RuOx Electrodes Research Articles

Charge injection characteristics of sputtered ruthenium oxide electrodes for neural stimulation and recording.

We have studied the charge-injection characteristics and electrochemical impedance of sputtered ruthenium oxide (RuOx ) films as electrode coatings for neural stimulation and recording electrodes. RuOx films were deposited by reactive DC magnetron sputtering, using a combination of water vapor and oxygen gas as reactive plasma constituents. The cathodal charge storage capacity of planar RuOx electrodes was found to be 54.6 ± 9.5mC/cm2 (mean ± SD, n=12), and the charge-injection capacity in a 0.2-ms cathodal current pulse was found to be 7.1 ± 0.3mC/cm2 (mean ± SD, n=15) at 0.6V positive bias versus Ag|AgCl, in phosphate buffer saline at room temperature for ~250 nm thick films. In general, the RuOx films exhibited high charge-injection capacities, with or without a positive interpulse bias, comparable to sputtered iridium oxide (SIROF) coatings. The charge-injection capacity increased monotonically with film thickness from 120 to 630 nm, and reached 11.30 ± 0.34 mC/cm2 (mean ± SD, n=5) at 0.6V bias versus Ag|AgCl at 630 nm film thickness. In addition, RuOx films showed minimal changes in electrochemical characteristics over 1.5 billion cycles of constant current pulsing at a charge density of 408 μC/cm2 (8nC/phase, 200 μs pulse width). The findings of low-impedance, high charge-injection capacity, and long-term pulsing stability suggest the suitability of RuOx as a comparatively inexpensive and favorable choice of electrode material for neural stimulation and recording.

Monitoring Contractile Cardiomyocytes via Impedance Using Multipurpose Thin Film Ruthenium Oxide Electrodes.

A ruthenium oxide (RuOx) electrode was used to monitor contractile events of human pluripotent stem cells-derived cardiomyocytes (hPSC-CMs) through electrical impedance spectroscopy (EIS). Using RuOx electrodes presents an advantage over standard thin film Pt electrodes because the RuOx electrodes can also be used as electrochemical sensor for pH, O2, and nitric oxide, providing multisensory functionality with the same electrode. First, the EIS signal was validated in an optically transparent well-plate setup using Pt wire electrodes. This way, visual data could be recorded simultaneously. Frequency analyses of both EIS and the visual data revealed almost identical frequency components. This suggests both the EIS and visual data captured the similar events of the beating of (an area of) hPSC-CMs. Similar EIS measurement was then performed using the RuOx electrode, which yielded comparable signal and periodicity. This mode of operation adds to the versatility of the RuOx electrode’s use in in vitro studies.

Measuring Both pH and O2 with a Single On-Chip Sensor in Cultures of Human Pluripotent Stem Cell-Derived Cardiomyocytes to Track Induced Changes in Cellular Metabolism

In vitro studies which focus on cellular metabolism can benefit from time-resolved readouts from the living cells. pH and O2 concentration are fundamental parameters upon which cellular metabolism is often inferred. This work demonstrates a novel use of a ruthenium oxide (RuOx) electrode for in vitro studies. The RuOx electrode was characterized to measure both pH and O2 using two different modes. When operated potentiometrically, continuous pH reading can be obtained, and O2 concentration can be measured chronoamperometrically. In this work, we demonstrate the use of the RuOx electrodes in inferring two different types of metabolism of human pluripotent stem cell-derived cardiomyocytes. We also show and discuss the interpretation of the measurements into meaningful extracellular acidification rates and oxygen consumption rates of the cells. Overall, we present the RuOx electrode as a versatile and powerful tool in in vitro cell metabolism studies, especially in comparative settings.

Effects of oxygen plasma generated in magnetron sputtering of ruthenium oxide on pentacene thin film transistors

Effects of oxygen plasma generated in a sputtering process for deposition of electrodes on pentacene thin films to configure top-contact (TC) transistors have been thoroughly investigated. Reactive oxygen species severely degraded electrical properties of pentacene films during the deposition of RuOx electrodes, leading to a failure of devices. In the off-region, the leakage current increased by about two orders of magnitude, and the subthreshold slope also increased by 6.5 times. The top surface of pentacene films was oxidized by oxygen plasma and C-O and C=O bonds awerere created. The pentacenequinone derivative was confirmed by X-ray photoelectron spectroscopy. The oxidation of pentacene films gives rise to charge traps at the pentacene/electrode interface, which produces a leakage channel between source and drain electrodes. We believe that this side effect of oxygen plasma on the fabrication of TC-devices should be considered carefully.

Synthesis of electro-deposited ordered mesoporous RuOx using lyotropic liquid crystal and application toward micro-supercapacitors

Synthesis of ordered mesoporous RuOx electrodes was conducted by electro-deposition using a lyotropic liquid crystal template method with Ti substrates and subsequent electro-oxidation. The obtained ordered mesoporous Ru metal was characterized by XRD, TEM and electrochemical measurements in 0.5 M H2SO4. After electro-oxidation by potential cycling, the ordered mesoporous RuOx afforded specific capacitance of ∼400 F (g-Ru)−1. A micro-supercapacitor with ordered mesoporous RuOx was fabricated by controlled electro-deposition of ordered mesoporous RuOx on an inter-digitated array electrode (IDA; 10 μm electrode width, 5 μm gap and 65 × 2 electrodes). This micro-supercapacitor exhibited good capacitive property with maximum specific capacitance of 12.6 mF cm−2 and specific energy of 12.5 Wh (kg-Ru)−1 based on the mass of the deposited material.

Effects of bottom electrode on the structural and electrical properties of PbTiO3 ferroelectric thin films

The effect of RuOx and Pt electrodes on the crystal structure, leakage current characteristics and dielectric properties of PbTiOs are compared with as- deposited and annealed samples. As a result, amorphous or microcrystalline PbTiO3films on RuOx and Pt are recrystallized along the <100> direction after annealing at 600°C for 30min in O2 ambient. The leakage current density for both samples are very similar, whereas the dielectric property of RuOx/PbTiO3 is superior to that of Pt/PbTiO3 due to the large grain growth of PbTiO3 on RuOx confirmed with cross- sectional transmission electron microscopy.

Conducting oxide electrodes for ferroelectric films

Abstract Suitability of oxide electronic conductors [e.g. ruthenium oxide (RuOx) and indium-tin-oxide (ITO)] as contact metallization for ferroelectric films (e.g. PbZrxTi1−xO3) was investigated using techniques such as Rutherford backscattering spectrometry, x-ray diffraction and electron spectroscopy for chemical analysis. Thin films of RuOx and ITO were deposited on Si substrates by reactive sputtering. Either PbO or PZT (x = 0.53) films were deposited onto the conducting oxides and the specimens were annealed at various temperatures between 400°C and 700°C. Less intermixing was found in Si/RuOx/ PZT films when compared to Si/ITO/PZT under similar processing conditions. The ferroelectric properties of PZT films on RuOx electrodes are compared to those on Pt electrodes. The PZT films show improved fatigue properties on RuOx electrodes.

Fatigue of ferroelectric PbZrxTiyO3 capacitors with Ru and RuOx electrodes

Fatigue of ferroelectric PbZr_<i>x</i>Ti_<i>y</i>O₃ capacitors with Ru and RuO_<i>x</i> electrodes

ChemInform Abstract: Charge Storage and Transport in Thermal Ruthenium Oxide Thin Films. In situ Detection of Local pH Changes and Asymmetries in Charge‐Discharge Cycles at the Oxide/Aqueous Electrolyte Interphase.

AbstractApplying voltammetry and a novel thin‐layer spectroelectrochemical technique to study the kinetic and reversibility of the charge‐discharge cycle in RuOx electrodes, deposited pyrolytically on Ti and Au supports.