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İf doping elements have strong affinity to form oxide clusters then their densities and distributions might play important role in the determination of the particle size of ZnO . This is due to fact that those doping oxide clusters may act as heterogeneous nucleation sites during the precipitation of the ZnO particle in sol-gel practises. Lower the number of those nucleation sites larger the size of the ZnO nano particles, which grows much longer extensions without over lapping with others simultaneously growing neighboring ZnO particles.

We have observed that phenomena very recently in our experiments during the CVD graphene formation over copper substrate having concave surface exposed to compressive prestraining (inner face of the copper tube), which had almost one order of magnitude less SiO2 clusters compared to the outer convex surface. As a result one obtains smooth inner surface having much less nucleation sites and much larger graphene patches, which even may cross over the existing copper grain boundaries during the extending CVD annealing to form the complete surface coverage.

This can have a different reason for each element. But in general, it can be said that the presence of an element in the structure of a compound such as ZnO causes a strain on the lattice and thus increases or decreases the lattice constant. By using of the Williamson-Hall method, the micro-strain on the nanostructure is analyzed.

It depends on the ionic size of the contributed Dopant species. When the smaller ionic radius of the dopant is included in the larger lattice (hOST symmetry) it just substitutes in between the host atom. On the other hand, it become larger, which affected the lattice strain field homogeneously or non-homogeneous way.

1. Arising peak shift ( caused by a change in electron scattering sites of ZnO)

2. Shifts in optical absorption

3. Increasing the crystallite size (because heterogeneous nucleation happens)

4. Enlarge in bandgap (because of impurity energy levels of the dopant. the Fermi energy levels are shifted towards the lower of the conduction band (CB).According to Burstein-Moss effect is responsible for the increase of the gap