How to measure band of semiconductor using uv spectroscopy
To measure the bandgap of a semiconductor using UV spectroscopy, you can follow these steps:
1. Set up the UV spectrophotometer: Ensure that the spectrophotometer is calibrated and in good working condition. Adjust the wavelength range to cover the UV region (typically around 200-400 nm).
2. Prepare the semiconductor sample: Clean the semiconductor sample to remove any impurities or contaminants that may interfere with the measurement. Cut the sample into a small, thin, and uniform shape to allow light to pass through it easily.
3. Mount the sample: Place the semiconductor sample onto a sample holder or mount it within a sample cell that fits into the UV spectrophotometer. Ensure that the sample is positioned securely and the surface of interest is exposed to the incident light.
4. Baseline measurement: Perform a baseline measurement by taking the spectrum of the reference material (typically an optically transparent material, such as glass or quartz) that matches the sample holder or cell. This establishes a reference for the background absorption.
5. Measure the sample: Replace the reference material with the semiconductor sample and obtain the absorption spectrum of the sample in the UV region. Ensure that the incident light passes through the sample perpendicularly to minimize any scattering effects.
6. Analyze the spectrum: Examine the absorption spectrum of the semiconductor sample. Look for a sharp increase in absorption (indicative of the band edge) near the UV region. The wavelength corresponding to this increase represents the bandgap energy. Plot absorption vs. wavelength, and determine the energy difference between the absorption onset and the baseline.
7. Calculate the bandgap energy: Use the following formula to calculate the bandgap energy of the semiconductor based on the measured wavelength: E = hc/λ, where E is the bandgap energy in eV, h is Planck's constant (6.626 x 10^-34 J.s), c is the speed of light (2.998 x 10^8 m/s), and λ is the measured wavelength.
Note: UV spectroscopy provides an approximate measurement of the bandgap energy, as other factors like impurities, defects, and lattice strain can influence the absorption peaks. Additional methods such as photoluminescence or conductivity measurements can be used to verify the bandgap energy.