The uses of polymeric materials in today's world are vast. Polymers are finding applications in the microelectronics industry as dielectric insulators and photoresists, in the aerospace and automobile industry as lightweight substitutes for metals, and in biotechnology as replacement components for bone, heart, and other organs. These are just a few of the many end uses of polymers.

Often, a polymer may have a particular, desirable property but processing of the polymer is difficult or the polymer's surface characteristics are undesirable. To circumvent such shortcomings there are several options. The first is to synthesize a new material, which is quite costly and time consuming. Alternatively, two polymers with complimentary properties can be mixed. Unfortunately, most polymer pairs are immiscible unless there are specific interactions (e.g., hydrogen bonding) between the two components. Consequently, coarse phase separation is often observed, leading to an ill-defined material. Finally, two chemically distinct homopolymers can be joined together at one point, forming a block copolymer. While phase separation may occur, the scale of the domains is restricted to the sizes of the individual homopolymers, which is typically on the tens of nanometers scale. The added advantage of this approach is that the size of the different blocks can be altered, varying the concentration of the different components. For copolymers that “microphase” separate, this variation in composition leads to a variation of the morphology of the microdomains ranging from spherical to cylindrical to lamellar.

Diamond synthesis has attracted attention ever since it was established in 1797 that diamond is a crystalline form of carbon. Initially, synthesis was attempted at high pressures because diamond is the densest carbon phase. As understanding of chemical thermodynamics developed through the 19th and 20th centuries, the pressure-temperature range of diamond stability was explored. These efforts culminated in the announcement in 1955 of a process for diamond synthesis with a molten transition metal solvent-catalyst at pressures where diamond is thermo-dynamically stable. Worldwide sales of synthetic diamond now approach 330 million carats (73 tons) with a market price of between $500 million to $1 billion.

Over the past 40 years a parallel effort has been directed toward the growth of diamond at low pressures, where it is metastable. Although diamond was successfully produced, low-pressure synthesis was plagued by extremely low growth rates. Recent developments have led to much higher growth rates, creating great interest in the field. Polycrystalline diamond films can now be produced on a variety of substrates at linear growth rates of tens to hundreds of micrometers per hour. In addition, the recognition of an entirely new class of solids, the so-called “diamondlike” carbons and hydrocarbons has arisen from this work. This article will discuss both crystalline diamond grown at low pressure and the diamondlike phases.

The interest in diamond is driven by its extreme properties, summarized in Table I. Diamond stands alone as the densest (number density), strongest (elastic modulus), and hardest known material.

There are many methods of depositing thin film materials: thermal evaporation, sputtering, electron or laser beam evaporation, chemical vapor deposition (CVD), and molecular beam epitaxy (MBE). A good survey of many of the deposition methods appears in the 1988 November and December issues of the MRS BULLETIN. One method not included in that survey, however, is metalorganic deposition (MOD), a powerful method for depositing a variety of materials.

Metalorganic deposition is not to be confused with metalorganic chemical vapor deposition (MOCVD), which is a gaseous deposition method. MOD is a nonvacuum, liquid-based, spin-on method of depositing thin films. A suitable organic precursor, dissolved in solution, is dispensed onto a substrate much like photoresist. The substrate is spun at a few thousand revolutions per minute, removing the excess fluid, driving off the solvent, and uniformly coating the substrate surface with an organic film a few microns thick. The soft metalorganic film is then pyrolyzed in air, oxygen, nitrogen, or other suitable atmosphere to convert the metalorganic precursors to their constituent elements, oxides, or other compounds. Figure 1 shows a schematic of the deposition process including a prebake and annealing (if necessary).

The discovery and demonstration of molecular shape-selective catalysis in zeolitic silicate structures has led to a large segment of new catalytic science as well as to chemical process technologies with broad impacts on industry and society. Manmade catalysts are beginning to acquire skills of molecular structure selectivity and activity seen in the world of enzymes.

All our activities, including those of life itself, are dominated by the presence and action of ever transforming molecules. Heat alone transforms them but, basically, decomposes them indiscriminately. Catalysts, on the other hand, can direct transformations with meticulous selectivity as if to preserve a continuing purpose and order, and life itself. However, manmade catalysts, although the major tool of the chemical industry, have been highly simplistic and crude in their discriminatory capabilities. For example, we have solid acidic catalysts called cracking catalysts that will break carbon-carbon bonds. They have been employed for decades in the petroleum fuels industries and represent the largest volume of any manufactured catalyst. They will rather indiscriminately break C—C bonds in nearly any aliphatic organic structure, with only some structural preference for tertiary over secondary over primary carbon links.

In another class of manmade catalysts, molecules with unsaturated bonds are hydrogenated by a variety of metal-based catalysts. This addition of hydrogen proceeds nearly regardless of where the bond occurs in the structure. Or, take a synthesis reaction, such as that of xylenes from the addition of methanol to toluene. The usual acidic catalysts will add the new methyl group in any and all of the three possible isomeric positions to produce ortho-, meta-, and para-xylenes.