Channeling transmission of protons through thin silicon membranes

Abstract

The emergent angular and energy distributions of 80–200 keV protons transmitted through thin (<1 μm) single-crystal silicon membranes were measured using a scanning surface barrier detector which had an energy resolution of 7 keV and an acceptance angle of less than 0.1°. Various crystal orientations, thicknesses, and membrane processing methods were examined to determine the appropriate parameters for use in masked ion beam lithography. The crystal alignment, surface disorder, and overall channeling quality of the crystal membranes were determined using proton backscattering. Membrane thickness measurements were made by determining the average energy loss of protons transmitted in a random equivalent direction and using available stopping power data. For a typical 〈100〉 oriented silicon membrane of 0.6 μm thickness, the half-width angle of the near Gaussian emergent particle distribution was 0.43° for an incident proton energy of 200 keV. The average energy loss of these particles was 10% less than for protons transmitted in random equivalent directions. Half-width angle measurements of the emergent distributions for the high-, intermediate-, and low-energy-loss components, as well as for the neutral component of the transmitted beam, are presented as functions of incident proton energy and film thickness for the major crystalline axes.