I have performed PL for my ZnO sample synthesized by hydrothermal method using NaOH and HMT. The PL emission was recorded at excitation wavelength of 320 and 400nm. Both the obtained emissions are different. On looking at the graph attached, it can be seen that the UV emission and visible emission peak is only half recorded. Since i am new to analyzing a PL spectrum I have a couple of questions.
1. It is so said that emission is recorded only within the range of (lamda excitation +20)nm to upto 2(lamda excitation -20)nm. Why is that so ?
2. Should i reduce the excitation wavelength to close to 280nm for the complete spectrum?
Thank you in advance.
Generally, PL of ZnO portrays three major peaks : an UV near-band-edge emission peak around 380 nm, a green emission around 510 nm, and a red emission around 650 nm. I hope the attachment would help you in the analysis of your results.
As always, you need to think about what you want to measure and how. You can only excite a feature by illumination with sufficient energy; so the illumination energy needs to be above the bandgap of your material (ZnO: Eg~3.4eV), so the excitation wavelength should be well under 365nm. Then you need to think about your detector which will have a certain wavelength range and not the same sensitivity everywhere. Finally, you should think about artefacts due to surface reflections and perhaps some rests from educts that did not react completely to ZnO.
Previous advices are good. Though one important point is omitted there. READ THE MANUAL. Fluoromax is good machine with reach menu. Scan excitation wavelength to maximize/optimize output, change PL spectra range from default values to the range of interest.
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