I have observed O1s peak shifted toward lower energy after some S ion are diffused into ZnO lattice. I got a paper stating that the lower electron density on oxygen lattice site due to replacement of some lattice oxygen by sulphur is the reason behind this shift. is it a reliable explanation? if yes what is the reason of reduced electron density on oxygen site?
Oxygen vacancies induces a lower energy shift of O 1S peak. This can be because of Sulfur ions are replacing O atoms from the ZnO crystal lattice or reduction of ZnO is taking place, depending upon the synthetic route you have adopted.
Both answer from Sorcar and Li are recommended but mo simpler explanation is by adding S ions to ZnO will create a case just like solid solution from ZnO-ZnS but with small portion of the second and since optical energy gap for ZnS is smaller then absorption peaks due to the new cobination will go to a lower energy
for mor details you can read articles on the optical properties binary compound solid solutions
Dear Sanjet
The previous answers are very right, but i add to that answers, the bond length between ZnS is weaker than for ZnO, therefore the required energy to broke the bond between Zn and S is smaller than with Zn and O, therefore energy gap for ZnS smaller than in ZnO.The reason of reduced electron density on oxygen site is founded in periodic table, where you can see atomic number for S and O elements, where you will see the density of electrons around S is greater than O atom.
With best my wishes
Thanks a lot Dr. Sorcar and Dr. Line for their valuable comments. It helps me a lot.
Thank you so much Prof. Omar and Dr. Taher for you comments. But the optical energy gap of ZnS is higher than that of ZnO. 3.3 eV for ZnO and 3.6 eV for ZnS. If the bond energy between Zn and S is lower than that of Zn and O, then how S can replace O by ion exchange process?
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