Deposition pulse

DEC coating was first prepared by Aisenberg and Chabot using ion beam deposition in 1971 [2]. At present, PVD, such as ion beam deposition, sputtering deposition, cathodic vacuum arc deposition, pulsed laser deposition, and CVD, like plasma enhanced chemical vapor deposition are the most popular methods to be selected to fabricate DEC coatings. 

ZnO thin films can be prepared by a variety of techniques such as magnetron sputtering, chemical vapor deposition, pulsed-laser deposition, molecular beam epitaxy, spray-pyrolysis, and (electro-)chemical deposition [24,74]. In this book, sputtering (Chap. 5), chemical vapor deposition (Chap. 6), and pulsed-laser deposition (Chap. 7) are described in detail, since these methods lead to the best ZnO films concerning high conductivity and transparency. The first two methods allow also large area depositions making them the industrially most advanced deposition techniques for ZnO. ZnO films easily crystallize, which is different for instance compared with ITO films that can... 

Table 1 Absolute and relative yields in functional groups at the surface of deposited pulsed plasma polymer layers measured with XPS after derivatization (cf. Experimental, 100 W)...

From the viewpoint of operation of LCVD, pulsed discharge provides effects somewhat similar to those that can be obtained by the remote or secondary plasma operation, namely, (1) reduction of the photoirradiation effect and (2) slowdown of the chemical reaction (surface modification or deposition of material), and allows uniform treatment or deposition. Pulsed discharge always decreases the substrate dangling bonds, which is the measure of the UV irradiation effect, as the value of r increases. Thus, the irradiation damage can be reduced dramatically. On the other hand, the concentration of chemically reactive species also decreases as the value of r increases. 

The formation of the smaller (and less different to each other) dendrites could be obtained by the increase of deposition overpotential. Unfortunately, the increased overpotential produces the hydrogen evolution in this system and the formation of degenerate dendrites and honeycomb-like deposits.76,77 Nevertheless, the dendritic growth in this system at larger overpotentials is possible by the application of appropriate square-wave pulsating overpotential (PO) regime. For example, the well-developed dendrites were formed with amplitude overpotential of 1,000 mV, deposition pulse of 10 ms, and pause of 100 ms (the pause to pulse ratio 10) (Fig. 26a). They can be well approximated by the cones shown in Fig. 23. Also, superficial holes due to attached hydrogen bubbles were formed between these dendrites, as can be seen from ref.78... 

Figure 26. (a) The copper dendrites formed by the pulsating overpotential (PO) regime deposition pulse of 10 ms, pause duration of 100 ms deposition time 18 min (b) The precursor of copper dendrite obtained by PO regime deposition pulse of 1 ms, pause duration of 10 ms deposition time 24 min. In both cases amplitude overpotential used was 1,000 mV. Reprinted from ref. 8 with permission of Elsevier. 

Additionally, by having an experimental setup with a high-speed data acquisition system, it is possible to control deposition pulses with durations below milliseconds. This ultrafast pulsing method was called precision electrodeposition and allowed the deposition of sub-monolayer quantities of material. Precision electrodeposition was demonstrated for the CuNi system, as shown in Fig. 14, where a sequence of ultrafast current pulses for the electrodeposition of a nanostructured CuNi alloy with a controlled composition of 48%i Cu and 52%i Ni is displayed. The duration of the pulses (tens of milliseconds), allows the deposition... 

The mechanical properties of sintered apatites has limited their application to low stress areas in the body. To overcome this difficulty, apatites are applied as coatings on the surface of metallic implants where high loads on the implant are expected. Various coating options are available including thermal spraying, sputter deposition, pulsed laser deposition, sol-gel deposition, electrophoretic coating, electrodeposition, and biomimetic deposition. These are discussed in turn. 

In Figure 12.17A a simple double pulse program is shown. In Figure 12.17B a third pulse that has zero current or even reversed current is added between the two deposition pulses. This pulse is applied to stop the non-noble metal deposition. In the low current pulse only the noble component will be deposited at higher currents and at more cathodic potential the non-noble component will be deposited together with the noble component. The concentration of the noble component must be so low that the amount of noble metal co-deposited with the non-noble component is negligible. This shows that the plating conditions are very restrictive. For this reason the dual bath technique could be an alternative for electrochemical deposition of a special metal combination. 

Reactive Ion Etching a (RIE), Fig. 7 (a) Bosch process schematic repetition of etch and deposit pulses. SEM images of etched structures ... 

Fig. 5.8 (a, b) The pyramid-like and (c, d) dendritic structures of Cu obtained by the pulsating overpotential (PO) regimes with the same pause-to-pulse ratio 10, but with the different durations of deposition pulse (4) and pause (tp) (a, b) t = ms and tp = 10 ms, (c, d) = 10 ms and tp= 100 ms (Reprinted from Refs. [49, 50] with permission from Elsevier and Refs. [5, 23, 51] with kind permission from Springer)... 

Figure 5.9 shows the honeycomb electrodes obtained at a constant overpotential of 1000 mV (Fig. 5.9a) and by the PO regime with the overpotential amplitude of 1000 mV, deposition pulse, t, of 10 ms, and pause duration, fp, of 50 ms (Fig. 5.9b). Holes obtained by these regimes of electrolysis of detached hydrogen bubbles are shown in Fig. 5.9c (the constant potentiostatic regime) and 5.9d (the PO regime). The bottom of the hole obtained at the constant overpotential was relatively smooth (Fig. 5.9c), while the one obtained by the PO regime was cmistructed from the small...

The increase of compactness of the honeycomb-Uke electrodes obtained by the PO regime is due to the effect of a current density during ofF periods i.e., during duration of pause). Although this current density can be neglected in comparison with the current density during on periods (i.e., during the duration of deposition pulse), it is clear that its effect on the formation of these deposits is very important [21, 23, 29, 51]. 

Figure 5.10 shows the honeycomb-like structures obtained by the PO regimes with an overpotential amplitude of 1000 mV, pause duration of 10 ms, and deposition pulses of 3 ms (Fig. 5.10a), 5 ms (Fig. 5.10b), and 20 ms (Fig. 5.10c). The quantities of evolved hydrogen spent for formation of these electrodes corresponded to the average current efficiencies of hydrogen evolution, //i,av(H2) of 16.4, 22.4, and 28.1 %, respectively [49]. As a reminder, the honeycomb-like electrode was obtained at the constant overpotential equal to this overpotential amplitude with //i,av(H2) of 30.0 % [4, 5, 23]. Analysis of the honeycomb-like...

Fig. 5.10 Honeycomb-like copper structures obtained by the PO regimes with deposition pulses of (a) 3 ms, (b) 5 ms, and (c) 20 ms. Morphology of deposits among holes (d) 3 ms, (e) 5 ms, and (f) 20 ms. Cross sections of the holes (g) 3 ms, (h) 5 ms, and (i) 20 ms. Overpotential amplitude 1000 mV. Pause duration 10 ms. Solution 0.15 M CUSO4 in 0.50 M H2SO4 (Reprinted from Ref. [23] with kind permission from Springer and Ref. [49] with permission from Elsevier)...

Morphology of deposits around holes strongly depended on the length of deposition pulse. Dendrites were formed with a deposition pulse of 3 ms (Fig. S.lOd). 

Dendrites were also formed with a deposition pulse of 5 ms (Fig. 5.10e), but they were more branchy than those obtained with a depositimi pulse of 3 ms. Very disperse cauMower-like agglomerates of Cu grains were formed with a deposition pulse of 20 ms (Fig. 5. lOf). The numerous micro- and nanopores are formed around small Cu agglomerates of grains inside large cauliflower-like agglomerates. 

Dendrites formed around hydrogen bubbles are clearly seen from Fig. 5.10g (tc = 3 ms). Analysis of cross section shown in Fig. 5.1 Oh confirmed formation of more branchy dendrites with a deposition pulse of 5 ms than with 3 ms. The increase of a dispersity of the internal structure is observed with the further increase of deposition pulse. The numerous channels formed around relatively small copper particles and degenerate dendrites are easily observed from Fig. 5.10i (tc = 20 ms). 

From the above consideration, it is clear that the maximal surface area of the honeycomb-like electrodes can be attained by the careful selection of parameters of the PO regimes. This is followed by the decrease in the quantity of evolved hydrogen and, hence, by the improvement of the structural stability of the honeycomb-like electrodes. Simultaneously, analysis of the specific energy consumption shows that energy saving is achieved in the production of the honeycomblike electrodes by the shortening of deposition pulse and by the decrease in the quantity of evolved hydrogen [23, 49]. 

Figure 5.11 shows Cu deposits obtained with the current density amplitudes of 0.20 A cm (Fig. 5.11a) and 0.44 A cm (Fig. 5.11b). In both cases, a deposition pulse of 1 ms and a pause duration of 10 ms were applied [22,23,55,57]. Formation of these deposits was accompanied by the quantity of evolved hydrogen which corresponded to the average current efficiency of hydrogen evolution, /i,av(H2), of 5.5 % with the applied current density amplitude, ic, of 0.20 A cm [57], and...

The first set of experiments was done applying square-waves PC with a constant pause duration, fp, of 10 ms, and deposition pulses, t, of 1, 2, and 50 ms (pause to pulse ratios, p, wherep = were 10,5,... 

Morphologies of copper deposits obtained with deposition pulses of 1, 2, and 50 ms and a pause duration of 10 ms are shown in Fig. 3.5. Holes formed by attached hydrogen bubbles, very branchy dendrites, and small agglomerates of copper grains are formed when the applied deposition pulse was 1 ms (Fig. 3.5a, b). The mixture of holes and degenerate dendrites was formed with a deposition pulse of 2 ms (Fig. 3.5c, d). Honeycomb-like copper stracture constructed of holes and cauliflower-like agglomerates of copper grains formed around them was obtained with a deposition pulse of 50 ms (Fig. 3.5e, f). 

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