The ability to control structural dimensions below 5 nm is essential for a systematic study of the optical and electrical properties of Si nanostructures. A combination of electron beam lithography, NF3 reactive ion etching, and dry thermal oxidation has been successfully implemented to yield 2-nm-wide Si nanowires with aspect ratio of more than 100 to 1. With a sideview transmission electron microscopy technique, the oxidation progression of Si nanowires was characterized over a range of temperature from 800 to 1200 °C. A previously reported self-limiting oxidation phenomenon was found to occur only for oxidation temperatures below 950 °C. A preliminary model suggests that increase in the activation energy of oxidant diffusivity in a highly stressed oxide may be the main mechanism for slowing down the oxidation rate in the self-limiting regime.

Fabricating well controlled nanostructures and obtaining precise structural, electrical, and optical information from them are essential for understanding die intrinsic properties of silicon (Si) nanostructures, which in turn is important for exploring the potential of quantum confinement induced light emission from crystalline Si. A combination of high resolution electron beam lithography, anisotropic reactive ion etching (RIE), and thermal oxidation has been successfully applied to obtain sub-5 nm Si columnar structures [1]. A transmission electron microscopy (TEM) technique has also been used to characterize die precise structural dimensions of these columns [1]. To obtain the electrical and optical information, a process based on polyimide planarization was developed to establish electrical contacts to these nanostructures. The same process is also applicable for fabricating device structures to study electrically pumped optical response. Preliminary transport studies have confirmed current conduction through die Si nano-pillars and yielded an estimate of die conductivity.