Lifetime of small polarons in strontium-barium-niobate single crystals doped with cerium or chromium
Lifetime of small polarons in strontium-barium-niobate single crystals doped with cerium or chromium
复制标题
掺杂铈或铬的铌酸锶钡单晶中小极化子的寿命
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
E. Krätzig
中科院分区：
文献类型：
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作者：
T. Woike;D. Berben;M. Imlau;K. Buse;R. Pankrath;E. Krätzig
用掺杂0.66 mol %铈或0.025 mol %铬的铌酸锶钡单晶的脉冲光照（λ=532 nm）激发出小极化子。通过监测λ=632.8 nm和λ=785 nm处的光诱导吸收，观察到极化子的暗衰变。在至少50年的时间里，弛豫满足一种扩展指数行为。根据Arrhenius定律，得到活化能EA=(0.58±0.02)eV，频率因子Z=（5±3）×1013 s−1。延迟双脉冲技术（λ=532 nm脉冲之后是λ=1064 nm脉冲）揭示了小极化子的距离依赖复合率，即创建的极化子的寿命是到下一个可用的深电子陷阱的距离的函数。在SBN:Cr中，R分支可以用λ=1064 nm的脉冲激发，并通过未知的X中心传递能量。激发和重组表现为单指数时间演化，没有明显的温度依赖性。
Small polarons are excited by pulsed illumination (λ=532 nm) of strontium–barium–niobate single crystals doped with 0.66 mol % cerium or with 0.025 mol % chromium. The dark decay of the polarons is observed by monitoring the light-induced absorption at λ=632.8 nm and at λ=785 nm. The relaxation fulfills a stretched-exponential behavior over at least five decades. Using the Arrhenius law the temperature dependence yields the activation energy EA=(0.58±0.02) eV and a frequency factor of Z=(5±3)×1013 s−1. Delayed double-pulse technique (λ=532 nm pulse followed by a λ=1064 nm pulse) reveals a distance dependent recombination rate of the small polarons, i.e., the lifetime of a created polaron is a function of the distance to the next available deep electron trap. In SBN:Cr the R branch can be excited by pulses of λ=1064 nm with energy transfer via an unknown X center. Excitation and recombination show a single-exponential temporal evolution without any significant temperature dependence.