研究目的
To investigate the magnetic properties of cobalt selenide (CoSe) and nickel selenide (NiSe) thin films and their heterostructure, examining how reduction from bulk to 2D films influences magnetic activity, with a focus on potential ferromagnetism.
研究成果
Thin films of CoSe and NiSe grown via ALD exhibit paramagnetic behavior with no evidence of ferromagnetism. CoSe shows a higher magnetic moment than NiSe. The ability to grow crystalline films without exfoliation is promising for device applications, but magnetic properties remain paramagnetic under the conditions tested.
研究不足
The films are polycrystalline, which may affect magnetic properties. No definitive ferromagnetism was observed, and the study is limited to the temperature range of 1.8 K to 300 K. Further DFT modeling and heterostructure analysis are in progress.
1：Experimental Design and Method Selection:
The study employed atomic layer deposition (ALD) for growing uniform, few-layer-thick films of CoSe and NiSe on silicon substrates with silicon oxide coating. Magnetic properties were characterized using a superconducting quantum interference device (SQuID).
2：Sample Selection and Data Sources:
Samples were grown on p-type Si wafers coated with 320 nm thermal silicon oxide. Films were cleaved to sizes from 5 mm2 to 1 cm2 for characterization.
3：List of Experimental Equipment and Materials:
ALD reactor (Microchemistry F-120), X-ray diffractometer (Rigaku Ultima IV), XPS system (ulvac Phi 5000 VersaProbe II), SQuID magnetometer. Precursors included nickel(II) acetylacetonate, H2Se (8% in N2), cobalt(II) acetylacetonate.
4：Experimental Procedures and Operational Workflow:
Films were grown via ALD with specific pulse sequences and temperatures (e.g., NiSe at 390°C, CoSe at various temperatures). Characterization involved XRD for crystal structure, XPS for composition, and SQuID for magnetic measurements with field sweeps from +70000 Oe to -70000 Oe at temperatures from 1.8 K to 300 K.
5：8 K to 300 K.
Data Analysis Methods:
5. Data Analysis Methods: XRD data analyzed with Rietveld refinement in WinPLOTR and indexing in DICVOL. XPS data processed with background subtraction and peak fitting. Magnetic data analyzed by subtracting substrate diamagnetism and checking for paramagnetic behavior using Curie's law.
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