NER: Development of an Ultrafast Scanning Probe Microscope

This Nanoscale Exploratory Research (NER) proposal was received in response to NSE, NSF 02-148. The one-year project involves developing a novel femtosecond apertureless scanning near-field optical microscope (FANSOM), which will provide moving images with the unprecedented combination of nanometer spatial resolution and femtosecond time resolution. The instrument will be used to probe the electronic excitation, dephasing, and population decay dynamics of individual artificial nanostructures such as quantum dots, as well as the photoinduced electronic and conformational dynamics of individual organic macromolecules. The microscope will be based on a proven apertureless near-field imaging technique, in which light scattering from a sharp metallic tip scanned across the substrate provides images with nanometer spatial resolution. Fast temporal resolution will be obtained using optical pump-probe techniques with femtosecond laser pulses. Multiple images corresponding to increasing delay time between pump and probe pulses will then be assembled as actual movies of nanometer-scale dynamical processes with femtosecond time resolution. Successful completion of this project will give rise to a powerful new tool to probe the nanoworld, with potential applications in virtually every field (physics, chemistry, materials science, life sciences, quantum computing, etc.) in which interesting dynamics occurs at the nanoscale and is obscured by inhomogeneous effects. The graphical nature of the moving images obtained, coupled with the fundamental and practical interest in the dynamics of nanostructures, make this instrument an ideal educational tool for both scientific students and the general public. Graduate and undergraduate students will be involved with the development of the instrument, as well as its use scientific studies. The project is jointly supported by the Divisions of Materials Research and Physics.

This Nanoscale Exploratory Research (NER) proposal was received in response to NSE, NSF 02-148. The one-year project involves developing a novel microscope that will provide moving images with the unprecedented combination of near-atomic spatial resolution and ultrafast time resolution. In particular, the instrument will be used to probe the excitation and decay of individual artificial nanostructures, as well as light-induced changes of individual organic macromolecules. The microscope will be based on a proven technique, in which light scattering from a sharp metallic tip scanned across a surface provides images with nanometer spatial resolution. Fast time resolution will be obtained with ultrashort laser pulses. A series of pump pulses excites the nanostructure, and time-delayed probe pulses are used for imaging. Multiple images corresponding to increasing time delay between pump and probe pulses will then be assembled as actual movies of the processes of interest. Successful completion of this project will give rise to a powerful new tool to probe the nanoworld, with potential applications in virtually every field (physics, chemistry, materials science, life sciences, etc.) in which interesting processes occur at the nanoscale. The graphical nature of the moving images obtained, coupled with the fundamental and practical interest in nanostructures, make this instrument an ideal educational tool for both scientific students and the general public. Graduate and undergraduate students will be involved with the development of the instrument, as well as its use scientific studies. The project is jointly supported by the Divisions of Materials Research and Physics.