Veronica Burrows - US grants

The principal investigators propose to acquire a Langmuir Trough thin film deposition system. This equipment will deposit monomolecular layers or multiple-monomolecular layers of organic molecules on substrates of various types by a highly-controlled dipping technique. Films deposited in this manner, so-called Langmuir-Blodgett films, show promise of application in the fields of electron beam microlithography, flat displays, chemical and biological sensors, and a number of other electronic applications. This support is co-funded by the Solid State and Microstructures Program in the Division of Electrical, Communications, and Systems Engineering and the Thermal Systems and Heat Transfer Program in the Division of Chemical, Biochemical and Thermal Engineering.

Surface infrared spectroscopy will be applied in this study of gallium arsenide anodic oxidation. The technique will be used both for the characterization of pre-oxidized gallium arsenide, and for investigation of the oxide as it is being formed. The surface infrared spectroscopy will be applied as an in-situ, multiple internal reflection geometry to directly measure the chemical composition and rate of growth of anodic oxides at the interface between gallium arsenide and the growth electrolyte. This will enable determination of the reaction mechanisms of the oxide growth, the chemical kinetics of the reactions, and the composition of the oxide layer produced. In addition, the effects of process parameters on kinetics and on composition will be investigated to determine optimum growth conditions. Advantages of native oxides as insulating layers on semiconductors include simplicity of processing, dependable film adhesion and system purity. The anodic oxidation process for gallium arsenide has been demonstrated as very promising. Previous studies have shown that the process is kinetically controlled, however the chemical kinetics and mechanisms of the oxidation reactions are not yet known. The successful passivation of gallium arsenide by native oxides has been a barrier to their full scale application in integrated electronics and optics.

The goal of this work is to understand and control the chemical nature of particular types of processing used to passivate GaAs surfaces for improved electronic device performance, uniformity and reliability. The chemical nature of sulfidation of GaAs, its dependence on particular processing parameters, and long term response to heat, light, and ambient gases are being studied. Infrared spectroscopy is used for real time in situ monitoring of specific chemical and physical processes which occur at the surface. Auxillary measurements using XPS and photoluminescence are used to correlate film structure and chemistry with electronic properties.

Applicants to Arizona State University's graduate programs in Chemical Engineering have expressed increasingly strong interest in environmental topics. A graduate training/research program is described in the focus area of Environmentally Friendly Technology, emphasizing Environmentally Benign Chemical Processing. Arizona State University's existing expertise, experience, and interest in environmental aspects of chemical engineering provide the necessary research and teaching base from which to pursue this new area of graduate training. A program in Environmentally Benign Chemical Processing will utilize both traditional chemical engineering training - process engineering, optimization and control - and newer, more specialized topics including air and water quality measurement, recycling technologies, hazardous materials handling, and risk assessment. Topics including point-of use abatement, sensor technology, shared load separations, process integration for pollution prevention, and biosynthesis will be the basis of the trainees' research experience. Local industry will support this effort: Motorola has agreed to provide seminar speakers, advise on coursework development, and begin planning for internships in appropriate areas within the company. Existing and new courses and activities will comprise the teaching component of the program. Minority recruiting activities through the Coalition to increase Minority Degrees will include faculty visits to schools and applicant visits to ASU. A structured program of peer and faculty mentoring will promote student retention.

Chemical-mechanical polishing (CMP) is a technology of tremendous interest to the semiconductor manufacturing community. It transforms wafers with varying surface topography into wafers with locally and globally flat surfaces. During CMP, a wafer is pressed face-down against a rotating polishing pad that is covered with an aqueous suspension of abrasive particles (slurry). Chemical and materials engineering faculty at Arizona State University will work with industry engineers from Motorola, Rodel, and SpeedFam-IPEC to develop fundamental descriptions of key chemical and mechanical polishing phenomena, and will combine these descriptions into unified, experimentally validated models of CMP processes. Polishing of SiO2 and Cu surfaces will be studied using these models. Molecular dynamic simulations of the interactions between slurry particles and the wafer surfaces will be performed, as well as the reactions that occur on and within thin films during CMP. Surface spectroscopy studies will be performed to assess the rates of surface passivation and dissolution reactions occurring during CMP, and the rate of slurry penetration into the wafer surfaces will be assessed. These fundamental chemical and physical descriptions will be combined with existing finite element removal rate models that are based on stress effects to produce unified CMP process models.

The project is expected to provide the identification and quantification of the physical and chemical phenomena of CMP and expression of these results in fundamental models. The models will be useful to industry in the optimization and development of polishing protocols for semiconductor wafers.

Project Pathways targets mathematics and science learning and achievement in grades 9-12. The project will produce a research-based and tested model to support secondary mathematics and science teachers. Core partners include four school districts (Chandler, Mesa, Tempe, and Tolleson) and the Center for Research on Education in Science, Mathematics, Engineering, and Technology (CRESMET) at Arizona State University (ASU). The Maricopa Community College District and Intel are collaborators with ASU in delivering the project's research-based services and products to these districts. The demographics of the partner school districts mirror those of Arizona, where 45% of students are persons of color and the Hispanic population is expanding rapidly.

Pathways will produce tools and knowledge to guide secondary mathematics and science teachers in promoting conceptual learning and STEM behaviors that the literature deems essential for continued STEM learning and course-taking. These key behaviors include competence and flexibility in scientific inquiry, mathematical problem solving, and engineering design. A central concept is that of function, which research identifies as a unifying concept of secondary mathematics and science. As the core strategy of the Pathways model, teams of engineers, mathematicians and scientists will partner with master teachers and STEM education faculty to generate instructional sequences for both teachers and students. The instructional materials will take the form of modules for secondary mathematics and science teachers, with companion modules for secondary STEM classrooms and companion tools for secondary STEM learning communities. The professional learning community tools will support teachers in adapting their new knowledge and instructional approaches to their own classrooms by engaging them in deep reflections on their instruction and their students' learning. Pathways materials will be easily adaptable in any learning environment. In this project, however, they will be packaged for use in four courses in an ASU graduate degree program for inservice teachers, delivered on-site in the teachers' schools. To better assist Arizona's many bilingual students, Pathways will adapt student modules to an innovative, research-developed English language learner technology platform. Other Pathways strategies include activities (such as science fairs for students and a regional conference for high school guidance counselors) to encourage all students to take challenging mathematics and science courses and to consider science-based careers.

Teams of STEM education faculty and graduate students will research the effectiveness of the courses and learning communities on teachers' understanding of mathematics and science concepts and their understanding of the process by which foundational STEM concepts and behaviors develop in students. They will also investigate the process by which teachers shift their classroom practices to promote improved STEM learning in their students. Graduate research assistants will be recruited to participate in the Pathways project, preparing many future faculty for careers as STEM education researchers. Pathways will establish new patterns of information-sharing and collaboration among STEM scientists and educators, community college faculty, secondary administrators and teachers, and industry partners. The project aims to narrow the majority/minority achievement gap, encourage students to take challenging STEM courses, increase high school student STEM learning and achievement, and improve the pass rates in ASU's introductory calculus, physics and biology courses.