Crystallization of a-Ge was performed on flexible plastic substrates at temperatures as low as 130 degreesC. Copper has been primarily used as the seed of crystallization, while an external stress was applied onto the flexible substrate to enhance the crystallization. The substrates used for this study were mainly 0. 1 mm thick Polyethylene terephthalate (PET) films, which remain flexible during post treatment at low temperatures. Various samples were subject to tensile or compressive stress for the annealing step. It has been observed that only in the case of a compressive stress, crystallization becomes possible. A final electrical sheet resistance of less than 45 kOmega/square is achieved after an annealing period of 3 h. XRD, SEM and Hall mobility measurement have been exploited to study the crystallization and explain the drastic drop of electrical resistance in samples subjected to external compressive stress. The <220> peak of Ge is discernible in the XRD spectra, confirming the crystallization. Also the study of surface morphology using SEM corroborates the crystalline nature of the annealed Ge film and the evolution of cracks. A carrier mobility of more than 110 cm(2)/V s is observed for holes using Hall measurement. The shrinkage of PET during annealing induces compressive stress both in the substrate and the over-layer, in addition to the externally applied stress. This causes the progressive evolution of cracks in the Ge layer and a weak interfacial buckling of the Ge film.