We produced a strain-relaxed SiGe thin film on a Si substrate using the method we proposed recently: we implanted Ar ions into Si substrates and then grew 100-nm-thick Si0.8Ge0.2 at 500 degrees C by the solid source molecular beam epitaxy method followed by an annealing at 900 degrees C for 2 h. Then we observed the distribution of dislocations both in the SiGe and Si from three different crystallographic directions by transmission electron microscopy. There are threading dislocations in the SiGe layer. However, it was also revealed that a large number of dislocations were localized around the SiGe/Si interface and it can be concluded that the dislocations around the interface mainly contribute to relax the SiGe. (c) 2005 Elsevier B.V. All rights reserved.