Modeling the Shape Evolution of Selective Area Grown Zn₃P₂ Nanoislands

Abstract

Selective area growth of zinc phosphide (Zn3P2) on InP provides a pathway to high-quality semiconductor nanostructures and textured thin films made of earth-abundant elements. In the precoalescence stage, Zn3P2 emerges in the form of nanoislands undergoing a peculiar shape transformation in the course of growth. We present a model based on the minimization of the surface energy with respect to the relevant geometrical parameters which quantitively describes the shape of nanoislands depending on their volume. The results are presented in the dimensionless variables which allow us to comprehend simultaneously the islands grown in differently sized pinholes and for different growth times. The shape transformation is driven by a competition of (112) and (101) side facets and (001) top facet. The islands are flat and regular octagonal at the beginning of growth, transitioning to the full nanopyramid restricted solely by (101) facets at the end.

Nanoscale Growth Initiation as a Pathway to Improve the Earth-Abundant Absorber Zinc Phosphide

“…The morphology of the nanostructure is a function of the shape of the hole. Nanopyramids are the result for circular holes, while nanowires, or even nanowire networks, are achieved from elongated slits as shown in Figure . − However, these shapes are only observed after a couple of intermediate stages. The intermediate morphology as zinc phosphide outgrows the hole depends on the relative surface energies of the dominating facets, namely, (001), (112), and (101).…”

“…The intermediate morphology as zinc phosphide outgrows the hole depends on the relative surface energies of the dominating facets, namely, (001), (112), and (101). DFT calculations showed that E (101) < E (112) < E (001) . ,, The morphology evolution can be determined through a dimensionless geometric parameter based on the relative surface energies and initial hole size . The facet fractions and shape evolution based on this model are shown in Figure .…”

“…(e) Graph showing the fraction of the different facets as a function of the dimensionless volume. (f) Illustrations of the nanostructure shape for the different regions in panel e. (a–c, e, f) Reprinted with permission from ref . Copyright 2021 American Chemical Society.…”

“…55,58,59 The morphology evolution can be determined through a dimensionless geometric parameter based on the relative surface energies and initial hole size. 57 The facet fractions and shape evolution based on this model are shown in Figure 4. The inherent pyramidal morphology is ideal for light trapping in the zinc phosphide layer, which is advantageous for PV applications.…”

Criterion for the growth selectivity of III-V and III-N nanowires on masked substrates

“…The growth of III−V and III-N NWs by selective area epitaxy (SAE) on masked substrates with regular arrays of pinholes [4][5][6][7][8][9][10][11] allows one to synthesize NW ensembles uniform in size with exactly determined positioning of NWs and distances between them. The SAE technique is also used to synthesize nanomembranes [12,13] and nanoislands [14] of various geometry. These structures hold much promise for application in nanophotonics and nanoelectronics with an option for integration into silicon electronic technology.…”