Low-temperature Cu-induced poly-crystallization of electrodeposited germanium thin film on flexible substrate

We investigated the low-temperature Cu-induced polycrystallization (150 degrees C) of electrodeposited Ge film on a flexible substrate. For a 50 nm-electrodeposited Ge film on a flexible substrate and annealed for 1 h, a Raman shift peak due to Ge-Ge bonding at 299 cm(-1) was not observed, but a broad amorphous Ge around 270 cm(-1). However, the Ge-Ge bond peak was observed after 5 h of annealing. The crystallization speed of Ge on the flexible substrate was slower than on a quartz substrate. The FWHM value of the Raman shift with respect to electro-deposition current had a minimum value of 9.2. cm(-1) at a electrodeposited current of 80 mA. The main XRD observed peaks were Ge(111) at 27 degrees and Ge(102) at 30 degrees. The stress evaluated by Stoney's equation was about 0.5 GPa. However, the stress increased with the electrodeposition current. The stress before and after annealing of 60 mA was weaker than those in the films at a higher electrodeposition current. We propose that the electrodeposition current dependence is related to the deposition rate. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim