We have obtained detailed capillary kinetic data for flow of a series of alcohols with various surface tension to viscosity ratios, γ/µ, spreading in open V-shaped grooves cut in Cu with three different groove angles. The location of the three-phase contact line, z, with time always follows the formula z 2) K(R,θ)-[γh0/µ]t where R is related to the included groove angle β (R ) 90 -β/2), θ is the contact angle, and h0 is the groove depth. Two theoretical models which assume Poiseuille flow and static advancing contact angles were tested against the experimental data. One is a detailed hydrodynamic model with the basic driving force resulting from the pressure drop across a curved interface. The second depends on the total interfacial energy change, independent of the shape of the liquid interface. Both agree with the experimental data. In agreement with experiment, both models predict that the rate approaches zero as R f θ, and both require R -θ > 0. Both, including a physically unrealistic approximation by a cylindrical capillary, correctly scale the experimental data. Both predict numerical values in general agreement with experiment and with each other. Differentiation between the models is possible only in the K(R,θ) term which is shown to be only weakly dependent on the range of R,θ values studied. In the threshold region where the transition occurs between filled and empty regions of the groove, the liquid height decreases linearly with distance, within experimental limitations, and forms an angle which roughly scales as the contact angle for a significant fraction of the threshold region. On the basis of the present detailed experimental data for both kinetics and threshold profile, the differences between experiment and theory and between the theoretical models are insufficient to allow a clear choice between the models.

Toluene solutions of monochlorosilane and trichlorosilane coupling agents are shown to react differently with hydrated and dry silicon surfaces. For typical hydrated surfaces produced by piranha (H2O2 + H2SO4) etching, the saturation coverages of octadecyldimethylchlorosilane (ODMS) (one reactive Si-O bond) are approximately a third that of octadecyltrichlorosilane (ODTS) (three reactive Si-O bonds). In contrast, for samples vacuum baked at 400°C, the saturation coverages of ODTS and ODMS are comparable. These data are consistent with coupling reactions limited to the surface hydroxyl groups. The ODTS saturation coverage on vacuum-fired silicon samples can be increased by soaking in water followed by a second ODTS exposure. From X-ray photoelectron spectra (XPS) and secondary ion mass spectra (SIMS) obtained as a function of solution exposure time, saturation coverage is shown to take at least 2 h and to be limited by the concentration of surface hydroxyl groups; a direct correlation is seen in SIMS between the exposure dependent gain in the surface alkyl signal and the loss of the SiOH signal. The coefficient of friction of silicon (piranha etched) is reduced by an order of magnitude by saturation coverages of ODTS, but continued rubbing for over 50 cycles at a normal loading of 245 mN results in decay of the friction coefficient to the value appropriate for uncoated silicon. These results as well as others from the literature are discussed in this paper in terms of a mechanism for the reaction of alkylchlorosilanes with silicon.

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Heptanol flow in irregularly shaped surface grooves in Pd-coated Cu is shown to be an example of Poiseuille flow with simple Washburn kinetics of the form z 2 ) C(γ/µ)t, where γ is the liquid surface tension, µ is the viscosity, and C is a function of the groove dimensions and the contact angle θ. A shape independent expression is derived for the geometric factor, C(S,w,θ) ) (S cos(θ)w)/4π, where w is the width of the groove at the surface and S is the arc length, or total length of groove surface in a plane perpendicular to the groove axis. This expression is general for any groove shape and reduces to the form derived previously for V-shaped grooves. Along with scanning electron microscopy, three different techniques, stylus profilometry, laser profilometry, and optical interferometry, were used to characterize the groove geometry, especially to determine S and w. While reasonable agreement is obtained between literature values of γ/µ and values obtained from the experimental kinetics, the main conclusion is that measurement of the groove dimensions is the main limitation to experimental verification of the form of C and to the use of the kinetics of groove flow as an absolute measure of the factor γ/µ. However, we show that if C is calibrated for a specific groove with a known liquid, the kinetics of capillary flow in open surface grooves furnishes a simple, easily applied method for measurement of the surface tension-to-viscosity ratio, γ/µ. LA9712247