RANGE MEASUREMENT OF BORON ISOTOPES IN SILICON FROM 600 KEV TO 2 MEV

Ranges of boron isotopes with masses 10 and 11 were measured in silico n for implantation energies of 600 keV, 1.0, 1.5 and 2.0 MeV by use of high-energy elastic recoil detection analysis (HE-ERDA). The measured ranges were compared with TRIM and PRAL calculations. The experimenta l data show a deviation to larger depth particularly at higher energie s. The ratio of the ranges of the isotopes is always lower than theore tically predicted. The experimental results can be interpreted as foll ows: the electronic stopping, which dominates this energy regime, incr eases slower than expected. The maximum of the stopping power is shift ed towards lower energies and is lower than calculated. In the lower e nergy range the stopping power must be larger than predicted leading t o smaller ranges for energies up to 1 MeV. Our experiment is in good a greement with former range measurements of Behar et al. [Nucl. Instr. and Meth. B34 (1988) 316] who used the very reliable B-10(n, alpha)Li- 6 nuclear reaction technique (neutron depth profiling: NDP), and of Sv ensson et al. [J. Appl. Phys. 68 (1990) 731 using secondary ion mass s pectroscopy (SIMS), who both found this behavior, too.