Vapor deposition of tantalum and tantalum compounds

Tantalum, and many of its compounds, can be deposited as coatings with techniques ranging from pure, thermal chemical vapor deposition to pure physical vapor deposition. This review concentrates on chemical vapor deposition techniques. The paper takes a historical approach. The authors review classical, metal halide-based techniques and current techniques for tantalum chemical vapor deposition. The advantages and limitations of the techniques will be compared. The need for new lower temperature processes and hence new precursor chemicals will be examined and explained. In the last section, they add some speculation as to possible new, low-temperature precursors for tantalum chemical vapor deposition

Improvement of luminescent properties of thin-film phosphors by excimer laser processing

Thin-films of europium doped yttrium oxide, (Y{sub 1{minus}x}Eu{sub x}){sub 2}O{sub 3}, were deposited on sapphire substrates by metallorganic chemical vapor deposition. The films, {approximately} 400 nm thick, were weakly luminescent in the as-deposited condition. A KrF laser was pulsed once on the surface of the films at a fluence level between 0.9--2.3 J/cm{sup 2}. One pulse was sufficient to melt the film, which increased the photoluminescent emission intensity. Melting of a rough surface resulted in smoothing of the surface. The highest energy pulse resulted in a decrease in luminous intensity, presumably due to material removal. Computational modeling of the laser melting and ablation process predicted that a significant fraction of the film is removed by ablation at the highest fluence levels

Optical diagnostics for a high power, rf-inductively coupled plasma

Emission spectroscopy and laser-induced fluorescence have been used to monitor the field and tail-flame regions of a Hull-design inductively coupled plasma. This plasma is used for a variety of syntheses including SiC, TiC, BN, A1N and diamond. Temporally- and spatially-resolved spectra of both pure Ar and Ar/gas mixtures have been studied as a function of RF power, pressure and flow rate. Preliminary data suggest that the system is far from local thermodynamic equilibrium

The Supposed Role of Microbiological Aerosol Stabilizers as Substitutes for Bound Water: A Study of an In Vitro Model System

In order to test a suggestion that inositol may take the place of water in maintaining the stability of desiccated cells, the reversible endothermic association of tobacco mosaic virus protein (TMVP) was studied turbidimetrically in presence of this substance. Its effect was to lower the temperature at which association takes place, the positive standard enthalpy and standard entropy of reaction both being increased by about 30%. The hypothesis of direct substitution of bound water by inositol at the site of macromolecular association leads to the contrary prediction that the association temperature would be raised. It is suggested that the observed effect of inositol may result from a conformation change in TMVP brought about by binding of inositol at positions adjacent to the site of reaction

Approach to single-molecule detection by laser-induced fluorescence

A sheath flow cuvette was evaluated in laser-induced fluorescence determination of aqueous rhodamine 6G. A detection limit of 18 attograms was obtained within a one-second signal integration time. The concentration detection limit was 8.9 x 10/sup -14/ mole per liter. An average of one-half rhodamine 6G molecule was present within the 11 pL excitation volume. However, during the signal integration time a total of 22,000 analyte molecules passed through the excitation in a 0.42 microliter volume

Characterization of photoluminescent (Y{sub 1{minus}x}Eu{sub x}){sub 2}O{sub 3} thin-films prepared by metallorganic chemical vapor deposition

Europium doped yttrium oxide, (Y{sub 1{minus}x}Eu{sub x}){sub 2}O{sub 3}, thin-films were deposited on silicon and sapphire substrates by metallorganic chemical vapor deposition (MOCVD). The films were grown in a MOCVD chamber reacting yttrium and europium tris(2,2,6,6-tetramethyl-3,5,-heptanedionates) precursors in an oxygen atmosphere at low pressures (5 Torr) and low substrate temperatures (500--700 C). The films deposited at 500 C were flat and composed of nanocrystalline regions of cubic Y{sub 2}O{sub 3}, grown in a textured [100] or [110] orientation to the substrate surface. Films deposited at 600 C developed from the flat, nanocrystalline morphology into a plate-like growth morphology oriented in the [111] with increasing deposition time. Monoclinic Y{sub 2}O{sub 3}:Eu{sup 3+} was observed in x-ray diffraction for deposition temperatures {ge}600 C on both (111) Si and (001) sapphire substrates. This was also confirmed by the photoluminescent emission spectra