研究目的
To fabricate UV Distributed Bragg reflectors (DBR) using porous silicon multilayers (PS-ML) through a two-step thermal oxidation process and study their optical behavior before and after oxidation.
研究成果
The thermal oxidation of PS-ML improved its optical behavior, modifying the refractive index of each layer and achieving a UV shift in the reflectance spectra. The increase in the optical band gap after oxidation suggests potential applications in UV optoelectronic devices based on silicon technology.
研究不足
The study notes the difficulty in achieving efficient reflectance response in the UV region due to increased silicon absorption at short wavelengths. The bandwidth and reflectance percent of the PS-ML decreased after oxidation, attributed to dispersion effects at short wavelengths.
1：Experimental Design and Method Selection:
The study involved the fabrication of PS-ML by electrochemical anodization of silicon wafers at room temperature, followed by a two-step thermal oxidation process to create UV-DBR. The optical behavior was analyzed through reflectance measurements.
2：Sample Selection and Data Sources:
p-type boron-doped (100) oriented crystalline silicon wafers were used. The porosity and thickness of the etched samples were measured by the gravimetric method.
3：List of Experimental Equipment and Materials:
A computer-controlled power supply (Keithley 2400) for anodization current density, HF and ethanol for the electrolyte, and an UV-vis spectrometer (Thermo Scientific Evolution 600) for reflectance measurements.
4：Experimental Procedures and Operational Workflow:
The process included electrochemical anodization of silicon wafers, followed by a two-step thermal oxidation (pre-oxidation at 350 °C and high-temperature annealing at 850 °C). Reflectance measurements were conducted before and after oxidation.
5：Data Analysis Methods:
The refractive index was calculated using the Bruggeman’s model, and the optical band gap energy was determined by the Kubelka-Munk approximation.
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