The tip of a scanning tunneling microscope was used to fabricate geometrically well-defined structures within organized, self-assembled monolayer resists that have critical dimensions ranging from 60 nm to 5 pm. To achieve nanometer-scale lithography, a Au(lll) substrate was coated with a self-assembled monolayer of HS(CH2)i7CH3, which functions as an ultrathin (~2.5 nm) resist, and then the resist was etched by an STM tip. This treatment results in windowlike features that penetrate the organic monolayer. Nanolithographically defined features have been characterized by scanning tunneling microscopy, scanning electron microscopy, and electrochemical methods. For example, since mass and electron transfer to the conductive Au substrate are blocked by the monolayer everywhere except in the STM-etched regions, the windows serve as ultramicroelectrodes. The limiting current that results from radial diffusion of a bulkphase redox species to the etched window is in close agreement with that predicted by theory.

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An electrochemical method for the preparation of high purity metal nitride ceramic precursors is described. Constant current electrolysis of an electrolyte solution containing NH3 and NH4Br at an Al electrode yields a solid mixture consisting of Al(NH3)6Br3 and [Al(NH2)(NH)]n after evaporation of excess NH3. Calcination of this mixture above 800 C in flowing NH3 results in sublimation of Al(NH3)6Br3 and conversion of the ceramic polymer precursor, [Al(NH2)(NH)]n, to pure, high surface area AlN. Here we discuss some electrochemical aspects of the polymer precursor synthesis, precursor processing parameters, and materials characterization of the AlN powder before and after sintering.

Nanometer‐scale manipulation of surfaces by scanning probe devices has expanded amazingly since the first reports in the mid‐1980s. General approaches to scanning probe microscope induced surface patterning are discussed. The Figure shows a scanning electron micrograph of an STM‐defined pattern of a HS(CH2)17CH3 monolayer resist on a Au(111) substrate.

This document has been approved for public release and sale; N00179 its distribution is unlimited. ABSTRACT (Maximum200 words)We have used self-assembly chemistry to synthesize monolayer assemblies that function as molecular recognition interfaces. In the first part of this paper, we show that onecomponent self-assembled n-alkanethiol monolayers with carboxylic acid functionalized -endgroups specifically adsorb vapor-phase acid-terminated molecules via hydrogen bonding or vapor-phase amine-terminate molecules via proton-transfer interactions. In the second part, we demonstrate that two-component monolayers, which consist of inert n-alkanethiol framework moleculesanddefect-inducing templat• molecules, can discriminate between "--solution-phase probe molecules based on their physical and chemical characteristics. By electrochemically etching the defects and then imaging the resulting surface by scanning tunneling microscopy the defect sites can be indirectly visualized. 93-2922393 1-. We have used self-assembly chemistry to synthesize monolayer .7 assemblies that function as molecular recognition interfaces. In • Dist first part of this paper, we show that one-component selfassembled n-alkanethiol monolayers with carboxylic acid functionalized endgroups specifically adsorb vapor-phase acid-_.terminated molecules via hydrogen bonding or vapor-phase amineterminate molecules via proton-transfer interactions. In the second part, we demonstrate that two-component monolayers, which consist of inert n-alkanethiol framework molecules and defectinducing template molecules, can discriminate between solutionphase probe molecules based on their physical and chemical characteristics. By electrochemically etching the defects and then imaging the resulting surface by scanning tunneling microscopy the defect sites can be indirectly visualized.Molecular recognition is the selective binding of a probe molecule to a molecular receptor. This binding interaction relies on both non-covalent intermolecular chemical interactions, such as hydrogen bonding or van der Waals forces, and steric compatibility, such as size or shape inclusion. At present, a detailed understanding of molecular recognition phenomena is hindered primarily by two experimental problems. First, in many natural systems the receptor is a large, flexible, and complex molecule with many potential binding sites, and as a result it is difficult to quantify the specific types and magnitudes of interactions that lead to probe binding. Second, there are only a few analytical methods that are sufficiently specific and sensitive that they can be used for studying individual molecular interactions in bound probe/receptor complexes. These and other difficulties associated with natural systems have resulted in the synthesis of simpler model receptors and characterization of their interactions with probe molecules (1-3).Two general strategies have been used for synthesizing and characterizing model receptors and their complexes with probe molecules. The first is based on interactio...

We discuss an electrochemical approach suitable for preparing nine metal nitride precursors and the corresponding metal nitrides. The method involves anodic dissolution of a metal electrode in a single-compartment electrochemical cell containing an electrolyte solution consisting of liquid NH 3 and NH 4 X (X ) Br or Cl). Following evaporation of the solvent and calcination of the resulting powder at temperatures between 375 and 1100°C, we obtain the metal nitride corresponding to the anode material. Using this approach metal nitride ceramic powders corresponding to Al, Ga, Mo, Nb, Ni, Ti, V, W, and Zr have been prepared. We also describe a simple modification to the metal nitride synthesis that is suitable for the preparation of composite metal nitride powders. The ceramic materials were characterized primarily by powder X-ray diffraction. The calcination conditions determine the resulting phase, composition, and morphology of the product. For example, when Ar is used to calcine the Mo nitride precursor Mo 2 N obtains, but when NH 3 is the calcination gas we obtain MoN. Calcination of the precursors at different temperatures results in ceramic powders having different phases.