$\alpha$-emission channeling investigations of the lattice location of Li in Ge

The $\alpha$-emission channeling and blocking technique is a direct method for lattice site determination of radioactive atoms in single crystals. Position-sensitive detection of emitted $\alpha$ -particles provides an efficient means of carrying out such experiments at very low doses (10$^{10}$-10$^{11}$ implanted probe atoms per spectrum). Comparison of the experimental data to Monte Carlo simulations of complete two-dimensional channeling patterns (e.g. ±2°C around <100>, <110> and <211> axes, which also includes all relevant planar directions) allows for straight-forward identification and rather accurate quantitative determination of occupied lattice sites, while at the same time the energy spectrum of emitted a particles gives information on the probe atom depth distribution. We illustrate this for the case of ion implanted $^8$Li (t_=0.8 s) in Ge, where we identify mainly tetrahedral Li at room temperature, and bond-centered Li at slightly elevated temperature.