研究目的
To investigate how focused ion beam (FIB) preparation of transmission electron microscopy (TEM) lamellae in kesterite solar cells can lead to artifacts, specifically voids, due to the presence of ZnSe secondary phases.
研究成果
The study identifies two types of voids in TEM lamellae: natural voids and artifacts from FIB preparation. The latter are linked to ZnSe secondary phases, which are preferentially sputtered during FIB milling. This can lead to misinterpretations in STEM analyses, emphasizing the need for complementary characterization methods and careful FIB protocol documentation.
研究不足
The findings might not be universal for all kesterites due to factors like grain boundaries, secondary phases, and sample conditions. The FIB preparation can introduce artifacts, and complex analyses are needed to fully understand the effects. Alternative preparation methods (e.g., cryo steps or rocking approaches) might mitigate issues but were not extensively explored.
1：Experimental Design and Method Selection:
The study uses a combination of scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), Raman scattering spectroscopy, and sputtering simulations to analyze CZTSe solar cell samples. The rationale is to identify and understand artifacts introduced during FIB sample preparation.
2：Sample Selection and Data Sources:
Solar cells were fabricated on soda lime glass substrates with a specific structure (SLG/SiO2/Mo/CZTSe/CdS/i-ZnO/ZnO:Al). Samples included one with a power conversion efficiency of 5.3% and an optimized sample with reduced secondary phases.
3：3% and an optimized sample with reduced secondary phases.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment includes an FEI Titan ChemiThemis 80–200 kV Cs-probe corrected transmission electron microscope, an FEI Dual-Beam Helios 450 S FIB system, a NovaNanoSEM 650 SEM system, a Jobin-Yvon LabRaman HR800 spectrometer, and Stopping and Range of Ions in Matter software for simulations. Materials include CZTSe absorbers, Mo back contact, CdS buffer layer, ZnO layers, carbon and Pt protective layers.
4：Experimental Procedures and Operational Workflow:
TEM lamellae were prepared using FIB lift-out technique with Ga+ ion milling at various acceleration voltages (30, 15, 2, 1 kV). SEM and Raman spectroscopy were performed on cross-sections and surfaces. Sputtering simulations were conducted to compare sputtering yields.
5：Data Analysis Methods:
EDS mapping for elemental analysis, HAADF and BF imaging for morphology, Raman spectra for phase identification, and simulation data for sputtering efficiency comparisons.
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