Profilometry oxide film thickness

Figure 4 shows the application (6) of potentials to the Pt and Au electrodes of the sandwich (vs. a reference electrode elsewhere in the contacting electrolyte solution) so that they span the E° of the poly-[Co(II/I)TPP] couple (Fig. 4B). There is a consequent redistribution of the concentrations of the sites in the two oxidation states to achieve the steady state linear gradients shown in the inset. Figure 4C represents surface profilometry of a different film sample in order to determine the film thickness from that the actual porphyrin site concentration (0.85M). The flow of self exchange-supported current is experimentally parameterized by applying Fick s first law to the concentration-distance diagram in Fig. 4B ...

A direct correlation exists between the redox state and the PPy film volume. Although, not surprisingly, this correlation confirms that the ion diffusion drives the actuation process. The film thickness was measured by profilometry across the phase boundary. A clear height step was observed at the boundary between the oxidized and reduced phases. The thickness of polymer was constant in the reduced (swollen) region behind the boundary, showing that the polymer was fiiUy reduced in this entire region. Thus, reduction of the polymer requires the diffusing ions to reach the next reduction site on the polymer. 

A serious complication of using profilometry to measure volume change becomes apparent when attempting to make measurements on thin films (<10 pm). Here the applied force from the stylus can lead to anomalous results such as a smaller PPy (DBS) film thickness in the expanded (reduced) state than in the contracted (oxidized) state. This is due to the lower stiffness (Young s modulus of elasticity) in the reduced state compared to the oxidized state resulting in the stylus sinking into the softer polymer. This is not a problem for relatively thick films provided absolute values are not required profilometry can serve as a useful tool to observe the actuation of thick conducting polymer films. 

SIMS studies of these same films, however, did add useful information. The film thicknesses were too low to be able to use a high-current Cs primary beam for depth profiling. An Ar beam was used instead at low currents, which would not have introduced many chemical perturbations into the film. The results of such profiling are shown in Figs. 19a-c for samples of alloy A after exposures in pH 10 solution at the corrosion potential for periods of 3, 12, and 24 h. The intensities of the oxide secondary ions NiO" and CuO" are shown as functions of equivalent sputter time. The depths profiled in these instances were so shallow that it was impossible to gauge them by profilometry thus only the product of sputter time and current density is given on the abscissa. As before, the RSFs for the two ions are considered to be approximately equal. 

SHG Sample Preparation. The polymer samples were dissolved in spectrophotonic grade chloroform (Mallinckrodt) to produce solutions with 10% polymer by weight. Solutions were filtered (5 pm) and then spun cast onto indium tin oxide (ITO) glass substrates. Film thicknesses varied finm 2 to 6 pm ( 0.5) thick, as measured by diamond stylus profilometry. Films were carefully dried to remove any excess solvent. 

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