We report on the characterization of high Sn-content (similar to 10% Sn) GeSn films grown on (001) Ge/Si substrates using reduced-pressure chemical vapor deposition. Pseudomorphic 30nm GeSn films were grown on relaxed Ge buffers, exhibit a smooth surface, and display strong photoluminescence (PL) with cavity-resonance fringes from the Ge buffer. Additional luminescence studies confirm that the measured PL originates from the GeSn film. A study on the effects of rapid thermal annealing is presented along with evidence of Sn surface segregation and formation of surface nanodots for anneals at 450 degrees C and above. Anneals at 400 degrees C for up to 500 s showed little change in PL intensity or material properties, which suggest that a critical temperature exists for post-growth thermal-processing of high Sn-content, compressively-strained GeSn films. (C) 2012 Elsevier B.V. All rights reserved.