Damage formation in Ge during Ar+ implantation at 15 K

Ar+ ions were implanted into Ge samples with (100), (110), (111) and (112) orientations at 15 K with fluences ranging from 1 × 1011 to 1 × 1014 cm−2. The Rutherford backscattering (RBS) technique in the channelling orientation was used to study the damage build-up in situ. Implantation and RBS measurements were performed without changing the target temperature. The samples were mounted on a four axis goniometer cooled by a close cycle He cryostat. The implantations were performed with the surface being tilted 7° off the ion beam direction to prevent channelling effects. After each 300 keV Ar+ implantation, RBS analysis performed with 1.4 MeV He+ ions. The damage efficiency per ion was found to be Pa =4.5 × 10−14 cm−2. There is no significant difference in the values found for the four different orientations. This, together with the high value (5 times higher than that found in Si), gives rise to the assumption of amorphous pocket formation per incident ion, i.e. direct impact amorphisation, already at low implantation fluences. At higher fluences, when collision cascades overlap, there is a growth of the already amorphised regions. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)