I am characterizing some metal-oxide for charge storage. I was interested in seeing the impedance spectroscopy of my material. The EIS was performed with a sine wave of 5mV amplitude from 1Mhz- 0.01Hz. In the EIS spectra, there seems to be a tail kind of structure in the high-frequency region, rather than a semi-circle. I'm suspecting that this is a potentiostat problem as I tried changing different variables like the amplitude and the scan range without any luck. I was wondering if some can help me solve this issue. Thanks
Instead of your cell[1], try to measure EIS for 3 dummy (Ohmic) cells, as troubleshooting tests of your setup. Measure, please, 3 commercial resistors near the proposal values : 20 Ohm, 5 Ohm, and 1 Ohm.
1. What is the metal in your metal-oxide ?
I guess, Ionnis Samaras is absolutely right.
Your impedance magnitude is quite small for the high frequencies. You need a very good setup (potentiostat, wiring,...) to measure up to 1 MHz. Usually, you would expect inductive behaviour at high frequencies, but at very small magnitudes of the impedance and high frequencies, the results often go crazy as in your case.
Maybe you even do not need these very high frequencies for your analysis. Apart from the last, say 10 points, your impedance looks nice and converges nicely to the real axis for high frequencies. The capacitive branch is characteristic for energy storage systems.
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