Controlled chemical phase separation in binary and ternary composites: A pathway to isotropic optical and electrical behavior for device applications



There are many applications for nanocrystalline thin films in optical devices that require isotropic optical properties. A novel way to obtain these isotropic properties for the index of refraction and/or optical absorption constant, etc., and at the same time to minimize microscopic strain is presented in this article. This approach is based on strain reduction mechanisms that occur in the intermediate phases, IPs, of non-crystalline glasses and thin films. In these compositional regimes, either site percolation, or volume percolation, each above an applicable critical value, provides a quantitative understanding of the microscopic bonding arrangements associated with strain-reducing chemical bonding self-organizations. A similar framework, presented for the first time in this article, develops a microscopic understanding of macroscopic strain reduction in several different phase-separated composites. This understanding has emerged from focussed research on qualitatively different hetero-structure device structure constituents, e.g.; (i) high-k replacement dielectrics for SiO2 in field effect transistors gate stacks for advanced semiconductor devices, and (ii) active and passive thin films for optically switched memory cells. In each instance strain reduction and its intrinsic relationship to low densities of defects and defect precursors has provided a driving force in the identification of a narrow range of compositions that satisfy technological needs. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)