Effective dielectric function of laser-pumped anatase nanoparticles: influence of free carriers trapping and depletion of valence band

Semiconductor-to-Insulator Transition in Inter-electrode Bridge-Like Ensembles of Anatase Nanoparticles under a Long-Term Action of the Direct Current

“…This effect is a direct consequence of localization of a significant number of conduction electrons on the traps, which leads to a significant decrease in polarizability of nanoparticles and, accordingly, of the entire substance forming the bridges. A similar effect associated with localization of photoinduced electrons on the traps during a long-term laser action on anatase nanoparticles in the fundamental absorption band was discussed in [17].…”

“…In addition, the presence of a large number of shallow traps increases the role of hopping conductivity in the transport of mobile charge carriers in anatase nanoparticles. Z-scan experiments with water suspensions of anatase nanoparticles irradiated by a pulse-periodic high-intensity laser light in the fundamental absorption band (at 355 nm, [16,17]) show the featured behavior of an effective dielectric function of nanoparticles under a long-term irradiation. Such behavior can be interpreted as transition from a "semiconducting" state of an anatase nanoparticle to an "insulating" state and manifests itself in a dramatic decay of the modulation depth of the time-averaged effective dielectric function with an increase in duration of pulse-periodic laser action.…”

“…Such behavior can be interpreted as transition from a "semiconducting" state of an anatase nanoparticle to an "insulating" state and manifests itself in a dramatic decay of the modulation depth of the time-averaged effective dielectric function with an increase in duration of pulse-periodic laser action. This effect can be explained in terms of a joint influence of low recombination rate of photo-induced charge carriers, high probability of trapping mobile carriers, and depletion of the ground state of anatase molecules in the nanoparticles [17].…”

Features of macroscopic charge transfer in the ensembles of close-packed anatase nanoparticles near the percolation threshold

“…1, b; the dU/dt ≈ const behavior is similar to a purely " capacitive" one and is indicative of the lack of a well-developed system of conduction channels in the sample subjected to repeat measurements). The localization of mobile carriers at traps in anatase nanoparticles affects not only the conduction in a constant field, which was discussed in the present study, but also the optical properties of isolated nanoparticles under pulse-periodic laser irradiation in the fundamental absorption band [11]. Such irradiation induces the transition from a "…”

Особенности Макроскопического Транспорта Зарядов В Ансамблях Плотноупакованных Наночастиц Анатаза Вблизи Порога Протекания

“…Величина падения напряжения на образцах регистрировалась измерителем Keithley DAQ-6510 В условиях постоянства полного тока в ансамбле частиц может быть записано соотношение для вариаций параметров, характеризующих транспорт зарядов: Предполагая статистическую независимость каналов проводимости, запишем емкостному" поведение dU/dt ≈ const, свидетельствующее об отсутствии развитой системы проводящих каналов в повторно испытываемом образце). Локализация подвижных носителей на ловушках в наночастицах анатаза оказывает влияние не только на проводимость в постоянном поле, как в рассматриваемом случае, но и на оптические характеристики изолированных наночастиц при импульсно-периодическом лазерном воздействии в полосе фундаментального поглощения [11], приводящем к переходу от " полупроводникового" механизма взаимодействия излучения с частицами к " диэлектрическому" механизму.…”