Real-time observation of nucleation and growth of Au on CdSe quantum dot templates

Neelima Paul,Matthias Schwartzkopf,Zhiyin Weng,Taidong Lin,Amitesh Paul,Zhaoyu Liu,Zhongyi Chen,Chunfeng Chen,Peter Müller-Buschbaum,Chang Liu,Stephan V Roth,Junyu Huang,Chenghao Ouyang

doi:10.1038/s41598-021-97485-z

Abstract

Semiconductor quantum dot (QD) arrays can be useful for optical devices such as lasers, solar cells and light-emitting diodes. As the size distribution influences the band-gap, it is worthwhile to investigate QDs prepared using different solvents because each of them could influence the overall morphology differently, depending on the ligand network around individual QDs. Here, we follow the nucleation and growth of gold (Au) on CdSe QD arrays to investigate the influence of surface ligands and thereby realized interparticle distance between QDs on Au growth behaviour. We particularly emphasize on the monolayer stage as the Au decoration on individual QDs is expected at this stage. Therefore, we sputter-deposit Au on each QD array to investigate the morphological evolution in real-time using time-resolved grazing-incidence small-angle X-ray scattering (GISAXS). The growth kinetics - independent of the template - signifies that the observed template-mediated nucleation is limited only to the very first few monolayers. Delicate changes in the Au growth morphology are seen in the immediate steps following the initial replicated decoration of the QD arrays. This is followed by a subsequent clustering and finally a complete Au coverage of the QD arrays.

Highlights

Semiconductor quantum dot (QD) arrays can be useful for optical devices such as lasers, solar cells and light-emitting diodes
We investigate the role of solvents on the morphological evolution of the Au electrode layer on top of QD arrays, which have been formed using different passivating ligands
We investigate the role of solvents on the morphological evolution of the Au electrode layer on top of QD arrays, which have been formed using various passivating ligands

Summary

Introduction

Semiconductor quantum dot (QD) arrays can be useful for optical devices such as lasers, solar cells and light-emitting diodes. Semiconductor quantum dots (QDs) expand the range of materials suitable for absorbers in solar cells due to their tunable bandgap[1]. Au growth on active semiconducting materials are important for their metallic contacts and or as charge recombination c enters[12] It is a suitable material for overgrowth and subsequent monitoring of correlation effects. Specific surface groups are maintained after each washing or exchange s tep[14] Such colloidal QDs are composed of inorganic core (e.g. CdSe) and different organic shells, depending on the surface ligands. For the CdSe QDs used in this work, Photoluminescence (PL), UV-vis absorption spectroscopy, spectral and time dependant surface photovoltage (SPV) data on these QDs in different ligands ot linker molecules show that the surface of QDs has a high influence on PL signal and charge separation in CdSe QD thin films[15]

Methods

Results

Conclusion