With increase of concentration of the dopant in the host,...the Band Gap energy of the nanostructure is increasing..may i know the reason..
with the increase in the concentration of the dopant,..the PXRD reveals the dopant peak also..what does it mean..is PXRD peak indicates that dopant is not fit in the host or is it a impurity..or doping is not done..
I request you to do the needful...
Could you please specify what was the host material and dopant element you have used. When there are peaks in PXRD spectra correspond to the dopant element, it means that there is a portion of dopant that is not incorporated in the crystal lattice of the host and is crystallized into a separate phase. It shows that the concentration of dopant is much more than it's solubility in the host lattice. It depends on some factor like crystal structure of host and dopant, substitutional and interstitial sites in host lattice and the difference between ionic radius of host element and dopant. Generally, doping narrows the band gap by introducing localized intermediate energy levels within the band gap or by extending VB or CB regions. You might also check the VB or CB positions of the host and the Fermi level of your dopant. DFT analysis would also be helpful to study the effect of dopant on the band gap structure. It's not recommended to use high concentration of dopant, because in high concentrations they acts as recombination sites for photo-excited e-/h+ and decrease the quantum yield.
Good luck.
" With increase of concentration of the dopant in the host,...the Band Gap energy of the nanostructure is increasing..may i know the reason "
assuming that your dopant actually enters the lattice and really acts as a dopant, the apparent increase of the band gap is linked to the Burstein-Moss effect. You can very easilly find plenty of ref about that effect:
https://scholar.google.fr/scholar?hl=en&as_sdt=0%2C5&q=burstein+moss+shift&btnG=
Regarding your XRD, I do agree with Seyed Mohsen Adyani, it means that part of your doping element does not enter the lattice and leads to secondary phase. (the concentration probably exceeded the solubility limit)
Dear colleague venkatesha babu kr rathnaiah setty
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This can be partially explained using the density of states model in amorphous solids
proposed by Mott and Davis [N.F. Mott, E.A. Davis, Electronic Processes in Non-Crystalline Materials, Clarendon Press, Oxford, 1979,p. 210, and M. Dongol, M. Abou Zied, G.A. Gamal, A. EI-Denglawey, Physica B 353 (2004) 169–175].According to this model, the width of the localized states near the mobility edge depends on the degree of disorder and on the defects present in the amorphous structure. In particular, it is known that unsaturated bonds are responsible for the formation of some defects in amorphous solids. Such defects produce localized states in the band structure. The presence of a high concentration of localized states is responsible for relatively low values of the optical gap in the case of as-deposited amorphous films. In the process of your doping treatment, the unsaturated defects are gradually satisfies, producing a large number of structure bonds. The reduction of the number of unsaturated defects reduces the density of localized states in the band structure and consequently increases the optical gap, this is accompanied by XRD peak in your case.
Also the density of this dangling bonds of localized states play an important role to classify any material to amorphous, poly crystalline or crystalline material, this depends on the presence ratio of such this dangling bonds of localized states which can be easily detected by X-ray diffraction (XRD), Scanning electron microscope(SEM) and Transmission electron microscope (TEM). You can distinguish between the amorphous, poly crystalline and the crystalline materials through the aforementioned three techniques:1- XRD the produced curve of amorphous materials has a broad hump and no any sharp diffraction peaks, the presence of sharp diffraction peaks is an indication of crystalline material. 2- SEM of of amorphous material don't release any features and no particles can be distinguished otherwise crystalline material. 3- TEM of amorphous material contains a hallow (white) and no diffraction rings otherwise crystalline material. 4- The presence of spotlight is an indication of single crystals. I wish this issue is useful
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