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Carrier Multiplication in PbS Quantum Dots Anchored on a Au Tip using Conductive Atomic Force Microscopy

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Title
Carrier Multiplication in PbS Quantum Dots Anchored on a Au Tip using Conductive Atomic Force Microscopy
Author(s)
Sung-Tae Kim; Ji-Hee Kim; Young Hee Lee
Subject
carrier multiplication, ; conductive atomic force microscopy, ; lead sulfide quantum dots, ; photocurrent measurement
Publication Date
2020-04
Journal
ADVANCED MATERIALS, v.32, no.17, pp.1908461
Publisher
WILEY-V C H VERLAG GMBH
Abstract
© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Carrier multiplication (CM) is the amplification of the excited carrier density by two times or more when the incident photon energy is larger than twice the bandgap of semiconductors. A practical approach to demonstrate the CM involves the direct measurement of photocurrent in the device. Specifically, photocurrent measurement in quantum dots (QDs) is typically limited by high contact resistance and long carrier-transfer length, which yields a low CM conversion efficiency and high CM threshold energy. Here, the local photocurrent is measured to evaluate the CM quantum efficiency from a QD-attached Au tip of a conductive atomic force microscope (CAFM) system. The photocurrent is efficiently measured between the PbS QDs anchored on a Au tip and a graphene layer on a SiO2/Si substrate as a counter electrode, yielding an extremely short channel length that reduces the contact resistance. The quantum efficiency extracted from the local photocurrent data with an incident photon energy exhibits a step-like behavior. More importantly, the CM threshold energy is as low as twice the bandgap, which is the lowest threshold energy of optically observed QDs to date. This enables the CAFM-based photocurrent technique to directly evaluate the CM conversion efficiency in low-dimensional materials
URI
https://pr.ibs.re.kr/handle/8788114/8699
DOI
10.1002/adma.201908461
ISSN
0935-9648
Appears in Collections:
Center for Integrated Nanostructure Physics(나노구조물리 연구단) > 1. Journal Papers (저널논문)
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