Electric Fields on Oxidized Silicon Surfaces: Static Polarization of PbSe Nanocrystals†
Electric Fields on Oxidized Silicon Surfaces: Static Polarization of PbSe Nanocrystals†
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DOI：
10.1021/jp037418e
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发表时间：
2004-05
影响因子：
2.9
通讯作者：
Chaya H. Ben-Porat;Oksana Cherniavskaya;L. Brus;Kyung‐Sang Cho;C. Murray
中科院分区：
文献类型：
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作者：
Chaya H. Ben-Porat;Oksana Cherniavskaya;L. Brus;Kyung‐Sang Cho;C. Murray
通过使用静电力显微镜，我们测量了具有 2 nm 热氧化层的 n 型和 p 型硅上 12 nm PbSe 纳米晶体的电荷和极化率。单个纳米晶体的介电常数>100。在环境光下，纳米晶体产生的静电场太弱，不足以由完整的基本电荷引起。这些纳米晶体被氧化物基底中固定电荷产生的表面电场静态极化。我们对这种效应进行定量建模并指定氧化物中的电荷位置。在 442 nm 光激发下，我们观察到一些纳米晶体 (∼35%) 发生光电离，并在一夜之间缓慢松弛回到初始状态。就在氧化物中的电荷上方，表面电场可接近 108 V/cm。
By use of electrostatic force microscopy, we measure the charge and polarizability of 12-nm PbSe nanocrystals on n- and p-type silicon with a 2-nm thermal oxide layer. Individual nanocrystals show a dielectric constant of >100. In ambient light, the nanocrystals generate static electric fields of magnitudes too weak to be caused by a full elementary charge. These nanocrystals are statically polarized by surface electric fields generated by fixed charges in the oxide substrate. We model this effect quantitatively and assign charge locations in the oxide. Upon 442-nm photoexcitation, we observe some of the nanocrystals (∼35%) photoionize and slowly relax overnight back to their initial states. Just above a charge in the oxide, the surface electric field can approach 108 V/cm.