Depth profiles of aluminum and sodium near surfaces: Nuclear resonance method

Abstract

Depth profiles of aluminum and sodium implanted into silicon carbide, silicon and silicon dioxide have been measured by means of sharp resonances in the reactions 27Al(p,γ)28Si and 23Na(p,γ)24Mg. The absolute number of impurity atoms has been determined and compared with that indicated by charge integration during implantation. Adjacent areas of some specimens have been measured by the Cameca ion-beam mass spectrometer and the nuclear resonance method; results are compared. A depth resolution of less than 20 A has been demonstrated for Al very near the surface of SiC. Information concerning the migration of sodium in SiO2 under ion bombardment is presented. Depth profiles are extracted from gamma-ray yield curves taking into account the beam energy distribution, the resonance shape, the average proton energy loss in the sample and the energy loss straggling.