If by CV you meant caapacitance-voltage characteristic of a solid state device, please ignore what I say below.  If by CV you mean cyclic voltammetry, initial scanning direction could have a significant effect, especially in irreversible systems, or in systems that can undergo both reduction and oxidation of the starting material.  Where you begin the scan and in which direction you scan first will affect the redox chemistry of the electroactive species at the electrode surface.  Sometimes varying this can give insightful results.  In your experiments, it really the electrode material that produces some electrochemistry or is it some species in solution?

C-V is capacitance-voltage characteristics , I hope I have understood correctly.

Pl specify on which device structure are you measuring the C-V characteristics.

I mean the material system. Is it metal-oxide-semiconductor (MOS) device structure,

or any other kind of device structure.

For example I have seen differences in the forward and retrace C-V characteristics, when I studied metal-ferroelectric oxide-semiconductor device structure.

It will be nice to know on which material system are you measuring CV characteristics, which are showing some difference.

K. Sreenivas

It depends on the interface layers of the top and bottom electrodes, defect densities and space charges at interface layers as well as work functions of the electrodes play pivotal role to decide the shape of C-V curve sweeps.

If by CV you meant caapacitance-voltage characteristic of a solid state device, please ignore what I say below.  If by CV you mean cyclic voltammetry, initial scanning direction could have a significant effect, especially in irreversible systems, or in systems that can undergo both reduction and oxidation of the starting material.  Where you begin the scan and in which direction you scan first will affect the redox chemistry of the electroactive species at the electrode surface.  Sometimes varying this can give insightful results.  In your experiments, it really the electrode material that produces some electrochemistry or is it some species in solution?

Thanks u all for the response. My question is regarding CV- cyclic voltammetry measurements conducted for supercapacitor applications to be specific. A transition metal oxide electrode materials like cobalt oxide, mangnaese oxide etc in electrolytes like KOH, KCl, Na2SO4 etc.

@Peter. Sir my electrode material undergoes oxidation/reduction by transferring electrons with electrolyte ions. In this case which direction is desirable or ideal for beginning the experiment.

I agree that the initial direction of the voltammetric scan can have significant effects on the resulting CV, particularly if, as you say your electrode material itself undergoes oxidation/reduction reactions. Unfortunately, I'm not sure it is easy to say which direction is best without knowing many more details... it depends on what you really want to know from these measurements, what you will be using your material for, etc. As Peter suggested, it is sometimes a good idea to try both directions (and even different starting potentials) to gain further information about the processes that are taking place.

Naveen: I expect you can work out the answer by considering the chemical processes happening during charge and discharge of the cell as a capacitor, if that is known or can be surmised.  If you start in an uncharged state, then you should scan that electrode in the direction that should charge the capacitor.  For instance, if you charge it by treating this electrode material as an anode (+ terminal during charging) then your CV should start by scanning in the positive direction.

@Peter and Daniela,

Thanks for the insight.

Nirmalesh: you said that CV experiments are performed on electrode materials based on transition-metal oxides (like cobalt oxide, manganese oxide, etc) in electrolytes like KOH, KCl, Na2SO4 etc.

While being substantially in agreement with the suggestions given by Peter and Daniela, I would like to add that the investigated materials must possess a given stability and, in order to be of practical interest, the produced signals must also be quite reproducible. This implies that a number of cycles has to be performed (not only one!) and, provided you remain within the window of potentials of material stability, the actual direction of the first scan becomes less important.

The choice of the potential interval to be explored (the "window of potentials") is more critical: I suggest you to refer to previous studies (if they are available); otherwise, you should prepare a few samples of the same electrode material and use one of these for carrying out some preliminary tests. In addition, when moving from a neutral pH toward an alkaline media, the "window of potentials" requires to be shifted, typically by -59mV per unit of pH variation.

Performing a proper CV investigation is often a matter of experience: some "trials and errors" are inevitable, at the beginning. If you have some specific questions, we can discuss further.