The effect of anodization voltage and surface morphology on the capacitance properties of Al–Al2O3–Al nanocapacitors

•Nanocapacitor with a higher aspect ratio has a more stability in high frequencies.•Nanocapacitor with a higher aspect ratio has a more surface trap charges.•Calculated breakdown electric fields of all capacitors are close to each other.•The breakdown electric field is independent of anodization voltage.•Anodization voltage is used to characterize nanocapacitors.

Al–Al2O3–Al nanocapacitors are fabricated using hard and mild anodization methods which is simple and inexpensive. Samples are prepared with various effective areas and dielectric thicknesses below 10 nm. The experiments are carried out for glass slides and porous anodic alumina as substrates. The capacitance characteristics of the fabricated capacitors were measured and studied. The capacitance of capacitor with a higher ratio of surface to volume has a good stability in high frequencies. The higher traps on a surface are responsible for this effect. The breakdown electric fields of all capacitors are close to each other. The capacitor with a smaller ratio of surface to volume has a lesser leakage current density. Capacitance densities ranged between 0.623 and 1.659 μF/cm2 at 1 kHz, with a low leakage current. The highest value of the capacitance density was obtained for the sample anodized at 3.5 V on the porous anodic alumina substrate.