Electrode Materials For Devices Research Articles

Source–drain contact impacts on electrical performances and low frequency noise of InZnO thin-film transistors down to 7 K

Source–drain contacts seriously affect low frequency noise (LFN) in amorphous IZO (a-IZO) thin-film transistors with bilayer ITO/Mo electrodes at cryogenic temperatures. In the range of 7–300 K, electrical and LFN performances of devices are measured, and the temperature dependence of channel resistances (Rch) and contact resistances (Rsd) is also analyzed. The carrier transport transition both occurs in a-IZO channels at 80 K and in ITO/Mo electrodes at 100 K, which causes the variation in Rsd and Rch. Below 80 K, the variable range hopping conduction dominates in the channels and contacts with Rsd/Rch ratio > 1. The LFN measured results indicate that the noise is contact-dominated. At higher temperatures above 120 K, the band conduction dominates in the channel, with Rsd/Rch ratio < 1, and the noise is channel-dominated. The main mechanism of noise transfers from the mobility fluctuation to the carrier number fluctuation. We consider that the contribution of contact noise to total LFN is determined by the Rsd/Rch ratio. This work provides comments for the selection of electrode materials in devices applied to cryogenic integration circuits.

Fabrication and Sensing Capability of Cholesterol Sensors Based on ZnO Nanofibers

In the present work, ZnO nanofibers were applied to electrode materials for the detection of cholesterol. ZnO nanofibers were synthesized using the electrospinning technique with zinc acetate as a precursor. Electrospinning-synthesized ZnO nanofibers were uniformly distributed by properly controlling the electrospinning parameters. After the calcination treatment, nanofibers of pure ZnO phase were synthesized. Then, these fibers were successfully placed on Au-coated glass substrates by dispersion of ZnO nanofibers in ethanol, dropping, and drying, in sequence. Cholesterol oxidase was then immobilized onto the surface of the ZnO nanofibers. To enhance the immobilization, Nafion was additionally applied. The sensing performances of the fabricated ZnO nanofibers-based sensors were analyzed by cyclic voltammetry in terms of cholesterol concentration ranging from 100 to 400 mg/dl. In the I-V curves, measured by cyclic voltammetry, the ZnO nanofiber-based sensor showed a proportional current behavior with cholesterol concentrations in phosphate buffered saline solution. The sensitivity was measured and found to be 30.7 nA/mM·cm2, which is comparable to the values reported in the literature. After not only optimizing the shape of the ZnO nanofibers but also improving the adhesion nature between the ZnO nanofibers and the Au conducting layer, these fibers can be a good candidate for electrode materials in devices used to detect low concentrations of cholesterol in blood.

Highly flexible pseudocapacitor based on freestanding heterogeneous MnO2/conductive polymer nanowire arrays

Flexible electronics such as wearable electronic clothing, paper-like electronic devices, and flexible biomedical diagnostic devices are expected to be commercialized in the near future. Flexible energy storage will be needed to power these devices. Supercapacitor devices based on freestanding nanowire arrays are promising high power sources for these flexible electronics. Electrodes for these supercapacitor devices consisting of heterogeneous coaxial nanowires of poly (3,4-ethylenedioxythiophene) (PEDOT)-shell and MnO(2)-core materials have been shown in a half cell system to have improved capacitance and rate capabilities when compared to their pure nanomaterials; however, their performance in a full cell system has not been fully investigated. Herein, these coaxial nanowires are tested in both a symmetric and an asymmetric (utilizing a PEDOT nanowire anode) full cell configuration in the aspect of charge storage, charge rate, and flexibility without using any carbon additives and polymer binders. It is found that the asymmetric cell outperforms the symmetric cell in terms of energy density, rate capability, and cycle ability. The asymmetric device's electrode materials display an energy density of 9.8 Wh/kg even at a high power density of 850 W kg(-1). This device is highly flexible and shows fast charging and discharging while still maintaining 86% of its energy density even under a highly flexed state. The total device is shown to have a total capacitance of 0.26 F at a maximum voltage of 1.7 V, which is capable of providing enough energy to power small portable devices.

Fabrication of atomically smooth SrRuO3 thin films by laser molecular beam epitaxy

High-quality SrRuO3 (SRO) thin films and SrTiO3/SRO bilayer were grown epitaxially on SrTiO3 (STO)(001) substrates by laser molecular beam epitaxy. The results of in situ observation of reflection high-energy electron diffraction and ex situ X-ray diffraction ϑ-2ϑ scan indicate that the SRO thin films have good crystallinity. The measurements of atomic force microscopy and scan tunneling microscopy reveal that the surface of the SRO thin film is atomically smooth. The resistivity of the SRO thin film is 300 μΘ·cm at room temperature. Furthermore, the transmission electron microscopy study shows that the interfaces of STO/SRO and SRO/STO are very clear and no interfacial reaction layer was observed. The experimental results show that the SRO thin film is an excellent electrode material for devices based on perovskite oxide materials.

Y1Ba2Cu3O7-x As an electrode material for ferroelectric devices

Y1Ba2Cu3O7-x (YBCO) was studied as a potential electrode material for devices utilizing perovskite ferroelectric materials. Electrode thick film coatings were made on Barium Titanate (BT), Lead Magnesium Niobate-Lead Zinc Niobate (PMN-24 PZN), Lead Magnesium Niobate-Lead Titanate (PMN-7.5PT) and Lead Zirconate Titanate (PZT). Conventional slow fire techniques with flowing oxygen were initially used to fire the electrode onto the substrate. These 24 hour firing cycles caused excessive interactions at the electrode-substrate interface, as determined by dielectric constant and loss data. PbO vapor pressure was found to play a key role in the adhesion of these coatings.An alternate “fast fire” technique was excellent in producing conductive, adhering electrode coatings. YBCO electroded PZT samples performed identical to PZT electroded with gold. The YBCO electrode was found to react more with the PMN based substrates.