Electrodeposition of Epitaxial Magnetite Films and Ferrihydrite Nanoribbons on Single-Crystal Gold

Magnetite (Fe 3 O 4 ), ferrihydrite (Fe 10 O 14 (OH) 2 ), and iron (Fe) films were electrodeposited by cathodic deposition from an alkaline Fe(III)−triethanolamine solution. The electrodeposited phase depended on the applied potential. Magnetite films were electrodeposited from −1.01 to −1.10 V vs Ag/AgCl, whereas ferrihydrite films were deposited from −1.10 to −1.20 V vs Ag/AgCl. Iron deposition occurred at more negative potentials. The polycrystalline films were characterized using X-ray diffraction, scanning electron microscopy, and Mössbauer spectroscopy. Epitaxial magnetite films on low-index gold crystals were produced at three different potentials. X-ray diffraction analysis of the magnetite films deposited at −1.01, −1.05, and −1.10 V vs Ag/AgCl showed [111] oriented films on Au(111) and Au(001). Because of twinning of the {111} planes, the [511] orientation was present in thicker films. Magnetite grew with a [110] orientation on Au(110). At the more negative potentials of −1.10 and −1.20 V vs Ag/AgCl, ferrihydrite deposited with an (112̅0) orientation.