Interfacial strain and shell thickness effect on core squeeze/stretch in core/shell quantum dots

Abstract

Large surface to volume ratio in zero dimension core/shell quantum dots makes lattice mismatch induced interfacial strain vital in determining structural and optical properties of nanostructures. In this study, changes in lattice mismatch induced strain from different compressive shell (CdS-ZnS) with different thicknesses (thin and thick) are evaluated and its effect on capped core diameter is theoretically calculated. Capped core squeeze amount is compared with its initial (bare) diameter obtained from transmission electron microscopy. The capped core diameter is first calculated theoretically using effective mass approximation. Then, same diameter is obtained from modified version of effective mass approximation method that considers interfacial strain amount. Comparison of the results with bare core size obtained from transmission electron microscopy revealed effect of shell thickness imposed on capped core diameter. Results show, larger lattice mismatch between core and shell induces higher strain amount on the core thereby larger squeezes the core. At the meantime, it is shown that, thicker compressive shell enforces lower stress on core as it widens its distance from core due to lattice relaxation. Hence, core is squeezes less under thicker shell.

Unusual Phase Behaviour for Organo-Halide Perovskite Nanoparticles Synthesized via Reverse Micelle Templating

“…We attribute the strain in both cases as resulting from the external pressure of the micelle core on the perovskite cage during particle formation. The induced strain has been previously observed for other types of ligated [125,126] and core-shell [127,128] nanoparticles. Quantitative nanomechanical mapping (QNM) using the AFM can provide information on the nanomechanical properties of soft materials [129][130][131].…”

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“…Experimentally, there have been several synthesis methods have been developed for group-II chalcogenide compounds, including colloidal approach 38 , colloidal ALD 39 , chemical bath deposition 40 , CVD 41 . Their unique properties have been revealed by a lot of theoretical cal-culations and analytical methods [42][43][44][45][46][47] .…”

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“…For more information on corrections related to hydrostatic strain arising from interfacial and surface elasticity, please refer to Refs. [ 48 , 49 ].…”