Diffusion-driven growth of nanowires by low-temperature molecular beam epitaxy

TL;DR

This study investigates the growth mechanisms of ZnTe nanowires via low-temperature gold-catalyzed molecular beam epitaxy, using microscopy and diffusion models to understand axial and radial growth characteristics.

Contribution

It introduces a diffusion-limited growth model tailored to low-temperature nanowire growth, validated by microscopy and statistical analysis, revealing growth dynamics and diffusion length evolution.

Findings

Diffusion lengths vary with temperature and flux conditions.

Analytical models accurately describe nanowire length and diameter relationships.

Growth exhibits a long incubation period before steady elongation.

Abstract

With ZnTe as an example, we use two different methods to unravel the characteristics of the growth of nanowires by gold-catalyzed molecular beam epitaxy at low temperature. In the first approach, CdTe insertions have been used as markers, and the nanowires have been characterized by scanning transmission electron microscopy, including geometrical phase analysis, and energy dispersive electron spectrometry; the second approach uses scanning electron microscopy and the statistics of the relationship between the length of the tapered nanowires and their base diameter. Axial and radial growth are quantified using a diffusion-limited model adapted to the growth conditions; analytical expressions describe well the relationship between the NW length and the total molecular flux (taking into account the orientation of the effusion cells), and the catalyst-nanowire contact area. A long incubation time is observed. This analysis allows us to assess the evolution of the diffusion lengths on the substrate and along the nanowire sidewalls, as a function of temperature and deviation from stoichiometric flux.