研究目的
Investigating the effect of deposition conditions and further annealing treatment on microstructure and optical properties of (Si,Er)-codoped HfO2 thin films.
研究成果
The variation of RF power density allows monitoring the dopant content in (Si,Er)-codoped HfO2 films. Annealing at high temperatures results in phase separation and the formation of HfO2, SiO2, and pure silicon phases. The films demonstrate red luminescence due to carrier recombination in Si nanocrystals and enhanced rare-earth luminescence under non-resonant excitation, indicating the formation of silicon nanoclusters. The excitation mechanism of Er ions involves energy transfer from Si nanocrystals and host defects.
研究不足
The study is limited to the effects of deposition conditions and annealing treatments on the structural and optical properties of (Si,Er)-codoped HfO2 thin films. The direct observation of Si nanocrystals formation was challenging due to the overlapping of diffraction peaks from (111) Si cubic- and (-111) HfO2 monoclinic-phases in the range of 2Θ=28.4-28.8°.
1：Experimental Design and Method Selection:
The films were grown on silicon substrates by RF magnetron co-sputtering of Si and erbium oxide pellets on a HfO2 target. As-deposited and annealed samples were examined by means of spectroscopic ellipsometry, Fourier transform infrared spectroscopy and photoluminescence method.
2：Sample Selection and Data Sources:
Thin films of (Si,Er) codoped HfO2 were deposited by radio frequency (RF) magnetron sputtering on Si wafers (B-doped, (100) oriented, resistivity of 5-15 Ω·cm).
3：List of Experimental Equipment and Materials:
RF magnetron sputtering setup, spectroscopic ellipsometer (UVISEL, HORIBA Ltd., Kyoto, Japan), Fourier-transform infrared spectroscopy (FTIR) Nicolet Nexus spectrometer, photoluminescence (PL) study setup with Ar+ ion laser, SRS lock-in amplifier (SP830 DPS), Jobin Yvon 1 m single grating monochromator, Northcoast Germanium detector.
4：Experimental Procedures and Operational Workflow:
The deposition was performed in pure argon plasma. The RF power density (RFP) was either 0.48 or 0.74 W/cm2. The substrate temperature (TS) was fixed to 100, 300 or 500 °C. Total plasma pressure and substrate-cathode distance were fixed at 0.04 mbar and 57 mm, respectively. Annealing treatment was performed in a conventional horizontal furnace in pure nitrogen (99.99%).
5：48 or 74 W/cmThe substrate temperature (TS) was fixed to 100, 300 or 500 °C. Total plasma pressure and substrate-cathode distance were fixed at 04 mbar and 57 mm, respectively. Annealing treatment was performed in a conventional horizontal furnace in pure nitrogen (99%).
Data Analysis Methods:
5. Data Analysis Methods: The fitting of the ellipsometry data for all the samples revealed that as-deposited films lead to n=2.08-2.34 and α=7·103-5·104 cm-1 (both being taken at 1.95 eV).
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