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Zhiming YU, Dept. of MSE, CSU Zhiming YU, Dept. of MSE * Surf. Sci. Thin Solid Films * Chapter 2 Thermodynamics of the Surface 1. Surface free energy (SFE) 3. Curvature surfaces Man points: 2. Anisotropy of the SFE of Crystal Gibbs, Josiah Willard, On The Equilibrium of Heterogeneous Substances(1875-1878), in The scientific papers of J. Willard Gibbs, Vol. 1,(Longmans, London and Dover, New York, 1901), p. 315. “ We may regard ? as expressing the work in forming a unit of the surface of discontinuity, but it cannot properly be regarded as expressing the tension of the surface. The latter quantity depends upon the work spent in stretching the surface, while the quantity ? depends upon the work spent in forming the surface. With respect to perfectly fluid masses, these processes are not distinguished, the work spent in increasing the surface infinitesimally by stretching is identical with that which must be spent in forming an equal infinitesimal amount of new surface. But when one of the masses is solid, there is no such equivalence between the stretching of the surface and the forming of new surface.” 12. Surface tension and s 3. Surface Energy 4. Surface Potential SFE 5. Surface Free Energy Born and Stern (1919): By dividing in vacuum a crystal along a plane (hkl), there is to spend the work Whkl(rev.) in order to separate to infinity both parts of the crystal during an isothermal (?T = 0) and reversible process, creating a surface area 2Ahkl. Per unit area surface free energy (SFE—?hkl) is M. Born and O. Stern, Ber. Berliner Akad. 48, 901(1919). Definition of the SFE §2-2 The surface free energy Cleavage Technique Anisotropy of the SFE determined by equilibrium forms Theoretic calculation. Determination of the SFE of Crystal gSi-111 = 1240 erg/cm2 by measurement, 1160 erg/cm2 from calculation 1) Cleavage Technique to measure the SFE (J. Gilman, 1960) crystal F F crystal F J. Heyraud and J. Metois, Equilibrium shape and temperatu