Cyclic Voltammetry is a study of electrochemistry, which is the formation of compounds under certain potential (or voltage) that drives ions in the solution resulting from an electric field. You sweep a voltage (for example -0.6V to +0.6 V)at a scan rate (for example, 0.5V/sec) for a selected range, if the reduction potential exist within that range (for material that desired to be deposited) you see a peak. Basically you are depositing a material on the forward sweep and stripping (anodic peaks) of the same material on the reverse sweep in order to find out the potential at which you can deposit the desired material (Or you also find out what others species could form during this process).

(1) The peaks that you see in the cyclic voltammogram on a forward sweep are the reduction peak. Deposition of a material at the surface of the cathode due to the reduction reaction. For example, if you are depositing CuInS2, you will see a reduction peak around -0.55-0.6 V. By flashing light while performing CV you can also determine whether it is a n-type or p-type material.

(2) After you reach peak current the current would start falling as thickness of the deposited material increases. Now the surface is less conductive compare to surface of the substrate.

(3) The peaks you see on forward sweep (hump shape followed by a plateau) is reductive and the one you see on a reverse sweep is oxidative peak (a downward hump).

Hope that answer your questions.

What will be the case if my deposited layer is conductive?

The deposited material my be conductive itself, it has significant higher resistance than the cathode/substrate, which is being coated. As the deposited material precipitates, the resistance increases. The increase in resistance is directly proportional to the thickness of the deposited material, and thus, at a given potential/voltage, the current decreases as the thickness increases. Eventually, it finally reaches a low point when deposition has slowed or stopped occurring (self-limiting).In addition to that, the currents are dependent upon the concentration of the solution and depletion of ions may result currents to fall.

If you are talking simply about a dissolved redox couple in solution then the peak is a direct result of diffusion. Assuiming this redox probe is fully reversible (a fast electron transfer probe not limited by electron transfer kinetics) then the peak is roughly defined by the Nernst equation once the reversible potential is achieved. The peak occurs when the diffusion gradient can no longer supply redox material at a rate to satisfy the equation and thus the current is seen to decrease. The diffusion gradient will decrease as the diffusion layer thickness increases with time. Thus the current will decrease to a diffusion limited region from the peak. If you supply an additional mixing force other than diffusion then often you will not see peaks, for example in rotating disc or even just with heating.

Which peak is which is merely a naming convention. Mostly the anodic peak is defined as having +ive current at +ive potentials, however different groups can have different naming conventions.

I suggest you read "Electrode Dynamics" by Adrian Fisher which is an excellent basic guide to concepts and really wasy to read.

Then "Electrochemical Methods" by Bard and Faulkner for more depth as well as "Understanding Voltammetry" by Richard Compton for more details and examples.

thank you very much John sir

Why sometimes 2  peaks are observed during reverse scan of cyclic voltammetry experiments as shown below in the attached file-