We will establish a new, non-equilibrium process for the preparation of quantum dots of arbitrary composition in a variety of hosts. This process features a versatile laser ablation supersonic expansion source for the synthesis of size-selected semiconductor quantum dots. Gas phase processing of the dots is extended with a molecule-particle CVD (MPCVD) technique which yields a dot/host composite which consists of semiconductor quantum dots grown epitaxially within a crystalline semiconductor host. These new materials systems are expected to yield new insights into the interfacial, morphological, and phase stability of small systems and to provide a high-performance materials platform for integrated photonic device structures. The goals of the research program are: 1) to provide a materials design knowledge base; 2) to discover new optical phenomena which evolve from the interacting fields within nanocomposite materials and to develop materials characterization methods for photonic materials; 3) to understand and demonstrate the fundamental limits in monodispersity of heterogeneous systems and in the stability of materials under intense photon fields; and 4) to lay the ground work for the design and fabrication of thin film optical components by employing varying dot and host compositions, sizes, and dot densities. %%% A new approach for the synthesis and processing of novel quantum dot thin film materials for nonlinear optical applications is being explored in this research program. The approach exploits a series of new gas-phase processing techniques to produce an array of materials consistingg of semiconductor clusters of nonlinear optical materials of the elemental systems, Ge and Si, in epitaxial environments of Si, GaAs, and ZnSe. These dots, ranging in sizes from the very small (~100 atoms) to the very large (~10,000 atoms) systems, are expected to provide greatly enhanced nonlinear optical properties over those of bulk semiconductors through quantum confinement effects. The resulting crystalline materials differ markedly from any quantum dot materials produced to date by using a confining matrix as a means not only to isolate the clusters from each other, but also to fully define and satisfy critical surface properties of the confined cluster. These materials represent a significant potential for future nonlinear optical devices for advanced applications in computing, information processing, and communications.
