Range-Energy Relation for Low-Energy Alpha Particles in Si, Ge, and InSb

The range-energy relations for alpha particles in Ge, Si, InSb, Al, Cu, Ag, and Au were determined by measuring the air equivalents of thin foils of the materials. The incident alpha particles had energies between 0.7 Mev and 4.45 Mev, which were obtained from a Po²¹⁰ source with air as a variable absorber. A CsI(Tl) crystal was employed as the detector and the pulse-height distributions of the alpha particles were observed with a 20-channel pulse-height analyzer. Approximate analytical expressions for the ranges in microns in Si, Ge, and InSb for alpha-particle energies above 0.5 Mev are: RSi=2.13E1.45+2.20, RGe=1.95E1.34+1.72, and RInSb=2.08E1.30+1.65. The ranges for the semiconductors interpolate smoothly between those of the metals, which are in good agreement with available data.