| 1. |
- Bruzzi, M, et al.
(författare)
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Radiation-hard semiconductor detectors for SuperLHC
- 2005
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 541:1-2, s. 189-201
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Tidskriftsartikel (refereegranskat)abstract
- An option of increasing the luminosity of the Large Hadron Collider (LHC) at CERN to 1035 cm-2 s-1 has been envisaged to extend the physics reach of the machine. An efficient tracking down to a few centimetres from the interaction point will be required to exploit the physics potential of the upgraded LHC. As a consequence, the semiconductor detectors close to the interaction region will receive severe doses of fast hadron irradiation and the inner tracker detectors will need to survive fast hadron fluences of up to above 1016cm-2. The CERN-RD50 project "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" has been established in 2002 to explore detector materials and technologies that will allow to operate devices up to, or beyond, this limit. The strategies followed by RD50 to enhance the radiation tolerance include the development of new or defect engineered detector materials (SiC, GaN, Czochralski and epitaxial silicon, oxygen enriched Float Zone silicon), the improvement of present detector designs and the understanding of the microscopic defects causing the degradation of the irradiated detectors. The latest advancements within the RD50 collaboration on radiation hard semiconductor detectors will be reviewed and discussed in this work.
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| 2. |
- Khirunenko, L.I., et al.
(författare)
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Complexes of self-interstitials with oxygen atoms in germanium
- 2008
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 11:5, s. 344-347
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Tidskriftsartikel (refereegranskat)abstract
- Interactions of germanium self-interstitials with interstitial oxygen atoms in Ge crystals have been studied by combining experimental and theoretical methods. Self-interstitials were created in oxygen-rich Ge crystals by irradiation with MeV electrons at 80 K, and I-O-related complexes were studied by means of infrared absorption spectroscopy, while the density functional theory was used to model structures, local vibrational modes and electronic properties of IO and I2O centers. It is argued that two absorption lines at 674 and 602 cm-1, which develop upon annealing of irradiated Ge:O crystals in the temperature range 180-220 K, are related to IO complexes, while another set of bands at 713 and 803 cm-1 is related to I2O. Those assignments are supported by the comparison with the calculated local vibrational modes of the defects.
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| 3. |
- Litvinov, V V, et al.
(författare)
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Calibration factor for determination of interstitial oxygen concentration in germanium by infrared absorption
- 2005
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Ingår i: Solid State Phenomena. - 1012-0394. ; 108-109, s. 735-740
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Tidskriftsartikel (refereegranskat)abstract
- Intensities of infrared absorption due to asymmetric stretching vibrations of interstitial oxygen atoms in Ge crystals enriched with O-16 and O-18 isotopes have been compared with oxygen concentrations determined by means of secondary ion mass spectrometry (SIMS). For Ge samples with oxygen content less than 510(17) cm(-3) a good correlation has been found between the values of oxygen concentration and values of absorption coefficient in maximum of the absorption band at 855.6 cm(-1) with a proportionality coefficient C-O = 0.95 10(17) cm(-2). It is argued that kinetics of oxygen-related thermal double donor formation and oxygen loss upon heat-treatments of Ge crystals at 350 degrees C cannot be described properly with the application of calibration coefficient C-O 510(16) cm(-2), which is widely used for the determination of oxygen concentration in Ge crystals.
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| 4. |
- Litvinov, V. V., et al.
(författare)
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Determination of interstitial oxygen concentration in germanium by infrared absorption
- 2006
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Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 100:3
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Tidskriftsartikel (refereegranskat)abstract
- The intensities of infrared absorption due to the asymmetric stretching vibrations of interstitial oxygen atoms in Ge crystals enriched with O-16 and O-18 isotopes have been compared with oxygen concentrations determined by means of secondary ion mass spectrometry. For Ge samples with oxygen content less than 5 x 10(17) cm(-3), a good correlation has been found between the values of oxygen concentration and the values of the absorption coefficient at the maximum of the O-16(i) related absorption band at 855.6 cm(-1) with a proportionality coefficient C-O = 1.05 x 10(17) cm(-2). (c) 2006 American Institute of Physics.
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| 5. |
- Litvinov, V V, et al.
(författare)
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Oxygen loss and thermal double donor formation in germanium
- 2006
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Ingår i: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001. ; 9:4-5, s. 619-624
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Tidskriftsartikel (refereegranskat)abstract
- Kinetics of interstitial oxygen loss and oxygen-related thermal double donor (TDD) generation upon heat treatments of Ge:O crystals at 350 degrees C have been studied. The TDD concentration (N-TDD) was derived from Hall effect measurements in the temperature range 77-400 K. The bistability of the first TDD species was taken into account. The interstitial oxygen concentration ([O-i]) in the crystals was determined from measurements of the intensity of the infrared absorption band at 855 cm(-1) at room temperature with the use of a recently obtained calibration coefficient Co = 1.05 x 10(17) cm(-2). From an analysis of the [O-i](t) and N-TDD(t) kinetics a confirmation of recent suggestions about faster diffusivity of small oxygen clusters compared to the diffusivity of single interstitial oxygen atoms was obtained. Average numbers (N) of oxygen atoms lost per TDD species created, N = Delta[O-i]/N-TDD, were calculated at different stages of the TDD generation. The obtained values of N are consistent with those expected in accordance with the recent models of the TDD structure. In particular, an average number of oxygen atoms per TDD species was about 5 at initial stages of the heat treatment when the first members (the TDD2 and TDD3 species) of the TDD family were dominant. N was found to be about 10 after extended anneals at 350 degrees C when the TDD6 and TDD7 species were dominant.
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| 6. |
- Klimkiewicz, A., et al.
(författare)
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Pygmy Dipole Strength in Exotic Nuclei and the Equation of State
- 2009
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Ingår i: AIP Conference Proceedings. - 1551-7616 .- 0094-243X. ; 1165, s. 181-184 461
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Konferensbidrag (refereegranskat)abstract
- A concentration of dipole strength at energies below the giant dipole resonance was observed in neutron-rich nuclei around Sn-132 in an experiment using the FRS-LAND setup. This so-called "pygmy" dipole strength can be related to the parameters of the symmetry energy and to the neutron skin thickness on the grounds of a relativistic quasiparticle random-phase approximation. Using this ansatz and the experimental findings for Sn-130 and 132 Sri, we derive a value of the symmetry energy pressure of (p) over bar (0) = 2.2 +/- 0.5 MeV/fm(3). Neutron skin thicknesses of R-n-R-p = 0.23 +/- 0.03 fm and 0.24 +/- 0.03 fm for Sn-130 and Sn-132, respectively, have been determined. Preliminary results on Ni-68 from a similar experiment using an improved setup indicate an enhanced cross section at low energies, while the results for Ni-58 are in accordance with results from photoabsorption measurements.
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