The emerging art of solid state synthesis. Organic chemists have refined the process of producing molecules with specific arrangements of atoms to a high art. Synthesized molecules from simple symmetric cubane structures to complex asymmetric natural products are metastable species. Taking advantage of activation barriers to kinetically trap the atoms in a desired configuration. Since some are structurally instable, concern in placed on the mechanisms of chemical reactions, and the majority of efforts are focused on compounds with only a few different elements (C,H,O,N). Solid state chemics work with 80 elements, concerned with thermodynamic products, which are the most stable configuration of the atoms at a particular temperature. Solid state synthetic techniques involves elements making a particular compound mixed and heated at high temperatures for an extended time until a stable configuration is found. So solid state chemists have not explored as many metastable compounds or kinetic products. Solid state synthesis is changing. Pioneering methods of production of metastable solid state structures and examination of the mechanisms of solid state reactions are underway. Borrowed techniques refined in semiconductor industry for the production of multilayered films of smiconduction materials, and extend them to the general probblem of solid state synthesis. The key technique is molecular beam epitaxy (MBE) which uses beams of atoms that encounter each other on a suitable substrate and react to form a desired compound. The substrate is usually heated to promote the formation of the crystalline layer, and one can then grow layers of various compositions by changing the atomic identities of the impinging beams. The highest quality semiconductor materials ever produced have been obtained with this and similar techniques. Self Assembling solids can be made this way. Structures of multiple thin layers of amorphous elements have been made. Then reactions of these thin elemental layers is initiated by raising the temperature and promoting the solid state diffusional interpenetration of the reactants and the nucleation and growth of crystalline phases. This is followed by xray diffraction, which is sensitive to the crystalline compounds present in the thin film, and calorimetry which gives information about the heats of reaction. Variation of the heating times (annealing) and rates provides a wealth of information abobut the kinetics (nucleation and growth), products and thermodynamics of the solid state reaction. Metastable compounds, or solid-state reaction intermediates can be seen in many experiments. A superlattice -= repeating units of distinct well defined phases is spontaneously assembled by control of the composition, thickness and annealing parameters. Layers of Nb, Se and Ti are deposited and heated, resulting in a superlattice w/ three nearly pure layers of the layered material NbSe2 are alternated with three layers of TiSe2 Higher tempeatures produced further intermixing and the more thermodynamically favorable solid solution of niobium and titanium diselenide. Changing the composition and thickness of the initial layers results in superlattices with different numbers of NbSe2 and TiSe2 layers in alternating structure. These superlattice structures can be built up one layer at a time by a variation of MBE called van der Waals epitaxy as has been demonstrated by several groups. Mechanistic and thermodynamic information about the crystallization of the new phases would not be available. These are also reminiscent of self assembbled structures, self assembly means that complex structures spontaneously form from simple components. Folded protein structures, micelles and vesicles, and some types of molecular monolayers are all examples of self assembly. Unique properties of self assembled systems can be identified, In NbSe2/TiSe2 superlattices, superconductivity is revealing. Bulk NbSe2 superconducts at 7K. Superconductivity in some superlattice structures occures. Tailoring of optical and magnetic properties will also be possible. /*---------------------------------------------------------------------*/ Real Space structure of Colloidal Hard-Sphere Glasses The real-space structure of hard-sphere glasses quenched from colloidal liquids in thermodynami equilibrium has bbeen determined. Particle coordinates obtained by combining the optical sectioning capability of confocal fluorescence microscopy with the structure of specially prepared fluorescent silica colloids . Both the average structure and the local structure of glasses, with volume fractions from .6 to .64 agree with glasses and random close packings generated by computer simulations. No evidence of a divergent correlation length was found. The method used to obtain the three dimensional particle coordinates is directly applicable to other colloidal structures, such as acrystals, gels and flocs /*---------------------------------------------------------------------*/ A Carbon Nanotube Field-Emission Electron Source A high intensity electron gun based on field emission from a film of aligned carbon nanotubes has been made. The gun consists of a nanotube film with a 1 millimeter diameter grid about 20 micrometers above it. Field-emission current densities of about 0.1 milliampere per square centimeter were observed for applied voltages as low as 200 volts and current densities greater than 100 milliamperes per square centimeter have been realized at 700 volts. The gun is air stable, easy and inexpensive to fabricate, and functions stably and reliably for long times (short-term fluctuations are on the order of 10%). The entire gun is 0.2 millimeters thick and can be produced with virtually no restrictions on its area, from less than 1 square millimeter to hundreds of square centimeters, making it suitable for flat panel display applications.