The technologically useful properties of a solid often depend upon the atomic-scale defects it contains. Despite the harmful sound of "defects", their presence is often essential to the operation of nanoscale devices based on semiconductors. The types and concentrations can sometimes be tuned precisely to enhance device performance. For example, silicon-based integrated circuits rely upon defects such as vacancies and interstitials to mediate the diffusion of dopant atoms that is necessary for device fabrication. Defects in TiO2 and/or ZnO affect the performance of photoactive devices such as blue-green emitters, the effectiveness of catalysts and photocatalysts for environmental and energy applications, the sensitivity of solid-state electrolyte sensors, the efficiency of devices for converting sunlight to electrical power, the electrical transmission of transparent conductors for solar cells, and the magnetic properties of spintronic devices.
Since defects affect many aspects of semiconductor behavior, the ability to control the type, concentration, spatial distribution, and mobility of such defects is important for practical applications. The practice of such control is termed "defect engineering." Research in this group focuses on developing new methods for defect engineering in semiconductors to make nanoscale devices of interest for energy, environmental, and nanoelectronics applications. We have discovered several new physical mechanisms to accomplish this control that work well at small length scales below about one micrometer. Our work employs both experiments and computations to develop a fundamental science base while simultaneously applying the findings to practical applications.
A text in engineering ethics: Fundamentals of Ethics for Scientists and Engineers
A text in charged defects: Charged Semiconductor Defects: Structure, Thermodynamics and Diffusion
A unique instructional program in microelectronic fabrication