The adsorption of gas on a solid surface can produce considerable variation in the electrical and optical properties of this surface and eventually lead to the identification of the gas adsorbed as well as a quantification of its presence in the environment (pollution). With semiconductor surfaces the adsorbed gas is able to play a role comparable to a "dopant" and therefore initiate drastic changes in electrical and optical properties. For example, one part of nitrogen dioxide in 109 parts of air can be detected on certain semiconductors. As the phenomenon occurs at the surface of the material, a high surface to volume ration is advantageous, thus leading to thin films structures. Such structures can be utilized in a small sensor tailored to a specific gas. The specificity will result from the compatibility of the electronic structure of the material near its surface and the atomic structure of the gas being detected. The main technical objectives of the project will be (a) to study the mechanism of adsorption over different types of materials (metal, inorganic and organic semiconductors); (b) to establish the conditions for specificity in adsorption; (c) to design electronic structures in materials providing selective adsorption with resulting changes in surface conductivity or optical reflection coefficients; (d) to prepare thin films of selected materials with the above structure and incorporate them in a sensor configuration; and (e) to carry on comparative sensitivity tests with existing sensors or methods of detection. The University of Texas at El Paso is requesting support from the RIMI program for equipment for this project, which would involve faculty and students from the Departments of Physics, Electrical Engineering, Chemistry, and Geological Sciences. The proposed project will enhance both our Minority Research Center of Excellence in Materials Science and our newly established Center for Environmental Resource Management.
