Oxide electrodes sputtered

Zhu Y, Uchida H, Yajima T, Watanabe M. 2001. Attenuated total reflection-Fourier transform infrared study of methanol oxidation on sputtered Pt film electrode. Langmuir 17 146-154. 

However, for the oxide electrode, such as SrRuOj, the structural similarity of the electrode and dielectric material allows a certain penetration of the dielectric polarization into the oxide electrode. As a result, the formation of the intrinsic low dielectric interfacial layer is effectively suppressed and film thickness independent dielectric constants are obtained, as reported by the author for the case of sputtered BST films on IrO electrodes and more recently reported by Toshiba researchers for the case of MOCVD BST films on SrRu03 electrodes. Under these circumstances dielectric constants are solely determined by processing conditions. The stoichiometric composition and good crystallization of the films are the two most important parameters for a high dielectric constant. 

NADH oxidation have been described. Stmad (1989) adsorbed LDH on a carbon electrode sputtered with a mixture of gold and palladium. At this electrode NADH is oxidized at potentials as low as +0.6 V. The adsorbed enzyme was sufficiently active for the determination of milli-molar pyruvate concentrations during 7 days. 

Dye sensitized solar cells built without any transparent metal oxide electrodes (ITO or FTO) were presented recently by Kashiwa et The layout of the device is shown in Figure 11. To fabricate such device, titanium dioxide paste was coated directly on a glass substrate. On the top of Ti02 layer, tetrapode-shaped nanocrystals of zinc oxide were deposited by electrospray technique. A layer of metal titanium was sputtered on the top. Following etching of the zinc oxide template produced pores in the titanium layer. 

It is stated in [3] that even completely symmetrical bi-phasic current waveforms would not result in charge balance and will cause a residual voltage and charge build-up on the electrodes. The reason is the presence of a faradaic resistor Rfw parallel to the electrode-electrolyte interface capacitor. This resistor models the electron transfer across the electrode-electrolyte surface. The resulting electrode model which is called Randles model is shown in Fig. 3.2. For example in [3], for sputtered iridium oxide electrodes with 400 p,m diameter in saline solution, Rp f = 17.12 kQ, Rs = 2.1 and Chw = 909nF were extracted using the step response of the electrode voltage to an input current. 

These iridium oxide electrodes can be prepared by sputtering, as well as by thermal or electrochemical oxidation of iridium wire. Electrochemical oxidation of an iridium substrate is the most common method of preparation, by potential cycling of iridium in sulfuric acid between potentials of-0.25 and +1.25 V vs. SCE. 

Several demonstrations of this concept have recently been published The first one is based on the pH dependence of redox transitions in oxide semiconductors that are connected with conductivity changes. If the bridging polymer layer in Fig. 6 is WO3 sputtered onto the electrode array or electrochemically deposited Ni(OH)j the transistor amplification is a function of the pH of the... 

Other solutions to dealing with interferences in the detection of H O have included the use of a copperfll) diethyldithiocarbamate precolumn to oxidize the sample before it reaches the immobilized enzyme, as well as the use of a palladium/gold sputtered electrode which catalyzes the oxidation of hydrogen peroxide In addition, peroxidase has been used to catalyze the reaction between hydrogen peroxide and iodide ferrocyanide and organo-fluorine compounds Am-... 

Figure 14.12 CO bulk electro-oxidation at PtRu alloys, (a, b) PcRui j /Ru(0001) (x = 0.07, 0.25, 0.47) surface alloys measured in a flow cell with a CO-saturated electrolyte, (c) Freshly sputtered Pto.sRuo.s bulk alloy in a rotating disk electrode setup (data from Gasteiger et al. [1995]), compared with a Pto.53Ruo,47/Ru((X)01) surface alloy.

In order to understand the observed shift in oxidation potentials and the stabilization mechanism two possible explanations were forwarded by Kotz and Stucki [83], Either a direct electronic interaction of the two oxide components via formation of a common 4-band, involving possible charge transfer, gives rise to an electrode with new homogeneous properties or an indirect interaction between Ru and Ir sites and the electrolyte phase via surface dipoles creates improved surface properties. These two models will certainly be difficult to distinguish. As is demonstrated in Fig. 25, XPS valence band spectroscopy could give some evidence for the formation of a common 4-band in the mixed oxides prepared by reactive sputtering [83],... 

The results of the above mentioned study on mixed oxides prepared by thermal decomposition [84] are not in contradiction to the results obtained on reactively sputtered electrodes. A premise for common d-band formation is the formation of a solid solution with homogeneous properties which is probably not obtained during thermal decomposition. Indeed the authors find a trend towards the behaviour of the sputtered electrodes when homogeneity is improved by changing the solvent for the starting compounds. 

K.G. Kreider, M.J. Tarlov, and J.P. Cline, Sputtered thin-film pH electrodes of platinum, palladium, ruthenium, and iridium oxides. Sens. Actuators B. 28, 167-172 (1995). 

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