The zero bias resistance-area products and current-voltage (I-V) characteristics as a function of temperature and infrared background radiation have been measured for HgCdTe photodiode samples with cutoff wavelengths near 9 μm at 80 K. A model is presented to account for the background and temperature dependence of the data. It is found that the reverse I-V curve shapes and magnitudes may be estimated as a function of both background and temperature by superposition of the total current from optical generation, thermal diffusion, and depletion region generation-recombination centers. The influence of background radiation was found to create an exceptionally linear reverse I-V characteristic that can be easily distinguished from other current generation mechanisms, and can be modeled by application of existing theory to HgCdTe photodiodes.

Three techniques for determining the composition (x CdTe) of Hg, _,Cd,Te are reviewed. These three techniques are infrared transmission (often called FTIR, for Fourier transform infrared) spectroscopy, energy dispersive x-ray analysis (EDX) and optical reflectance (OR). A brief summaryofseveral methodsfordetermining composition in Hg,-xCdxTe is included.

Radio frequency heating (RFH) is a technology that increases the cost-effectiveness of a variety of site remediation technologies by accelerating the rate of contaminant removal. Heating makes the physical, chemical, and biological properties of materials such as contaminants, soil, and groundwater more amenable to remediation. RFH brings controlled heating to the subsurface, enhancing the removal of contaminants by soil vapor extraction (SVE), groundwater aeration (air sparging), bioremediation, and product recovery. The results presented are from a bench-scale study and a field demonstration that both used RFH to enhance the performance of SVE. The bench-scale study performed on PCE-contaminated soil revealed an increase, by a factor of 8, in the removal rate when RFH was used to heat soil to 90 °C. The application of RFH for a three-week period at a former gasoline station near St. Paul, MN, resulted in raising the ambient soil temperature from 8 °C to 100 °C in the immediate vicinity of the RFH applicator and to 40 °C 1.5 m (5 ft) away. Most significantly, the use of an integrated RFH/SVE system achieved an overall 50% reduction in gasoline range organics (GRO) in soil over a two- to three-month period. The discussion includes applications of RFH for enhancing bioremediation and product recovery.

No abstract

No abstract