For example, Si amorphous is doped with pentavalence element such as As and P.
I know that there will be charge effect contribution due to this doping (according to its Kroger Vink Eq.)
What I am not sure is what happens with the structure itself?
As we know, if it is in crystalline state it is either doped with As or P, and we can easily know that there should be changes of lattice parameter. But for amorphous state what will happen?
Dear Firman Mangasa,
If you dope Si with a pentavalent element, you will promote only the creation of defect on the structure, i.e., charge carriers will be created. The doping effect will be a substitution, replacing Si by the other element (As or P) and an extra electron for each atom added will be incorporated in the structure not changing its nature (it will remain amorphous), even if a slight variation in the network that surrounds the atom added in the place of Si exist. Addionally to that, what can happen is a change in the band gap of your compound, being shorter than that of the undoped amorphous Si.
Thanx for your reply Andre,
If I may conclude, there ll be changes in charge only, but none in structure at all. what about its free volume (empty space) and long-short order chain/link due to this dopant contribution? (w/o any heat treatment yet)
Both, free volume and structural changes depends on concentration of the dopant.. If its high enough both will definitely change.. Monitor the changes in 220 peak in XRD and peaks in 400-600 in Raman spectra
I agree with Sridhar. All this factor will depend on the concentration of the dopant. You will have also a critical point that avoid you to have more dopant in your material, if you add more dopant than expected you will change the nature and the structure of the samples may be not the same and the long, middle and short range disorder/order will be affected. So, you can monitore with other characterization tecniques like XRD and Raman as suggested by Sridhar, but you can also use Infrared and UV-vis spectroscopies and also photoluminescence.
I work with disordered and ordered samples, if interest see two of my papers and you can see the effects of the quantity of dopant in shor/long rang order in oxide samples.
Article Crystallization study of SrSnO3:Fe
The second one. I hope it helps you!
Article SrSnO3:Nd obtained by the polymeric precursor method
Amorphous state is completely a different property altogether and one can not estimate it. In your compound both the facts can be possible, either increase or decrease amorphous nature. Amorphous nature is mainly related with the synthesis condition/parameters and more precisely depend on the temperature, If the synthesis temperature during the preparation of the samples or if the samples were annealed after the preparation amorphous state will change to well defined crystalline state.
Thank you for your reply Sridhar,
Did you mean a 220 broad peak will appear on X-ray?
If it is so, that means we may say that under appropriate dopant we may change amorphous to be semi-crystalline or even crystalline?
I am sorry if it is a stupid question, I am quite new to amorphous stuff.. bear with me please :)
Thank you once again Andre, I ll take a look the references.
Thank you for your reply, Dr.Sagar,
What do you mean by can't be estimated?
In this case, every sample suffered the same treatment and keep it in amorphous structure. The difference is only the dopant content.
Could anyone give me some other characterization methods to investigate amorphous structure?
(except; SEM/TEM, and X-Ray, Raman, UV, photoluminescence as Sridhar and Andre have suggested)
Is it possible to calculate "the amount" of free volume?
Is it possible to simulate their amorphous structure?
Thank you guys..
AFM method; amorphous regions won't show the same appearance as those of crystallites.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Material Characterization