In case of ZnO nanowire gas sensor, gas sensing depends directly on oxygen vacancy which is closely related to aspect ratio. But what is the function of crystallinity? if my samples are well crystalline with higher aspect ratio and density, won't it give better sensing response than samples with low crystallinity and lower aspect ratio and density?
Please share your ideas briefly...
i think density and high aspect ration are most important rather than crystalline behavior.
Aspect ratio is a key factor for detecting, but the response of gas sensor is crucially dependent how fast the surface empty states is occupied. Thus crystallinity become dominant in terms of response and recovery times. if the traps on surface are not be recovered the response become worse.
Thank you dear Tekmen. However, in case of ZnO nanowires, which is better, high crystallinity or low crystallinity? can you give me some reference please...
I have not come across gas sensor studies investigating gas sensing behavior depending on crystalline structure. However you can expect that better crystalline structures give better results in terms of gas sensing behavior and repeatability. Because surface states interact similarly with gas molecules. Any imperfection from crystalline structure may results in different surface states with different binding or adsorption energy. Thus this degrades device performance.
My practical experience taught me that it is not crystallinity which is the main factor for sensing but the nano junctions play the main role. Refer yo my papers.
Agree that the specific surface area plays the main role at the sensor sensitivity. As for the crystallinity and the role of the barriers and junctions, I would say: if you have nanocrystals with the size smaller than the mean free path of electron – the barriers stop working and the material “plays as the whole thing”
The crystalline material has different planes, which determines the adsorption of gas molecules. Since every plane has some unique ending which might be metal or non-metals. This enhances the sensing response by attracting the gas molecules.
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