HI,

With these two articles you should be okay to resolve your question. Hope this helps.

Article ZnO: Growth, doping & processing

Article Epitaxial growth of ZnO films

MBE can be used for layer-by-layer growth with superior deposition control of the purity and crystalline quality of the resulting film. On the other hand it seems that sputtering can be a bit harder to control. " This relationship can be simply explained by assuming that an optimum exists for the kinetic energy of the species reaching the surface of the growing film. Too low an energy does not allow the surface diffusion of these species and thus precludes the formation of high quality crystalline films. On the other hand, too high an energy leads to surface sputtering and the creation of defects in the growing film."

Thank you, John, for your reply but in both papers, the author does not discuss saturation velocity.

HI,

As saturation velocity is more a material property, you are asking for the possible difference of saturation velocity for a material created by MBE and sputtering. The saturation velocity is influenced by the electric field. You can find the term saturation velocity is used sometimes and other times I am finding drift velocity.

http://blogs.cimav.edu.mx/daniel.glossman/data/files/Francisco_C/Zinc%20Oxide%20Bulk,%20Thin%20Films%20and%20Nanostructures.pdf (Figure 11.2).

In an article for the "Derive An Expression For Drift Velocity Of Free Electrons"

https://www.urbanpro.com/iit-jee/-derive-an-expression-for-drift-velocity

You find the drift velocity as a function of m = mass of election, e = charge, E = electric field and relation time. The literature says that the saturation velocity is impacted by the electric field which can be varied. The focus of the first article above reports on the electron saturation-velocities of semiconductors and ZnO as a function of electric field. Now the electron mobility and holes impact the saturation velocity.

I don't think it is clear to say that MBE verse sputtering is the right problem to be focused. Assuming the same film thickness from MBE and sputtering the ZnO film saturation velocity will be impacted based on factors like the electron mobility behavior of a material is more impacted by doping than by method of deposition of ZnO. Temperature also impacts electron mobility and velocity as mobility drops with increasing temperature overall: Article Recent Advances in ZnO Materials and Devices

The saturation velocity has been considered more about the property of a material. If you have statistically significant data that either says that MBE or sputtering impact saturation velocity then please publish that.

Thinking about uniformity, as I stated the first post MBE has superior control for layer-by-layer deposition while sputtering is harder to control. Sputtering can produce films that are nanostructured without grain boundaries exhibiting locally

epitaxial nanoregions of film growth layer-by-layer. If you agree then MBE should have more film continuity and sputtered will have a quasi-continuity. This small difference might then inherently have some minor mobility resistance due the nano-regional depositional zones of continuity. I am not sure I would say this is a big enough difference to make a statistically significant saturation velocity. I hope this helps you in your thought process. But as I forgot to address the sat. vel... I owed it to you to give a good faith response. Good luck!

Saturation velocity is the maximum velocity a charge carrier in a semiconductor, generally an electron, attains in the presence of very high electric fields (wikipedia). It is related with drift velocity.