Emission channeling studies in semiconductors

Emission Channeling with Short-Lived Isotopes (EC-SLI) at CERN's ISOLDE Facility

“…The 111 In isotope used for the studies was commercially available and could therefore be bought and introduced into the samples at the home laboratory by means of an ion implanter. However, in order to make the method more versatile, access to a wider range of radioactive isotopes was needed, and in 1985 the group therefore began to conduct experiments at the ISOLDE on-line isotope separator facility at CERN [1][2][3][4][5]16]. At ISOLDE, currently more than 800 different radioisotopes of 60−70 chemical elements can be produced by nuclear reactions and are available as 30−60 keV ion beams, which is a very suitable energy range for implantation of emission channeling probes.…”

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“…The MANYBEAM code was found to accurately describe electron emission channeling effects in a variety of cases [1][2][3][4], provided of course that a sufficient number of Fourier components, which increases with electron energy and nuclear charge of the crystal atoms, were considered. For instance, in order to calculate the yields from 150 keV electrons in Si within a convergence precision better than 0.5%, at least "16-beam" simulations are needed, i.e.…”

“…1. The detectors consist of 30×30 mm 2 Si wafers of 0.3 mm, 0.5 mm or 1 mm thickness, which are segmented on one side into 22×22 pads, each of 1.3×1.3 mm 2 . The 484 pads are coupled to 4 very-large-scale-integrated (VLSI) preamplifier chips of 128 channels each, which are read out by a digital signal processor (DSP) via an analog to digital converter (ADC) capable of a maximum sampling frequency of 1 MHz.…”

“…This nucleus decays into an excited state of 8 Be, which immediately breaks up into two α particles with energies around 1.6 MeV. Position-sensitive detectors for MeV α particles were already available, and allowed studies of the lattice sites of 8 Li in all of the semiconductors mentioned above, as a function of implantation temperature and, often also, for different types of doping [1,2,5,8,9,[12][13][14]. As a general feature it was found that following implantation at low temperatures Li preferred tetrahedral interstitial sites, while high-temperature implantation lead to the occupancy of substitutional sites in the III-V and II-VI semiconductors, and to bond-centered, substitutional or random sites in Si and Ge.…”

“…determining the lattice location of impurity atoms in single crystals by means of channeling and blocking of charged particles emitted in nuclear decay, is a well-established technique among the various nuclear solid state methods at CERN's on-line isotope separator facility ISOLDE. It has been reviewed several times in the past [1][2][3][4][5]. Rather than discussing general aspects of the technique this paper focuses mainly on recent new developments and the current status of the research on the lattice locations of rare earth and transition metal atoms in semiconductors.…”