To measure the carrier concentration of conducting thin films, we generally use Hall measurement. But if the film has carrier concentration in 10^16 or 10^17 Cm-3, how can we measure it? Which technique would be more reliable? Can Hall measurement still measure it?
The carrier concentration you have mentioned is very common for many semiconductors to the order of 1016 cm-3.
Either Hall measurement or Mott-Schottky will be suitable to find it. Carrier concentration can be measured as low as 1012 - 1013 using both these methods. Metals usually possess more than 1020 cm-3.
But, Hall mobility can not be done of thin films on a conductive substrate. Therefore, electrodeposited films are rendered difficult. In this scenario, Mott-Schottky is suitable for thin films on a conductive substrate. Otherwise, Hall measurement is the most reliable method to obtain carrier concentration easily. Additionally, you will also able to find the resistivity of the material via Hall measurement, thereby mobility can be calculated. Mott-Schottky won't provide any information about resistivity.
Yes, it is possible to measure the carrier concentration using Hall measurement as per your mentioned range.
Such measurements depends on the resistance of the material under study.
The Keithley source material may help for understanding the measurement requirement related to your requirment.
http://physics.oregonstate.edu/~tatej/TateLabWiki/lib/exe/fetch.php?media=hall:keithley021711_halleffectmeasurements.pdf
As Chandan pointed out, it's still possible to do Hall measurements in the range you mentioned. As the density reduces further, data can become noisy especially due to contact resistances and you might consider using a measurement setup with a lock-in amplifier. Joule heating also increases as the sample becomes more insulating, so you need to carefully consider input current choices. Of course, make sure to have at least an order of magnitude difference in the conductivities of the film and substrate. For more insulating films, you're going to have to use more and more insulating substrates. Insulating Si is great, but can be expensive. Depending on what your thin film growth/deposition method is, you might want to use glass/quartz/sapphire substrates.
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