| In recent years, carbon nanotubes have emerged as a subject of considerable curiosity and attention, due to their unique properties. From an electronic materials perspective, carbon nanotubes have been repeatedly touted as the future of micro- and nano-electronics technology. Capable of being both metallic and semiconducting, single wall carbon nanotubes have generated visions of an all-nanotube architecture in the not too distant future. Single wall carbon nanotubes have also displayed exotic behavior at low temperatures, spurring a rush of new discoveries and advances down to the level of manipulating individual electrons in nanotubes, the ultimate miniaturization. As research makes significant advances towards these goals, a number of challenges have also appeared. Particularly, it has been realized that single wall carbon nanotubes are extremely sensitive to perturbations in their immediate environment, which might drastically alter their fundamental properties. While single wall nanotubes are physically robust, they appear to electronically very fragile. On the other hand, the effect of external perturbations has actually opened a new door to providing further insights into the fundamental electronic structure and properties of these nanotubes.; The research leading to this thesis has focused on unraveling the origin and effect of some such perturbations on electronic and electrical transport properties of individual single wall carbon nanotubes. In order to reach this stage, a number of recent fundamental observations pertaining to nanotube field effect transistors, single electron transistors and ballistic conductors were first reproduced. Single wall carbon nanotubes were grown by thermal chemical vapor deposition techniques on silicon dioxide substrates under optimum conditions. The nanotubes were characterized by techniques like scanning probe microscopy and Raman spectroscopy. Test structures were fabricated by photolithography and electron beam lithography and metallization. Electrical measurements were conducted at temperatures ranging from room temperature to 25K.; One of the most obvious environmental effects appeared in the form of hysteresis in the transfer characteristics of nanotube field effect transistors and single electron transistors. While this hysteresis has been reported previously, its origins have remained a subject of significant debate. A detailed study of the hysteresis phenomenon as a function of various parameters revealed convincing evidence to support the theory that the origin of this hysteresis is in fact different from similar hysteresis observed in silicon bases MOSFETs. Based on these findings, a model was developed allowing us to simulate the effect of various parameters on the hysteresis, and show excellent fitting of experimental data to the model. |
