Electrostatic Supercapacitors by Atomic Layer Deposition on Nanoporous Anodic Alumina Templates for Environmentally Sustainable Energy Storage

Abstract

In this work, the entire manufacturing process of electrostatic supercapacitors using the atomic layer deposition (ALD) technique combined with the employment of nanoporous anodic alumina templates as starting substrates is reported. The structure of a usual electrostatic capacitor, which comprises a top conductor electrode/the insulating dielectric layer/and bottom conductor electrode (C/D/C), has been reduced to nanoscale size by depositing layer by layer the required materials over patterned nanoporous anodic alumina membranes (NAAMs) by employing the ALD technique. A thin layer of aluminum-doped zinc oxide, with 3 nm in thickness, is used as both the top and bottom electrodes’ material. Two dielectric materials were tested; on the one hand, a triple-layer made by a successive combination of 3 nm each layers of silicon dioxide/titanium dioxide/silicon dioxide and on the other hand, a simple layer of alumina, both with 9 nm in total thickness. The electrical properties of these capacitors are studied, such as the impedance and capacitance dependences on the AC frequency regime (up to 10 MHz) or capacitance (180 nF/cm2) on the DC regime. High breakdown voltage values of 60 V along with low leakage currents (0.4 μA/cm2) are also measured from DC charge/discharge RC circuits to determine the main features of the capacitors behavior integrated in a real circuit.

Influence of ALD Coating Layers on the Optical Properties of Nanoporous Alumina-Based Structures

“…For the double layered samples, schematized in Figure 1e, a SiO 2 layer was first deposited on the NPAS as described above; afterwards, the samples were coated with Al 2 O 3 or AZO with a layer thickness of about 3.5 nm, which were the corresponding growth rates of the Al 2 O 3 and AZO layers at 200 • C that had been previously studied by means of mechanical profilometry and ellipsometry measurements [32]. It is worth clarifying that the AZO layer consisted of a mixture of Zn and Al oxides obtained by performing 20 deposition cycles of ZnO, followed by one cycle of Al 2 O 3 , which corresponded to most of the external surface; through this approach, a doping of around 3% of Al in the ZnO layer was obtained [33,34]. According to previous results by SEM image analysis [30], a single layer coverage caused a reduction in pore size (d p ) and porosity (θ) of around 20% and 30%, respectively (d p = (25 ± 2) nm, θ = 6%), while in the case of the double layer, these reductions increased by up to around 30% and 50%, respectively (d p = (21 ± 1) nm, θ = 4%).…”

Influence of Anodization Temperature on Geometrical and Optical Properties of Porous Anodic Alumina(PAA)-Based Photonic Structures

“…Porosity of PAA is related to both interpore distance and pore diameter via the equation: [ 12 ]. PAA can be used as a template to fabricate various functional nanostructures [ 13 , 14 , 15 ] or itself is a functional material used in gas separation [ 16 ], medicine (tissue engineering) [ 17 ], or electronics (supercapacitors) [ 18 ]. One of the recent applications of PAA is related with a possibility to engineer PAA-based photonic structures.…”

High-Temperature Atomic Layer Deposition of GaN on 1D Nanostructures

“…These oxygen atoms are compensated, where ~10% are electrically active, which produces unintentionally doped n-type GaN when V Ga are kept relatively lower than the concentration of oxygen donors [97]. The concentration of oxygen in the sample in this study are in the range of 10 16 /cm 3 -10 21 /cm 3 . With high concentrations one should observe surface abnormalities, such as cracking and pitting [98],which are not present in the AFM images in Figure 5.…”

“…Atomic layer deposition (ALD) is an extremely valuable technique for growing conformal and precision ultrathin films for transistors, light emitting diodes [1,2], capacitors [3,4], solar cells [5,6], as well as different types of storage media, such as dynamic random-access memory (DRAM) and hard disk drives (HDD) [7,8], and recently solid-state batteries [9,10]. Due to the excellent surface conformation of ALD coatings, it is ideally suited for coating complex nanostructures.…”