Controlled Growth of ZnO Nanowires and Their Optical Properties

TLDR

The study builds on a VLS nanowire growth framework that enables positional, orientational, diameter, and density control, as further validated by near‑field scanning optical microscopy of single nanowires. The article reviews recent advances in rational synthesis of single‑crystalline ZnO nanowires and their distinctive optical properties. ZnO nanowires were synthesized via a simple chemical vapor transport and condensation (CVTC) system, facilitating controlled growth. Power‑dependent emission studies revealed lasing in ZnO nanowires above ~40 kW cm⁻², producing short‑wavelength, room‑temperature nanolasers with areal densities up to 1 × 10¹⁰ cm⁻², demonstrating that single‑crystalline, well‑faceted nanowires act as self‑contained optical resonance cavities without fabricated mirrors.

Abstract

This article surveys recent developments in the rational synthesis of single-crystalline zinc oxide nanowires and their unique optical properties. The growth of ZnO nanowires was carried out in a simple chemical vapor transport and condensation (CVTC) system. Based on our fundamental understanding of the vapor–liquid–solid (VLS) nanowire growth mechanism, different levels of growth controls (including positional, orientational, diameter, and density control) have been achieved. Power-dependent emission has been examined and lasing action was observed in these ZnO nanowires when the excitation intensity exceeds a threshold (∼40 kW cm–2). These short-wavelength nanolasers operate at room temperature and the areal density of these nanolasers on substrate readily reaches 1 × 1010 cm–2. The observation of lasing action in these nanowire arrays without any fabricated mirrors indicates these single-crystalline, well-facetted nanowires can function as self-contained optical resonance cavities. This argument is further supported by our recent near-field scanning optical microscopy (NSOM) studies on single nanowires.