Heteroconfinement in Single CdTe Nanoplatelets

Area of Science:

• Materials Science
• Nanotechnology
• Quantum Dots

Background:

• Atomically thin II-VI nanoplatelets (NPLs) are crucial for optoelectronic applications.
• Synthesizing dimension-engineered cadmium selenide (CdSe) NPLs with controlled thickness (2-11 monolayers) is established.
• Cadmium telluride (CdTe) NPLs present significant synthesis and separation challenges, hindering advanced applications.

Purpose of the Study:

• To elucidate the mechanistic insights into the layer-by-layer growth kinetics of CdTe NPLs.
• To understand the challenges in synthesizing higher monolayer (ML) CdTe NPLs beyond 2 ML.
• To explain the observed differences in growth kinetics between CdTe and CdSe NPLs.

Main Methods:

• Ensemble and single-particle spectroscopy and microscopy.
• Transient absorption spectroscopy.
• Atomic force microscopy (AFM) and simulations of growth conditions.

Main Results:

• Higher ML CdTe NPLs (>2 ML) initially form as heteroconfined structures with colocalized multilayer emissions (e.g., 3 and 4 ML).
• Single NPLs exhibit islands of different MLs, confirmed by AFM and optical analyses.
• Simulations revealed that lower monomer binding energy in CdTe, compared to CdSe, dictates growth kinetics and limits higher ML synthesis.

Conclusions:

• The nonstandard nucleation and growth of heteroconfined CdTe NPLs are driven by kinetic factors related to monomer binding energy.
• Lower CdTe bond energy compared to CdSe limits the synthesis of higher ML CdTe NPLs.
• These findings provide crucial understanding for advancing the synthesis of dimension-engineered CdTe nanomaterials.