Electrodeposition of germanium at elevated temperatures and pressures from ionic liquids

The electrodeposition of germanium at elevated temperatures up to 180 °C and pressures was studied from the ionic liquids 1-butyl-1-methylpyrrolidinium dicyanamide and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide containing [GeCl4(BuIm)2] (where BuIm = 1-butylimidazole) or GeCl4. Cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), rotating ring-disk electrode (RRDE), scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and Auger electron spectroscopy (AES) were used to investigate the electrochemical behavior and the properties of the electrodeposited germanium. Electrodeposition at elevated temperatures leads to higher deposition rates due to: (1) increase in the diffusion rate of the electroactive germanium compounds; (2) faster electrochemical kinetics in the electrolyte; and (3) higher electrical conductivity of the electrodeposited germanium film. Moreover, the morphology of the germanium film is also of a better quality at higher electrodeposition temperatures due to an increase in adatom mobility.