In my experience, when you have seedlayer, buffer layer, ZnO will be easier to growth than without seed or buffer layer. I have ever growth ZnO rods, density and orient of rods will many and orthogonal

(perpendicular) with substrate.

attention that, when you treat silicon substrate, should according to my treat of my silicon substrate which presented in some my paper in researchgate.

Because there are some chemical group on silicon surface make your preparing very difficult. So you should have a suitable treat of substrate before grow ZnO nanostructure.

seed and buffer layer may be a thin film.

good luck.

@Khoi Quang Nguyen @Jiaqi Luo

Thank you for your answers.

Yes, indeed the buffer and seed layers will assist the growth of ZnO nw. I got confused with the exact term, to use in my writing. Let say, i grow ZnO nw on ZnO/Si substrate. So in this case,ZnO layer is the buffer layer, isnt it?

One more thing, can buffer or seed layer forms during the growth of ZnO? (i mean unintentionally)

For your information, my experiment is on fabrication of ZnO nw on glass substrate via thermal evaporation without seed and buffer layer. From fesem image of my sample, the buffer layer-like was formed below the ZnO nw. As we know the lattice mismatch between glass and ZnO is large,so i believe that the form of ZnO layer (either seed or buffer layer) during the growth is the main cause for the formation of well-aligned and high density ZnO nw in my work. 

Dear Dzetty ..

Thank you for sharing the questions .. in my opinion .. the term seed layer and buffer layer is just a term that researcher always used to describe their thin film layer .. in my experience .. the seed layer is referring to the catalyst layer for the upper layer especially if you are intended to grow nano structure .. this seed layer will help in the nanostructure growing .. you may detect the element of the seed layer that commonly at the tip of the nanowire when scanning using FESEM ..

Regarding the buffer layer .. in thin films .. the buffer layer is always referred as barrier layer or shield layer .. buffer layer is used to reduce defects generates between two different types of materials ..   

in your experiment , i think you should call ZnO layer is seed layer.

example you fabricate a/b/substrate. if a same b, then b is seed layer. if b different a, then b is buffer layer. pre -existing thin film is a thin films. if it same a, then it is seed. if it is a other material, then it is buffer layer.

I agree with Jiaqi Luo. A seed layer is related to a nucleation process or the beginning of an induced preferential direction growth. On the other hand, buffer layers are used to accomodate the lattice parameter between the substrate and the subsequent thin film, or to improve the adhesion. Finally, I have never read about "pre-existing thin film", but I guess that it can be related to native oxides, i.e. oxides on the surface of the substrate, such as for instance SiOx, about 2nm thick, on top of Si wafers.   

thank you so much for the answers. really helpful :)

@jose @khoi @ahmad @jiaqi

I interest...............that is fantastic