Measuring the stopping power for alpha particles channeled in InP

The ratio of channeled to nonchanneled stopping powers for He ions in InP has been measured by RBS on a strained layer of InAs under a cap layer of InP. The average ratio for 2.5 MeV ions in the left angle 110 right angle channel is 0.51 ± 0.02 while it is 0.72 ± 0.02 in the left angle 111 right angle channel. The stopping power is very sensitive to the alignment of the beam with the crystal axis; a deviation as small as 0.05 produces a measurable change in stopping power. (orig.)