Low-temperature formation (similar to 150 degrees C) of Ge films on insulator is investigated for realization of advanced flexible devices. We propose utilization of Sn as catalyst to enhance the crystallization at low-temperatures. By annealing (150-200 degrees C) of a-Ge/Sn stacked structures formed on insulators, the composition distributions of Ge/Sn layers are inverted, and Sn/poly-Ge stacked structures are obtained. The results demonstrate that the crystallization occurs at 150 C, which is slightly below the eutectic temperatures. This Sn-induced crystallization technique is useful to obtain poly-Ge on low-cost flexible substrates (softening temperature: similar to 200 degrees C). (c) 2013 Elsevier B. V. All rights reserved.