研究目的
To grow a large size CdS bulk single crystal with high infrared transmittance using physical vapor transport and characterize its structural, electrical, and optical properties.
研究成果
A large size CdS single crystal with good structural quality and high infrared transmittance was successfully grown. The crystal shows consistent structure but varying electrical properties between top and bottom parts due to growth conditions. It is suitable for infrared window applications, with transmittance exceeding 70% in the 2.5-4.5 μm range. The absorption mechanism is attributed to free carrier absorption, influenced by carrier concentration differences.
研究不足
The study is limited to CdS single crystals grown by PVT; other growth methods or materials were not explored. The crystal size and properties may vary with different conditions, and the analysis focuses on infrared range without extensive comparison to other wavelengths or materials.
1：Experimental Design and Method Selection:
The CdS single crystal was grown using the physical vapor transport (PVT) method with two different growth conditions to vary properties from top to bottom. X-ray diffraction (XRD) was used for structural analysis, Hall measurements for electrical properties, and Fourier transform infrared spectroscopy for optical transmittance.
2：Sample Selection and Data Sources:
High purity (99.9999%) CdS powder was used as raw material. The grown crystal was divided into top and bottom parts for measurements.
3：9999%) CdS powder was used as raw material. The grown crystal was divided into top and bottom parts for measurements.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Quartz tubes, sapphire wafer, electric furnace with five growth zones, X-ray diffractometer with Cu Kα radiation, Hall measurement system, VERTEX 70 Fourier transform infrared spectrometer.
4：Experimental Procedures and Operational Workflow:
CdS powder was placed in a quartz tube with a sapphire wafer, heated in an electric furnace for 48 hours to form a polycrystal source, then used with a seed crystal to grow the single crystal over seven days. The crystal was cut into wafers, polished, and measured for XRD, Hall properties, and transmittance.
5：Data Analysis Methods:
XRD rocking curve FWHM for structural quality, Hall measurements for resistivity, mobility, and carrier concentration, and transmittance data used to calculate absorption coefficient using formulas involving refractive index and sample thickness.
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