I measuring the IV characteristics of InAsP nanowires. The InAsP nanowires are deposited on Si/SiO2 substrate and Ti/Ni(10/150nm) are deposited by electron beam evaporation for metal electrode. I measure the IV characterictics using etcp-2000(ecopia thermal control probe statio) and I applied the following voltage range(-0.1 to 0.1V) and I am getting a peak current around 25mA. i know this wrong because here the resistance is around 4ohms and expect the resistance of the nanowire to be within Kohms to Mohms range.
What factors could lead to this mA value? I repeat measurement several times and get same value.
Dear rochelle,
welcome,
There are missing information to give a correct interpretation of the results. One would like to know the geometrical construction of you structure. Where are the two metallic electrodes are situated. Give a picture or drawing?
However one of the most probable causes to get lower resistance than expected is the formation of short circuit metal paths during the evaporation process. There may be some deposition on the clynderical surface of the nanowires. Or the existance of voids and pinholes through the film which will be also metallized.
I agree Mr Zekry. Before ebeam evaporation, you have to put down some kind of shadow mask, in our case, it would be PMMA, which is a lithography photoresist. After you expose it to electrons, or UV light, and develop it, the places where it was exposed would be washed away. Only then you can move on to evaporation. Without that, you are just simply evaporating on the whole thing. No wonder you will get shorted measurement result.
As mentioned before, it seems that your terminals are shortcuted. There are a couple of things that you can do to try to troubleshoot your problem
1. Prepare a sample with the metal contacts exactly with the same conditions, but this time don't put any nanowire. If you still see the signal it is obviously not coming from the nanowire
2. Increase the separation between terminals (you don't mention the separation by the way) and try to repeat the measurements in vacuum.
3. Change the substrate. If the Si underneath is conductive maybe the shortcut somehow is coming from the substrate and not the nanowire. Try using a not conductive substrate.
4. Use another measuring station and test it with a regular resistor. It is risky (you can burn your sample), but maybe you can just try a regular multimeter. Applying 0.1V it sounds to high for me, 25mA sounds too high for me for a nanowire. What about trying other ranges?
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