Why Mobility Of Thin Film Changes With Deposition Temperature

Question

A metal oxide thin film is a p-type semiconductor (say copper oxide Cu2O) due to metal vacancies in the film. This thin film can be deposited using some form of vacuum/vapor deposition.

I know that if the hall mobility increases with increasing deposition temperature, this is likely due to having larger grains when grown at higher temperatures, and hence lesser grain boundary scattering.

However I cannot seem to understand the underlying reason for the following scenarios (if they even possible):

the carrier concentration decreases with increasing deposition temperature
the hall mobility to decrease with increasing deposition temperature
the carrier concentration increases with increasing deposition temperature

Any ideas will be greatly appreciated!

DrFalcon · Answer

All of the scenarios are possible.  There are plausible reasons for each, they may not be the actual reasons but they can be tested.

If you are depositing an imperfect film (many vacancies) and you raise the temperature, you may get a better film with fewer vacancies so you would see this as a decrease in your mobile carrier concentration.  A phase change from one phase Cu2O to CuO may also be responsible.

If you increase deposition temperature you could be diffusing in species that cause enhanced scattering.  That would decrease your mobility.  You could have both 1 and 2 simultaneously, a film with fewer carriers but more scattering centers.  A phase change from one phase Cu2O to CuO may also be responsible.

An increase in carrier concentration could occur if the vacancy concentration is somehow increased (the opposite of 1).  This could occur if there is a phase change in the heating process.

This reference talks about some of the main findings by others and provides an extensive list of references:
Ho Soonmin.2016, A Review on Copper Oxide Thin Films. Int J Recent Sci Res. 7(6), pp. 11914-11918.

Why Mobility Of Thin Film Changes With Deposition Temperature

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