Persistence of magic cluster stability in ultra-thin semiconductor nanorods

Abstract

The progression from quasi zero-dimensional (Q0D) nanoclusters to quasi one-dimensional (Q1D) nanorods, and, with increasing length, to nanowires, represents the most conceptually fundamental transition from the nanoscale to bulk-like length scales. This dimensionality crossover is particularly interesting, both scientifically and technologically, for inorganic semiconducting (ISC) materials, where striking concomitant changes in optoelectronic properties occur.^1,2 Such effects are most pronounced for ultra-thin³ ISC nanorods/nanowires, where the confining and defective nature of the atomic structure become key. Although experiments on ISC materials in this size regime have revealed especially stable (or “magic”) non-bulk-like Q0D nanoclusters,^4,5 all ISC Q1D nanostructures have been reported as having structures corresponding to bulk crystalline phases. For two important ISC materials (CdS and CdSe) we track the Q0D-to-Q1D transition employing state-of-the-art electronic structure calculations demonstrating an unexpected persistence of magic cluster stability over the bulk-like structure in ultra-thin nanorods up to >10 nm in length. The transition between the magic-cluster-based and wurtzite nanorods is found to be accompanied by a large change in aspect ratio thus potentially providing a route to nano-mechanical transducer applications.