Atomic Layer Deposition of Fe₂O₃ Using Ferrocene and Ozone

Abstract

Growing interest in Fe 2 O 3 as a light harvesting layer in solar energy conversion devices stems from its unique combination of stability, nontoxicity, and exceptionally low material cost. Unfortunately, the known methods for conformally coating high aspect ratio structures with Fe 2 O 3 leave a glaring gap in the technologically relevant temperature range of 170-350 °C. Here, we elucidate a self-limiting atomic layer deposition (ALD) process for the growth of hematite, R-Fe 2 O 3 , over a moderate temperature window using ferrocene and ozone. At 200 °C, the self-limiting growth of Fe 2 O 3 is observed at rates up to 1.4 Å/cycle. Dense and robust thin films grown on both fused quartz and silicon exhibit the expected optical bandgap (2.1 eV). In situ mass spectrometric analysis reveals the evolution of two distinct cyclic reaction products during the layer-by-layer growth. The readily available and relatively high vapor pressure iron precursor is utilized to uniformly coat a high surface area template with aspect ratio ∼150.

Photoelectrochemical and Impedance Spectroscopic Investigation of Water Oxidation with “Co–Pi”-Coated Hematite Electrodes

“…The thin film hematite was prepared by atomic layer deposition (ALD), [34][35][36] and were subsequently coated with Co-Pi films by photoelectrodeposition. These thin hematite films have been shown to be a good model system for studying the limitations of water oxidation at the hematite surface.…”

Atomic Layer Deposition on Porous Materials: Problems with Conventional Approaches to Catalyst and Fuel Cell Electrode Preparation

“…One ALD study of MnO on 200-m 2 /g SiO 2 achieved an Mn loading of 0.33 wt % after five ALD cycles [32], even though the reported growth rate of 0.08 nm/cycle for the precursor that was used should have given an MnO loading nearly 100 times that value for uniform film growth [33]. In another example, 75 ALD cycles of Fe 2 O 3 on 40-m 2 /g Al 2 O 3 achieved a loading of only 1.1 wt %, which corresponds to a growth rate of only 0.0007 nm/cycle if the film grew uniformly over the surface [34,35].…”

Analysis of Optical Losses in a Photoelectrochemical Cell: A Tool for Precise Absorptance Estimation

“…[24][25][26] Hematite is an abundant, cheap, and nontoxic PEC semiconductor for water splitting [27] that has served for a long time as a model system for studying oxidation kinetics of water (four-electron process) [28] or of simpler one-electron redox couples. [29] It continues to raise interest with respect to nanostructuring but also forming pn-junctions for enlarged charge collection.…”