Li on bond-center sites in Si

Alpha-emission channeling investigations of the lattice location of Li in Ge

“…At a first glance it may appear surprising that we identify Li on BC sites in Ge and Si [10] despite the fact that in our measurements the normalized yield along {111} planes was below unity. Since BC sites are located in the middle of the interstitial region between {111} planes, geometric arguments suggest that emitter atoms occupying these sites cause strong emission channeling effects.…”

“…1a and 1b show the normalized α-emission yield χ ex within about ±2.5ϒ around the <100> and <211> axes of the Ge crystal observed after 60 keV implantation of 8 Li at T=300 K. As indicated in the figure, the <100> axis, and the {100} and {110} planes show blocking effects while the <211> axis, and {111} and {311} planes exhibit emission channeling effects, which is clearly evidence that the majority of Li atoms occupy tetrahedral interstitial sites [10].…”

“…An important consequence of the reciprocity theorem is that direct quantitative information on the fraction of emitter atoms on distinct lattice sites can be obtained by fitting the results of Monte Carlo ion beam channeling simulations to the emission channeling and blocking data [10]. As a new approach to extracting the maximum information from our measurements, we have chosen to fit complete two-dimensional spectra, as is outlined in the following.…”

“…The α emission yield in the vicinity of major crystallographic directions is conveniently measured using a twodimensional position-sensitive Si detector. Details of our experimental setup at the ISOLDE facility [11] at CERN have been published earlier [9,10,12]. The p-Ge crystal used in the experiment was Ga-doped (0. )…”

“…[9]. We have recently applied this technique to radioactive 8 Li ions implanted into high-purity Si, and established that Li occupies tetrahedral interstitital sites after implantations in the temperature regime 50-300 K, and bond-centered sites at slightly higher implantation temperatures (T=400-475 K) [10]. The incorporation on BC sites is due to short-range diffusion of Li in Si and its capture at certain defects which could, for example, be divacancies created during implantation.…”