Correction of Ziegler's stopping powers of Al, Si and their oxides for MeVHe ions

The stopping powers of Al, Si and their oxides were measured by Rutherford backscattering (RBS) with 1.1, 1.6, 2.1 and 2.6 MeV Het beams. We prepared polycrystal Al sheets, single crystal substrates of Al2O3(0 0 0 1) and Si(0 0 1) and thermally oxidized SiO2(600 nm)/Si(0 0 1) onto which Au layers wi th thickness about 50 nm were deposited with ionized cluster beams. The sim ulated spectrum heights were best-fitted to the observed ones by varying th e correction coeffcients of the Ziegler's stopping powers S-Z(E) assuming t he validity of the Ziegler's stopping power of Au. The accuracy of our anal ysis methods is estimated to be better than 3%. The present result shows th at the stopping powers of Al agree well with the Ziegler's ones but those o f Si and O in Al2O3 significantly smaller than the Ziegler's stopping power s. The stopping powers of O in SiO2 are almost the same as those in Al2O3 i n the energy range 0.7-1.1 MeV but about 15% smaller than the Ziegler's one s. In the energy range 1.3-2.6 MeV, the stopping powers of O in SiO2 coinci de well with the Ziegler's stopping powers. This method does not need the k nowledge of the film thickness and provides a simple and powerful tool to c heck and correct the fitting formulas for stopping powers. (C) 2000 Elsevie r Science B.V. All rights reserved.