Determination of the carbon depth profiles of Si112Cx13Cy layers using RBS and NRRA

Si112Cx13Cy layers were prepared by successive implantation of the carbon isotopes 12C and 13C into c-Si(1 1 1). The samples were kept near RT. Ion energy was 40 keV. Ion fluences ranged from 2x1017 to 6x1017 ions/cm2. The total carbon concentration (12C and 13C) was obtained by Rutherford backscattering spectrometry (RBS) using 1.8 MeV 4He+ projectiles and a backscattering angle of 171 deg. . Its depth distribution was determined by simulating the backscattering yield of the near surface silicon part of the spectrum where the yield is reduced due to the presence of the implanted carbon. The 13C depth distributions were measured using the narrow resonance of the nuclear reaction 13C(p,γ)14N at Eres=1748 keV. The raw data of this measurement (γ-yield vs proton beam energy) and the data of the RBS simulation were converted to concentrations depth profiles of the 12C and 13C isotopes with a common depth scale by means of a new developed computer algorithm