Ultrafast carrier dynamics in ZnO nanorods

Abstract

Articles you may be interested inUltrafast dynamics of the dielectric functions of ZnO and BaTiO3 thin films after intense femtosecond laser excitation Free exciton and above-band-gap free carrier dynamics in ZnO nanorods have been investigated at room temperature with a femtosecond transient transmission measurement. Following the photoexcitation of above-band-gap free carriers, an extremely fast external thermalization time on the order of 200 fs can be observed. Under high excitation, hot phonon effects were found to delay the carrier cooling process. While the photoexcitation energy was tuned to match the free exciton transition, stable exciton formation can be uncovered while no evident exciton ionization process can be found unless the photoexcited exciton density exceeded the Mott density.

Two types of excited electron dynamics in zinc oxide

“…The value exp is evaluated by adjusting to the experimental data, hence it is influenced by the effects of temperature and the effect of backflow of energy from the phonons to electrons which can be important at high fluences of excitation. The An essential role of such process has been remarked in the pump-probe experimental studies of Sun et al 13 In our approach the temperature factor in neglected and our relaxation times refer to the relaxation of a single particle, which is not the case of experimental works. So our relaxation time is not identical to the experimental relaxation time exp ͑⑀͒.…”

“…The experiments of Yamamoto et al 12 have been performed for 230 nm thick epitaxial films of ZnO, the experiments of Sun et al 13 have been done for 80 nm thick nanorods, and the results of Hendry et al 9 were obtained from measurements of bulk ZnO samples. So the data obtained in these experiments can be associated with the bulk ZnO.…”

“…Yamamoto et al 12 performed two-photon time-resolved experiments with the energy of quanta from 3 to 3.5 eV and deduced the time of cooling of the electron-hole plasma in ZnO shorter than 1 ps. Sun et al 13 studied the carrier dynamics in ZnO in the excitation energy interval from 3.33 to 3.48 eV and found at 3.33 eV a faster thermalization time, about 200 fs. In the pump-probe experiments of Wen et al 6 the electron relaxation time at room temperature has been estimated as about 800 fs at the energy above 3.45 eV but essentially increasing with the reduction in energy, up to 34 ps at 3.26 eV.…”

Three-photon absorption in ZnO and ZnS crystals

“…Recently, ultrafast carrier dynamics in nanostructured ZnO [8,9], and huge nonlinear refraction and absorption in ZnO thin films have been observed [10]. Ultrafast all-optical switching devices are the key component for next generation broadband optical networks.…”

Nanolaminate structures fabricated by ALD for reducing propagation losses and enhancing the third-order optical nonlinearities

“…Furthermore, zinc oxide is also an interesting material because of its outstanding nonlinear optical properties [8][9][10][11][12][13] . The third-order optical nonlinearity, χ (3) , is important for many applications in optical signal processing and telecommunications.…”