Oxidation of freestanding silicon nanocrystals probed with electron spin resonance of interfacial dangling bonds
Oxidation of freestanding silicon nanocrystals probed with electron spin resonance of interfacial dangling bonds
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DOI：
10.1103/physrevb.83.155327
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发表时间：
2011-04-28
影响因子：
3.7
通讯作者：
Kortshagen, U.
中科院分区：
文献类型：
--
作者：
Pereira, R. N.;Rowe, D. J.;Kortshagen, U.
利用电子自旋共振（ESR）研究了Si-H键钝化的独立硅纳米晶（Si-NC）在不同氧化时间（从几分钟到几个月）的氧化过程，这些氧化时间由NC核和氧化物壳之间的界面处自然形成的悬挂键（DBs）决定。这些测量与傅里叶变换红外光谱的表面化学分析相辅相成。从ESR谱对氧化时间的依赖关系推断出两种起始时间阈值为15 min和30 h的表面现象。第一个在表面Si-Si键氧化和NC氢终止破坏之前启动（诱导期），并导致DB密度降低和DB轨道在中心Si原子处的定位。在Cabrera-Mott氧化机制中，我们将此过程与水和氧分子的表面吸附所导致的中间界面构型的形成相关联。第二种表面现象导致缺陷密度急剧增加，并与表面Si-O-Si桥的形成相关，为理论上提出的界面缺陷形成机制提供实验支持，该机制涉及晶体Si和生长氧化物之间界面处的Si发射。
The oxidation of freestanding silicon nanocrystals (Si-NCs) passivated with Si-H bonds has been investigated for a wide range of oxidation times (from a few minutes to several months) by means of electron spin resonance (ESR) of dangling bonds (DBs) naturally incorporated at the interface between the NC core and the developing oxide shell. These measurements are complemented with surface chemistry analysis from Fourier transform infrared spectroscopy. Two surface phenomena with initiation time thresholds of 15 min and 30 h are inferred from the dependence of ESR spectra on oxidation time. The first initiates before oxidation of surface Si-Si bonds and destruction of the NC hydrogen termination takes place (induction period) and results in a decrease of the DB density and a localization of the DB orbital at the central Si atom. Within the Cabrera-Mott oxidation mechanism, we associate this process with the formation of intermediate interfacial configurations, resulting from surface adsorption of water and oxygen molecules. The second surface phenomenon leads to a steep increase of the defect density and correlates with the formation of surface Si-O-Si bridges, lending experimental support to theoretically proposed mechanisms for interfacial defect formation involving the emission of Si interstitials at the interface between crystalline Si and the growing oxide.