Unraveling temperature-dependent photocarrier dynamics using plasmonic effects of metal nanoparticles*

In this presentation, first the optical properties of metal nanoparticles will be discussed with a particular emphasis on localized surface plasmon resonances, which is defined as collective oscillation of conductive electrons induced by electromagnetic radiation of certain frequency. Since the dimensions of the nanoparticles is less than 100 nm, the surface field is confined to size scales much smaller than the wavelength of the incident radiation, resulting in a local field that is several orders of magnitude larger than the excitation field. The local field can further be enhanced and squeezed down to volume of single cubic nanometer by coupling the resonant plasmonic nanoparticles. These plasmonic properties have been exploited for various applications including for single molecule detection, biosensing and photothermal cancer therapy as well as for enhancing the efficiency of optoelectronic devices. In this presentation, examples of high resolution near-field images of surface plasmon modes obtained using apertureless near-field scanning optical microscope will be discussed. The application of plasmonic effects for enhancing photocarrier generation in semiconductors and understanding the carrier dynamics will be discussed based on our very recent results on InGaAs/GaAs quantum well.