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Spin-exchange of axially symmetric Mu states in polycrystalline media
Duarte, J. Piroto; Vilão, R. C.; Alberto, H. V.; Gil, J. M.; Ayres de Campos, N.http://www.sciencedirect.com/science/article/B6TVH-4V2NP2J-11/2/65b0f0e28203effcfd90613c3eeadf23
Muoniated radicals in the organic semiconductor zinc-phthalocyanine
Duarte, J. Piroto; Vilão, R. C.; Gil, J. M.; Alberto, H. V.; Ayres de Campos, N.; Weidinger, A.[mu]SR experiments were conducted on the organic semiconductor zinc-phthalocyanine (Zn-Pc) in order to identify and characterize the muon states in this material. Transverse-field experiments at 0.5 mT reveal the existence of paramagnetic muon states in Zn-Pc, with the formation probability of nearly 100%. Two different muoniated radicals were detected, with hyperfine parameters of 127 and 142 MHz; muonium is t...
Muon diffusion and trapping in chalcopyrite semiconductors
Vilão, R. C.; Gil, J. M.; Alberto, H. V.; Duarte, J. Piroto; Campos, N. Ayres de; Weidinger, A.; Yakushev, M. V.; Cox, S. F. J.The diffusion parameters of diamagnetic muons in chalcopyrites CuInSe2, CuInS2, CuInTe2, CuGaTe2 and (Ag0.25Cu0.75)InSe2 were obtained by [mu]SR methods. The variations among the different compositions were found to validate the anion-antibonding localization model. The application of a two-state model to the zero-field data revealed muon trapping by defects. The dipolar width at the trap and the number of jump...
Muon and hydrogen states in II-VI semiconductor compounds. A muSR study
Weidinger, A.; Alberto, H. V.; Gil, J. M.; Vilão, R. C.; Duarte, J. Piroto; Campos, N. Ayres deAdditional hydrogen in II-VI semiconductors may occur in two different configurations, either bound to the anion in a position along the bond direction, or at an open interstitial site surrounded by four cations. The electronic character of these states is very different: the bound hydrogen forms a donor with an extended electronic wave function, whereas the interstitial hydrogen is acceptor-like and has an alm...
Probing the shallow-donor muonium wave function in ZnO and CdS via transferred ...
Lord, J. S.; Cottrell, S. P.; King, P. J. C.; Alberto, H. V.; Ayres de Campos, N.; Gil, J. M.; Duarte, J. Piroto; Vilão, R. C.; Lichti, R. L.The assignment of muon spin rotation spectra to muonium counterparts of hydrogen shallow-donor states is reviewed in four II-VI widegap semiconductors, CdS, CdSe, CdTe and ZnO. The existence of extended electronic orbitals is argued from the muon-electron hyperfine parameters and supported by the new muon spin repolarization data for CdS and ZnO, characterizing the superhyperfine parameters on the sparse Cd and...
Powder Pattern Hyperfine Spectroscopy of Shallow- Donor Muonium Centres
Alberto, H.; Vilão, R.; Duarte, J. Piroto; Gil, J.; Campos, N. Ayres de; Lichti, R.; Davis, E.; Cottrell, S.; Cox, S.Abstract The hyperfine spectroscopy of muonium in II–VI semiconductors is reviewed, suggesting that whereas hydrogen is a deep-level defect in ZnS, ZnSe and ZnTe, it constitutes a shallow donor in ZnO, CdS, CdSe and CdTe. Shallow and deep states coexist in CdTe. Using new data for ZnO, it is shown that the principal values of the muonium hyperfine tensor may be obtained with equal facility from measurements in...
Shallow-level muonium centre in CdS
Gil, J. M.; Alberto, H. V.; Vilão, R. C.; Duarte, J. Piroto; Mendes, P. J.; Campos, N. Ayres de; Weidinger, A.; Krauser, J.; Niedermayer, Ch.A new type of muonium defect centre has been observed in undoped CdS at low temperatures (T<20Â K). The hyperfine parameters are A[short parallel]=335 (7)Â kHz and A[perpendicular]=199 (6)Â kHz (approximately 10-4 of the vacuum value) with the symmetry axis along the Cd-S bond direction. The disappearance of the centre at around 20Â K is in agreement with the binding energy of a shallow centre. The extremely we...
High-temperature trapping of muons in CuInSe2 and CuInS2
Gil, J. M.; Alberto, H. V.; Vilão, R. C.; Duarte, J. Piroto; Mendes, P. J.; Campos, N. Ayres de; Weidinger, A.; Niedermayer, Ch.; Yakushev, M. V.Zero-field [mu]SR measurements were performed at the EMU muon beamline of the ISIS facility on single crystals of p- and n-type CuInSe2 and on crystallites of p-type CuInS2.The diamagnetic centre, thought to be located in all these compounds at the Se anti-bonding interstitial site at low temperatures, is seen to diffuse above 200 K in the Se compound and above 250 K in the S compound. At 380 K the muons are ag...
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