研究目的
Investigating the effect of materials chemistry associated with oxygen flow ratio during deposition on structural and electrical properties of CuFeO2?x thin films prepared by RF sputtering deliberately at low oxygen percentages in sputtering gas, in attempt to provide essential guidance for the photoelectronic applications.
研究成果
Delafossite CuFeO2?x thin films with high electrical conductivity and transparency were fabricated on quartz substrate using RF sputtering deposition. The as-deposited films were amorphous and crystallized into rhombohedral 3R (R3m) delafossite structure after post annealing at 900?C for 2 h in N2 flow. The ability of controlling carrier concentration makes it possible to tailor I–V rectifying characteristics of CuFeO2 based junctions for functional photoelectronic applications.
研究不足
The practical conductivity of synthesized p-type CuFeO2 film is several orders of magnitude smaller than n-type TCOs. The electrical conductivities of delafossite CuFeO2 thin films prepared by sol–gel method were (1.62–6.37) × 10?1 S · cm?1, with carrier concentrations measured to be (1.52–8.84) × 1017 cm?3.
1：Experimental Design and Method Selection:
CuFeO2?x thin films were deposited on quartz substrates by RF sputtering with high purity CuFeO2 ceramic target at room temperature. The sputtering chamber was pumped up to 9.1 × 10?4 Pa and then the films were deposited in varied Ar/O2 gas flow ratios with total gas pressure maintained at 1 Pa. The oxygen percentage in the reactive sputtering varied from 9% to 0%. The as-deposited thin films were then post-annealed in a tube furnace at 900?C for 2 h in flowing N2 atmosphere.
2：1 × 10?4 Pa and then the films were deposited in varied Ar/O2 gas flow ratios with total gas pressure maintained at 1 Pa. The oxygen percentage in the reactive sputtering varied from 9% to 0%. The as-deposited thin films were then post-annealed in a tube furnace at 900?C for 2 h in flowing N2 atmosphere.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Quartz substrates were washed successively with acetone, ethanol and deionized water for 20 min.
3：List of Experimental Equipment and Materials:
X-ray diffractometer (XRD, Bruker D8), field emission scanning electron microscope (FE-SEM) fitted with an energy dispersive X-ray (EDX) accessory, step profiler (Dektak-IV, Bruker Corp.), UV–Vis-NIR spectrometer (UV-3600, Shimadzu), laser confocal microscopy Raman spectrometer (DXR Raman Microscope), AC field Hall measurement system (8400, Lake Shore Cryotronics, Inc.).
4：Experimental Procedures and Operational Workflow:
The crystalline structure of thin films was measured by XRD. The surface morphology and oxygen content of films were examined by FE-SEM. The thicknesses of films were determined by a step profiler. Optical transmission spectra of films were measured using a UV–Vis-NIR spectrometer. Raman spectra were obtained using a laser confocal microscopy Raman spectrometer. I–V characteristics of CuFeO2?x thin films with dot copper electrodes deposited on top of the films were measured with a typical two-probe method. Hall effects of films, with Cu point electrodes deposited by sputtering, were measured by a four-point probe method.
5：Data Analysis Methods:
The optical band gaps were estimated by Tauc’s relation. The carrier concentration and carrier mobility of thin films were determined by Hall measurement.
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