Pulse height response of Si surface barrier detectors to 5–70 MeV heavy ions

Abstract

An extensive series of pulse height measurements have been performed in partially depleted Si surface barrier detectors, using various heavy ions (Li, B, C, O, Al and Cl), at energies between 5 and 70 MeV. After correcting for the small energy loss of the incident ions in traversing the gold surface barrier layer of the detector and for the residual nuclear stopping, the resulting pulse heights per MeV for the various heavy ions were found to be up to 2.5% larger than for the 241Am (5.486 MeV) alpha particle. This increase, although significant, is smaller than had been anticipated from an extrapolation of the earlier study of H, He and Li pulse heights by Lennard et al. [Nucl. Instr. and Meth. A248 (1986) 454, and B24/25 (1987) 1035.] A new method of analysis of pulse height data, which significantly reduces the uncertainties associated with the dead layer energy loss and nuclear stopping corrections, was used in order to determine directly the variation of the average energy for electron-hole pair creation with increasing particle stopping power in Si. The dependence of the detector energy resolution (FWHM) on the energy and atomic number of the particle has also been measured in order to provide a suitable data base for selecting the optimum ion beams for various backscattering analysis problems.