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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Scanning Tunneling Spectroscopy of Free-Standing CdS Nanocrystals Fabricated by the Langmuir-Blodgett Method
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Scanning Tunneling Spectroscopy of Free-Standing CdS Nanocrystals Fabricated by the Langmuir-Blodgett Method

机译：朗缪尔-布洛杰特方法制备的自由站立CdS纳米晶体的扫描隧道光谱

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摘要

The energy spectrum and tunneling transport through ensembles of closely packed CdS nanocrystals (NCs) obtained by the Langmuir-Blodgett (LB) method have been investigated using the scanning tunneling spectroscopy (STS) technique at room temperature. NC ensembles were obtained by annealing the solid LB matrix in a vacuum or in an ammonia atmosphere. The STS data indicate the formation of point defects attributed to an excess of Cd atoms in NC capturing tunneling electrons and the effect of the ammonia atmosphere on the defect formation process. A high density of defects arising as a result of sintering NCs that lost a protective organic shell during the migration on the substrate surface is likely to cause a band gap narrowing in NCs located near the ensemble edge. The analysis of a dependence of the zero-conduction gap value on the NC size gives evidence of a strong effect of the Coulomb interaction between the carriers located in NCs and their polarization charges in the shells on the NC energy spectrum. A dielectric constant of the shell (epsilon(out) = 10-16.5) and the energy barrier height for electrons (V-0 = 0.6-0.8 eV) were determined. The shell comprises ammonia and organic molecules, the anunonia molecules making a major contribution to the shell dielectric constant and the organic molecules determining the barrier height.
机译：在室温下，使用扫描隧道光谱法（STS）研究了通过Langmuir-Blodgett（LB）方法获得的紧密堆积的CdS纳米晶体（NC）集合体的能谱和隧道传输。 NC集成体是通过在真空或氨气氛中对固体LB基体进行退火获得的。 STS数据表明归因于NC捕获隧道电子的过量Cd原子的点缺陷的形成以及氨气对缺陷形成过程的影响。由于烧结NC造成的高密度缺陷，在基材表面迁移过程中失去了保护性有机壳，这很可能导致位于整体边缘附近的NC中的带隙变窄。零传导间隙值对NC尺寸的依赖性分析表明，位于NC中的载流子与壳中的极化电荷之间的库仑相互作用对NC能谱产生了强烈影响。确定了壳的介电常数（ε（out）= 10-16.5）和电子的能垒高度（V-0 = 0.6-0.8 eV）。壳层包含氨和有机分子，其中的非氨分子对壳层的介电常数起主要作用，而有机分子则决定了势垒高度。

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