Highly N-doped Silicon Nanowires as a Possible Alternative to Carbon for On-chip Electrochemical Capacitors

Abstract

Highly n-doped silicon nanowires (SiNWs) have been grown by a chemical vapor deposition process and have been investigated as possible electrodes for electrochemical capacitors (ECs) micro-devices. Their performances have been compared to existing literature on the field, which shows the use of SiNWs fabricated via different techniques, SiC coated SiNWs and porous silicon layers. The double layer capacitance of n-doped silicon wafer is ≈6 µF cm −2 in standard organic electrolyte, and this value can be increased by nanostructuration of SiNWs up to 440 µF cm −2 by tuning deposition parameters. Similar values are found in the literature. Symmetrical microdevices based on two identical SiNWs electrodes can be operated in organic based electrolytes within a 1.2 V voltage window. The devices show excellent cycling efficiency over more than 2000 cycles, with capacitance value of 51 µF cm −2 and an energy density of 10 nWh cm −2 (37 µJ cm). The increase of specific surface area by different techniques may drastically boost these values in the near future.

An innovative 3-D nanoforest heterostructure made of polypyrrole coated silicon nanotrees for new high performance hybrid micro-supercapacitors

“…25 % of the initial capacitance was found to be lost). This value was found to be higher than SiNW-based µ-SC (C: 23 -50 µF cm -2 ), 15,22 demonstrating the potential of branched nanowires as advanced electrodes for electrochemical energy storage devices. 18 This approach is linked mainly with the enhancement of the developed active surface of electrodes, which is directly proportional to the specific capacitance (C).…”

High performance of symmetric micro-supercapacitors based on silicon nanowires using N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide as electrolyte

“…Over the past years new nanostructured materials, as for example nanowires, have emerged as promising materials in different technological applications such as photovoltaic cells or energy storage devices [1]. Within this context, SiNWs have attracted a great attention in the field of batteries [2] and supercapacitors [3]. Specifically, microsupercapacitor electrodes made of SiNWs [3][4][5][6][7] and silicon carbide nanowires (SiCNWs) [8][9][10] can be considered as one of the next generation energy storage devices according to their interesting properties in terms of stable cycling life, fast charging-discharging rate and high power density.…”

“…diodes or transistors), [11] which represents an important advantage compared with micro-supercapacitor electrodes based on nanostructured carbon. Recently, SiNWs grown by using CVD on silicon substrates were proved as excellent micro-supercapacitors in propylene carbonate (PC) based electrolyte [3][4][5]. In order to improve the performance of SiNWs as microsupercapacitor electrodes, different strategies have already been reported by using metallic oxides (NiO) [12,13] or cermets (SiC) [14] in the presence of aqueous electrolytes (KOH or KCl respectively).…”

New electrolyte mixture of propylene carbonate and butyltrimethylammonium bis(trifluoromethylsulfonyl)imide (N1114 TFSI) for high performance silicon nanowire (SiNW)-based supercapacitor applications

“…Power and energy density values were ranged from 0.2Á10 3 to 16Á10 3 mWcm À2 (1.4 to 50.8 mWcm À3 ) and from 0.25 to 0.3 mWhcm À2 (0.75 to 0.95 mWhcm À3 ) at current densities ranging from 0.1 to 11 mA.cm À2 respectively. These values were compared to the state-of-the-art using similar studies dealing with silicon nanostructures such as CVD-SiNWs [1,[4][5][6]8,21], silicon nanotrees (SiNTrs) [15] or silicon carbide nanowires (SiCNWs) [34] in presence of various electrolytes. Additionally, a comparison with other micro-supercapacitors based on the functionalization of CVD-SiNWs by using pseudocapacitive materials such as electroactive conducting polymers (PEDOT and PPy) [35,36] or transition metal oxides (MnO 2 ) [37] has been also reported.…”

“…SiNWs were grown in a CVD reactor (EasyTube3000 First Nano, a Division of CVD Equipment Corporation) by using the vaporliquid-solid (VLS) method via gold catalysis using an optimal procedure reported previously [20]. A SiNWs mass of approximately 750 mg cm À2 was estimated according to our previous work [21]. The developed surface (S dev ) of SiNWs was calculated using the following equation S dev : p*D*L*d*S sample , where D is the SiNWs average diameter, L is the length of SiNWs, d is the density of SiNWs and S sample is the sample's plain surface (1.76 cm 2 ) [3].…”