Structural, Vibrational, and Optical Characterization of Anodically Electroplated Germanium Thin Films

Germanium thin films were anodically electrodeposited from ethylenediamine solutions of K4Ge9 which contain the well known Ge-9(4-) deltahedral Zintl ions. The anodes were p-doped Si(100) wafers or ITO-covered glass slides. The films were studied for their optical and structural properties by Raman spectroscopy, TEM, and luminescence measurements. The Raman spectra of the films show peaks shifted to lower frequencies compared to the same peaks in bulk germanium and indicate nanocrystalline structure for the films. This is further corroborated by the TEM observations. Laser-induced crystallization at selected areas of the films results in significant growth of the nanocrystals. The films exhibit photoluminescence in the visible light range. This has been attributed to a combination of nanocrystallinity and surface defects. Overall, the optical and structural properties of the anodically electrodeposited thin germanium films can be effectively adjusted by tuning the electrodeposition parameters. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3499609] All rights reserved.