TMS deposition

TMS deposition on PE showed only substrate signals with no detectable TMS signal (Fig. 6.12b). The absence of the TMS signal in this system could be due to the fast reaction of TMS radicals with the surface radicals generated from PE. The more likely explanation is that the number of free radicals in the plasma polymer layer is too small in comparison with the free radicals created in the bulk of the substrate, PE. What we see in Figure 6.13 is the decay of PE polymer free radicals, which were created by the luminous gas of TMS. With substantial decay of the PE free radicals, TMS dangling bonds, which decay much slower, became discernible. 

It is important to emphasize that O2 plasma treatment collects much more F-containing contaminants on the alloy surface than without O2 plasma treatment, although this treatment virtually eliminated the interference of the contaminants to the subsequent TMS deposition as described in the previous section. In other words, O2 plasma treatment does not reduce the amount of fluorine on aluminum alloy surface but reduces plasma-ablatable fluorine on aluminum alloy surface. 

Figure 10.15 Schematic representation of the mechanism how F-containing contaminant interfere with plasma pol5mierization of trimethylsilane (TMS) (a) migration of F-containing oligomers, (b) the interference of TMS deposition by F-containing moieties.

TMS deposition rate profiles in DC, 40-kHz, and 13.56-MHz discharges are shown for electrode in Figure 13.2. It can be seen that, regardless of the frequency of electrical power source used, a uniform deposition of TMS polymers was observed in the three plasma processes, although an appreciable edge effect occurred in the DC and a less pronounced effect occurred in the 40-kHz discharge when the substrate was used as the cathode or powered electrode. The uniform distribution of deposition rates justifies the use of single measurement at the center of the electrode to represent the characteristic deposition rate of a system. 

In DC cathodic polymerization conducted in a bell jar reactor, the cathode (substrate) is positioned in the middle between the two anodes. In such electrode arrangement, the distance between the cathode and the anode is expected to have some effects on the deposition rate and deposition profile with respect to those without anode assembly. Figures 13.4 and 13.5 show the influence of the distance between two anodes (one-half of which is the cathode-anode distance) on TMS deposition rate on cathode (i.e. substrate) and anode, respectively. 

TMS DEPOSITION ON MULTIPLE CATHODES WITHOUT ANODE ASSEMBLY... 

It can be seen from Figure 13.8 that very uniform TMS deposition profiles were achieved on all five panels in both cases of 4- and 6-cm panel spacing. As noted from Figure 13.8b and c, one interesting aspect is that, in DC cathodic polymerization with a row of cathodes (panels), the deposition rate on the internal panels is about 200-300 A/min higher than that on the outside surface of the external panels. 

Figure 13.9 shows the TMS deposition profile with five panels in a row at lOOmtorr under different DC power inputs. The increase of DC power input from 5 W to 25 W significantly increased the deposition rate of TMS on the cathodes. Two interesting facts were noted from Figure 13.9. The first is that the deposition difference disappeared between the two sides of the outer panels as noted in...

Figure 13.11 shows the change of TMS deposition rate with DC power input at system pressures of 50 and lOOmtorr. As anticipated, a linear dependence of the deposition rate on DC power input was observed at both 50 and lOOmtorr system... 

Figure 13.11 The dependence of TMS deposition rate on DC power input under different system pressures with 5 panels in a row TMS flow rate was 1 seem and the deposition rates were obtained on panel 1 as shown in Figure 13.7 with panel spacing of 6 cm.

Figure 13.12 The influence of panel numbers on (a) the plasma voltage and current, as well as (b) the current density and TMS deposition rate on the cathode (the panels) TMS, 1 seem, 50 mtorr, DC 5 W, 6-cm panel spacing.

Eight of 10 TMS-treated polymers exhibited contact angles within an average cos 0D a,i =—0-381 (0D,a,i = 112 3.6), and all of them showed the negative cos 0. This indicates that the surface of plasma polymer of TMS-deposited films is clearly hydrophobic and independent of the substrate material for these polymers. TMS-treated PTFE and UHMWPE were slightly more hydrophobic with average cos 0D,a,i = -0.785 (0D,a,i = 141 4.2). 

Figure 32.8 TMS deposition profile in no anode assembly plasmas with different operation modes 1 seem TMS, 50 mtorr, 1 min.

Besides the advantageous features described earlier, DC cathodic plasma polymerization of TMS mixed with argon also provides an opportunity to combine the two processes of TMS deposition and second plasma treatment into a single step. TMS plasma coating thus produced also maintains excellent corrosion protection properties on the aluminum alloy substrates. 

Figures clearly distinguish the difference between these two TMS depositions on different substrate surface states. Table 33.1 lists the peak assignments for both (a) and (b). In Figure 33.1a, two distinct bands are observed near 3394 and 3190 cm These locations and peak shapes would be consistent with the presence of either isolated O-H bonds or N-H functionality. The strong, sharp peaks at...

Figure 33.8 XPS depth profile of plasma polymer of TMS deposited on (a) (Ar-hH2) plasma treated pure iron, (b) O2 plasma treated pure iron.

The world s biggest mercury deposit is at Almaden (Spain). Exploitation of tMs deposit began at the time of the Roman Empire, and Romans extracted 4.5 tons of mercury annually. 

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