherford backscattering spectrometry, nuclear reaction analysis and time-of-flight elastic recoil detection analysis. Results show that damage production enhances in both Zn- and O-sublattices with increasing the Mg content in the MgZnO. However, MgZnO as well as pure ZnO exhibits a high degree of dynamic annealing and MgZnO can not be amorphized even at the highest ion fluence used. Annealing of heavily damaged ZnO leads to a strong surface erosion and thinning of the film. Increasing the Mg content suppresses the surface evaporation in high fluence implanted MgZnO but leads to a strong surface decomposition accompanied with a Mg-rich surface layer formation during post-implantation annealing.
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| 27. |
- Azarov, A. Yu., et al.
(författare)
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Effect of composition on damage accumulation in ternary ZnO-based oxides implanted with heavy ions
- 2010
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 108:3, s. 033509-
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of wurtzite MgxZn1-xO (x <= 0.3) grown by molecular beam epitaxy and wurtzite CdxZn1-xO (x <= 0.05) grown by metal organic chemical vapor deposition were implanted at room temperature with 150 keV Er+ ions and 200 keV Au+ ions in a wide dose range. Damage accumulation was studied by Rutherford backscattering/channeling spectrometry. Results show that the film composition affects the damage accumulation behavior in both MgZnO and CdZnO dramatically. In particular, increasing the Mg content in MgZnO results in enhanced damage accumulation in the region between the bulk and surface damage peaks characteristically distinguished in the pure ZnO. However, the overall damage accumulation in MgZnO layers, as well as in pure ZnO, exhibits saturation with increasing ion dose and MgZnO cannot be amorphized even at the highest ion dose used (3 X 10(16) Er/cm(2)). Increasing the Cd content in CdZnO affects the saturation stage of the damage accumulation and leads to an enhancement of damage production in both Cd and Zn sublattices. (C) 2010 American Institute of Physics. [doi:10.1063/1.3467532]
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| 28. |
- Azarov, A. Yu, et al.
(författare)
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Effect of implanted species on thermal evolution of ion-induced defects in ZnO
- 2014
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:7, s. 073512-
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Tidskriftsartikel (refereegranskat)abstract
- Implanted atoms can affect the evolution of ion-induced defects in radiation hard materials exhibiting a high dynamic annealing and these processes are poorly understood. Here, we study the thermal evolution of structural defects in wurtzite ZnO samples implanted at room temperature with a wide range of ion species (from B-11 to Bi-209) to ion doses up to 2 x 10(16) cm(-2). The structural disorder was characterized by a combination of Rutherford backscattering spectrometry, nuclear reaction analysis, and transmission electron microscopy, while secondary ion mass spectrometry was used to monitor the behavior of both the implanted elements and residual impurities, such as Li. The results show that the damage formation and its thermal evolution strongly depend on the ion species. In particular, for F implanted samples, a strong out-diffusion of the implanted ions results in an efficient crystal recovery already at 600 degrees C, while co-implantation with B (via BF2) ions suppresses both the F out-diffusion and the lattice recovery at such low temperatures. The damage produced by heavy ions (such as Cd, Au, and Bi) exhibits a two-stage annealing behavior where efficient removal of point defects and small defect clusters occurs at temperatures similar to 500 degrees C, while the second stage is characterized by a gradual and partial annealing of extended defects. These defects can persist even after treatment at 900 degrees C. In contrast, the defects produced by light and medium mass ions (O, B, and Zn) exhibit a more gradual annealing with increasing temperature without distinct stages. In addition, effects of the implanted species may lead to a nontrivial defect evolution during the annealing, with N, Ag, and Er as prime examples. In general, the obtained results are interpreted in terms of formation of different dopant-defect complexes and their thermal stability.
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| 29. |
- Azarov, A. Yu., et al.
(författare)
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Thermally induced surface instability in ion-implanted Mg(x)Zn(1-x)O films
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 84:1, s. 014114-
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Tidskriftsartikel (refereegranskat)abstract
- Thermal stability of originally single crystalline wurtzite Mg(x)Zn(1-x)O (x <= 0.3) films implanted at room temperature with (166)Er ions is studied by a combination of Rutherford backscattering spectrometry, time-of-flight elastic recoil detection analysis, x-ray diffraction analysis, and atomic force microscopy. The MgZnO films exhibit a complex behavior during postimplantation annealing associated with compositional changes and surface erosion in addition to Er accumulation at the surface. The importance of these processes depends on the Mg content, annealing temperature, and amount of implantation damage. Specifically, increases in the Mg content as well as the implantation damage enhance the compositional changes in the near-surface region and give rise to altered stoichiometry and Mg-enriched phase separation. In its turn, the rate of surface erosion in MgZnO under the thermal treatment depends on temperature, MgZnO composition, and the amount of implantation damage nontrivially, which is attributed to the compositional changes in the near-surface region assisted by the implantation damage.
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| 30. |
- Liang, H. L., et al.
(författare)
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Growth of single-phase Mg0.3Zn0.7O films suitable for solar-blind optical devices on RS-MgO substrates
- 2012
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 520:6, s. 1705-1708
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Tidskriftsartikel (refereegranskat)abstract
- Single-phase rock-salt Mg0.3Zn0.7O film was fabricated on MgO (100) substrate by radio-frequency plasma assisted molecular beam epitaxy. A smooth surface was observed by in-situ reflection high-energy electron diffraction and ex-situ atomic force microscopy. X-ray diffraction characterization demonstrated a high-quality single-phase structure with highly (200) orientation and cube-on-cube epitaxial relationship. Zn fraction in the single-phase rock-salt Mg0.3Zn0.7O film was determined by Rutherford backscattering spectrometry. Optical property of the film was investigated by reflectance spectroscopy, which indicated a solar-blind band gap of 255.5 nm. The reason why Zn solubility limit is greatly enhanced in non-polar (100) film compared with (111) polar epilayer is tentatively discussed in this work, suggesting MgO (100) is more suitable for the synthesis of single-phase rock-salt MgZnO with high Zn content towards solar-blind opto-device applications.
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| 31. |
- Liang, H. L., et al.
(författare)
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High Zn content single-phase RS-MgZnO suitable for solar-blind frequency applications
- 2010
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Ingår i: 2010 Wide Bandgap Cubic Semiconductors. - : American Institute of Physics (AIP). - 9780735408470 ; , s. 185-190
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Konferensbidrag (refereegranskat)abstract
- Single-phase rock-salt MgZnO films with high Zn content were successfully fabricated on the templates of MgO (111)/α-sapphire (0001) by radio-frequency plasma assisted molecular beam epitaxy. The influence of growth temperature on epitaxy of MgZnO alloy films was investigated by the combined studies of crystal structures, compositions, and optical properties. It is found that the incorporation of Zn atoms into the rock-salt MgZnO films is greatly enhanced at low temperature, confirmed by in-situ reflection high-energy electron diffraction observations and ex-situ X-ray diffraction characterization. Zn fraction in the single-phase rock-salt Mg 0.53Zn0.47O film was determined by Rutherford backscattering spectrometry. Optical properties of the films were investigated by transmittance spectroscopy and reflectance spectroscopy, both of which demonstrate the solar-blind band gap and its dependence on Zn content.
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| 32. |
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| 33. |
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| 34. |
- Wolska, A., et al.
(författare)
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Study of the Local Environment of Mn Ions Implanted in GaSb
- 2010
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Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 117:2, s. 286-292
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Tidskriftsartikel (refereegranskat)abstract
- The first attempts to establish an implantation process leading to formation of ferromagnetic inclusions inside the GaSb matrix are presented. Gallium antimonide containing ferromagnetic MnSb precipitations is considered as a promising material for novel spintronic applications. It is possible to obtain such inclusions during the molecular beam epitaxy (MBE) growth. However, for commercial application it would be also important to find an optimal way of producing this kind of inclusions by Mn ions implantation. In order to achieve this goal, several parameters of implantation and post annealing procedures were tested. The ion energy was kept at 10 keV or 150 keV and four different ion doses were applied, as well as various annealing conditions. The analysis of X-ray absorption spectra allowed to estimate the local atomic order around Mn atoms. Depending on the implantation energy and annealing processes, the manganese oxides or manganese atoms located in a heavily defected GaSb matrix were observed. The performed analysis helped in indicating the main obstacles in formation of MnSb inclusions inside the GaSb matrix by Mn ion implantation.
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| 35. |
- Audren, A., et al.
(författare)
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Damage recovery in the oxygen sublattice of ZnO by post-implantation annealing
- 2012
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 272, s. 418-421
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Tidskriftsartikel (refereegranskat)abstract
- Hydrothermally grown zinc oxide bulk samples were implanted with 200 key-Co ions with a fluence of 4.5 x 10(16) cm(-2) and then annealed in air during 30 min at different temperatures up to 900 degrees C. After the implantation and each annealing step, the samples were analyzed using the nuclear reaction O-16(alpha,alpha)O-16 at 3.045 MeV He in random and channeling directions to follow the annealing of the disorder profile in the O sublattice. For comparison, the disorder in the Zn sublattice was also observed by Rutherford backscattering spectrometry (RBS) in random and channeling directions. The results reveal that the disorder created during the Co implantation is slightly higher in the O sublattice than in the Zn sublattice. The disorder recovery induced by the thermal treatments, starts at 500 degrees C in the O sublattice and at 700 degrees C in the Zn sublattice. Although, the most part of the disorder recovery occurs between 700 and 800 degrees C in both sublattices.
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| 36. |
- Audren, A., et al.
(författare)
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Damage recovery in ZnO by post-implantation annealing
- 2010
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 268:11-12, s. 1842-1846
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- ZnO bulk samples were implanted with 200 key-Co ions at room temperature with two fluences, 1 x 10(16) and 8 x 10(16) cm(-2), and then annealed in air for 30 min at different temperatures up to 900 degrees C. After the implantation and each annealing step, the samples were analyzed by Rutherford backscattering spectrometry (RBS) in random and channeling directions to follow the evolution of the disorder profile. The RBS spectra reveal that disorder is created during implantation in proportion to the Co fluence. The thermal treatments induce a disorder recovery, which is however, not complete after annealing at 900 degrees C, where about 15% of the damage remains. To study the Co profile evolution during annealing, the samples were, in addition to RBS, characterized by secondary ion mass spectrometry (SIMS). The results show that Co diffusion starts at 800 degrees C, but also that a very different behavior is seen for Co concentrations below and above the solubility limit. (C) 2010 Elsevier B.V. All rights reserved.
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| 37. |
- Azarov, Alexander, et al.
(författare)
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Dopant incorporation in thin strained Si layers implanted with Sb
- 2010
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 518:9, s. 2474-2477
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Tidskriftsartikel (refereegranskat)abstract
- The effect of tensile strain on Sb incorporation in Si and its activation during post-implantation annealing has been Studied by a combination of Rutherford backscattering/channeling spectrometry, secondary ion mass spectrometry. X-ray diffraction and 4-point probe measurements Our results show that, for Sb implanted samples a tensile strain has an important role for dopant behavior Particularly, increasing the tensile strain in the Si layer from 0 to 0 8% leads to an enhancement of the fraction of incorporated Sb atoms in substitutional sites already during implantation from similar to 7 to 30% Furthermore, 0 8% strain in antimony doped Si gives similar to 20% reduction in the sheet resistance in comparison to the unstrained sample.
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| 38. |
- Carlsson, Eva, 1959, et al.
(författare)
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Concerns and quality of life before surgery and during the recovery period in patients with rectal cancer and an ostomy
- 2010
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Ingår i: Journal of Wound, Ostomy and Continence Nursing (WOCN). - : Lippincott, Williams & Wilkins. - 1071-5754 .- 1528-3976. ; 37:6, s. 654-661
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Rectal cancer is the most common reason for a person to undergo ostomy surgery. The aim of this study was to assess concerns and health-related quality of life (HRQOL) before surgery and during the first 6 months following ostomy surgery in the presence of rectal cancer. SUBJECTS AND SETTINGS: The sample comprised 57 patients at a university hospital in Gothenburg, Sweden. Their median age was 66 years (range, 30-87); 35 men and 22 women participated in the study. METHODS: Participants prospectively answered questionnaires preoperatively, and at 1, 3, and 6 months postoperatively.Concerns were assessed using the rating form of the Inflammatory Bowel Disease Patient Concerns, and HRQOL was evaluated using the 36-Item Short Form Health Survey. Results were compared with population norms. RESULTS: Participants expressed concerns associated with developing cancer, being a burden on others, and related to the uncertain nature of disease. Health-related quality of life scores dropped significantly in 6 of 8 domains when preoperative scores were compared to those obtained 1 month postoperatively, but scores improved at 6 months. There were significant differences between preoperative study group scores and population norms on physical and emotional role function, social function, and for mental health domains. Significant differences persisted when population norms were compared to study group scores 6 months following surgery on all these domains except mental health. Participants identified good relations with significant others, social and leisure activities, psychological issues, and health as important for maintaining QOL. Obstacles to maintaining QOL included fatigue, pain, illness-induced limitations in life, and worries over what their new life would entail. CONCLUSION: Surgical management of rectal cancer raises concerns and profoundly impairs QOL during the first several postoperative months. © 2010 Wound, Ostomy and Continence Nurses Society.
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| 39. |
- Chotteau, Veronique, 1963-, et al.
(författare)
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Development of a fed-batch process for the production of a recombinant protein X in CHO-GS system : Case study from the cell to reactor process ready for pilot scale cultivation
- 2010
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Ingår i: Cells and Culture. - Dordrecht : Springer Science+Business Media B.V.. - 9789048134182 ; , s. 723-725
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A new cell line was created using CHO-GS system. The most promising clones were adapted to different base cultivation media leading to the selection of one medium. The fed-batch process development was performed in spinner, shake flask and bioreactor scale. It included the selection of a feed medium, the choice of the feed strategy and the optimisation of the glucose feeding. The process was then simplified by using a single feed including the feed medium and the glucose feed. Finally up-scaling parameters like aeration and CO2 stripping were studied in 3 L and 15 L bioreactors in preparation for pilot scale operation. This process proved to be robust, reproducible and suitable for large and commercial scale operation.
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| 40. |
- Domeika, Marius, et al.
(författare)
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Guidelines for the laboratory diagnosis of genital herpes in eastern European countries
- 2010
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Ingår i: Eurosurveillance. - 1560-7917. ; 15:44, s. 21-27
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Tidskriftsartikel (refereegranskat)abstract
- These guidelines aim to provide comprehensive information about sexually transmitted herpes simplex virus (HSV) infection and its laboratory diagnosis in eastern European countries. They are primarily intended for professionals testing specimens from patients at a sexual healthcare clinic but may also be helpful for community-based screening programmes. In particular, the guidelines recommend: (i) either viral culture or validated and approved nucleic acid amplification tests (NAATs) as the tests of choice for symptomatic patients, which should be promoted for laboratory confirmation of HSV infection; (ii) if culture or NAATs are not available, antigen detection - a direct immunofluorescence test or enzyme immunoassay from samples from symptomatic patients - could be employed, but HSV type determination is of importance; (iii) only type-specific serology should be used for detecting asymptomatic individuals, testing pregnant women at risk of acquiring HSV infection close to delivery, men who have sex with men and people who are HIV positive; (iv) widespread screening for HSV antibodies should be discouraged; and (v) any non-validated diagnostic tests should be validated against a recommended, approved gold standard.
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| 41. |
- Domeika, Marius, et al.
(författare)
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Guidelines for the laboratory diagnosis of trichomoniasis in East European countries
- 2010
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Ingår i: Journal of the European Academy of Dermatology and Venereology. - : Wiley. - 0926-9959 .- 1468-3083. ; 24:10, s. 1125-1134
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Forskningsöversikt (refereegranskat)abstract
- The laboratory diagnosis of sexually transmitted infections in many Eastern European countries remains suboptimal. The main objective of the present evidence-based guidelines is to provide comprehensive information regarding the laboratory diagnosis of infections caused by Trichomonas vaginalis in East European countries. In particular, the present guidelines recommend: (i) to encourage examination of the wet mounts of vaginal exudates, instead of stained smears, at all clinical settings; (ii) nucleic acid amplification tests (NAATs) or culture could be employed if no trichomonads are detected on microscopic examination of the wet preparation and there is a strong indication of infection and (iii) the use of NAATs is encouraged in screening, using non-invasive specimens, or high volume testing situations. In the absence of internationally recognized commercial NAAT systems, tests developed in-house should be validated using obtainable international standards and quality assured strictly. Individual East European countries may be required to make minor national adjustments to these guidelines as a result of lack of accessibility to some reagents or equipment, or laws in a specific country.
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| 42. |
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| 43. |
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| 44. |
- Hanssen, K. E., et al.
(författare)
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The effect of strength training volume on satellite cells, myogenic regulatory factors, and growth factors
- 2013
-
Ingår i: Scandinavian Journal of Medicine and Science in Sports. - Hoboken, USA : Wiley-Blackwell. - 0905-7188 .- 1600-0838. ; 23:6, s. 728-739
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to study the effect of training volume on activation of satellite cells. Healthy untrained men were randomly assigned into two groups. The 3L-1UB group (n = 10) performed three-set leg exercises and single-set upper body exercises, and the 1L-3UB group (n = 11) performed single-set leg exercises and three-set upper body exercises. Both groups performed three sessions (80-90 min) per week for 11 weeks. Biopsies were taken from m. vastus lateralis and m. trapezius. The number of satellite cells, satellite cells positive for myogenin and MyoD, and the number of myonuclei were counted. Homogenized muscle was analyzed for myogenin and MyoD, and extracted ribonucleic acid (RNA) was monitored for selected growth factor transcripts. Knee extensor strength increased more in the 3L-1UB group than in the 1L-3UB group (48 ± 4% vs 29 ± 4%), whereas the strength gain in shoulder press was similar in both training groups. The number of satellite cells in m. vastus lateralis increased more in the 3L-1UB group than in the 1L-3UB group. The number of myonuclei increased similarly in both groups. The messenger RNA expression of growth factors peaked after 2 weeks of training. In conclusion, increasing training volume enhanced satellite cell numbers in the leg muscle, but not in the upper body muscle.
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| 45. |
- Jensen, J., et al.
(författare)
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Localized 56Fe+ ion implantation of TiO2 using anodic porous alumina
- 2010
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Ingår i: Ion beams and nano-engineering. - : Materials Research Society. - 9781605111544 ; , s. 3-8
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Konferensbidrag (refereegranskat)abstract
- We present result following localized ion implantation of rutile titanium dioxide (TiC2) using anodic porous alumina as a mask. The implantation were performed with 100 keV 56Fe+ ions using a fluence of 1.3-1016 ions/cm2. The surface modifications where studied by means of SEM, AFM/MFM and XRD. A well-defined hexagonal pattern of modified material in the near surface structure is observed. Local examination of the implanted areas revealed no clear magnetic signal. However, a variation in mechanical and electrostatic behavior between implanted and non-implanted zones is inferred from the variation in AFM signals.
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| 46. |
- Lansåker, Pia C, et al.
(författare)
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Characterization of gold nanoparticle films : Rutherford backscattering spectroscopy, scanning electron microscopy with image analysis, and atomic force microscopy
- 2014
-
Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 4:10, s. 107101-
-
Tidskriftsartikel (refereegranskat)abstract
- Gold nanoparticle films are of interest in several branches of science and technology, and accurate sample characterization is needed but technically demanding. We prepared such films by DC magnetron sputtering and recorded their mass thickness by Rutherford backscattering spectroscopy. The geometric thickness d(g)-from the substrate to the tops of the nanoparticles-was obtained by scanning electron microscopy (SEM) combined with image analysis as well as by atomic force microscopy (AFM). The various techniques yielded an internally consistent characterization of the films. In particular, very similar results for d(g) were obtained by SEM with image analysis and by AFM.
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| 47. |
- Li, Shu-Yi, et al.
(författare)
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Bandgap widening in thermochromic Mg-doped VO2 thin films : Quantitative data based on optical absorption
- 2013
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:16, s. 161907-
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Tidskriftsartikel (refereegranskat)abstract
- Thermochromic Mg-doped VO2 films were deposited by reactive direct current magnetron sputtering onto heated glass and carbon substrates. Elemental compositions were inferred from Rutherford backscattering. Optical bandgaps were obtained from spectral transmittance and reflectance measurements-from both the film side and the back side of the samples-and ensuing determination of absorption coefficients. The bandgap of Mg-doped films was found to increase by 3.9 +/- 0.5 eV per unit of atom ratio Mg/(Mg + V) for 0 < Mg/(Mg + V) < 0.21. The presence of similar to 0.45 at. % Si enhanced the bandgap even more.
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| 48. |
- Linnarsson, Margareta K, et al.
(författare)
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Manganese in 4H-SiC
- 2010
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Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 645-648, s. 701-704
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Tidskriftsartikel (refereegranskat)abstract
- Manganese diffusion in 4H-SiC for possible spintronic applications is investigated. Ion implantation is used to introduce manganese in n-type and p-type 4H-SiC and subsequent heat treatment is performed in the temperature range of 1400 to 1800 degrees C. The depth distribution of manganese is recorded by secondary ion mass spectrometry and Rutherford backscattering spectrometry in the channeling direction is employed for characterization of crystal disorder. After the heat treatment, the crystal order is improved and a substantial rearrangement of manganese is revealed in the implanted region. However, no pronounced manganese diffusion deeper into the sample is recorded.
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| 49. |
- Moschetti, Giuseppe, 1982, et al.
(författare)
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Planar InAs/AlSb HEMTs With Ion-Implanted Isolation
- 2012
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Ingår i: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 33:4, s. 510-512
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Tidskriftsartikel (refereegranskat)abstract
- The fabrication and performance of planar InAs/AlSb high-electron-mobility transistors (HEMTs) based on ion-implantation isolation technology are reported. Ar atoms have been implanted at an energy of 100 keV and with a dose of 2 x 10(15) cm(-2) in order to induce device isolation. The InAs/AlSb HEMT exhibited a maximum drain current of 900 mA/mm, a peak transconductance of 1180 mS/mm, and an f(T)/f(max) ratio of 210 GHz/180 GHz at a low drain bias of 0.3 V. The combination of excellent stability against oxidation with the high device isolation demonstrated by the implantation technique can dramatically improve the suitability of InAs/AlSb HEMTs for high-frequency and ultralow-power MMIC applications.
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| 50. |
- Neuvonen, P. T., et al.
(författare)
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Transportation of Na and Li in hydrothermally grown ZnO
- 2010
-
Ingår i: Zinc oxide and related materials 2009. - : Materials Research Society. - 9781605111742 ; , s. 29-34
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Konferensbidrag (refereegranskat)abstract
- Secondary ion mass spectrometry has been applied to study the transportation of Na and Li in hydrothermally grown ZnO. A dose of 10 15 cm-2 of Na+ was implanted into ZnO to act as a diffusion source. A clear trap limited diffusion is observed at temperatures above 550 °C. From these profiles, an activation energy for the transport of Na of 7 ∼1.7 eV has been extracted. The prefactor for the diffusion constant and the solid solubility of Na cannot be deduced independently from the present data but their product estimated to be ∼ 3 × 1016 cm-1 s-1. A dissociation energy of ∼2.4 eV is extracted for the trapped Na. The measured Na and Li profiles show that Li and Na compete for the same traps and interact in a way that Li is depleted from Na-rich regions. This is attributed to a lower formation energy of Na-on-zinc-site than that for Li-on-zinc-site defects and the zinc vacancy is considered as a major trap for migrating Na and Li atoms. Consequently, the diffasivity of Li is difficult to extract accurately from the present data, but in its interstitial configuration Li is indeed highly mobile having a diffasivity in excess of 10-11 cm2 s-1 at 500 °C .
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