On Some Properties Of The Two-dimensional Phases Condensed On A Foreign Substrate. Ii. Surface Roughness Of Condensed Layers And Variation Of The Surface Free Energy During Multiple Layer Adsorption

Abstract

The roughness of the surface resulting from a multiple-layer adsorption is treated as a function of the temperature and the supersaturation. It is shown that the supersaturation Δμ(i) v7, at which the number of vacancies and admolecules of the i-th top-layer are equal, is the arithmetic mean of the equilibrium supersaturations Δμ(i) 0 and Δμ(i + 1) 0 of the i-th and (i + 1)-th layers respectively, contrary to a three-dimensional phase, where Δμv7 and Δμ0 are identical (nil). The further use of Δμ(i) v7, as origin for the supersaturation scale, leads to reduced equations, permitting to calculate easily roughness and surface free energy variations in the stability range (Δμ(i) 0 < Δμ < Δμ(i + 1) 0) of the i-th layer. The total free surface energy variation due to multiple layer adsorption is decomposed into two parts: the first, due to the deposition of i compact layers, and the second, due to the roughness of the top monomolecular layer. A method is proposed for determining the absolute specific adhesion energy between two substances (A and B) in the case when only the positions of the steps of the experimental step-wise isotherm of A on B are known. The method is applied to the adhesion energy xenon/graphite. © 1976.61193108Mutaftschiev, (1976) Surface Sci., 60Champion, Halsey, (1953) J. Phys. Chem., 57, p. 646Singleton, Halsey, (1954) J. Phys. Chem., 58, p. 1011Hill, (1946) J. Chem. Phys., 14, p. 263Mutaftschiev, (1965) Adsorption et Croissance Cristalline, p. 231. , CNRS, ParisTemkin, (1966) Crystallization Processes, p. 15. , Consultants Bureau, New YorkFrumkin, (1925) Z. Physik. Chem., 116, p. 466Fowler, Guggenheim, (1960) Statistical Thermodynamics, p. 466. , CambridgeBragg, Williams, The Effect of Thermal Agitation on Atomic Arrangement in Alloys (1934) Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 145, p. 699Bragg, Williams, The Effect of Thermal Agitation on Atomic Arrangement in Alloys. II (1935) Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 151, p. 540Born, Stern, (1919) Sitz. Ber. Preuss. Akad. Wiss., 48, p. 901Thomy, Duval, (1965) Adsorption et Croissance Cristalline, p. 81. , CNRS, ParisQuentel, Rickard, Kern, (1973) Vide, 28, p. 65J. Regnier and B. Mutaftschiev, to be publishe