I synthesized ZnO nanowires on glass substrates without any template by thermal evaporation method (using horizontal quartz tube furnace). The source material is Zn powder and no foreign catalyst involved in this work.
A vertically well-alligned, high density of ZnO nanowires were successfully formed on the glass substrates as shown in figure below.
I proposed two growth mechanism: VS and self-catalyzed VLS mechanism since this work involved no metal catalyst.
My question is how am I suppose to explain in detail about the formation of ZnO nanowires on amorphous surface like glass (as we know glass and ZnO have large lattice mismatch). I wanted to explain how the formation of droplet (perhaps self-catalyzed droplet) will lead to the formation of nanowires structures.
Perhaps anyone have any related link or diagram for suggestion?
Thank you.
Hi, Soraya.
To the best of my knowledge, you have given a real contribution in the nanowire growth field. First time I am seeing "Single step growth of perfect vertically oriented ZnO nanowire growth".
According to me:
1. This effect has also been observed by Jeong et al using metal-vapor-deposition technique. I am attaching the paper in support. In that paper they reported the "Self-seeding" behaviour of ZnO nanoparticle upon evaporation. Please go through the PDF file care fully, you will get the growth kinetics.
2. In your case this self seeding may happen, which after some critical (appropriate) thickness, acts as the (buffer or seed layer) lattice compensation layer for the ZnO nanowire growth. As your SEM image shows the seed or layer beneath nanowire is more than 3 micron. Which is more than enough for lattice matching with ZnO nanowires. Therefore in this case the substrate effect may not be a concern. You can get the same result in any substrate of choice.
3. Please do the FESEM, AFM or TEM of these self-seeds just after the seed formation.
If you can successfully find out the growth kinetics of your single step/ direct grown ZnO nanowire on glass (by your process recipe), then I think this paper will be highly cited in future.
Wish you good luck.
@avishek Thank you so much for the kind words, explanation & paper link ..
Very useful for my writing :)
Hi,
I am so happy that someone is finally is going to solve the problem of direct growth of nanowire.
Good luck.
You might do a search using terms such as "zinc oxide field emission". If the films are slightly yellow, they would be n-conducting. From your photograph, your deposition method might provide an excellent method for making field-emitting arrays, which might be useful for anti-static discharge coatings (on space satellites, for example) or other applications. Also you might do a search under the terms "zinc oxide tetrapods" to investigate the crystal growth mechanism and morphology. See perhaps the paper by Lee and Lee et al. in Appl Phys Lett 81(19)(2002) 3648 for an example of field emitting ZnO nanowires, but many other publications also exist.
You might also check the review paper by Zhong Lin Wang, Zinc oxide nanostructures: growth, properties and applications in J. Phys. Condens. Matter 16(2004)R829-R858).
Presumably you have an ideal concentration and concentration gradient of both zinc vapor and oxygen that allows nucleation of many growth sites (presumably flat platelets of zinc oxide that must align parallel to the glass substrate without need of epitaxial fit). The concentration gradient must be such that the whiskers grow perpendicular to the substrate and into the regions of high vapor concentration. With so many nuclei, the vapor pressure between whiskers must be very low so that the nano-wires can only grow into the areas of high concentration as in dendritic growth. Probably best not to change any of your parameters as you have a near-ideal arrangement. In any case, your micrograph shows spectacular growth morphology.
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