Mapping Charge Distribution in Single PbS Core - CdS Arm Nano-Multipod Heterostructures by Off-Axis Electron Holography

被引:9
作者
Chalasani, Rajesh [1 ,2 ]
Pekin, Alexander [4 ,5 ]
Rabkin, Alexander [4 ,5 ]
Abutbul, Ran E. [4 ,5 ]
Dieguez, Oswaldo [1 ,3 ]
Kauffmann, Yaron [6 ]
Golan, Yuval [4 ,5 ]
Kohn, Amit [1 ,2 ]
机构
[1] Tel Aviv Univ, Dept Mat Sci & Engn, IL-6997801 Tel Aviv, Israel
[2] Tel Aviv Univ, Res Ctr Nanosci & Nanotechnol, IL-6997801 Tel Aviv, Israel
[3] Tel Aviv Univ, Raymond & Beverly Sackler Ctr Computat Mol & Mat, IL-6997801 Tel Aviv, Israel
[4] Ben Gurion Univ Negev, Dept Mat Engn, IL-84105 Beer Sheva, Israel
[5] Ben Gurion Univ Negev, Ilse Katz Inst Nanoscale Sci & Technol, IL-84105 Beer Sheva, Israel
[6] Technion Israel Inst Technol, Dept Mat Sci & Engn, IL-32000 Haifa, Israel
基金
以色列科学基金会;
关键词
PbS core-CdS arm nanomultipod heterostructures; off-axis electron holography; electrostatic phase mapping; built-in potential; 3D electrostatic simulations; focal series exit wave phase reconstruction; TRANSISTORS; SCATTERING; JUNCTIONS; GROWTH;
D O I
10.1021/acs.nanolett.6b04957
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
We synthesized PbS core-CdS arm nanomultipod heterostructures (NMHs) that exhibit PbS{111}/CdS{0002} epitaxial relations. The PbS CdS interface is chemically sharp as determined by aberration corrected transmission electron microscopy (TEM) and compared to density functional theory (DFT) calculations. Ensemble fluorescence measurements show quenching of the optical signal from the CdS arms indicating charge separation due to the heterojunction with PbS. A finite-element three-dimensional (3D) calculation of the Poisson equation shows a type-I heterojunction, which would prevent recombination in the CdS arm after optical excitation. To examine charge redistribution, we used off-axis electron holography (OAEH) in the TEM to map the electrostatic potential across an individual heterojunction. Indeed, a built-in potential of 500 mV is estimated across the junction, though as opposed to the thermal equilibrium calculations significant accumulation of positive charge at the CdS side of the interface is detected. We conclude that the NMH multipod geometry prevents efficient removal of generated charge carriers by the high energy electrons of the TEM. Simulations of generated electron hole pairs in the insulated CdS arm of the NMH indeed show charge accumulation in agreement with the experimental measurements. Thus, we show that OAEH can be used as a complementary methodology to ensemble measurements by mapping the charge distribution in single NMHs with complex geometries.
引用
收藏
页码:2778 / 2787
页数:10
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