Channeling and random equivalent depth distributions of 150 keV Li, Be, and B implanted in Si

Atomic depth distributions for the low atomic number ions 73Li, 94Be, and 115B implanted into channeled and random equivalent orientations in crystalline silicon have been studied. The atomic depth distributions were obtained by secondary ion mass spectrometry measurements on samples implanted to fluences low enough to preserve the integrity of the channeling components. All implants were performed at 150 keV into the <100> and <110> directions and into the (111) random equivalent orientation of float-zoned (low-oxygen) silicon crystals. The results show that in the three orientations studied the ion ranges decrease with increasing atomic number Z1. This is indicative of the strong increase in electronic stopping S/sub e/ for the Z1=3, 4, 5 sequence. The increase in ion penetration in the channeling orientation is greater with decreasing Z1 in the lower electronic stopping <110> channel than in the higher electronic stopping <100>. Values of S/sub e/ determined for channeled Li and Be at an ion velocity of 1.5 x 108 cm/s are in agreement with published calculations and the S/sub e/ for B is consistent with experimental measurements