Direct determination of electron mobility in photorefractive Bi12SiO20 by a holographic time-of-flight technique

Abstract

The time development of a photorefractive grating created by intersecting 30 ps (532 nm) beams in a well-characterized Bi12SiO20 crystal (in a static field around 1 kV/cm) unambiguously reveals the mobility of photoexcited electrons to be 0.24±0.07 cm2/V s through what is essentially a ‘‘time-of-flight’’ measurement.

L'effet photoréfractif

“…Le champ £, comporte une composante rapide qui oscille à une fréquence \jz E directement liée à la mobilité des charges [59,60]. Cette oscillation s'amortit avec une constante de temps de f. L'existence de deux constantes de temps provient de ce que le champ de charge d'espace E l résulte de la superposition d'un champ provenant de la modulation spatiale dans les centres profonds E'°n et d'un champ dû à la modulation spatiale des porteurs de charge E\ c : ||A/fi=-r + /r_||«l .…”

Sign of the dominant charge carriers in photorefractive crystals determined by a phase-locked holographic technique

“…It is therefore very important to have access to reliable techniques for determining the photocarrier sign and the corresponding charge transport parameters; a fact that was recognized since the early days of the development of photorefractive materials. Some well known techniques that were adapted and applied to different crystals include: direct photoconductivity measurements [6], different approaches of energy transfer measurements based on holographic techniques [5,[7][8][9][10][11], photoinduced Hall-current measurements [12,13], classical and holographic time-of-flight techniques [14,15], electron paramagnetic resonance spectroscopy [16], among others [17,18].…”

Photorefractivity in poly(N-vinylcarbazole)-based polymer composites

“…As charge separation advances, a space charge field builds up that can be probed with a CW laser beam through the electro-optic effect. One measures the diffraction efficiency η(t) [24] …”

“…As the mobile carriers drift relative to the immobile distribution of the countercharges, the space charge field shows an oscillatory behaviour, that is reflected in the temporal behaviour of the diffraction efficiency [24,25]. Transient holographic experiments of this kind are used to provide valuable information related to the charge transport process and to determine the carrier drift mobility [25,26].…”