I would like to ask your opinion about hysteres on ZnO nanowires samples; in particular sweeping applied voltages from negative to positive values and then coming back again the measured current do not follow the same values coming back with the voltages. Could you suggest solutions in order to reduce this effect? There is some author that talk on this effect in some work?
Thanks
I am just wondering if you are charging defects or ionizing dopants in the first sweep. Then different NWs should give you different hysteresis.
As a matter of interest do the IV curves (or lines) look symmetric to you for positive and negative bias?
I agree with Vitalie, change the time delay and maybe also disconnect the voltage source between measurements.
First thing to check are the contacts. Having ohmic contacts is very important to be sure you are actually characterizing the nanowire an is not an artifact coming from a bad contact. If your contacts are not ohmic it is worth it to try to improve them, a possibility is a rapid annealing process or a different metal contact.
Another thing is the environment. Metal oxide nanowires are very sensitive to the environment where they are place. Have you try to measure under different light conditions? Maybe under different gas environments? Humidity could be a mayor issue.
Once you are sure your contacts are good, then try to control the environment as best as you can and try to play with the factors involve in it.
Everything here is true. I'm trying to understand if hysteresis is to be related mainly to materials and contacts, to atomic structure and defects or to other effects (i.e light, environment, ..). From this answers it seems that hysteresis in i(v) curves could be related to many causes.
So anyway it is now clear that the contact of nanowire with metal is not ohomic due to the mismatch of fermi level the contact layer is acts as Metal-Insulator junction. So there is a way which can help you to overcome the contact barrier.
Peoples generally uses graded doping concept. Using ion beam you can dope from one end of the nanotube using ion beam and then you make contact with metal so that the change in fermi level when you are going from metal to ZnO is not sharp, rather gradual.
Another alternative is that you can try to deposit a metal whose lattice constant is less than that of ZnO and then anneal it so that metal atom can diffuse through ZnO gradually.
Hello everyone, thanks again for your answers. From the literature it seems that the hysteresis can be related mainly to the capacitive effects resulting from polar oxygen molecules connected to the surface of NWs by lattice defects. Furthermore, oxygen can create depletion of electrons in the conduction band. Increased amount of defects on the surface of ZnO nanowires, more oxygen attached, the greater the effect of hysteresis. What do you think about? Thank You.
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering
- Powders