We have deposited Indium doped (1, 2, 3 vol % ) ZnO i.e IZO by reflux method. We have recorded room temperature PL spectra of undoped and IZO samples. We observed that with increase in conc of In upto 2 vol % , the peak intensity at 600 nm increases and further decreases with increase in Indium dopant (i.e 3 vol % of In).
what is the possible reason for decrease in peak intensity of 3 vo % indium doping in ZnO and also why there is non-linear variation in the band gap energy of the same.
1. At low In-concentrations, In-atoms are far apart with respect to each other and they behave as impurities. This low doping levels is illustrated by the beahvior of PL- peak intensity:
- It is well resolved confirming low In-In interactions and ,
- the peak intensity increases with increasing In-concentrations as expected for
normal low level doping.
2. At higher concentrations In incorporation becomes more and more difficult and leads to In-In interaction as well as disorder effects, In impurities are distributed inhomogeneously and these effects increase with further increasing In-concentrations.
- This is evidenced by PL-peak broadening and the decrease of peak intensity.
- This is also evidenced by energy bandgap decrease as a result of the formation of increasing band tail.
3. At much heavier In-doping levels close to solubility limit, IZO becomes totally disordered with no well defined energy band structure.
Best regards,
Dr A. Kadri
Dear Dalavi,
Concerning the second part of your question, the non-linear variation of the band gap energy with doping typically nonlinear with doping concentration. The simplest model, witch assume proportional decrease of inter-atomic distance of dopant atoms (In in your case), will result in decrease in Eg ~ N^1/3, where N is concentration of In. Of course, the real case, involve more sophisticated correlations at high doping.
The doping concentration shows different intensities because atoms are far with each other and they behave as impurities or produced In-In interaction leads to disorder effects in large concentrations.
Dhanaji Dalavi , please refere to the following article's XRD section, hope it answers your query:
Article Effect on the dielectric properties due to In–N co-doping in...
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