Anodic Electrodeposition of Germanium Films from Ethylenediamine Solutions of Deltahedral Ge-9(4-) Zintl Ions

In this work, we report studies of germanium electrodeposits galvanostatically electroplated anodically onto p-doped Si(100) wafers for three different current densities under ambient conditions. The electrodeposition is carried out in ethylenediamine solutions of K4Ge9, which contain deltahedral Ge-9(n-) (n=2, 3, 4) Zintl anions. The observed current efficiencies of the deposition are at least 2 orders of magnitude higher than those of cathodic electroplating reported. The samples were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray analysis, X-ray photoemission spectroscopy, and mass spectrometry. Their morphology is sheetlike with overlayers of aggregated particles with a median particle size of similar to 225 nm. The overlayer spread increases progressively with increasing current densities. Cross-sectional SEM measurements indicate film thicknesses in the range of 60-320 nm. Electrolytic electrodeposition carried out at 100 V for the same concentration reveals a very similar morphology with significant enhancement in thickness of up to similar to 6 mu m and median particle size of 625 nm. X-ray diffraction shows that the as-deposited samples are amorphous; however, high temperature annealing results in the crystallization of elemental germanium in the thicker samples (similar to 320 nm and similar to 6 mu m).