Condensation and structure of multiphase thin films

Multi-source vacuum deposition processes allow manufacture of composite mat erials which are impossible to produce by conventional techniques. The cond ensation mechanisms of physical vapour deposition (PVD) may also favour the formation of new material structures which are not known from techniques s uch as, e.g., solidification from the melt. This paper summarizes the influ ence of different deposition modes on the phase distribution within vapour- deposited two-component films. Special emphasis is laid on the immiscible b inary material combination Al-Sn as a model system. Two deposition modes, s equential deposition and co-deposition from two separate sources, are treat ed in detail. From experiments as well as from theoretical considerations, it is concluded that there are two key parameters determining the phase dis tribution: the different mobilities of the constituents in the growth zone and their mutual sticking coefficients. The latter parameter reflects the r elation of the different surface energies. Growth models for sequential and codeposition which reproduce the general types of phase distributions are formulated. Methods of a detailed morphological characterization of the sin gle phases are presented. Finally possible influences of impurities present at the growth front of two component films on the mobilities and surface e nergies of the constituents are discussed. (C) 2001 Elsevier Science Ltd. A il rights reserved.