I have bombarded Si surface by different energetic ion beam and measured Pl. I got a peak for bombarded Si surface whereas for pristine Si no peak is observed. Now from this peak what information can I get? Can I get band gap, defect, plasmon energy loss or anything else and if so then how (procedure to extract from that peak)? Thank you in advance.
Dear Dipak,
unless you are not alloying the Si with the ion beam, the band gap of crystalline Si shoud not change. However, if the ion beam energy is so high that you can amorphize the Si, then the band gap will change. Crystalline Si has a indirect band gap of 1.1 eV and amorphous of 1.7 eV.
So, by checking your peak energy you will know which phase of Si you have and, hence, which band gap value. Then, you can still determine the difference between your peak energy the band gap, which gives you an idea of the energy of the observed defect level.
Maybe you create different kind of defects and defect densities depending on your bombardment energy.
Have look here for some more ideas:
Article Impurity enhancement of the 1.54‐μm Er3+ luminescence in silicon
Hope that will help a bit.
Thanks Dr. Torsten Schwarz . Does the PL intensity depend on the excitation wavelength? I mean I excite the surface by 300nm and 400 nm will I get different peak? How to choose the excitation wavelength?
The intensity should not depend on the excitation wavelength since you don't have sub band gap excitation, i.e. the excitation energy in your case is not smaller than the band gap of Si.
So, the excitation energy should be larger than the band gap if you want to get emission of all possible transitions. However, if you want to excite or suppress certain transitions, you should use accordingly an excitation energy which is just above or below, respectively, your desired transition energy.
Pristine Si have indirect band gap, that's why you do not have any PL coming out of pristine Si. Where as when you bombard Si, it may result in various defects or formation of nano structured Si, which may show PL due quantum confinement.
Dear Harsh Gupta, Thank you for your reply. But, what type of information from PL peak could we get?
From PL you can also get the information about defects in the sample. The NBE comes from the free exciton emmision but the DLE (deep level emission) contains the information about defects.
Good luck!
The photo luminescence peak observed in an irradiated sample is mainly due to generation of defects. You have to find out what kind of defect are being generated in the sample. It may be due to trapping of electron or hole in the lattice. Vacancies will also be created.
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