Single-crystal Ge1-xSnx alloys (x=0.025, 0.052, and 0.078) with diamond cubic structure have been grown on Si(0 0 1) substrates by molecular beam epitaxy (MBE), using high-quality Ge thin films as buffer layers. The Ge1-xSnx alloys are nearly fully strained and have high crystalline quality without Sn surface segregation, revealed by the measurements of high resolution X-ray diffraction (HRXRD). Rutherford backscattering spectra (RBS), and transmission electron microscopy (TEM). In addition, thermal stability investigations show that the alloy with Sn composition of about 2.5% can be stable at 500 degrees C, which may enable it for device applications. (C) 2011 Elsevier B.V. All rights reserved.