| 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. |
- Hourahine, B., et al.
(författare)
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Evidence for H2* trapped by carbon impurities in silicon
- 2001
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Ingår i: Physica. B, Condensed matter. - 0921-4526 .- 1873-2135. ; 308, s. 197-201
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Tidskriftsartikel (refereegranskat)abstract
- Local mode spectroscopy and ab initio modelling are used to investigate two trigonal defects found in carbon-rich Si into which H had been in-diffused. Isotopic shifts with D and 13C are reported along with the effect of uniaxial stress. Ab initio modelling studies suggest that the two defects are two forms of the CH2* complex where one of the two hydrogen atoms lies at an anti-bonding site attached to C or Si, respectively. The two structures are nearly degenerate and possess vibrational modes in good agreement with those observed.
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| 3. |
- Linnarsson, M, et al.
(författare)
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Electronic structure of the GaAs:Mn-Ga center
- 1997
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 55, s. 6938-6944
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Tidskriftsartikel (refereegranskat)abstract
- The excitation spectrum of the O.11-eV Mn acceptor in GaAs has been thoroughly investigated by uniaxial stress and Zeeman fourier transform infrared spectroscopy. The results give strong evidence for the 3d(5) + shallow hole model for the Mn-0 center. The deformation potentials as well as the g values determined for the hole are in close agreement with those previously reported for the 1S(3/2)(Gamma(8)) State for shallow accepters in GaAs. All experimental results are in accordance with a J = 1 ground-state level derived from exchange coupling of the shallow 1S(3/2)(Gamma(8)) hole and the S = 5/2 Mn- core. A splitting between J = 2 and J = 1 levels in the range from 9 to 12 meV is inferred and is considerably larger than the 2-3 meV splitting previously suggested.
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| 4. |
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| 5. |
- Murin, L.I., et al.
(författare)
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Early stages of oxygen clustering in hydrogenated Cz-Si : IR absorption studies
- 2001
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Ingår i: Physica. B, Condensed matter. - 0921-4526 .- 1873-2135. ; 302-303, s. 180-187
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The formation kinetics of small oxygen clusters in hydrogenated Si has been studied by means of infrared absorption measurements. Hydrogen was introduced into the crystals by in-diffusion from H2 gas at 1200-1300°C. The samples were heated at temperatures in the range of 280-370°C for different durations. At initial stages of heat-treatment, enormous generation rates of the oxygen dimer have been observed in hydrogenated samples. This indicates highly enhanced diffusion of the interstitial oxygen atoms. The maximum achievable concentration of the dimers is found to be limited by their dissociation rate even at temperatures of about 300°C, while in as-grown crystals the capture processes are known to be dominant in this temperature region. An explanation of this phenomenon is presented. © 2001 Published by Elsevier Science B.V.
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| 6. |
- Hermansson, J., et al.
(författare)
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Complexes of the self-interstitial with oxygen in irradiated silicon : A new assignment of the 936 cm-1 band
- 2001
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Ingår i: Physica. B, Condensed matter. - 0921-4526 .- 1873-2135. ; 302-303, s. 188-192
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Three vibrational infrared absorption bands at about 936, 944 and 956 cm-1 appear commonly in spectra of Czochralski-grown silicon irradiated at low temperatures. All three bands have earlier been assigned to local vibrational modes related to oxygen in the complex of the silicon and the oxygen interstitials (IOi). However, it is shown that such an assignment of the 936 cm-1 band clearly is inconsistent with many facts and observations and that the band is most likely due to oxygen vibrations in the Si interstitial pair and interstitial oxygen complex, I2Oi. © 2001 Published by Elsevier Science B.V.
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| 7. |
- Ivanov, Ivan Gueorguiev, 1955-, et al.
(författare)
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Effective-mass approximation for shallow donors in uniaxial indirect band-gap crystals and application to 4H-SiC
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 73:4
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Tidskriftsartikel (refereegranskat)abstract
- The effective-mass theory is applied for description of the electronic states of shallow donors in indirect band-gap uniaxial crystals, which have three different components of the electron effective-mass tensor, and two different components of the tensor of the dielectric constant. The Hamiltonian in the resulting Schrödinger equation for the envelope function has D2h symmetry and, after proper parametrization, a nonvariational numerical method is used for its solution. Two particular cases of D∞h symmetry are identified and discussed separately. The comparison between theory and experiment for the 4H polytype of silicon carbide is revised using the least-squares method to determine the binding energies of the ground state of the most shallow nitrogen donor in this material, its valley-orbit split-off counterpart, and the mean value of the dielectric constant, and completed with calculation of the theoretical transition probabilities. In addition, the lowest-lying binding energies of the states, between which optical transitions are allowed, are calculated on a grid of values of the two parameters describing the anisotropy and the tabulated values can be used for interpolation to describe other materials. © 2006 The American Physical Society.
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| 8. |
- Ivanov, Ivan Gueorguiev, et al.
(författare)
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Effective-mass theory of shallow donors in 4H-SIC
- 2005
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Ingår i: Materials Science Forum(ISSN 0255-5476), Vols. 483-485. - : Trans Tech Publications. ; , s. 511-514
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Konferensbidrag (refereegranskat)abstract
- The one-valley effective-mass approximation is developed for the case of uniaxial crystals with indirect bandgap and applied to the donor states in 4H-SiC. Good agreement is found between the theory and experiments providing data on the electronic states of the shallowest nitrogen donor in 4H-SiC. The ionization energy of this donor is deduced to be 61.35 &PLUSMN, 0.2 meV.
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| 9. |
- Lindstrom, J.L., et al.
(författare)
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Interaction between self-interstitials and the oxygen dimer in silicon
- 2001
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Ingår i: Physica. B, Condensed matter. - 0921-4526 .- 1873-2135. ; 308-310, s. 284-289
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Tidskriftsartikel (refereegranskat)abstract
- Interactions between the oxygen dimer (O2i) and silicon self-interstitials (I) and vacancies (V) have been studied in Czochralski-grown silicon (Cz-Si) crystals using infrared absorption and deep level transient spectroscopies. The focus in this report is on reactions of O2i with I. The first step in this interaction is found to be the formation of a self-interstitial-dioxygen centre (IO2i) with oxygen-related local vibrational mode (LVM) bands at 922 and 1037 cm-1. During the second formation step, another centre, I2O2i, with LVM bands at 918 and 1034 cm-1 is suggested to appear. A Si-related band at about 545 cm-1 is also assigned to both the IO2i and I2O2i centres. The IO2i centre is found to be electrically active with an acceptor level at Ec - 0.11 eV. The both defects, IO2i and I2O2i, are stable at room temperature and anneal out at about 400 and 550 K, respectively. © 2001 Elsevier Science B.V. All rights reserved.
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| 10. |
- Markevich, VP, et al.
(författare)
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Stable hydrogen pair trapped at carbon impurities in silicon
- 2003
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Ingår i: Defect and Diffusion Forum. - 1012-0386 .- 1662-9507. ; 221-2, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Local mode spectroscopy and ab initio modeling are used to investigate two trigonal defects found in carbon rich Si into which H had been in-diffused. Isotopic shifts with D and C-13 are reported along with the effect of uniaxial stress. Ab-initio modeling studies suggest that the two defects are two forms of the CH2* complex where one of the two hydrogen atoms lies at an anti-bonding site attached to C or Si respectively. The two structures are nearly degenerate and possess vibrational modes in good agreement with those observed experimentally. The defects are energetically favorable in comparison with separated C-s and H-2 in Si and may represent aggregation sites for hydrogen.
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