Adding some dopants may be useful but why it works? I have studied lots of papers but i did not find good discussions.
It depends on bulk or nanostructures, surface to volume ratio. It could be achieved varying dopant concentration and it is achieved using proper deposition tecniques.Therefore Chemical spray pyrolysis is beneficial and advantageous.
The ZnO gas sensor's signal comes from O-depletion (when reacting with the analyst). Hence the variations in resistance.
Unfortunately these sensors are highly affected by changes in ambient humitidy that overlay the signal desired.
I know of a single sensor based on ZnO and claiming room-temperature operation. And I know it's "performance" :(
This is why I recommend to raise the temperature to at least 120 °C - to get rid of effects of ambient humidity as well as changes in ambient temperature. YES - in principle you should be able to correct these influences. But especially when it comes to humidity it is far better to avoid it than to try to correct the effects.
Regards
In case of operating at room temperature, ZnO nano rods or nano wires can be suitable for the sensor. Nano structures can increase the selectivity and sensitivity of the device to sense target gas.
Sensitivity and Selectivity depends on nature of target gas also, whether it is reducing or oxidizing gas. How the nano rods formed vertical or horizontal predicts surface to volume ratio and current flow path. Its' nanostructures surface morphology enhances sensing layer ability and can increase the sensitivity.
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