Formation and Characterization of Various ZnO/SiO2-Stacked Layers for Flexible Micro-Energy Harvesting Devices

Abstract

Abstract:In this paper, we present a study of various ZnO/SiO 2 -stacked thin film structures for flexible micro-energy harvesting devices. Two groups of micro-energy harvesting devices, SiO 2 /ZnO/SiO 2 micro-energy generators (SZS-MGs) and ZnO/SiO 2 /ZnO micro-energy generators (ZSZ-MGs), were fabricated by stacking both SiO 2 and ZnO thin films, and the resulting devices were characterized. With a particular interest in the fabrication of flexible devices, all the ZnO and SiO 2 thin films were deposited on indium tin oxide (ITO)-coated polyethylene naphthalate (PEN) substrates using a radio frequency (RF) magnetron sputtering technique. The effects of the thickness and/or position of the SiO 2 films on the device performance were investigated by observing the variations of output voltage in comparison with that of a control sample. As a result, compared to the ZnO single-layer device, all the ZSZ-MGs showed much better output voltages, while all the SZS-MG showed only slightly better output voltages. Among the ZSZ-MGs, the highest output voltages were obtained from the ZSZ-MGs where the SiO 2 thin films were deposited using a deposition power of 150 W. Overall, the device performance seems to depend significantly on the position as well as the thickness of the SiO 2 thin films in the ZnO/SiO 2 -stacked multilayer structures, in addition to the processing conditions.

A Feasibility Study of Fabrication of Piezoelectric Energy Harvesters on Commercially Available Aluminum Foil

“…In particular, the sample B of the Ag/ZnO/AlN/Cr/ITO/Al-foil structure showed the highest output voltage. Similarly to other reports [12][13][14], we fabricated additional devices including each material (AlN, SiO 2 , or a-Si) used in our earlier researches for a further study, as shown in Figure 10. Here, each target of AlN (5N, iTASCO), n-type a-Si (5N, iTASCO), or SiO 2 (4N, iTASCO) were used to fabricate the devices shown in Figure 10.…”

“…For the ZnO deposition in particular, a mixture of 18 sccm Ar and 12 sccm N 2 O gas was flowing during the sputtering process to reduce the free-carrier concentration in the ZnO film, leading directly to the improvement of device performance [16]. Many previously reported devices fabricated on flexible plastic substrates [10,[12][13][14]16,17] have an intrinsic limitation to increasing process temperatures. Thus, in this work, instead of flexible plastic substrates, we have attempted to employ the Al-foil as a substrate to further increase the process temperatures, which helpfully allows for annealing heat treatments at higher temperatures.…”

“…However, lead-free ZnO-based piezoelectric energy harvesters produce lower output voltages than lead zirconate titanate (PZT)-based harvesters, containing toxic piezoelectric materials [7]. Many research results have reported on various piezoelectric energy harvesters using polyethylene naphthalate (PEN), polyethylene terephthalate (PET), various metal wires, various flexible substrates, etc., in order to enhance the output voltages [8][9][10][11][12][13][14][15][16]. Also, various piezoelectric energy harvesters have been fabricated which exploit insulators to inhibit the so-called screening effect of free carriers, compensating for the positively polarized parts of ZnO, thus reducing the piezoelectric effect [7,8,11,13,14].…”

“…Many research results have reported on various piezoelectric energy harvesters using polyethylene naphthalate (PEN), polyethylene terephthalate (PET), various metal wires, various flexible substrates, etc., in order to enhance the output voltages [8][9][10][11][12][13][14][15][16]. Also, various piezoelectric energy harvesters have been fabricated which exploit insulators to inhibit the so-called screening effect of free carriers, compensating for the positively polarized parts of ZnO, thus reducing the piezoelectric effect [7,8,11,13,14]. To suppress the screening effect, wide-band-gap or p-type semiconductor materials have been combined with ZnO [7,8,11,12,[15][16][17].…”

Novel developments of ZnO/SiO2 nanocomposite: a nanotechnological approach towards insect vector control

“…Hence, it has been reported that ZnO and SiO 2 nanoparticles provides a lay down of a novel green nanotechnology to control insect pest including mosquitoes' larvae [5][6][7][8]. ZnO/SiO 2 nanocomposites have been synthesized using various techniques such as chemical vapor deposition, sputtering, chemical etching and sol gel process and they are used in different applications such as an-timicrobial, photonic crystals, photocatalysts, gas sensors, vacuum fluorescent display and varistors etc., [9][10][11][12][13][14][15][16][17][18][19]. But based on our search, there was no report on the effect of ZnO/SiO 2 nanocomposites against mosquito larvae except for the individual ZnO and SiO 2 nanoparticles.…”