| The technologically useful properties of a solid often depend upon the types and concentrations of the defects it contains. Defects mediate foreign-atom diffusion in semiconductors, affect the performance of photo-active devices, the effectiveness of catalysts, the sensitivity of solid-state electrolyte sensors, and the efficiency of devices for converting sunlight to electrical power. Current methods for controlling defect behavior suffer from problems with solid consumption, implantation damage, or foreign atom incorporation. My laboratory has recently discovered two entirely new methods for controlling defect concentration and diffusion in silicon, based on separate mechanisms involving surface chemistry and optical stimulation. In the present work, the science base describing the surface and optical phenomena, observed in silicon, is placed on firmer ground, and to show more specifically how they might be employed usefully in practical applications such as ultrashallow junction (USJ) formation. The results show that it possible to simultaneously reduce junction depth, improve percentage dopant activated and minimize implantation damage, the key parameters in USJ formation. The basic physical explanations outlined for silicon suggest that similar chemistry and physics should also govern the behavior of other semiconductors as well, such as metal oxides. Titanium dioxide (TiO2) is an ideal test case because of the presence of charged point defects and also its broad applications. Through nonthermal optical stimulation the results show that illumination inhibits the diffusion of oxygen in TiO2. |
