TY - JOUR

T1 - Untangling the intertwined

T2 - metallic to semiconducting phase transition of colloidal MoS2 nanoplatelets and nanosheets

AU - Niebur, André

AU - Söll, Aljoscha

AU - Haizmann, Philipp

AU - Strolka, Onno

AU - Rudolph, Dominik

AU - Tran, Kevin

AU - Renz, Franz

AU - Frauendorf, André Philipp

AU - Hübner, Jens

AU - Peisert, Heiko

AU - Scheele, Marcus

AU - Lauth, Jannika

N1 - Funding Information: The authors appreciate the Laboratory for Nano- and Quantum Engineering (LNQE) in Hannover for access to the TEM. The authors would like thank Armin Feldhoff for providing the XRD facility, Nadja C. Bigall and Dirk Dorfs for access to the UV-Vis-NIR absorption spectrometer and Jürgen Caro for access to the ATR-FTIR spectrometer. K. T. is grateful for being funded by the Hannover School for Nanotechnology (HSN). M. S. acknowledges funding by the DFG under grant SCHE1905/9-1. The authors thank Fabian Strauß for preparing wafer cuts as substrates for XPS experiments. J. L. gratefully acknowledges funding by the German Research Foundation (DFG) under the Excellence Strategy of the Cluster of Excellence PhoenixD (EXC 2122, Project ID 390833453) and access to the Ti:sapphire amplifier system (major equipment DFG, Project ID 231415720, Michael Oestreich). J. L. is grateful for funding through the Caroline Herschel Program of Leibniz Universität Hannover.

PY - 2023/3/28

Y1 - 2023/3/28

N2 - 2D semiconducting transition metal dichalcogenides (TMDCs) are highly promising materials for future spin- and valleytronic applications and exhibit an ultrafast response to external (optical) stimuli which is essential for optoelectronics. Colloidal nanochemistry on the other hand is an emerging alternative for the synthesis of 2D TMDC nanosheet (NS) ensembles, allowing for the control of the reaction via tunable precursor and ligand chemistry. Up to now, wet-chemical colloidal syntheses yielded intertwined/agglomerated NSs with a large lateral size. Here, we show a synthesis method for 2D mono- and bilayer MoS2 nanoplatelets with a particularly small lateral size (NPLs, 7.4 nm ± 2.2 nm) and MoS2 NSs (22 nm ± 9 nm) as a reference by adjusting the molybdenum precursor concentration in the reaction. We find that in colloidal 2D MoS2 syntheses initially a mixture of the stable semiconducting and the metastable metallic crystal phase is formed. 2D MoS2 NPLs and NSs then both undergo a full transformation to the semiconducting crystal phase by the end of the reaction, which we quantify by X-ray photoelectron spectroscopy. Phase pure semiconducting MoS2 NPLs with a lateral size approaching the MoS2 exciton Bohr radius exhibit strong additional lateral confinement, leading to a drastically shortened decay of the A and B exciton which is characterized by ultrafast transient absorption spectroscopy. Our findings represent an important step for utilizing colloidal TMDCs, for example small MoS2 NPLs represent an excellent starting point for the growth of heterostructures for future colloidal photonics.

AB - 2D semiconducting transition metal dichalcogenides (TMDCs) are highly promising materials for future spin- and valleytronic applications and exhibit an ultrafast response to external (optical) stimuli which is essential for optoelectronics. Colloidal nanochemistry on the other hand is an emerging alternative for the synthesis of 2D TMDC nanosheet (NS) ensembles, allowing for the control of the reaction via tunable precursor and ligand chemistry. Up to now, wet-chemical colloidal syntheses yielded intertwined/agglomerated NSs with a large lateral size. Here, we show a synthesis method for 2D mono- and bilayer MoS2 nanoplatelets with a particularly small lateral size (NPLs, 7.4 nm ± 2.2 nm) and MoS2 NSs (22 nm ± 9 nm) as a reference by adjusting the molybdenum precursor concentration in the reaction. We find that in colloidal 2D MoS2 syntheses initially a mixture of the stable semiconducting and the metastable metallic crystal phase is formed. 2D MoS2 NPLs and NSs then both undergo a full transformation to the semiconducting crystal phase by the end of the reaction, which we quantify by X-ray photoelectron spectroscopy. Phase pure semiconducting MoS2 NPLs with a lateral size approaching the MoS2 exciton Bohr radius exhibit strong additional lateral confinement, leading to a drastically shortened decay of the A and B exciton which is characterized by ultrafast transient absorption spectroscopy. Our findings represent an important step for utilizing colloidal TMDCs, for example small MoS2 NPLs represent an excellent starting point for the growth of heterostructures for future colloidal photonics.

UR - http://www.scopus.com/inward/record.url?scp=85149564623&partnerID=8YFLogxK

U2 - 10.1039/d3nr00096f

DO - 10.1039/d3nr00096f

M3 - Article

AN - SCOPUS:85149564623

VL - 15

SP - 2

JO - NANOSCALE

JF - NANOSCALE

SN - 2040-3364

IS - 12

ER -