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The electronic energy loss of hydrogen ions (protons and deuterons) in thin supported films of LiF has been studied in backscattering geometry for specific energies from 700 eV/u to 700 keV/u, using Rutherford backscattering spectroscopy and time-of-flight low-energy ion scattering spectroscopy. For specific energies below 8 keV/u, our data confirm velocity proportionality for the stopping cross section epsilon (like in a metal) down to 3.8 keV/u, as observed previously for protons and antiprotons despite the large band gap (14 eV) of LiF. Below 3.8 keV/u, the present results indicate an apparent velocity threshold at about 0.1 a.u. for the onset of electronic stopping.

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We investigate the electron spin resonance of electrons in Si1−xGex quantum wells defined by SiGe barriers (19%–25%Ge). Adding small amounts of Ge changes both g-factor and linewidth and their anisotropy. We explain these effects in terms of the Bychkov–Rashba field that originates from one-sided modulation doping. The main effect arises from the increase in spin–orbit interaction with increasing x. We argue that these effects may be used to tune the g-factor of electrons in quantum dots for a selective spin manipulation.