Surface Modification on the Sputtering‐Deposited ZnO Layer for ZnO‐Based Schottky Diode

Mirzaei

et al. 2020

Sci Rep

Herein, we report the electrowetting-on-dielectric (eWoD) characteristics of Zno nanorods (nRs) prepared via the hydrothermal method with different initial Zn 2+ concentrations (0.03, 0.07, and 0.1 M). Diameter of the resultant ZnO NRs were 50, 70 and 85 nm, respectively. Contact angle (CA) measurements showed that the Teflon-coated ZnO NRs with diameters of 85 nm prepared from the 0.1 M solution had the highest CA (137°). During the EWOD studies, on the application of a voltage of 250 V, the water CA decreased to 78°, which demonstrates the potential application of this material in EWOD electronics. Furthermore, we explained the relationship between the applied voltage and CA based on the substrate nanostructures and our newly developed NR-on-film wetting model. In addition, we further validated our model by introducing the homo-composite dielectric structure, which is a composite of thin layered ZnO/Teflon and nano-roded ZnO/Teflon. Electrowetting (EW) is defined as the decrease in contact angle (CA) when a sufficiently large driving voltage is applied to the interface of solid/liquid. In direct EW, a voltage is used between a liquid and an electrode. Charges and dipoles redistribute at the interface between the liquid and solid, which changes the surface tension, leading to a decrease in the CA of the liquid droplets. However, direct EW can electrolyze the liquid before any change in the water contact angle (WCA), which limits its application 1. To overcome this issue, electrowetting-on-dielectric (EWOD) can be used. In this technique, a dielectric material is sandwiched between the liquid of interest and the underlying electrode (Fig. 1). EWOD is very effective for significantly changing the CA, because the dielectric layer effectively blocks the process of charge transfer at the liquid/electrode interface, which eliminates unwanted electrolysis 2. Therefore, EWOD is used to facilitate EW on solids, for practical applications. Although EWOD devices permit a large CA change, they generally need a high driving voltage. The dielectric layer blocks the transfer of electrons, while sustaining high voltage at the interface, which results in an electric double layer (EDL) formation in the presence of the applied voltage. When a hydrophobic dielectric material is used, the large initial WCA can result in a large change in the WCA 3. The advantages of EWOD include low power consumption, large WCA change, and fast response. It is therefore promising for diverse applications, including lab-on-chips 4 , liquid lenses 5 , optical waveguides 6 , electronic displays 7, 8 , microprism arrays 9 , and smart microbatteries 10. SiO 2 is a highly popular material for EWOD studies 11 because of its excellent compatibility with the microelectronic industry. In our previous study 12 , we investigated the EWOD properties of electrospray-deposited SiO 2 layers and found that the WCA of the optimal SiO 2 layer underwent a hydrophobic-to-hydrophilic transition under a driving voltage of 150 V in air. A novel EWOD mechanism, wherein the ...

Section: Deposition Ofmentioning

confidence: 99%

Electrowetting-on-dielectric characteristics of ZnO nanorods

Mirzaei

et al. 2020

Sci Rep

“…A peroxide surface treatment on ZnO surface may transform ZnO hexagonal into ZnO 2 cubic phase [ 27 – 37 ]. The ZnO 2 phase is found to have superior resistivity; thus, it can be exploited for Schottky contact and photodiodes applications; however, the potential of ZnO 2 for switching memory, especially the switching characteristics modulation by controlling peroxide treatment is still less investigated [ 26 , 29 – 38 ]. Therefore, a detail investigation on the impact of peroxide surface treatment on switching characteristics is necessary for further adoption and realization of ZnO 2 -based switching memory.…”

Section: Introductionmentioning

confidence: 99%

Switching Failure Mechanism in Zinc Peroxide-Based Programmable Metallization Cell

et al. 2018

The impact of peroxide surface treatment on the resistive switching characteristics of zinc peroxide (ZnO2)-based programmable metallization cell (PMC) devices is investigated. The peroxide treatment results in a ZnO hexagonal to ZnO2 cubic phase transformation; however, an excessive treatment results in crystalline decomposition. The chemically synthesized ZnO2 promotes the occurrence of switching behavior in Cu/ZnO2/ZnO/ITO with much lower operation current as compared to the Cu/ZnO/ITO (control device). However, the switching stability degrades as performing the peroxide treatment for a longer time. We suggest that the microstructure of the ZnO2 is responsible for this degradation behavior and fine tuning on ZnO2 properties, which is necessary to achieve proper switching characteristics in ZnO2-based PMC devices.

“…Furthermore, ZnO has advantages of excellent resistance to the radiation damage, suitable for the wet-etching process, and large exciton binding energy of 60 meV at room temperature; some ZnO-based optoelectronic applications are expected to be a good substitute for gallium nitride (GaN), another wide band gap ( E g ~3.4 eV at 300 K) semiconductor that is the current state-of-the-art approach used for the production of green, blue-ultraviolet, and white light-emitting devices. ZnO has much simpler types of crystal-growth methods, such as sputtering, pulse laser deposition, and hydrothermal methods, resulting in cost-effective approaches for the production of ZnO-based devices [ 4 , 5 , 6 ]. Among these deposition methods, sputtering technology is a widely used technology for preparing quality and large-sized ZnO film on substrates at a relatively low temperature.…”

Section: Introductionmentioning

confidence: 99%

Origin of the Electroluminescence from Annealed-ZnO/GaN Heterojunction Light-Emitting Diodes

et al. 2015

Self Cite

This paper addressed the effect of post-annealed treatment on the electroluminescence (EL) of an n-ZnO/p-GaN heterojunction light-emitting diode (LED). The bluish light emitted from the 450 °C-annealed LED became reddish as the LED annealed at a temperature of 800 °C under vacuum atmosphere. The origins of the light emission for these LEDs annealed at various temperatures were studied using measurements of electrical property, photoluminescence, and Auger electron spectroscopy (AES) depth profiles. A blue-violet emission located at 430 nm was associated with intrinsic transitions between the bandgap of n-ZnO and p-GaN, the green-yellow emission at 550 nm mainly originating from the deep-level transitions of native defects in the n-ZnO and p-GaN surfaces, and the red emission at 610 nm emerging from the Ga-O interlayer due to interdiffusion at the n-ZnO/p-GaN interface. The above-mentioned emissions also supported the EL spectra of LEDs annealed at 700 °C under air, nitrogen, and oxygen atmospheres, respectively.