Chemically-specific time-resolved surface photovoltage spectroscopy: Carrier dynamics at the interface of quantum dots attached to a metal oxide

SURFACE SCIENCE

卷:641

Article; Proceedings Paper

Spencer, Ben F.^1,2,3  Cliffe, Matthew J.^1,2,3  Graham, Darren M.^1,2  Hardman, Samantha J. O.^1,2  Seddon, Elaine A.^1,2,3  Syres, Karen L.^1,2  Thomas, Andrew G.^1,2  Sirotti, Fausto⁴  Silly, Mathieu G.⁴  Akhtar, Javeed⁵  O'Brien, Paul⁵  Fairclough, Simon M.⁶  Smith, Jason M.⁷  Chattopadhyay, Swapan³  Flavell, Wendy R.^1,2 

[1] Univ Manchester, Sch Phys & Astron, Manchester M13 9PL, Lancs, England

[2] Univ Manchester, Photon Sci Inst, Manchester M13 9PL, Lancs, England

[3] Sci Tech Daresbury, Cockcroft Inst, Warrington WA4 4AD, Cheshire, England

[4] Synchrotron SOLEIL, F-91192 Gif Sur Yvette, France

[5] Univ Manchester, Dept Chem, Manchester M13 9PL, Lancs, England

[6] Univ Oxford, Dept Chem, Oxford OX1 3QR, England

[7] Univ Oxford, Dept Mat, Oxford OX1 3PH, England

关键词: Surface photovoltage;    Time-resolved photoemission;    Semiconductor surface;    Carrier dynamics;    Photovoltaics;    Colloidal quantum dots;   

DOI  :  10.1016/j.susc.2015.03.010

来源: Elsevier

【 摘 要 】

We describe a new experimental pump-probe methodology where a 2D delay-line detector enables fast (ns) monitoring of a narrow XPS spectrum in combination with a continuous pump laser. This has been developed at the TEMPO beamline at Synchrotron SOLEIL to enable the study of systems with intrinsically slow electron dynamics, and to complement faster measurements that use a fs laser as the pump. We demonstrate its use in a time-resolved study of the surface photovoltage of the m-plane ZnO (10 (1) over bar0) surface which shows persistent photoconductivity, requiring monitoring periods on ms timescales and longer. We make measurements from this surface in the presence and absence of chemically-linked quantum dots (QDs), using type I PbS and type II CdSe/ZnSe (core/shell) QDs as examples. We monitor signals from both the ZnO substrate and the bound QDs during photoexcitation, yielding evidence for charge injection from the QDs into the ZnO. The chemical specificity of the technique allows us to observe differences in the extent to which the QD systems are influenced by the field of the surface depletion layer at the ZnO surface, which we attribute to differences in the band structure at the interface. Crown Copyright (C) 2015 Published by Elsevier B.V. All rights reserved.

【 授权许可】

Free