Focussed helium ion channeling through Si nanomembranes

Channeling of low energy (25 to 35 keV) focussed He ions transmitted through crystalline Si (001) nanomembranes (50 nm) has been observed using a He ion microscope. Planar (110) and (100) channeling was detected with critical incident angles of 1.0° at 35 keV. Beam steering of up to 2° occurs. The technique has potential for He ion diffraction and femtometer-scale detection of interstitial atoms and impurities.