Channeling effects on positron transmission through thin crystals

We present results of low-energy positron-channeling studies in Si(100) crystals at incident energies of 10--50 keV. Strong channeling effects are observed for 50-keV positrons in several axes and planes of the submicrometer single crystals. The traditionally shaped channeling dips observed for the 〈100〉 axial case have (for most of the energy range studied) minimum yields that are consistent with extrapolations from previously reported high-energy proton studies of silicon and half-widths that are consistent with classical predictions. At this energy, variations in electron scattering with incident angle are known to be associated with diffraction phenomena. Multiple scattering of the low-energy positrons prohibits the observation of fine structure that is expected from diffraction effects.