研究目的
Investigating the crystal structures and optical properties of iron oxide thin films deposited at various oxygen partial pressures and temperatures using pulsed laser deposition.
研究成果
The α-Fe2O3 phase exhibited the direct transition of 2.18 – 2.42 eV between O2? 2p and Fe3+ 3d. At growth pressure at 0.5 mTorr, the α-Fe2O3 phase and Fe3O4 phase also coexisted. Further systematic investigation can provide the way to tune the band gap and crystal structures of iron oxide thin films for potential energy applications.
研究不足
The formation of Fe3O4 phase was governed by non-equilibrium condition and high kinetic energy during the PLD process. Systematic and controlled experiments on the local coordinate near Fe ions and the two phases would be needed.
1：Experimental Design and Method Selection:
The iron oxide thin films were deposited on Al2O3 (0001) substrates using the PLD technique. Temperatures were calibrated using the thermocouple contacted with the substrates directly. The oxygen partial pressure was controlled from about 0.5 mTorr to 40 mTorr. Fe metal target was ablated by a KrF excimer laser with a repetition of 3 Hz and 248 nm. The laser fluence was approximately 4.0 J cm?2 at the target.
2：5 mTorr to 40 mTorr. Fe metal target was ablated by a KrF excimer laser with a repetition of 3 Hz and 248 nm. The laser fluence was approximately 0 J cm?2 at the target.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: The crystal structures of iron oxide thin films were characterized by X-ray diffractometer (XRD). The optical properties of thin films were measured by Ultraviolet-Visible (UV-vis) spectrometer.
3：List of Experimental Equipment and Materials:
KrF excimer laser (COMPex Pro, Coherent, USA), X-ray diffractometer (X'Pert-MPD, Philips, Netherlands), Ultraviolet-Visible (UV-vis) spectrometer.
4：Experimental Procedures and Operational Workflow:
The iron oxide thin films were deposited on Al2O3 (0001) substrates using the PLD technique. The oxygen partial pressure was controlled from about 0.5 mTorr to 40 mTorr. The crystal structures and optical properties were then characterized.
5：5 mTorr to 40 mTorr. The crystal structures and optical properties were then characterized.
Data Analysis Methods:
5. Data Analysis Methods: The optical bandgap, Eg, was calculated from the absorption edge of the UV spectra using Tauc equation.
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