Etching cathodic

Cr-Ni Wet chemical etching Cathode sputtering Glass isotrope... 

Defects in arc-grown nanotubes place limitations on their utility. Since defects appear to arise predominantly due to sintering of adjacent nanotubes in the high temperature of the arc, it seemed sensible to try to reduce the extent of sintering by cooling the cathode better[2]. The most vivid assay for the extent of sintering is the oxidative heat purification treatment of Ebbesen and coworkers[7], in which amorphous carbon and shorter nanoparticles are etched away before nanotubes are substantially shortened. Since, as we proposed, most of the nanoparticle impurities orig-... 

The determination of polarisation curves of metals by means of constant potential devices has contributed greatly to the knowledge of corrosion processes and passivity. In addition to the use of the potentiostat in studying a variety of mechanisms involved in corrosion and passivity, it has been applied to alloy development, since it is an important tool in the accelerated testing of corrosion resistance. Dissolution under controlled potentials can also be a precise method for metallographic etching or in studies of the selective corrosion of various phases. The technique can be used for establishing optimum conditions of anodic and cathodic protection. Two of the more recent papers have touched on limitations in its application and differences between potentiostatic tests and exposure to chemical solutions. ... 

Chemical vapor deposition Plasma etching Photoresist Photolithography Resistance heating Ion implantation Spin-on glass deposition Cathodic arc Ion plating... 

De Souza et al. (1997) used spectroscopic ellipsometry to study the oxidation of nickel in 1 M NaOH. Bare nickel electrodes were prepared by a series of mechanical polishing followed by etching in dilute HCl. The electrode was then transferred to the spectroelectrochemical cell and was cathodicaUy polarized at 1.0 V vs. Hg/HgO for 5 minutes. The electrode potential was then swept to 0.9 V. Ellipsometry data were recorded at several potentials during the first anodic and cathodic sweep. Figure 27.30 shows a voltammogram for Ni in l.OM NaOH. The potentials at which data were recorded are shown. Optical data were obtained for various standard materials, such as NiO, a -Ni(OH)2, p-Ni(OH)2, p-NiOOH, and y-NiOOH. 

It was argued by Saito et al. [509] that a hydrogen plasma treatment as used in the LBL technique causes chemical transport the a-Si H film deposited on the cathode prior to the hydrogen treatment is etched and transferred to the anode. Hence, in the hydrogen plasma silane-related molecules and radicals are present. In fact, material is deposited on the anode under the same conditions as in the case of high dilution of silane with hydrogen. 

Aluminum foil capacitors occupy an important position in circuit applications due to their unsurpassed volumetric efficiency of capacitance and low cost per unit of capacitance.328 Together with tantalum electrolytic capacitors, they are leaders in the electronic discrete parts market. Large capacitance is provided by the presence of extremely thin oxide layers on anodes and cathodes, and high surface areas of electrodes could be achieved by chemical or electrochemical tunnel etching of aluminum foils. The capacitance of etched eluminum can exceed that of unetched metal by as much as a factor of 50.328... 

The surface segregation of Sr is of particular interest as SrO affects the surface reactivity and the activation behavior of the LSM electrode. Jiang and Love [36] studied the activation behavior of Lao72Sr018Mn03 cathode after treatment of the LSM coating with diluted hydrochloric acid (HC1) solution. The etched solution... 

The sputtering process shown in Figure 19.1, utilizes the phenomena associated with a low-pressure gas discharge. The system comprises an anode and cathode generally the low-pressure chamber is earthed and forms an infinite area anode the small cathode surface is the target material from which gas ion-etching occurs, resulting in condensation of the material onto workpieces within the vacuum chamber. 

Aqueous electrolytes of high pH etch silicon even at open circuit potential (OCP) conditions. The etch rate can be enhanced or decreased by application of anodic or cathodic potentials respectively, as discussed in Section 4.5. The use of electrolytes of high pH in electrochemical applications is limited and mainly in the field of etch-stop techniques. At low pH silicon is quite inert because under anodic potentials a thin passivating oxide film is formed. This oxide film can only be dissolved if HF is present. The dissolution rate of bulk Si in HF at OCP, however, is negligible and an anodic bias is required for dissolution. These special properties of HF account for its prominent position among all electrolytes for silicon. Because most of the electrochemistry reported in the following chapters refers to HF electrolytes, they will be discussed in detail. 

The OCP etch rate of p-type and highly doped n-type Si electrodes in HF-HNO3 mixtures increases by an order of magnitude under sufficiently anodic bias [Le20]. In the cathodic regime significant dark-currents are observed for p-type electrodes, as shown in Fig. 4.12. This is ascribed to hole injection from the electrolyte [Kol4]. Note that hole injection is not observed in aqueous HF free of oxidants. 

As shown in Fig. 3.3, the I-V curve in this regime shows a cathodic potential shift and a slight change of slope, if the doping density is increased. Compared to p-type substrates the I-V curve of p+ is shifted cathodically by about 0.1 V and that of n+ by about 0.2 V [Gal, Zh5[. This shift can be exploited for etch stops and selective formation of PS, as discussed in Section 4.5. 

In contrast to acidic electrolytes, chemical dissolution of a silicon electrode proceeds already at OCP in alkaline electrolytes. For cathodic potentials chemical dissolution competes with cathodic reactions, this commonly leads to a reduced dissolution rate and the formation of a slush layer under certain conditions [Pa2]. For potentials slightly anodic of OCP, electrochemical dissolution accompanies the chemical one and the dissolution rate is thereby enhanced [Pa6]. For anodic potentials above the passivation potential (PP), the formation of an anodic oxide, as in the case of acidic electrolytes, is observed. Such oxides show a much lower dissolution rate in alkaline solutions than the silicon substrate. As a result the electrode surface becomes passivated and the current density decreases to small values that correspond to the oxide etch rate. That the current density peaks at PP in Fig. 3.4 are in fact connected with the growth of a passivating oxide is proved using in situ ellipsometry [Pa2]. Passivation is independent of the type of cation. Organic compounds like hydrazin [Sul], for example, show a behavior similar to inorganic ones, like KOH [Pa8]. Because of the presence of a passivating oxide the current peak at PP is not observed for a reverse potential scan. 

The etch rate of an illuminated area on p-type Si is reduced under cathodic potential in alkaline solutions, while an area kept in the dark shows the OCP etch rate [Ve2]. 

Defects in a SCR, which is present under reverse bias, can be tested in a similar way. Figure 10.6 c shows the same wafer as in Fig. 10.6 e after removal of the oxide and under cathodic polarization in the dark. Hydrogen bubbles caused by the dark current now decorate nickel silicide precipitates that short-circuit the SCR. Nickel precipitates are known to increase the dark current of a p-type Si electrode under reverse bias by orders of magnitude [Wa4]. If the bias is increased the copper silicide precipitates also become visible, as shown in Fig. 10.6 d. This method, like defect etching (Fig. 10.4f), is only sensitive to precipitated metals. Metals that stay in solution, like iron, do not show up in defect mapping and have to be determined by other methods, for example diffusion length mapping. 

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