Self-ion-induced swelling of germanium

Ge substrates of (1 0 0) orientation were irradiated with 1.0 MeV Ge ions a t temperatures in the range from -180 degreesC to 500 degreesC. Pronounced swelling of the irradiated material up to 4000 Angstrom, associated with th e formation of a porous surface layer, was evident only for temperatures be tween -50 degreesC and 200 degreesC. The extent of swelling was found to be insensitive to temperature in this range and exhibited an approximately li near dose dependence for doses up to 1 x 10(17) Ge cm(-2). For temperatures outside this range, only sputtering effects were observed. The structure o f the porous surface layer was examined by transmission electron microscopy . For samples irradiated at 22 degreesC, it was shown to have a density sim ilar to 30% that of bulk Ge. These layers were further shown to be stable d uring subsequent annealing to 500 degreesC, (C) 2001 Elsevier Science B.V. All rights reserved.