9503853 Jackson This award is for partial support of a time-resolved near-field optical spectrometer (TRNFOS) to be used fop .semiconductor nanostructure research. By combining two commercially available instruments, we can configure a spectrometer that achieves both ultrafast (<100 fs) time-resolution and spatial-resolution (< 500 A) more than an order of magnitude better than previously achievable using the best far field optics. The unique combination of capabilities of the instrument will allow us to consider experiments that previously were not possible. In particular, this instrument will allow for the first time: (A) Optical observation of spatially local potential fluctuations no longer masked by the inhomegeneously broadened photoluminescence lines (following Hess et al.) (B) The study of exciton dynamics in confinement to, and scattering from, these spatially local potential fluctuations. (C) The study of exciton dynamics in quantum wires and dots. Namely spatially resolved capture of excitons to wires and dots, as well as spatial transport of excitons along wires. %%% The principal aspects of the proposed research are the study of III-V and II-VI nanostructures. In the III-V multiple quantum wells the availability of the TRNFOS instrument will provide a spatial resolution that will allow optical observation of exciton confinement to lower dimensions through both "intrinsic" local potential fluctuations, as well as "extrinsic" potentials fabricated through focused ion beam mixing. For the case of focused ion beam mixing, the instrument will be capable of providing in a unique manner the lateral potential profile created by compositional intermixing. This understanding is an essential step in creating quantum wire and quantum dot structures. For quantum wire-like structures the TRNFOS instrument will provide local information on exciton lifetimes and exciton anisotropic diffusion to contrast with our p resent far field results. Similarly, in II-VI diluted magnetic heterostructures this instrument will allow us to observe directly the affect of magnetic ion clustering and alloy fluctuations on exciton dynamics and the magnetization dynamics of the magnetic ion themselves. In particular, we are interested in the dynamics of exciton self-localization in the formation of lower dimensional exciton magnetic polarons, and in the affect of d-d superexchange on the magnetization dynamics of magnetic ion clusters. The acquisition of this time-resolved near-field optical spectrometer will significantly advance present NSF supported efforts as well as open new opportunities to explore semiconductor material science and physics. The understanding of confined structures, quantum wires, quantum dots, and arrays will be strongly influenced by the acquisition of this instrument. ***
