Plasma polymer deposition, measurement

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)...

The circulation of a temperature-controlled liquid controlled the temperature of the crystal surface on which the plasma polymer deposits. In order to measure the substrate temperature accurately, two thermocouples are placed in the fluid-circulating tubes (inlet and outlet) just outside of the plasma reactor. The substrate temperature is estimated from the average of the thermocouple readings. 

Likewise, bond energies for the sum of the Is-electrons of the elements 0, C and N in the deposited plasma polymers are measured and summarized in TABLE 4. It should be noted that the polymer films were deposited with 15 seem Ar as carrier gas. 

Contact angles were measured on plasma polymers deposited from numerous hydrocarbon monomers of different structure containing triple bond, olefinic double bonds, aromatic and aliphatic structures. The results of contact angle measurements and evaluated surface energy properties for these polymers are summarized in Table II, column A. The data for plasma polymers from acetylene, ethylene, and hexane indicate that monomer unsaturation does not change substantially the dispersion component but increases the polar component to a considerable extent as in the case of acetylene. This, undoubtedly, is due to the high concentration of radicals in PP-AC and resulting rapid formation of carbonyls and... 

For each of the four cases an expression for the rate of polymer deposition was derived in terms of the gas pressure, p, the plasma current, I, the measure of the average electron energy, V/p, and the ratio of the monomer pressure to its saturation vapor pressure, x. The functional dependencies of rp on these variables are given in Table 3. The constants a, c, and n, are taken to be parameters whose values are adjusted to obtain a fit between the measured and predicted values... 

Characterization of this tumbler reactor was carried out via the deposition rate measurement of a plasma polymer film on silicon wafers under different conditions. In the longitudinal direction, the deposition rate decreases significantly when the plasma moves from the central plasma zone to the remote zone. With appropriate shielding, the decay in deposition rate in the longitudinal direction can be effectively reduced. By means of the stirring, a uniform distribution of the plasma deposition is achieved within the chamber. 

Plasma polymer layers were deposited in the same reactor as described before. However, in this case, the pulsed plasma mode was applied. The duty cycle of pulsing was adjusted generally to 0.1 and the pulse frequency to 103Hz. The power input was varied between P 100 ()() V. Mass flow controllers for gases and vapours, a heated gas/vapour distribution in the chamber, and control of pressure and monomer flow by vaiying the speed of the turbomolecular pump were used. The gas flow was adjusted to 75-125 seem and the pressure was varied between 10 to 26 Pa depending on the respective polymerization or copolymerization process. The deposition rate was measured by a quartz microbalance. 

For measuring the Al-polymer (PP) peel strengths the plasma polymerization was performed using the previously described reactor. Then, the plasma polymer coated polymer samples were transferred into a separate electron beam metallizer (Auto 306, Edwards, UK). The thickness of deposited aluminium layers was adjusted to 150-200 nm using a quartz microbalance. The metal peel-... 

Pulsed Plasma Polymerization. Allyl alcohol, allylamine and acrylic acid were polymerized in pulsed plasma to retain a maximum in functionalities in the resulting plasma polymer. The retention of functional groups during the plasma process, introduced by functional-group carrying monomers and followed by deposition to polymer layers, was primarily measured by XPS including the chemical derivatization of these groups as described in Experimental. These layers were also checked for side-products by respective IR spectra. The results are summarized in Table 1. 

Completing a circuit and measuring the current that flows on contact or separation can quantify the transfer of electrons [2]. A typical result on contact electrification is shown in Figure 24.3. The time constants associated with the current peaks can be adjusted by inserting a series resistance in the measurement circuit. In real time, the equilibration of surface state electrons occurs instantaneously. In these experiments, the plasma polymer of tetrafluoroethylene (TFE) was deposited on two different substrate, nylon film and polished brass, and the contact and separation currents were measured with a (uncoated) brass probe... 

Figure 24.4 depicts the change of surface electron energy level as a function of the thickness of a plasma polymer. In this case, plasma polymer of acetylene/N2 was deposited on brass and the contact current was measured against nylon 66. The result indicates the following two important aspects of the surface state First, the surface state electron energy level at a thin-coating thickness is influenced by that of the substrate material but becomes independent of the thickness above a threshold... 

None of the smooth surfaces prepared by the depositing of plasma polymer on the smooth surface of Silastic tubing showed detectable thrombus formation by gamma camera imaging. Therefore, they were evaluated by measurement of relative rates of platelet consumption. Table 35.7 shows the results obtained using the plasma polymers described previously [5]. 

After correction for the photo-electric cross-sections of these lines, the peak areas indicate the relative number of each element at the surface. As will be shown below, these results cannot be Interpreted in terms of the F/C ratio in the plasma polymer because bonding of fluorine to aluminum can also occur. However, a measure of the F/C ratio in the deposited plasma polymer can be obtained from the shape of the Cj ... 

This work was supported by the Office of Water Research and Technology of the U. S. Department of the Interior under Contract Nos. 14-30-3301 and 14-34-0001-7537. Measurement of deposition rates and plasma polymer preparation was carried out by Barry Hill whereas the ESCA spectra were obtained by E. S. Brandt under the supervision of C. N. Reilley at the Department of Chemistry of the University of North Carolina at Chapel Hill. 

Figure 9-19. Schematic of an RF plasma system for plasma polymerization (polymer film deposition) (1) RF generator, (2) plasma zone (3) heated window (4) engine (5) rotating substrates (6) flexible connection (7) air valve (8) vacuum valve (9) manometer, (10) cooled trap (11) vacuum pump (12) quartz gauge for measurements of the film thickness (13) photodiode (14) registration system (15) polymer deposition chamber (16) laser (17) argon tank (18) valve (19) dose valve (20) tank with a manometer, (21) manometer.

Table 3.3 shows that plasma-treated wool can have a greater reduction in DFE than wool treated with chemicals. This reduction in DFE implies that the felting tendency of wool is lower. In addition, the value of the density (D) of the felt baU is an inverse measure of the degree of felting. It is observed that untreated wool fiber has the greatest D values whereas the plasma-treated wool shows the greatest reduction in D among oxidized, reduced, and polymer deposited wool. 

IR spectroscopy can be used for the identification of functional groups in plasma polymer films. Although primarily a qualitative analytical tool, it has been used to quantitatively measure the concentrations of functional groups and the crosslinking density of plasma polymer films [42-44]. IR spectra might be obtained by depositing the plasma polymer on IR transparent substances or on other surfaces by using attenuated total reflectance (ATR). 

AFM can be used to follow the deposition of thin films over time. Simple thickness measurements can be performed by either scoring the film with a scalpel after deposition or masking part of the substrate before deposition of the film, and measuring the height of the step created. In Fig. 2.5, plasma polymer films grown from acrylic acid monomer are shown to grow initially as discrete islands, which then coalesce and eventually form a flat, pinhole-free film after approximately 240 s. This result is contrary to the often-stated view of plasma deposition that films always grow as a conformal layer. 

Figure 31 (a)AFM picture of a flame-annealed Au surface. The measurement was done in the tapping mode. The brightness increases with the height, (b) AFM picture of a flame-aimealed Au surface coated with an about 3-nm-thick hexamethyldisilazane [(CHjljSi— NH—SiCCHjlj, HMDSZ] plasma polymer that was deposited atPhmdsz ... 

The delamination rate was determined with a scanning Kelvin probe. A small amount of fine sodium chloride was introduced into a circular deepening in the middle of the polished and ethanol-cleaned iron sample. After the sample was introduced into the plasma reactor, it was cleaned and activated in one step by an oxygen plasma, leading to a carbon-free and highly oxidized iron surface. In the next step an ultrathin plasma polymer of hexamethyldisilane was deposited on the cleaned substrate, leading to a well-defined metal-polymer interface. The thickness of the deposited polymer was controlled by the in situ measurement of the resonance frequency of the quartz crystal and was about 5 nm, so that the film thickness is in the range of the escape depth of the photoelectrons. 

Figure 36 shows a 3D plot of a scaiming Kelvin probe measurement of an iron sample that was coated with a 5-mn-thick HMDS plasma polymer on one half of the sample surface prior to the deposition of the primer [115]. The water contact angle... 

With a cross linked structure, it is often characteristic of plasma polymers, that internal stress builds up as the film thickness increases. The internal stress can in fact be measured from the curling force produced when plasma polymer films of known thickness are deposited on a substrate (e.g. LIffE) for which the bulk modulus is known. Typical data are shown in Figure 13. 

Wettability studies were carried for plasma polymer films deposited from structurally different organosilicaon monomers such as siloxanes, silazanes and silanes. To minimize the oxidation of polymer film surface in the ambient, the contact angles were measured immediately after deposition process. The contact angle values and calculated surface energy data for these polymers are summarized in Table I, column A. An examination of the dispersion, 7, and polar, Y, components of the surface energy reveals distinct differences in their values resulting from various structures of monomers. The lowest values of Yg are noted for siloxane plasma polymers as compared with those for silazane and silane polymers. 

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