Growth of InN quantum dots to nanorods: A competition between nucleation and growth rates

TL;DR

This study investigates how InN nanostructures evolve from quantum dots to nanorods during chemical vapor deposition, highlighting the influence of temperature, time, and gas flow on morphology and strain development.

Contribution

It provides a detailed analysis of the morphological transition mechanism from quantum dots to nanorods based on nucleation and growth rates at different temperatures.

Findings

Nanorods start forming at 630°C.

Morphology depends on growth temperature, time, and flow rate.

Strain increases with higher growth temperature due to impurities.

Abstract

Growth evolution of InN nanostructures via a chemical vapor deposition technique is reported using In_2O_3 as precursor material and NH_3 as reactive gas in the temperature range of 550-700 ^oC. Morphology of the nanostructures solely depends on the growth temperature, evolving from quantum dot sized nanoparticles to nanorods. It is found that 630 ^oC is the threshold temperature for nanorod growth. At 630 ^oC, nucleation starts with multifaceted particle having {10-12} surface planes. Subsequently, hexagonal polyhedral NRs are grown along the [0001] direction with non-polar surfaces of m-planes {10-10}. A comprehensive study is carried out to understand the evolution of nanorods as a function of growth parameters like temperature, time and gas flow rate. Change in the morphology of nanostructures is explained based on the nucleation rate and the growth rates during the phase formation. Raman studies of these nanostructures show that a biaxial strain is developed because of unintentional impurity doping with the increase in growth temperature.