I am growing Zinc Oxide nanowires via a hydrothermal process. The devices I try to make from them are always shorted, there seems to be a lot of several micron size precipitate particles from the growth solution ontop of the nanowire array. I always turn my substrate upside down so that the precipitate falls on the back of the substrate, but it does not help much. In the attached SEM image you can see them sitting ontop of the NW array (but they are covered in polymer and Aluminum)
I have tried
1) Rinsing with DI water
2) Aggressively sonicating in DI water
3) Aggressively sonicating in Proponal
2 and 3 help some, but there are still particles and the device performance is not great. There is also some concern about the wires breaking. Is there a good way to clean these arrays?
I use a stirbar in the solution when growing, could that be an issue?
Use a diluted acid solution such HCl, or H2NO3 or H2SO4 acid to react with metal oxides or metal particles. Then remove it with water.
Did you run EDS on those large micron size precipitates to find out what actually theyr are ? Are they ZnO? or other related compound based on your starting material ?
Use dilute KOH solution, and you can add a few aluminum filings, and a few drops of HCl. Be careful, it should be very dilute, or else you will etch away all your ZnO nanowire arays in a few seconds, if the concentration is not well diluted.
K. Sreenivas
are you sure the growth conditions you are using are optimized? the SEM image does not clearly show the nanowire growth. It seems like a seeds rather then wire. Can you share a magnified image of wires without coating? What Kind of polymer are you using ? Are you sure this is precipitate from Growth and not from polymer or aluminium coating. What coater are you using? For nanowire based devices try to coat at a very very slow speed. Close to 1 nm per minute till 10 nm. after that you may increase the speed of deposition. Also do check the bottom electrode. is it reacting in solution? ITO doesn't react but copper does!
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