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Contamination of silicon with copper impurities has been a longstanding problem in processing devices, which causes degradation of their performance because of the fast diffusivity and formation of deep levels in the band gap [1]. β-NMR studies with a short lived nucleus 58Cu(Iπ = 1+, T1/2 = 3.2 s) as a microscopic probe should be able to provide unique information on the mechanism of Cu diffusion and behavior of Cu-dopant complex (ex. Cu-B pair) in Si. In this report we present the first result on the β-NMR measurements of 58Cu in silicon.
A spin polarized 58Cu beam was produced through the charge exchange reaction of 58Ni with a Be target, using a 63A-MeV 58Ni beam provided by the K540 RIKEN Ring Cyclotron. The 58Cu nuclei emitted at angles in between 0.75° and 4.1° were separated by RIPS and implanted into a catcher sample of single crystalline Si (B doped) at 15 K. The β-ray yield from 58Cu was ~103 counts/s. The finite polarization of about 0.2% was observed and then the β-NMR spectrum for 58Cu in Si was obtained as shown in Fig. 1. The magnetic moment of 58Cu was determined to be (0.46 ± 0.03)μN which is in agreement with the recent results on the laser spectroscopy [2]. The spin lattice relaxation rate 1/T1 = (0.7 ± 0.6) s-1 for 58Cu in Si(B) was also obtained at 15 K. The present result has shown that the 58Cu nucleus is promising as a nuclear probe for the microscopic study of copper impurities in silicon.
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