4 December 2003 Transient photoconductivity in CdSe nanoparticles and nanocrystalline TiO2 as measured by time-resolved terahertz spectroscopy
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Abstract
The transient photoconductivity of dye-sensitized nanocrystalline colloidal TiO2 has been measured time-resolved THz spectroscopy (TRTS), a non-contact electrical probe with sub-picosecond temporal resolution. The photoconductivity deviates strongly from Drude behavior and is explained by disorder-induced carrier localization and/or backscattering of the photogenerated carriers. In addition, the carriers are found to thermally equilibrate with the lattice in roughly 300 femtoseconds. The size-dependent photoconductivity of CdSe nanoparticles ranging from 2.54 nm up to >25 nm has also been measured using TRTS. The measured change in the frequency-dependent optical density and change in phase of the transmitted THz pulse fall into three distinct groupings as a function of size and can be classified for diameters smaller than the Bohr exciton radius, diameters greater than the Bohr exciton radius but smaller than the bulk mean free path, and diameters greater than the bulk mean free path. The underlying cause of the grouping is a size-dependent mobility (or carrier scattering rate).
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Charles A. Schmuttenmaer, Charles A. Schmuttenmaer, Gordon M. Turner, Gordon M. Turner, Matthew C. Beard, Matthew C. Beard, } "Transient photoconductivity in CdSe nanoparticles and nanocrystalline TiO2 as measured by time-resolved terahertz spectroscopy", Proc. SPIE 5223, Physical Chemistry of Interfaces and Nanomaterials II, (4 December 2003); doi: 10.1117/12.508218; https://doi.org/10.1117/12.508218
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