Novel ultrananocrystalline diamond probes for high-resolution low-wear nanolithographic techniques

A hard, low-wear probe for contact-mode writing techniques, such as dip-pen nanolithography (DPN), was fabricated using ultrananocrystalline diamond (UNCD). Molding within anisotropically etched and oxidized pyramidal pits in silicon was used to obtain diamond tips with radii down to 30 nm through growth of UNCD films followed by selective etching of the silicon template substrate. The probes were monolithically integrated with diamond cantilevers and subsequently integrated into a chip body obtained by metal electroforming. The probes were characterized in terms of their mechanical properties, wear, and atomic force microscopy imaging capabilities. The developed probes performed exceptionally well in DPN molecular writing/imaging mode. Furthermore, the integration of UNCD films with appropriate substrates and the use of directed microfabrication techniques are particularly suitable for fabrication of one- and two-dimensional arrays of probes that can be used for massive parallel fabrication of nanostructures by the DPN method.     

Kalman filtering of tunable diode laser spectrometer absorbance measurements

A recursive Kalman time-series filter was applied to absorbance measurements obtained with a tunable diode laser spectrometer. The spectrometer uses frequency modulation spectroscopy and a nearinfrared diode laser operating at 1.604 μm to monitor the CO(2)-vapor concentration in a 30-cm absorption cell. The Kalman filter enhanced the signal-to-noise ratio of the spectrometer by an order of magnitude when an absorbance of 6 × 10(-5) was monitored.     

The GAO natural gas supply model

This paper presents a small, annual model of natural gas supply used for policy analysis by the US General Accounting Office. The model incorporates a realistically complex lag structure and complex dynamics while maintaining a simple theoretical framework and manageable size. It simulates the historical record very well and is employed in this paper to generate three scenarios concerning gas supply from 1982–1990 under alternative price control policies.     

A regional linear logit fuel demand model for electric utilities

We investigate a short-term forecasting and simulation model of utility fuel demand based on the linear logit model. The forecasting properties of the model are surprisingly good for such a simple econometric model of factor demand. The model ignores the distinctive characteristics of electric utilities (load curves, wheeling, etc.) yet produces remarkably good forecasts at both the national and regional levels. Because the model is based on neoclassical theory it can be used for simulations, making it more useful, and less ad hoc, than a pure forecasting model.     

Characterization of the performance and failure mechanisms of boron-doped ultrananocrystalline diamond electrodes

This research investigated the anodic stability of boron-doped ultrananocrystalline diamond (BD-UNCD) film electrodes on a variety of substrates (Si, Ta, Nb, W, and Ti) at a current density of 1 A cm⁻². At an applied charge of 100 A h cm⁻², measurable BD-UNCD film wear was not observed using SEM cross-sectional measurements. However, anodic treatment of the electrodes resulted in surface oxidation and film delamination, which caused substantial changes to the electrochemical properties of the electrodes. The substrate roughness, substrate electroactivity, and compactness of the substrate oxide were key parameters that affected film adhesion, and the primary mechanism of electrode failure was delamination of the BD-UNCD film. Substrate materials whose oxides had a larger coefficient of thermal expansion relative to the reduced metal substrates resulted in film delamination. The approximate substrate stability followed the order of: Ta > Si > Nb > W ≫ Ti.