Ion range distributions in multilayered structures: Bi in Si/Ge

Abstract
Bismuth-ion range distributions have been measured in Si/Ge multilayered structures by glancing-angle Rutherford-backscattering spectrometry. The structures were formed by ultrahigh vacuum deposition of various combinations of Si and Ge layers, with thicknesses ranging from 25 to 60 nm, and then implanted with Bi ions at energies ranging from 70 to 385 keV. The measured distributions exhibit, as expected, discontinuities at the Si/Ge interfaces and depend markedly both on the exact sequencing and thicknesses of the layers, as well as on the range-to-layer–thickness ratio. The measured distributions are compared to those calculated by a recently developed approximate method for determining such distributions, the method of equivalent atomic stopping (MEAS). The overall agreement is good and illustrates the usefulness of MEAS in predicting implant distributions in multilayers not yet studied experimentally.

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