Index to NASA Tech Briefs, 1975

This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

A non-destructive analytic tool for nanostructured materials : Raman and photoluminescence spectroscopy

Modern materials science requires efficient processing and characterization techniques for low dimensional systems. Raman spectroscopy is an important non-destructive tool, which provides enormous information on these materials. This understanding is not only interesting in its own right from a physicist's point of view, but can also be of considerable importance in optoelectronics and device applications of these materials in nanotechnology. The commercial Raman spectrometers are quite expensive. In this article, we have presented a relatively less expensive set-up with home-built collection optics attachment. The details of the instrumentation have been described. Studies on four classes of nanostructures - Ge nanoparticles, porous silicon (nanowire), carbon nanotubes and 2D InGaAs quantum layers, demonstrate that this unit can be of use in teaching and research on nanomaterials.Comment: 32 pages, 13 figure

Free-carrier effects in polycrystalline silicon-on-insulator photonic devices

Photonic systems integrated into microelectronic systems using the well established integrated chips fabrication technologies offer immense opportunity in overcoming the bandwidth and power limitations IC faces. The use of deposited polycrystalline silicon in the fabrication of photonic devices has the potential of offering monolithic integration, promising electrical and optical properties, under optimized micro-fabrication, and lower costs. In this thesis, the design, fabrication and optical testing of waveguide devices on polycrystalline silicon platform is presented. Single mode polysilicon waveguide devices were fabricated at the RIT SMFL. The polysilicon waveguides fabricated successfully coupled and guided light. The transmission was measured over several lengths and the cut back method was used to quantify the free carrier absorption and propagation losses of polysilicon at 1550 nm wavelength. Comparisons were made with data for crystalline silicon. The absorption coefficient for polysilicon was found to be 25.9% higher than that of crystalline silicon

Studies of the Mechanism of Electron Beam Induced Deposition (EBID)

The controlled deposition of metals resulting from the passage of an ion beam through an atmosphere of a suitable precursor gas is a well-established procedure for micro scale materials manipulation. While the ion beam technique is rapid and reliable it has the disadvantage that the beam itself can ablate and contaminate the target with Gallium or other materials, and the fact that ion optics are less widely accessible than electron optical columns. We have therefore been investigating the theory and practice of depositing metal using an electron beam and variety of precursor gases. The aim of this work is to develop techniques that can be applied to the repair of the optical, ultra-violet (UV) and extreme ultra-violet (EUV) masks used in high performance photo-lithography. This thesis is concentrated on electron beam induced deposition (EBID) performed in a commercial Scanning Electron Microscope (SEM). For EBID experiments, we have developed a gas injection system for the specimen chamber of a standard SEM which is able to control the pressure and the delivery flow rate of gas for experiment. Studies of factors that control the properties of the deposition - such as the electron-gas interactions, the effects of gas pressure, and the temperature of the substrate – have been made and experiments to determine the fundamental mechanisms of EBID - such as which types of electrons are responsible for the initial interaction event with the precursor – have been carried out and analyzed and systematically studied to determine the optimum conditions for the practical application of the EBID approach. Finally the practical applications of the EBID have been applied to repair of masks