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首页> 外文会议>Conference on multiphoton absorption and nonlinear transmission processes: Materials, theory, and applications >Two-photon excitation induced transient valence switching in Eu-doped Si/SiO_2 nanocomposites
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Two-photon excitation induced transient valence switching in Eu-doped Si/SiO_2 nanocomposites

机译：双光子励磁诱导Eu-掺杂Si / SiO_2纳米复合材料中的瞬时价值切换

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Eu~(3+)-doped crystalline Si-enriched SiO_2 nanocomposite thin films were prepared using Ar sputtering deposition on quartz substrates. By conventional laser spectroscopy the material was characterized in either frequency or time domain. The results show that the doped europium ions are present in trivalent state, as Eu~(3+). They are distributed in SiO: matrix and on the boundary surface of c-Si nanoparticles. With increased excitation intensity at 532nm, two-photon absorption (TPA) induced new emission was observed. It is characterized by an additional broadband emission with a peak at 560nm and lifetime of～0.8μs. This feature has been identified as the emission from Eu~(2+) ions. Further measurements reveal that the observed phenomenon originates from charge transfer process giving rise to a photoinduced transient valence switching from Eu~(3+) to Eu~(2+) in this particular material. Free carriers were originally created in the conduction band (CB) of c-Si nanoparticles by TPA, then trapped at the surrounding Eu~(3+) center due to strong Coulomb interaction. Luminescence of the formed divalent Eu~(2+) is characterized by a broadband d→f transition with fast decay rate. Degenerate four-wave-mixing experiment further revealed that in undoped sample TPA-created charge carriers in CB were trapped in shallow centers of Si nanoparticles. The trapping has an average time period of 500ps, and the carriers were then released for recombination. In Eu~(3+) -doped sample, however, the average time period of 500ps was no longer observable. It therefore suggests that the strong Coulomb attraction results in immediately capturing of the created charges by positive Eu~(3+) center.
机译：使用Ar溅射沉积在石英底物上制备Eu〜（3 +） - 掺杂的结晶Si富含SiO_2纳米复合薄膜。通过常规激光光谱，该材料的特征在于频率或时域。结果表明，掺杂的铕离子以三价状态存在，如Eu〜（3+）。它们分布在SiO：基质和C-Si纳米粒子的边界表面上。随着532nm的激发强度提高，观察了双光子吸收（TPA）诱导的新发射。其特征在于额外的宽带发射，峰值为560nm，寿命为0.8μs。该特征已被识别为来自欧盟〜（2+）离子的排放。进一步的测量表明，观察到的现象来自电荷转移过程，从而产生从Eu〜（3+）到这种特定材料中的eu〜（3+）的光诱导的瞬时价值。通过TPA在C-Si纳米颗粒的导通带（CB）中最初在C-Si纳米粒子的导通带（CB）中产生了游离载体，然后由于强的库仑相互作用而被捕获在周围的Eu〜（3+）中心。形成的二价EU〜（2+）的发光特征在于具有快速衰减速率的宽带D→F转变。退化的四波混合实验进一步表明，在未掺杂的样品中，Cb中的TPA产生的电荷载体被捕获在Si纳米颗粒的浅中心。诱捕具有500ps的平均时间段，然后释放载体以进行重组。然而，在Eu〜（3+）的样品中，500ps的平均时间段不再可观察到。因此，它表明强大的库仑吸引力导致立即通过正欧欧〜（3+）中心捕获产生的电荷。

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