This research project will lead to the development of a new experimental tool for materials research to study unique light emitting materials, so called carbon nanotubes. These tubular structures are about 100,000 times thinner than a human hair and are considered to be among the most promising candidates for use in tomorrow's microelectronic circuitry. The new research tool will be used for a detailed investigation of the forces that govern the motion of electric charges in carbon nanotubes and of the processes which enable these charges to emit light. Information gained from such experiments should lead to the discovery and development of improved materials with favorable and efficient light emitting properties. Continued innovations and improvement of such optical materials is essential for key technologies and to ensure economic competitiveness in the 21st century. The project also facilitates interdisciplinary training of students at the interface of Physics, Chemistry and Materials Science. Moreover, graduate and undergraduate students will acquire skills for preparing and safe handling nanomaterials and for the operation of traditional as well as cutting-edge tools for optical characterization of materials.
The project is aimed at the development of a new spectroscopic tool for enhanced pump-probe spectroscopy of excited state dynamics in semiconducting carbon nanotubes and other nanomaterials. The instrument will be based on an existing Ti:Sapphire femtosecond laser system that provides broadly tunable 50 fs laser pulses from near infrared- and visible optical parametric amplifiers (OPAs). Both OPAs will be modified for computer controlled continuous tuning of excitation wavelengths. This will provide the unique opportunity to probe a new spectroscopic dimension of excited state dynamics. Three-dimensional pump and probe wavelength as well as pump-probe delay resolved spectroscopic mapping of exciton dynamics in a variety of carbon nanotube samples in different environments is expected to yield new insights into the nature and character of radiative and non-radiative exciton decay. Specifically, pump-probe excitation-spectroscopy will cast new light onto the role of the coupling between excitons and phonons for intra- and interband relaxation. Moreover, the project will allow training of graduate and undergraduate students in the use of a variety of interdisciplinary research tools with various level of complexity. Students will be educated in optical and materials science concepts, in the use of traditional tools of colloidal chemistry and femtosecond spectroscopy.
