Electrode crystal substrate

Spontaneous deposition of other metal nanoislands on Pt and Au single crystal substrates has also been reported. For instance, Os deposition on single crystal platinum electrodes was studied by both ex situ6,7,18 and in situ STM.19,20 In addition, in situ STM studies of the spontaneous depositions of Os,21,22 Pt23,24 and Sn25 on Au(lll) single crystal as well as Pt on Ru(0001)26 and Pb on Ru(0001)27 were also carried out. 

Electrochemical atomic layer epitaxy (EC-ALE) is the combination of underpotential deposition (UPD) and ALE. UPD is the formation of an atomic layer of one element on a second element at a potential under, or prior to, that needed to deposit the element on itself [5, 6]. The shift in potential results from the free energy of the surface compound formation. Early UPD studies were carried out mostly on polycrystalline electrode surfaces [7], This was due, at least in part, to the difficulty of preparing and maintaining single-crystal electrodes under well-defined conditions of surface structure and cleanliness [8]. The definition of epitaxy is variable but focuses on the formation of single crystal films on single crystal substrates. This is different from other thin film deposition methods where polyciystalline or amorphous film deposits are formed even on single crystal substrates. Homoepitaxy is the formation of a compound on itself. Heteroepitaxy is the formation of a compound on a different compound or element and is much... 

To illustrate the primary effects of adatom addition, single-crystal electrodes are discussed here. Feliu and Herrero have extensively studied formic acid electrooxidation on Pt single-crystal substrates modified with an array of various adatoms. They have established a connection between the electronegativity of the adatoms in relation to Pt and the type of active enhancement mechanism incurred as a function of adatom coverage [42]. Their results support inhibition of the indirect pathway on Pt(lll) terraces and they have demonstrated that COads formation occurs at step and defect sites. For Pt(l 11) substrates decorated with electropositive adatoms, such as Bi, Pb, Sb, and Te, the electronic enhancement is extended to the second or third Pt atom shell from the adatom. While for electronegative adatoms, in respect to Pt, the third-body effect dominates with increased coverages, such as S and Se. 

Mecca VM (2005) From quartz crystal microbalance to fundamental principles of mass measurements. Artal Lett 38 753-767 Bucur RV, Carlsson J-O, Mecea VM (1996) Quartz-crystal mass sensors with glued foil electrodes. Sens Actuators B 37 91-95 Bucur RV, Mecea VM, Carlsson J-O (2003) EQCM with air-gap excitation electrode. Calibration tests with copper and oxygen coatings. Electrochim Acta 48 3431-3438 Mecea V, Bucur RV (1979) The mechanism of the interaction of thin films with resonating quartz crystal substrates the energy transfer model. Thin Solid Films 60 73-84 Mecea V, Bucur RV, Indrea E (1989) On the possibility of thin film structure study with a quartz crystal microbalance. Thin Solid Films 171 367-375... 

Nanocrystalline particulate films, which exhibit pronounced quantum size effects in three dimensions, are of great interest due to applications in solar cell (108-112) and sensor (57, 113-115) applications. They exhibit novel properties due to not only the SQE manifested by individual nanoparticles but also the total surface area. Unlike MBE and MOCVD methods used to prepare quantum well electrodes, these electrodes can be prepared by conventional chemical routes described in Section 9.5.2.2. For example, II-VI semiconductor particulate films were prepared by using low concentrations of precursors and by controlling the temperature of the deposition bath. Nodes demonstrated the SQE for CdSe thin films deposited by an electroless method (98). The blue shift in the spectra of CdSe films has been demonstrated to be a function of bath temperature. As described in Section 9.5.2.1, electrodeposition of semiconductors in non-aqueous solvents leads to the formation of size-quantized semiconductor particles. On a single-crystal substrate, electrodeposition methods result in epitaxial growth (116, 117), and danonstrate quantum well properties. 

The nature of the electrochemical reactions in a cell, especially with d.c. drive, depends amongst other factors on the molecular constitution of the nematic substances, on impurities in the liquid crystal and on the conductivity and orientation additives [84]. Even the electrodes and substrates, their contamination and the drive voltage and its duty cycle can also affect these reactions. The primary failure mechanisms are breakdown of the surface alignment, formation of bubbles, discoloration of the liquid crystal layer or a narrowing of the liquid crystalline temperature range. 

The next logical step would have been to study single-crystal electrodes, which represent well-defined surfaces. This is not the way the field developed historically, because it took a long time before high-quality single-crystals of metals could be prepared in the laboratory or purchased commercially but we need not be concerned with that here. The use of a single-crystal substrate has now become common in fundamental studies of UPD for three decades or more. 

More recently, photoemission studies have been extended to polarized light excitation of single-crystal substrates of known epitaxy. This approach is definitely rewarding because it provides an additional parameter to delineate the roles of volume and surface contributions, as well as clarify the basic internal excitation mechanism. We are not aware of any semiconductor/electrolyte studies using these techniques, but their application will prove extremely helpful in resolving the various contributions to the net photocurrents and scattering effects. There is, clearly, a need for better experimentation and theoretical development for the photoemission phenomena into condensed media from each class of electrode. 

Toyoda T, Kobayashi J, Shen Q (2008) Correlation between crystal growth and photosensitization of nanostructured HO2 electrodes using supporting H substrates by self-assembled CdSe quantum dots. Thin SoUd Films 516 2426-2431... 

We prepared thin film Pt alloy electrodes by Ar-sputtering Pt and the second metal targets simultaneously onto a disk substrate at room temperature (thickness approximately 200 nm). The resulting alloy composition was determined by gravimetry and X-ray fluorescent analysis (EDX). Grazing incidence (i7= 1°) X-ray diffraction patterns of these alloys indicated the formation of a solid solution with a face-centered cubic (fee) crystal stmeture. 

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