Prof. Jan Fransaer/Minxian Wu
Department of materials engineering, KU Leuven, Belgium
The electrodeposition of germanium thin films is receiving a lot of attention lately, due to the importance of germanium in micro-electronics, including thin film solar cells. Due to the low overpotential for hydrogen evolution on germanium, only ultrathin germanium layers could be obtained from aqueous solutions. The current efficiency for electrodeposition from organic molecular solvents is also very low. In our research, we used ionic liquids as the electrolyte. Black germanium films can be electrodeposited from the ionic liquid [BMP][DCA] containing a new germanium compound [GeCl4(BuIm)2]. Electropolymerization of [DCA]- anions was observed on the anode during electrodeposition. The polymerization could be suppressed by adding chloride ions into the solution. We also performed electrodeposition of germanium at elevated temperatures up to 180 °C from [BMP][Tf2N] using GeCl4. Shiny grey germanium films were obtained with deposition rates as high as 6 μm/h.