Thin film electrochemical fabrication

In order to address the needs of field sensing of explosives, it is necessary to move away from traditional bulky electrodes and cells (commonly used in research laboratories). The exploitation of advanced microfabrication techniques allows the replacement of conventional ( beaker-type ) electrochemical cells and electrodes with easy-to-use sensor strips. Both thick-film (screen-printing) and thin-film (lithographic) fabrication processes have thus been used for high-volume production of highly reproducible, effective and inexpensive electrochemical sensor strips. Such strips rely on... 

McGregor SM, Dharmadasa IM, Wadsworth 1, Care CM (1996) Growth of CdS and CdTe by electrochemical technique for utilisation in thin film solar cells. Opt Mater 6 75-81 Morris GC, Das SK (1992) Some fabrication procedures for electrodeposited CdTe solar cells. Int J Sol Energy 12 95-108... 

V Brusic, J. Horkans, and D. J. Barklay offer an authoritative review of the electrochemical aspects of fabrication and of evalution of the stability of thin film storage media. Recent developments have led to improved thermodynamic stability, thereby rendering thin film disks suitable for high density storage applications. 

Dr. Hui has worked on various projects, including chemical sensors, solid oxide fuel cells, magnetic materials, gas separation membranes, nanostruc-tured materials, thin film fabrication, and protective coatings for metals. He has more than 80 research publications, one worldwide patent, and one U.S. patent (pending). He is currently leading and involved in several projects for the development of metal-supported solid oxide fuel cells (SOFCs), ceramic nanomaterials as catalyst supports for high-temperature PEM fuel cells, protective ceramic coatings on metallic substrates, ceramic electrode materials for batteries, and ceramic proton conductors. Dr. Hui is also an active member of the Electrochemical Society and the American Ceramic Society. 

Metal in gap (MIG) or ferrite heads are produced with a combination of machining, bonding, and thin-film processes. Thin-film inductive heads are manufactured using thin-fihn processes similar those of semiconductor 1C technology (discussed in Chapter 19). The thin-film head production process is rather unusual, as it involves both very thin and very thick films. We choose to present here a detailed summary of the fabrication process of thin-film inductive heads with a single-layer spiral coil. This may serve, once again to, illustrate the centrally important role of electrochemical deposition in connection with modem information technology. 

Before a more extended explanation of the different strategies for the immobilisation of ssDNA probe on the electrodes surfaces and the different strategies for electrochemical detection of the hybridisation event, some aspects of the fabrication of thick- and thin-film electrodes will be given in the next section. 

The objective of this protocol is the fabrication of a light-addressable potentiometric sensor (LAPS) for the detection of the pH value and the cadmium-ion concentration in aqueous solutions. For the pH-sensitive LAPS, use, e.g., Ta205 as a sensor membrane, and for the cadmium-selective LAPS, use a Cd2+-selective chalcogenide glass thin film as a heavy metal-sensitive material. The electrochemical sensor characterisation of the LAPS structure perform current vs. voltage (I/V) and constant current (CC) measurements. 

Nanocrystals of Si trapped in some matrix form an attractive system for device fabrication when compared with Jt-Si, because of the increased surface stability and material rigidity. Visible EL has been observed, for example, from Si nanocrystals embedded in films of a-Si H78 and from an electrochemically-formed nanocrystalline Si thin film deposited on SnCL.79 In the latter case the p-i-n LED at room temperature emitted orange-red light (1.8 eV) that was readily visible to the eye. The light emission is ascribed variously to near surface states78 and the quantum size effect.79 Also, infrared emission near 1.1 eV has been obtained from a room-temperature EL device comprised of Si nanocrystals embedded within a Si-rich Si02-x matrix.80 The PL from this structure has an external quantum efficiency of 10 3. Substantial progress in the development of such nanocrystalline-Si EL structures can be expected over the next few years. 

Our previous work with PPNVP and GOx-PPNVP/PEUU (6,12,25), which focused on characterization of the surface modified thin films, has demonstrated that a reasonable amount of control can be exerted over the chemistry of plasma modification. The techniques used here to attach active GOx to PEUU may be applied to a wide variety of biomolecules and a wide variety of organic and inorganic substrates. Incorporation of GOx-PPNVP/PEUU into the thin-layer cells extended the potential applicability of GOx-PPNVP/PEUU and similar materials to specific practical applications such as sensing devices. Similarly, the ease of fabrication of the thin-layer cells and the wide variety of electrochemical techniques which are available for use with thin-layer cells warrant further development of this system. 

Electrochemical deposition has attracted increasing attention as a technique for nanowire fabrication. Traditionally, electrochemistry has been used to grow thin films on conducting surfaces. Because electrochemical... 

Baeck, S.H., K.S. Choi, T.F. Jaramillo, G.D. Stucky and E.W. McFarland (2003). Enhancement of photocatalytic and electrochromic properties of electrochemically fabricated mesoporous WO3 thin films. Advanced Materials, 15(15), 1269-1273. 

Badawy, W. A. (1997). Preparation, electrochemical, photoelectrochemical and solid-state characteristics of indium-incorporated Ti02 thin films for solar cell fabrication. J. Mater. Sci. 32(18), 4979 1984. 

The third method is to grow the polymer into its desired shape and form. An insulating polymer impregnated with a catalyst system is fabricated into its desired form. This is then exposed to the monomer, usually a gas or a vapour. The monomer then polymerises on the surface of the insulating plaslic producing a thin film or a fibre. This is then doped in the usual manner. A variation of this technique is electrochemical polymerisation with the conducting polymer deposited on an electrode either at the polymerisation stage or before the electrochemical polymerisation. 

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