研究目的
To investigate the effect of thickness on the crystallographic and optical properties of ZnS thin films deposited by electron beam evaporation technique.
研究成果
ZnS thin films with cubic structure were successfully deposited using EBE without annealing. Film crystallinity improved with thickness, while RMS roughness increased slightly. The optical band gap decreased from 3.45 eV to 3.36 eV with increasing thickness, attributed to quantum size effects and impurity levels. Refractive index and dielectric constants showed thickness-dependent variations. These findings are significant for applications in thin-film solar cells as buffer layers, offering an environmentally friendly alternative to CdS. Future studies should focus on minimizing impurities and exploring annealing effects.
研究不足
The study is limited to ZnS thin films deposited without annealing, which may affect crystallinity compared to annealed films. The presence of oxygen impurities due to potential micro-leakage in the deposition chamber could influence film properties. The range of thicknesses (350-1700 nm) and substrates (Si and glass) may not cover all possible applications. Future work could optimize deposition parameters to reduce impurities and extend to other substrates or annealing treatments.
1：Experimental Design and Method Selection:
ZnS thin films were deposited on Si (100) and glass substrates using an electron beam evaporation (EBE) system without annealing. The method was chosen for its ability to produce films with low roughness and good control over thickness.
2：Sample Selection and Data Sources:
High purity ZnS powder (
3：99%) was used as the evaporating source. Si and glass substrates were cleaned with distilled water and dried with nitrogen. Film thicknesses ranged from 350 to 1700 nm, controlled by deposition time (5-20 minutes). List of Experimental Equipment and Materials:
EBE system (Elettrorava, Italy), ZnS powder (Aldrich,
4：99%), SEM (TSCAN Vega\XMU, Czech Republic), AFM (Autoprobe CP, Park Scientific Instruments, USA), EDX, XPS spectrometer (SPECS UHV/XPS/AES), XRD (Stoe Transmission X-ray diffractometer Stadi P, Germany), Raman spectrometer (Jobin-Yvon LabRAM HR), UV-Vis spectrophotometer (Specord S100, Analytik Jena). Experimental Procedures and Operational Workflow:
Substrates were mounted in the vacuum chamber evacuated to <9×10^{-6} mbar. Electron beam was focused on the ZnS source. Deposition was performed with a target-substrate distance of 110 mm. Post-deposition, films were characterized using SEM for thickness and morphology, AFM for surface relief, EDX and XPS for composition, XRD for crystallographic properties, Raman for vibrational modes, and UV-Vis for optical transmittance.
5：Data Analysis Methods:
XRD data analyzed using Integral Breadth Analysis and Scherrer's formula for crystallite size. Optical data analyzed using envelope method for refractive index and extinction coefficient. Band gap determined from (αhν)^2 vs. hν plots.
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