Crystalline nano-structures of Ga₂O₃ with herringbone morphology

Abstract

Highly crystalline β-Ga₂O₃ nanowires with two morphologies have been synthesized through physical evaporation of Te doped GaAs powder in Ar atmosphere. Growth is not based on VLS mechanism due to absence of Te. S in place of Te resulted in similar nanostructures. Some of the nanowires exhibit herringbone morphology with presence of hexagonal crystallites in regular spacing along the nanowire axis. The crystal planes of the nanowires were found to be parallel to one of the facets of the crystallites implying these crystallites may serve as the nucleation centers for the growth. Other dominant nanowire morphology is single crystalline nanoribbons.

Introduction

Nanostructures have attracted a great deal of interest and attention due to their interesting fundamental properties and potential applications such as gas sensors, field emitters, and advanced optoelectronic devices [1], [2], [3]. Metal oxide crystals in particular exhibit unique structures and physico-chemical properties especially at nano meter scale. Variety of nanostructures with different geometrical morphologies including tubes (single or multiple), wires, rods, sheets, belts, diskettes have been synthesized in a predicable way. Functionalized oxide nanostructures are used as functional materials due to their tunable physical properties as a result of the presence of vacancies and mixed valence states. Ga₂O₃ is one of the mostly studied metal oxide nano structures [4]. β-Ga₂O₃ is a wide bandgap (E_g = 4.9 eV) compound with interesting electrical and optical properties. In order to grow Ga₂O₃ nanostructure, various methods including vapor–liquid–solid technique [5], arc-discharge method [6], physical deposition [7] and thermal evaporation of oxide powders at high temperature [8] have been employed. Also Ga₂O₃ nanobelts have been grown by heating the metallic Ga in a furnace through vapor–solid process [9] and by evaporating GaN powders at 100 °C in flowing oxygen [10]. Ho et al. have synthesized β-Ga₂O₃ nanoribbons by plasma immersion ion implantation of nitrogen into undoped GaAs and post-implant rapid thermal annealing [11]. Here, we present a novel process for the synthesis of β-Ga₂O₃ nanowires and nanoribbons with unique nano-structures by simple thermal decomposition of GaAs mixed with a chalcogenide such as Tellurium or Sulfur in the presence of trace amount of oxygen. Other growth methods have been conducted associating chalcogenide elements in the growth of nanostructures [12].